Interior Communications Electrician, Volume 2

Interior Communications Electrician, Volume 2
NONRESIDENT
TRAINING
COURSE
February 1993
Interior
Communications
Electrician, Volume 2
NAVEDTRA 14121
DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited.
Although the words “he,” “him,” and
“his” are used sparingly in this course to
enhance communication, they are not
intended to be gender driven or to affront or
discriminate against anyone.
DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited.
COMMANDING OFFICER
NETPDTC
6490 SAUFLEY FIELD RD
PENSACOLA, FL 32509-5237
28 Jul 1997
ERRATA #2
Specific Instructions and Errata for
Nonresident Training Course
INTERIOR COMMUNICATIONS ELECTRICIAN, VOLUME 2
1. This errata supersedes all previous erratas. No attempt has been made to
issue corrections for errors in typing, punctuation, etc., that do not affect
your ability to answer the question or questions.
2. To receive credit for deleted questions, show this errata to your local
course administrator (ESO/scorer). The local course administrator is
directed to correct the course and the answer key by indicating the question
deleted.
3.
Assignment Booklet
Delete the following questions, and leave the corresponding spaces blank
on the answer sheets:
Questions
Questions
1-25
3-28
1-42
3-40
1-46
3-60
2-51
4-26
3-4
4-28
PREFACE
By enrolling in this self-study course, you have demonstrated a desire to improve yourself and the Navy.
Remember, however, this self-study course is only one part of the total Navy training program. Practical
experience, schools, selected reading, and your desire to succeed are also necessary to successfully round
out a fully meaningful training program.
COURSE OVERVIEW: In completing this nonresident training course, you will demonstrate a
knowledge of the subject matter by correctly answering questions on the following subjects: manual bus
transfers, frequency regulators, and motor controllers; anemometer systems; the stabilized glide slope
indicator (GSI) system; and technical administration.
THE COURSE: This self-study course is organized into subject matter areas, each containing learning
objectives to help you determine what you should learn along with text and illustrations to help you
understand the information. The subject matter reflects day-to-day requirements and experiences of
personnel in the rating or skill area. It also reflects guidance provided by Enlisted Community Managers
(ECMs) and other senior personnel, technical references, instructions, etc., and either the occupational or
naval standards, which are listed in the Manual of Navy Enlisted Manpower Personnel Classifications
and Occupational Standards, NAVPERS 18068.
THE QUESTIONS: The questions that appear in this course are designed to help you understand the
material in the text.
VALUE: In completing this course, you will improve your military and professional knowledge.
Importantly, it can also help you study for the Navy-wide advancement in rate examination. If you are
studying and discover a reference in the text to another publication for further information, look it up.
1993 Edition Prepared by
ICCS Bert A. Parker
Published by
NAVAL EDUCATION AND TRAINING
PROFESSIONAL DEVELOPMENT
AND TECHNOLOGY CENTER
NAVSUP Logistics Tracking Number
0504-LP-026-7830
i
Sailor’s Creed
“I am a United States Sailor.
I will support and defend the
Constitution of the United States of
America and I will obey the orders
of those appointed over me.
I represent the fighting spirit of the
Navy and those who have gone
before me to defend freedom and
democracy around the world.
I proudly serve my country’s Navy
combat team with honor, courage
and commitment.
I am committed to excellence and
the fair treatment of all.”
ii
CONTENTS
Page
CHAPTER
1. Manual Bus Transfers, Motor Controllers,
and Frequency Regulators . . . . . . . . . . . . . . . . . . .1-1
2. Anemometer Systems . . . . . . . . . . . . . . . . . . . . . . . . .2-1
3. Stabilized Glide Slope Indicator System . . . . . . . . . . . . . . .3-1
4. Technical Administration . . . . . . . . . . . . . . . . . . . . . . .4-1
APPENDIX
I. Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AI-1
II. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . AII-1
INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . INDEX-1
iii
INSTRUCTIONS FOR TAKING THE COURSE
assignments. To submit your
answers via the Internet, go to:
ASSIGNMENTS
The text pages that you are to study are listed at
the beginning of each assignment. Study these
pages carefully before attempting to answer the
questions. Pay close attention to tables and
illustrations and read the learning objectives.
The learning objectives state what you should be
able to do after studying the material. Answering
the questions correctly helps you accomplish the
objectives.
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SELECTING YOUR ANSWERS
Read each question carefully, then select the
BEST answer. You may refer freely to the text.
The answers must be the result of your own
work and decisions. You are prohibited from
referring to or copying the answers of others and
from giving answers to anyone else taking the
course.
COMMANDING OFFICER
NETPDTC N331
6490 SAUFLEY FIELD ROAD
PENSACOLA FL 32559-5000
Answer Sheets: All courses include one
“scannable” answer sheet for each assignment.
These answer sheets are preprinted with your
SSN, name, assignment number, and course
number. Explanations for completing the answer
sheets are on the answer sheet.
SUBMITTING YOUR ASSIGNMENTS
To have your assignments graded, you must be
enrolled in the course with the Nonresident
Training Course Administration Branch at the
Naval Education and Training Professional
Development
and
Technology
Center
(NETPDTC). Following enrollment, there are
two ways of having your assignments graded:
(1) use the Internet to submit your assignments
as you complete them, or (2) send all the
assignments at one time by mail to NETPDTC.
Grading on the Internet:
Internet grading are:
•
•
assignment
Do not use answer sheet reproductions: Use
only the original answer sheets that we
provide—reproductions will not work with our
scanning equipment and cannot be processed.
Follow the instructions for marking your
answers on the answer sheet. Be sure that blocks
1, 2, and 3 are filled in correctly. This
information is necessary for your course to be
properly processed and for you to receive credit
for your work.
Advantages to
COMPLETION TIME
you may submit your answers as soon as
you complete an assignment, and
you get your results faster; usually by the
next working day (approximately 24 hours).
Courses must be completed within 12 months
from the date of enrollment. This includes time
required to resubmit failed assignments.
In addition to receiving grade results for each
assignment, you will receive course completion
confirmation once you have completed all the
iv
PASS/FAIL ASSIGNMENT PROCEDURES
For subject matter questions:
If your overall course score is 3.2 or higher, you
will pass the course and will not be required to
resubmit assignments. Once your assignments
have been graded you will receive course
completion confirmation.
E-mail:
Phone:
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Comm: (850) 452-1001, Ext. 1826
DSN: 922-1001, Ext. 1826
FAX: (850) 452-1370
(Do not fax answer sheets.)
Address: COMMANDING OFFICER
NETPDTC N314
6490 SAUFLEY FIELD ROAD
PENSACOLA FL 32509-5237
If you receive less than a 3.2 on any assignment
and your overall course score is below 3.2, you
will be given the opportunity to resubmit failed
assignments. You may resubmit failed
assignments only once. Internet students will
receive notification when they have failed an
assignment--they may then resubmit failed
assignments on the web site. Internet students
may view and print results for failed
assignments from the web site. Students who
submit by mail will receive a failing result letter
and a new answer sheet for resubmission of each
failed assignment.
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completion letter questions
grading,
or
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FAX: (850) 452-1370
(Do not fax answer sheets.)
Address: COMMANDING OFFICER
NETPDTC N331
6490 SAUFLEY FIELD ROAD
PENSACOLA FL 32559-5000
COMPLETION CONFIRMATION
After successfully completing this course, you
will receive a letter of completion.
NAVAL RESERVE RETIREMENT CREDIT
ERRATA
If you are a member of the Naval Reserve,
you may earn retirement points for successfully
completing this course, if authorized under
current directives governing retirement of Naval
Reserve personnel. For Naval Reserve retirement, this course is evaluated at 6 points. (Refer
to Administrative Procedures for Naval
Reservists on Inactive Duty, BUPERSINST
1001.39, for more information about retirement
points.)
Errata are used to correct minor errors or delete
obsolete information in a course. Errata may
also be used to provide instructions to the
student. If a course has an errata, it will be
included as the first page(s) after the front cover.
Errata for all courses can be accessed and
viewed/downloaded at:
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We value your suggestions, questions, and
criticisms on our courses. If you would like to
communicate with us regarding this course, we
encourage you, if possible, to use e-mail. If you
write or fax, please use a copy of the Student
Comment form that follows this page.
v
Student Comments
Course Title:
Interior Communications Electrician, Volume 2
NAVEDTRA:
14121
Date:
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NETPDTC 1550/41 (Rev 4-00
vii
CHAPTER 1
MANUAL BUS TRANSFERS, MOTOR
CONTROLLERS, AND FREQUENCY REGULATORS
CHAPTER LEARNING OBJECTIVES
Upon completing this chapter, you should be able to do the following:
Describe the procedures to use when performing
corrective maintenance on motor controllers.
Describe the troubleshooting and maintenance
procedures for manual bus transfer (MBT)
switches.
Identify the different types of electric controllers.
Describe the principles of operation of
frequency regulators.
Describe the principles of operation of various
types of motor controllers.
Identify the components of motor generators and
their principles of operation.
Describe the procedures for troubleshooting
motor controllers.
Describe the procedures for troubleshooting and
performing corrective maintenance on
frequency regulators.
This chapter discusses the troubleshooting and
maintenance procedures for manual bus transfers
(MBTs), motor controllers, and frequency regulators. To
troubleshoot and maintain these components, you need
to have an understanding of the characteristics, uses, and
operating principles of the components. Because
interior communications and weapons systems aboard
modern Navy ships require closely regulated electric
power for proper operation, you also need to have an
understanding of closely regulated power supplies to
troubleshoot and maintain frequency regulators.
Because equipage in special power applications aboard
ship is so diverse, little is said about troubleshooting or
maintenance of MBT switches and frequency regulators. In studying this chapter, you should remember to
refer to the manufacturer’s technical manual when
troubleshooting the equipment and to the applicable
maintenance requirement card (MRC) for maintenance
requirements.
normal power to ship’s emergency power, the locking
bar must be manually loosened and moved before the
positions of the switches can be changed. Troubleshooting should be done according to the technical
manual associated with the equipment. Maintenance of
the MBT switch should be done according to the
applicable PMS cards.
MOTOR CONTROLLERS
Controllers are commonly used for starting large
motors aboard ship to reduce the amount of current they
require when started. The starting current of huge
motors is usually several times higher than the running
current. If controllers are not used for starting, motors
and the equipment they drive may be damaged, or the
operation of other equipment in the same distribution
MANUAL BUS TRANSFER SWITCHES
system may be affected adversely. By definition, a
MBT switches are commonly used for nonvital
equipment aboard ship. They consist of two make or
break switches and a locking bar. To transfer from
motor controller is a device (or set of devices) that serves
to govern, in some predetermined manner, the operation
of the dc or ac motor to which it is connected.
1-1
TYPES OF MOTOR CONTROLLERS
Ac Primary Resistor
A motor controller protects a motor from damage,
starts or stops it, increases or decreases its speed, or
reverses its direction of rotation.
In an ac primary resistor controller, resistors are
inserted in the primary circuit of an ac motor for both
starting and speed control. Some of these controllers
only limit the starting currents of large motors; others
control the speed of small motors, as well as limit the
starting current.
Manual
A manual (nonautomatic) controller is operated by
hand directly through a mechanical system. The
operator closes and opens the contacts that normally
energize and de-energize the connected load.
Ac Secondary Resistor
In an ac secondary resistor controller, resistors are
inserted in the secondary circuit of a wound-rotor ac
motor for starting or speed control. Although they are
sometimes used to limit starting currents, secondary
resistor controllers usually function to regulate the
speeds of large ac motors.
Magnetic
In a magnetic controller, the contacts are closed or
opened by electromechanical devices operated by local
or remote master switches. Normally, all the functions
of a semiautomatic magnetic controller are governed by
one or more manual master switches; automatic
controller functions are governed by one or more automatic master switches, after it has been initially
energized by a manual master switch. Either controller
can be operated in the semiautomatic or automatic
mode, depending on the mode of operation selected.
Static Variable-Speed
A static variable-speed motor controller consists of
solid-state and other devices that regulate motor speeds
in indefinite increments through a predetermined range.
Speed is controlled by either manual adjustment or
actuation of a sensing device that converts a system
parameter, such as temperature, into an electric signal.
This signal sets the motor speed automatically.
Across-the-Line
Autotransformer
An across-the-line controller throws the connected
load directly across the main supply line. This motor
controller may be either manual or magnetic, depending
on the rated horsepower of the motor. Normally, acrossthe-line dc controllers are used for starting small (fractional horsepower) motors. However, they also may be
used to start average-sized, squirrel-cage induction
motors without any damage. This is because these
motors can withstand the high starting currents due to
starting with full-line voltage applied. Most squirrelcage motors drive pumps, compressors, fans, lathes, and
other auxiliaries. They can be started “across the line”
without producing excessive line-voltage drop or
mechanical shock to a motor or auxiliary.
The autotransformer controller (or compensator) is
an ac motor controller. It starts the motor at a reduced
voltage through an autotransformer, and then it connects
the motor to line voltage after the motor accelerates.
There are two types of compensators: open transition
and closed transition. The open-transition compensator
cuts off power to the motor during the time (transition
period) the motor connection is shifted from the autotransformer to the supply line. In this short transition
period, it is possible for the motor to coast and slip out
of phase with the power supply. After the motor is
connected directly to the supply line, the resulting
transition current may be high enough to cause circuit
breakers to open. The closed-transition compensator
keeps the motor connected to the supply line during the
entire transition period. In this method, the motor cannot
slip out of phase and no high transition current can
develop.
Dc Resistor
In a dc resistor motor controller, a resistor in series
with the armature circuit of the dc motor limits the
amount of current during starts, thereby preventing
motor damage and overloading the power system. In
some resistor controllers, the same resistor also helps
regulate the speed of the motor after it is started. Other
dc controllers use a rheostat in the motor shunt field
circuit for speed control.
Reactor
A reactor controller inserts a reactor in the primary
circuit of an ac motor during starts, and later it short
1-2
fit the motor it is intended to protect, it can be reset after
tripping so the motor can be operated again with
overload protection. Some controllers feature an
emergency-run button that enables the motor to be run
without overload protection during an emergency.
circuits the reactor to apply line voltage to the motor.
The reactor controller is not widely used for starting
large ac motors. It is smaller than the closed-transition
compensator and does not have the high transition
currents that develop in the open-transition
compensator.
Thermal Overload Relays
TYPES OF MASTER SWITCHES
A master switch is a device, such as a pressure or a
thermostatic switch, that governs the electrical
operation of a motor controller. The switch can be
manually or automatically actuated. Drum, selector, and
push-button switches are examples of a manual master
switch. The automatic switch is actuated by a physical
force, not an operator. Examples of automatic master
switches include float, limit, or pressure switches.
The thermal overload relay has a heat-sensitive
element and an overload heater that is connected in
series with the motor load circuit. When the motor
current is excessive, heat from the heater causes the
heat-sensitive clement to open the overload relay
contact. This action breaks the circuit through the
operating coil of the main contractor and disconnects the
motor from the power supply. Since it takes time for the
parts to heat up, the thermal overload relay has an
inherent time delay, which allows the motor to draw
excessive current at start without tripping the motor.
Depending on where it is mounted, a master switch
is either local or remote. A local switch is mounted in
the controller enclosure; a remote switch is not.
To make a coarse adjustment of the tripping current
of thermal overload relays, change the heater element.
Fine adjustment depends on the type of overload relay.
To make a fine adjustment, change the distance between
the heater and the heat-sensitive element. An increase in
this distance increases the tripping current. You can
make another form of adjustment by changing the
distance the bimetal strip has to move before the
overload relay contact is opened. Check the related
technical manual for additional information and
adjustments.
Master switches may start a series of operations
when their contacts are either closed or opened. In a
momentary contact master switch, the contact is closed
(or opened) momentarily; it then returns to its original
condition. In the maintaining contact master switch, the
cent act does not return to its original condition after
closing (or opening) until it is again actuated. The
position of a normally open or normally closed contact
in a master switch is open or closed, respectively, when
the switch is de-energized. The de-energized condition
of a manual controller is considered to be in the off
position.
Thermal overload relays must be compensated; that
is, constructed so the tripping current is unaffected by
variations in the ambient (room) temperature. Different
means are used for different types. Refer to the technical
manual furnished with the equipment on which the
controller is used for information on the particular form
of compensation provided. There are four types of
thermal overload relays: solder pot, bimetal, single
metal, and induction.
OVERLOAD RELAYS
Nearly all shipboard motor controllers provide
overload protection when motor current is excessive.
This protection is provided by either thermal or
magnetic overload relays, which disconnect the motor
from its power supply, thereby preventing the motor
from overheating.
Overload relays in magnetic controllers have a
normally closed contact that is opened by a mechanical
device that is tripped by an overload current. The
opening of the overload relay contact de-energizes the
circuit through the operating coil of the main contactor,
causing the main contactor to open, securing power to
the motor.
SOLDER POT.– The heat-sensitive element of a
solder-pot relay consists of a cylinder inside a hollow
tube. The cylinder and tube are normally held together
by a film of solder. In case of an overload, the heater
melts the solder (thereby breaking the bond between the
cylinder and tube) and releases the tripping device of the
relay. After the relay trips, the solder cools and solidifies.
The relay can then be reset.
Overload relays for naval shipboard use can usually
be adjusted to trip at the correct current to protect the
motor. If the rated tripping current of the relay does not
BIMETAL.– In the bimetal relay, the heat-sensitive
element is a strip or coil of two different metals fused
together along one side. When heated, the strip or coil
1-3
tripping armature. More current is needed to move the
armature when the distance is increased. Compensation
for changes in ambient temperature is not needed for
magnetic relays because they are practically unaffected
by changes in temperature.
deflects because one metal expands more than the other.
The deflection causes the overload relay contact to open.
SINGLE METAL.– The heat-sensitive element of
the single-metal relay is a tube around the heater. The
tube lengthens when heated and opens the overload
relay contact.
Overload Relay Resets
INDUCTION.– The heater in the induction relay
consists of a coil in the motor circuit and a copper tube
inside the coil. The tube acts as the short-circuited
secondary of a transformer and is heated by the current
induced in it. The heat-sensitive element is usually a
bimetal strip or coil. Unlike the other three types of
thermal overload relays that may be used with either ac
or dc, the induction type is manufactured for ac use only.
After an overload relay has operated to stop a motor,
it must be reset before the motor can be started again.
Magnetic overload relays can be reset immediately after
tripping. Thermal overload relays must cool a minute or
longer before they can be reset. The type of overload
reset may be manual, automatic, or electric.
The manual, or hand, reset is usually located in the
controller enclosure, which contains the overload relay.
This type of reset usually has a hand-operated rod, lever,
or button that returns the relay tripping mechanism to its
original position, resetting interlocks as well, so the
motor can be run again with overload protection. (An
interlock is a mechanical or electrical device in which
the operation of one part or mechanism automatically
brings about or prevents the operation of another.)
Magnetic Overload Relays
The magnetic overload relay has a coil connected in
series with the motor circuit and a tripping armature or
plunger. When the normal motor current exceeds the
tripping current, the contacts open the overload relay.
Though limited in application, one type of magnetic
overload relay operates instantly when the motor current
exceeds the tripping current. This type must be set at a
higher tripping current than the motor-starting current
because the relay would trip each time you start the
motor. One use of the instantaneous magnetic overload
relay is in motor controllers used for reduced voltage
starting where the starting current peaks are less than the
stalled rotor current.
The automatic type of reset usually has a spring- or
gravity-operated device, resetting the overload relay
without the help of an operator. The electric reset is
actuated by an electromagnet controlled by a push
button. This form of overload reset is used when it is
desired to reset an overload relay from a remote
operating point.
The operation of a second type of magnetic overload
relay is delayed a short time when the motor current
exceeds the tripping current. This type of relay is
essentially the same as the instantaneous relay except
for the time-delay device. This is usually an oil dashpot
with a piston attached to the tripping armature of the
relay. Oil passes through a hole in the piston when the
tripping armature is moved by an overload current. The
size of the hole can be adjusted to change the speed at
which the piston moves for a given pull on the tripping
armature. For a given size hole, the larger the current,
the faster the operation. The motor is thus allowed to
carry a small overload current. The relay can be set to
trip at a current well below the stalled rotor current
because the time delay gives the motor time to accelerate
to full speed before the relay operates. By this time, the
current will have dropped to full-load current, which is
well below the relay trip setting.
Overload Relay–Emergency Run
Motor controllers having emergency-run features
are used with auxiliaries that cannot be stopped safely
in the midst of an operating cycle. This type of feature
allows the operator of the equipment to keep it running
with the motor overloaded until a standby unit can take
over, the operating cycle is completed, or the emergency
passes.
NOTE: Use this feature in an emergency only. Do
not use it otherwise.
Three methods of providing emergency run in
magnetic controllers are an emergency run pushbutton,
a reset-emergency run lever, or a start-emergency run
push button. In each case, the lever or push button must
be held closed manually during the entire emergency.
Figure 1-1 is a schematic diagram of a controller
showing a separate EMERGENCY RUN push button
with normally open contacts in parallel with the
normally closed contact of the overload relay. For
In either the instantaneous or time-delay magnetic
overload relays, you can adjust the tripping currents by
changing the distance between the series coil and the
1-4
Figure 1-1.-Schematic of controller with emergency run push
button.
Figure 1-2.-Schematic of controller with reset-emergency run
lever or rod.
emergency run operation, the operator must hold down
this push button and press the START button to start the
motor. While the emergency run push button is
depressed, the motor cannot be stopped by opening the
overload relay contact.
short circuits in motor controllers is obtained through
other devices. To protect against these short circuits,
circuit breakers are installed in the power supply system,
thereby protecting the controller, motor, and cables.
Short-circuit protection is provided in controllers where
it is not otherwise provided by the power distribution
A REST-EMERGENCY RUN lever is shown in
figure 1-2. As long as the lever or rod is held down, the
overload relay contact is closed. The start button must
be momentarily closed to start the motor. Figure 1-3
shows a START-EMERGENCY RUN pushbutton. The
motor starts when the button is pushed, and it continues
to run without overload protection as long as it is held
down. For this reason, push buttons that are marked
start-emergency run should not be kept closed for more
than a second or two unless the emergency run operation
is desired.
system or where two or more motors are supplied power
Manual controllers also may be provided with an
emergency run feature. The usual means is a startemergency run push button or lever, which keeps the
main contactor coil energized despite the tripping action
of the overload relay mechanism.
SHORT-CIRCUIT PROTECTION
Overload relays and contractors are usually not
designed to protect motors from currents greater than
about six times normal rated current of ac motors or four
times normal rated current of dc motors. Since shortcircuited currents are much higher, protection against
Figure 1-3-Schematic of controller with start-emergency run
push button.
1-5
but the circuit breaker rating is too high to protect each
motor separately.
Short-circuit protection for control circuits is
provided by fuses in the controller enclosure, which
provides protection for remote push buttons and
pressure switches.
FULL-FIELD PROTECTION
Full-field protection is required in the controller for
a dc motor when a shunt field rheostat or a resistor is
used to weaken the motor field and obtain motor speeds
more than 150 percent of the speed at rated field current.
Full-field protection is provided automatically by a relay
that shunts out the shunt field rheostat for the initial
acceleration of the motor, and then cuts it into the motor
field circuit. In this way, the motor first accelerates to
100 percent or full-field speed, and then further
accelerates to the weakened-field speed determined by
the rheostat settings.
The controller for an anchor windlass motor
provides stepback protection by automatically cutting
back motor speed to relieve the motor of excessive load.
Figure 1-4.-Across-line, 3-phase controller.
LOW-VOLTAGE RELEASE (LVR)
contactor coil, M to
When the coil is energized, it
closes line contacts
and
which connect the
full-line voltage to the motor. The line contactor
auxiliary contact, MA, also closes and completes a holding circuit for energizing the coil circuit after the start
push button has been released.
When the supply voltage is reduced or lost
altogether, an LVR controller disconnects the motor
from the power supply, keeps it disconnected until the
supply voltage returns to normal, and then automatically
restarts the motor. This type of controller is equipped
with a maintaining master switch.
LOW-VOLTAGE PROTECTION (LVP)
When the supply voltage to an LVP controller is
reduced or lost, the motor is disconnected from the line.
Upon restoration of power, the motor will not start until
you manually depress the start push button.
MAGNETIC ACROSS-LINE
CONTROLLERS
A typical 3-phase, across-line controller is shown in
figure 1-4. Figure 1-5 shows a small cubical contactor
for a 5-horsepower motor. All contractors are similar in
appearance, but they vary in size.
An elementary or schematic diagram of a magnetic
controller is shown in figure 1-2. The motor is started
by pushing tie strut button. The action completes the
circuit from
through the control fuse, stop button,
start button, the overload relay contacts, OL, and the
Figure 1-5.-Contactor for a 5-horsepower motor.
1-6
Momentary-contact push buttons provide LVP with
manual restart in the circuit shown in figure 1-6. If either
the For R operating coil is de-energized, the contactor
will not reclose and start the motor when voltage is
restored unless either the forward or reverse pushbutton
is pressed. The circuit arrangement of the pushbuttons
provides an electrical interlock that prevents the
energizing of both coils at the same time.
The motor will continue to run until the contactor
coil is de-energized by the stop push button, failure of
the line voltage, or tripping of the overload relay, OL.
Reversing
The rotation of a three-phase induction motor is
reversed by interchanging any two of the three leads to
the motor. The connections for an ac reversing controller
are shown in figure 1-6. The stop, reverse, and forward
push-button controls are all momentary-contact
switches. Note the connections to the reverse and forward switch contacts. (Their contacts close or open
momentarily, then return to their original closed or
opened condition.)
Speed Control
When you desire to operate an ac motor at different
speeds, you must use a controller with a circuit as shown
in figure 1-7.
An ac induction motor designed for two-speed
operation may have either a single set of windings or
two separate sets of windings, one for each speed.
Figure 1-7 is a schematic diagram of the ac controller
for a two-speed, two-winding induction motor. The lowspeed winding is connected to terminals
and
The high-speed winding is connected to terminals
and
Overload protection is provided by the
low-speed overload (LOL) coils and contacts for the
low-speed winding and the high-speed overload (HOL)
contacts and coils for the high-speed winding. The LOL
and HOL contacts are connected in series in the
maintaining circuit, and both contacts must be closed
before the motor will operate at either speed.
If the forward pushbutton is pressed (solid to dotted
position), coil F will be energized and will close its
holding contacts,
These contacts will remain closed
as long as coil F is energized. When the coil is energized,
it also closes line contacts F1, F2, and F3, which apply
full-line voltage to the motor. The motor then runs in a
forward direction.
If either the stop button or the reverse button is
pressed, the circuit to the F contactor coil is broken, and
the coil releases and opens line contacts F1, F2, F3, and
maintaining contact
If the reverse pushbutton is pressed (solid to dotted
position), coil R is energized and closes, holding conand line contacts R1, R2, and R3. Note that
tacts
contacts R1 and R3 reverse the connections of lines 1
and 3 to motor terminals T1 and T3. This causes the
motor rotor to rotate in the reverse direction. The F and
R contactors are mechanically interlocked to prevent
troth being closed at the same time.
The control push buttons are the momentarycontact type. Pressing the high-speed push button closes
the high-speed contactor by energizing coil HM. The
Figure 1-6-Reversing ac controller.
Figure 1-7.-Two-speed, ac controller.
1-7
coil remains energized after the push button is released,
closing holding contacts HA. The coil, HM, also closes
and
applying fullmain line contacts
line voltage to the motor high-speed winding. The motor
will run at high speed until coil HM is de-energized
either by opening the stop switch, a power failure, or an
overload.
than the source voltage can be obtained by tapping the
proper point on the winding between terminals A and C.
Some autotransformers are designed so a knobcontrolled slider makes contact with wires of the
winding to vary the load voltage.
The directions for current flow through the line,
transformer winding, and load are shown by the arrows
in figure 1-8. Note that the line current is 2.22 amperes
and that this current also flows through the part of the
winding between B and C. In the part of the winding that
is between A and B, the load current of 7 amperes is
opposed by the line current of 2.22 amperes. Therefore,
the current through this section is equal to the difference
between the load current and the line current. If you
subtract 2.22 amperes from 7 amperes, you will find the
secondary current is 4.78 amperes.
Pressing the low-speed push button closes the lowspeed contactor by energizing coil LM. The coil remains
energized after the button is released, through the holding coil contacts, LA. The coil, LM, also closes the
mainline contacts,
and
which apply the
full-line voltage to the low-speed motor winding. The
motor will run at low speed until coil LM is deenergized. The LM and HM contractors are mechanically
interlocked to prevent both from closing at the same
time.
Autotransformers are commonly used to start threephase induction and synchronous motors and to furnish
variable voltage for test panels. Figure 1-9 shows an
autotransformer motor starter, which incorporates
Autotransformer Controllers
A single-phase autotransformer has a tapped
winding on a laminated core. Normally, only one coil is
used on a core, but it is possible to have two autotransformer coils on the same core. Figure 1-8 shows
the connections for a single-phase autotransformer
being used to step down voltage. The winding between
A and B is common to both the primary and the secondary windings and carries a current that is equal to the
difference between the load current and the supply
current.
Any voltage applied to terminals A and C will be
uniformly distributed across the winding in proportion
to the number of turns. Therefore, any voltage that is less
Figure 1-8.-Single-phase autotransformer.
Figure 1-9.-Autotransformer controller.
1-8
symbol is shown, which can be compared to the
electrical circuit in figure 1-10, view B.
starting and running magnetic contractors, an auto
transformer, a thermal overload relay, and a mercury
timer to control the duration of the starting cycle.
NOTE: Both switches, A AND B, must be closed
to energize the lamp.
Logic Controllers
In figure 1-11, view A, art OR symbol is shown,
which can be compared to the electrical circuit in figure 1-11, view B, where either switch A OR B needs to
be closed to energize the lamp.
Some of the controlled equipment that you will
encounter use logic systems for circuit control. For
additional information in this area the Navy Electricity
and Electronics Training Series (NEETS), module 13,
is an excellent basic reference.
Using the characteristics of the AND and OR logic
symbols, we will now discuss how they can be used in
a logic controller.
The basic concept of logic circuits is shown in
figures 1-10 and 1-11. In figure 1-10, view A, an AND
One common application of logic control that is
being incorporated on newer ships is the elevator
system. Since this system is large and consists of many
symbols, we will show only a small portion of this
system.
Let us assume that the elevator platform is on the
third deck and that you require it on the main deck—Refer
to figure 1-12. Three conditions must be met before the
elevator can be safely moved. These conditions are
detected by electronic sensors usually associated with
the driven component. One of the conditions is that the
platform must be on EITHER the second or third deck
(on a certain deck as opposed to somewhere in between).
If this condition is sensed, the OR symbol will have an
input, and since only one input is needed, the OR symbol
also will have an output.
Figure 1-10.-AND symbol and circuit.
The other two conditions to be met are that the
locking devices must be engaged and the access doors
must be shut. If the sensors are energized for these two
conditions, the AND symbol will have the three inputs
necessary to produce an output. This output will then set
up a starting circuit, allowing the motor to be started at
your final command.
The advantages of these electronic switches over
mechanical switches are low power consumption, no
moving parts, less maintenance, quicker response, and
Figure 1-11.-OR symbol and circuit.
Figure 1-12.-Basic logic circuit.
1-9
connected in the line at start and are cut out in steps as
the motor accelerates to the running speed.
Motors used with cargo winches and other deck
auxiliaries operate over a wide range of speeds. Since
the speed of a dc motor with a constant load varies
almost directly with the voltage, stages of line resistance
are used to make speed changes and to limit the current
at starting. These stages of line resistance are connected
in various combinations, manually selected by a master
switch operating with a magnetic controller. Thus, the
operator directly controls the amount of resistance in the
line and the resulting speed of the motor at all times.
less space requirements. A typical static logic panel
found aboard ship is shown in figure 1-13.
Although there are logic symbols other than AND
and OR, they all incorporate solid-state devices, For
more information on solid-state devices refer to NEETS,
module 7.
DC CONTROLLERS
The starting of all dc motors, except those with
fractional horsepower, requires a temporary placing of
resistance in series with the armature circuit to limit the
high current at start. The starting resistance cannot be
removed from the line until the motor has accelerated in
speed and the counter electromotive force has increased
to limit the current to a safe value.
Auxiliary motors located below deck generally
drive constant-speed equipment. A rheostat in the shunt
field circuit may be provided to furnish speed control
for motors operating with ventilation fans, forced draft
blowers, and certain pumps where conditions may
require operation at more than one speed.
Small motors use one stage of starting resistance in
the line for a few seconds to limit the starting current.
With larger motors, two or more stages of resistance are
One-Stage Acceleration
Figure 1-14 shows a typical dc controller. The connections for this motor controller with one stage of
acceleration are shown in figure 1-15. The letters in
parentheses are indicated on the figures. When the start
button is pressed, the path for current is from the line
terminal (L2) through the control fuse, the stop button,
the start button, and the line contactor coil (LC), to the
line terminal (L1). Current flowing through the
contactor coil causes the armature to pull in and close
the line contacts (LC1, LC2, LC3, and LC4).
Figure 1-13.-A static logic panel for a cargo elevator.
1-10
Figure 1-14.-A typical controller.
Figure 1-15.-A dc controller with one stage of acceleration.
1-11
If the motor becomes overloaded, the excessive
When contacts LC1 and LC2 close, motor-starting
current flows through the series field (SE), the armature
(A), the series relay coil (SR), the starting resistor (R),
and the overload relay coil (OL). At the same time, the
shunt field winding (SH), is connected across the line
and establishes normal shunt field strength. Contacts
LC3 close and prepare the circuit for the accelerating
contactor coil (AC). Contacts LC4 close the holding
circuit for the line contactor coil (LC).
The motor armature current flowing through the
series relay coil causes its armature to pull in, opening
the normally closed contacts (SR). As the motor speed
picks up, the armature current drawn from the line
decreases. At approximately 110 percent of normal
running current, the series relay current is not strong
enough to hold the armature in; therefore, it drops out
and closes its contacts (SR). These contacts are in series
with the accelerating relay coil (AC) and cause it to pick
up its armature, closing contacts AC1 and AC2.
Auxiliary contacts (AC1) on the accelerating relay
keep the circuit to the relay coil closed while the main
contacts (AC2) short out the starting resistor and the
series relay coil. The motor is then connected directly
across the line, and the connection is maintained until
the STOP button is pressed.
current through the overload coil (OL) (at the top right of
fig. 1-15) will open the overload contacts (OL) (at the
bottom of fig. 1-15), disconnecting the motor from the line.
If the main contactor drops out because of an
excessive drop in line voltage or a power failure, the
motor will remain disconnected from the line until an
operator restarts it with the start pushbutton. This prevents automatic restarting of equipment when normal
power is restored.
Speed Control
Figure 1-16 illustrates a rheostat that is added to the
basic controller ciruit to obtain varying speed.
If resistance is added in series with the shunt field
the field will be weakened and the motor will speed up.
If the amount of resistance in series is decreased, the
field strength will increase, and the motor will slow
down.
Contacts FA (fig. 1-16) are closed during the
acceleration period, providing fill shunt field strength.
After the motor has accelerated to the across-the-line
position, contacts FA open, placing the rheostat in the
shunt field circuit to provide full field protection.
Figure 1-16.-A dc controller with shunt field rheostat.
1-12
contacts
are electrically interlocked open when the
forward contactor (F) coil is energized.
After the line contactor is energized, acceleration is
accomplished in the manner described previously.
Reversing
In certain applications, the direction in which a dc
motor turns is reversed by reversing the connections of
the armature with respect to the field. The reversal of
connections can be done in the motor controller by
adding two electrically and mechanically interlocked
contractors.
A dc motor reversing connection is shown in figure 1-17. Note there are two start buttons-one marked
START-EMERG FORWARD and the other marked
START-EMERG REVERSE. These buttons serve as
master switches, and the desired motor rotation is
obtained by pressing the proper switch.
Assuming that the forward button has been pressed,
the line voltage will be applied through the button to the
forward contactor coil (F). This pulls in the armature and
closes the normally open contacts
and
in the
motor armature circuit, the forward contactor holding
circuit contacts
and the line contactor circuit
and opens the normally closed contacts
contacts
of the reverse contactor circuit. The normally closed
Dc Contactor
A dc contactor is composed of an operating magnet
energized by either switches or relays, fixed contacts,
and moving contacts. It maybe used to handle the load
of an entire bus, or a single circuit or device. Larger
contacts must be used when heavy currents are to be
interrupted. These contacts must snap open or closed to
reduce contact arcing and burning. In addition to these,
other arc-quenching means are used.
Blowout Coils
When a circuit carrying a high current is interrupted,
the collapse of the flux linking the circuit will induce a
voltage, which will cause an arc. If the spacing between
the open contacts is small, the arc will continue once it
is started. If the arc continues long enough, it will either
melt the contacts or weld them together. Magnetic
Figure 1-17.-Reversing dc controller.
1-13
blowout coils overcome this condition by providing a
magnetic field, which pushes the arc away from the
contact area.
The magnetic blowout operation is shown in figure 1-18. It is important that the fluxes remain in the
proper relationship. Otherwise, if the direction of the
current is changed, the direction of the blowout flux will
be reversed and the arc will actually be pulled into the
space between the contacts.
When the direction of electron flow and flux areas
shown in figure 1-18, the blowout force is upward. The
blowout effect varies with the magnitude of the current
and with the blowout flux. The blowout coil should be
chosen to match the current so the correct amount of
flux may be obtained. The blowout flux across the arc
gap is concentrated by the magnetic path provided by
the steel core in the blowout coil and by the steel pole
pieces extending from the core to either side of the gap.
Figure 1-19.–Detailed view of arcing contacts.
Arcing Contacts
Shunt-type contractors will handle up to 600
amperes at 230 volts. The blowout shield has been
removed in this detailed view. The diagram shows the
main sections of the contactor. The arcing contacts (1)
The shunt contactor shown in figure 1-19 uses a
second set of contacts (1) to reduce the amount of arcing
across the main contacts (5 and 6) when closing. The
numbers that are in parentheses are indicated on the
figure.
are made of rolled copper with a heavy protective coating of cadmium. These contacts are self-cleaning because of the sliding or wiping action following the initial
Figure 1-18.-Action of a magnetic blowout coil.
1-14
The lowest leaf of brush contact 6 should just barely
touch contact 5. If the lower leaf hits the plate too soon,
bend the entire brush assembly upward slightly.
The contact dimensions should be measured with
the contactor in the OPEN position.
Refer to the manufacturer’s instruction book when
making these adjustments.
contact. The wiping action keeps the surface bright and
clean, and thus maintains a low contact resistance.
The contactor is operated by connecting the coil (2)
directly across a source of dc voltage. When the coil is
energized the movable armature (3) is pulled toward the
stationary magnet core (4). This action causes the
contacts that carry current (5, 6, 7, and 1) to close with
a sliding action.
The main contacts (5 and 6), called brush contacts,
are made of thin leaves of copper, which are backed by
several layers of phosphor bronze spring metal. A silver
brush arcing tip (7) is attached to the copper leaves and
makes contact slightly before the leaf contact closes.
The stationary contact (5) consists of a brass plate,
which has a silver-plated surface. Since the plating
lowers the surface resistance, the contact surfaces
should never be filed or oiled. If excessive current
causes high spots on the contact, the high places maybe
smoothed down by careful use of a fine ignition-type
file.
You can check the operation and contact spacing by
manually closing the contactor (be sure the power is off).
ELECTRIC BRAKES
An electric brake is an electromagnetic device used
to bring a load to rest mechanically and hold it at rest.
Aboard ship, electric brakes are used on motor-driven
hoisting and lowering equipment where it is important
to stop the motor quickly. The type of electric brakes
used depends on whether the motor is ac or dc and
whether a dc motor is series or shunt wound.
AC SOLENOID BRAKE
The magnetic brake assembly shown in figure 1-20
is the main component of this electric brake. When the
coil is energized, two armatures are pulled horizontally
Figure 1-20.-Magnetic brake assembly.
1-15
into the coil. The armatures are mechanically linked to
the levers. The levers pivot on the pins. When the
magnetic pull overcomes the pressure of the coil
springs, the pressure of the brake shoes on the drum is
removed, allowing the drum to turn. The drum is
mechanically coupled to the motor shaft or the shaft of
the device driven by the motor. The coil is connected to
the voltage supply lines. The method of connecting the
coil (series or parallel) is determined by the coil design.
The magnetic brakes are applied when the coil is not
energized. A spring or weight holds the band, disk, or
shoes against the wheel or drum. When the coil is
energized, the armature or solenoid plunger overcomes
the spring tension and releases the brake.
The ac solenoid brake frame and solenoid are of
laminated construction to reduce eddy currents, which
are characteristic of ac systems. Because the magnetic
flux passes through zero twice each cycle, the magnetic
pull is not constant. To overcome this, shading coils are
used to provide pull during the change of direction of
the main flux. The principal disadvantage of an ac
solenoid is that it draws a heavy current when the voltage
is first applied.
Figure 1-21.-Torque-motor brake and ball-jack assembly.
AC TORQUE-MOTOR BRAKE
against the brake drum. This action stops and holds the
windlass drive shaft.
The torque-motor brake uses a specially wound
polyphase, squirrel-cage motor in place of a brakerelease solenoid. The motor may be stalled without
injury to the winding and without drawing heavy currents. Figure 1-21, view A, shows the complete mechanical arrangement of the torque-motor brake assembly,
and figure 1-21, view B, is an enlarged view of the balljack assembly. his assembly is used with an anchor
windlass.
The torque-motor brake can be released manually
by raising the lever(1). However, the lever must be held
manually in the UP position; otherwise, the brake will
be applied.
Dc Dynamic Brake
Dynamic braking is similar to the slowing down of
a moving truck by the compression developed in its
engine. A dc motor also slows down when being driven
by its load if its field remains excited. In this case, the
motor acts as a generator and returns power to the
supply, thereby holding the load. In an actual braking
system, however, the dc motor is disconnected from the
line. Its armature and field are connected in series with
a resistor to form a loop. The field connections to the
armature are reversed so the armature countervoltage
maintains the field with its original polarity.
The mechanical connection between the torquemotor shaft and the brake operating lever (1) is through
a device called a ball-jack assembly, which converts the
rotary motion of the torque-motor shaft to a straight line
motion.
When power is applied to the torque motor, the shaft
turns in a clockwise direction, resulting in an upward
movement of the jack screw (2). The thrust element (3)
in the jack screw pushes upward against the operating
lever (1) to release the brake. As soon as the brake is
fully released, the torque motor stalls across the line and
holds pressure against the spring (4), keeping the brake
released.
Figure 1-22 shows the connections in the dynamic
braking system of a series-wound dc motor. The field
switching is carried out by switches S1, S2, and S3,
which are parts of a triple-pole double-throw (TPDT)
assembly. These switches are magnetically operated
When the voltage supply to the torque motor is
interrupted, the torque spring forces the brake shoes
1-16
the switch arms are in position 1, the armature is disconnected from the line and connected to the resistor.
The shunt field remains connected to the line. As the
armature turns, it generates a countervoltage that forces
the current through the resistor. The remainder of the
action is the same as described for the circuit in figure 1-22.
Although dynamic braking provides an effective
means of slowing motors, it is not effective when the
field excitation fails or when an attempt is made to hold
heavy loads; without rotation, the countervoltage is
zero, and no braking reaction can exist between the
armature and the field.
Dc Magnetic Brake
Magnetic brakes are used for complete braking
protection. In the event of field excitation failure, they
will hold heavy loads. A spring applies the brakes, and
the electromagnet releases them.
Figure 1-22.-Connections for dynamic braking of a
series-wound dc motor.
Disk brakes are arranged for mounting directly to
the motor end bell. The brake lining is riveted to a steel
disk, which is supported by a hub keyed to the motor
shaft. The disk rotates with the motor shaft.
from a controller. With the switch arms in position 1,
the motor operates from the line. When the switch arms
are in position 2, the resistor is connected in series with
the field, and, at the same time, the field coil connection
to the armature is reversed. Thus, as long as the armature
turns, it generates a countervoltage, which forces current through the resistor and the series field. Although
the direction of current flow through the armature is
reversed (because of the countervoltage), the direction
through the series field coil is not reversed. When
operating in this way, the motor is essentially a generator
that is being driven by the momentum of the armature
and the mechanical load. Energy is quickly consumed
in forcing current through the resistor, and the armature
stops turning.
The band-type brake has the friction material
fastened to a band of steel, which encircles the wheel or
drum and may cover as much as 90 percent of the wheel
surface. Less braking pressure is required and there is
less wear on the brake lining when the braking surface
is large.
The dc brakes are operated by a solenoid similar in
design to the ac solenoid brake (fig. 1-20), except that
The time required to stop the motor maybe varied
with different resistor values. The lower the resistance,
the faster the braking action. If two or more resistors are
connected by switches, the braking action can be varied
by switching in different load resistors. Usually, the
same braking resistors that are used to stop the motor
are also used to reduce the line voltage during
acceleration.
When dynamic braking is used with a dc shuntwound motor, resistance is connected across the
armature (fig. 1-23).
Switches S1 and S2 are part of a double-pole
double-throw (DPDT) circuit breaker assembly. When
the switch arms are connected to position 2, the armature
is across the line, and motor operation is obtained. When
Figure 1-23.-Connections for dynamic braking of a
shunt-wound dc motor.
1-17
the dc brake construction is of solid metals and requires
no lamination as does the ac magnetic brake.
CONTROLLER TROUBLESHOOTING
Although the Navy maintains a policy of preventive
maintenance, sometimes trouble is unavoidable. In
general, when a controller fails to operate, or signs of
trouble (heat, smoke, smell of burning insulation, and so
on.) occur, the cause of the trouble can be found by
conducting an examination that consists of nothing more
than using the sense of feel, smell, sight, and sound. On
other occasions, however, locating the cause of the
problem will involve more detailed actions.
Troubles tend to gather around mechanical moving
parts and where electrical systems are interrupted by the
making and breaking of contacts. Center your attention
in these areas. See table 1-1 for a list of common
troubles, their causes, and corrective actions.
When a motor-controller system has failed and
pressing the start button will not start the system, press
the overload relay reset push button. Then, attempt to
start the motor. If the motor operation is restored, no
further checks are required. However, if you hear the
controller contacts close but the motor fails to start, then
check the motor circuit continuity. If the main contacts
do not close, then check the control circuit for continuity.
An example of troubleshooting a motor-controller
electrical system is given in a sequence of steps that may
be used in locating a fault (fig. 1-24). We will start by
analyzing the power circuit.
Figure 1-24-Troublesboottng a 3-phase magnetic tine starter.
connections within the controller. However, if voltage
is indicated at all three terminals, then the trouble is
either in the motor or lines leading to the motor.
POWER CIRCUIT ANALYSIS
CONTROL CIRCUIT ANALYSIS
When no visual signs of failure can be located and
an electrical failure is indicated in the power circuit, you
must first check the line voltage and fuses. Place the
voltmeter probes on the hot side of the line fuses as
shown at position A. A line voltage reading tells you that
your voltmeter is operational and that you have voltage
to the source side of the line fuses, L1-L2. You also may
check between L1-L3 and L2-L3. To check the fuse in
line L1, place the voltmeter across the line fuse as shown
at position B between L1-L2. A voltage reading shows
a good fuse in L1. Likewise, check the other two fuses
between L1-L3 and L2-L3. A novoltage reading would
show a faulty fuse.
Suppose the overload reset buttons have been reset
and the start switch is closed. If the power contacts do
not close, then the control circuit must be checked. The
testing procedure is as follows:
1. Check for voltage at the controller lines, L1, L2,
and L3.
2. Place the voltmeter probes at points C and D
(fig. 1-24). You should have a voltage reading when the
stop switch is closed and a no-voltage reading when the
stop switch is open. The conditions would indicate a
good stop switch.
If the line fuses check good, then check the voltage
between terminals T1-T2, T2-T3, and T1-T3. The
controller is faulty if there aren't voltmeter readings on
all three of the terminal pairs, and you would then
proceed to check the power contacts, overloads, and lead
3. Next, check the voltage between points C and
E. If you get a no-voltage reading when the start switch
is open and a voltage reading when the start switch is
closed, then the start switch is good.
1-18
Table 1-1.-Troubleshootlng Chart
1-19
Table 1-1.-Troublesbooting Chart-Continued
1-20
Table 1-1.-Troubleshooting Chart-Continued
4. Place the voltmeter probes at C and F. A voltage
reading with the start button closed would indicate a
good OL1, but also would indicate an open OL3, an open
relay coil, or an open connection to line 3.
5. Place the voltmeter probes at points C and G
and close the start switch. A no-voltage reading indicates
the OL3 contacts are open.
When starting a three-phase motor and the motor
fails to start and makes a loud hum, you should stop the
motor immediately by pushing the stop button. These
symptoms usually mean that one of the phases to the
motor is not energized. You can assume that the control
circuit is good since the main operating coil has operated
and the maintaining contacts are holding the main
A faulty holding relay contact will be indicated
when the system operates as long as the start switch is
held in, but stops when the start switch is released.
operating contactor in. Look for trouble in the power
circuit (the main contacts, overload relays, cable, and
motor).
1-21
double row width, and a “Warning Do Not Lubricate
Bearings” instruction plate is mounted on the unit.
FREQUENCY REGULATORS
Frequency regulators are used to provide a regulated
frequency for frequency-sensitive equipment. To
troubleshoot frequency regulators, you need to have an
understanding of motor generators, as frequency and
voltage regulators are part of the control circuits for
motor generators. The following paragraphs will discuss
motor generators and the troubleshooting of frequency
regulators. Detailed troubleshooting charts for
frequency regulators can be found in the service manual
Motor Generator Set 30 KW, 440.450 V AC, 60/400
Cycle, 3 Phase with Control Equipment.
MOTOR GENERATOR
In a 30-kW motor generator, since a constant speed
is required for a constant frequency, the change in motor
rotor current for changes in torque requirement is
accomplished through the external means of varying the
tiring angle of three silicon controlled rectifiers (SCRs).
The basic operation of an SCR is as follows. The
SCR has a positive-negative-positive-negative (PNPN)
device structure and is the semiconductor equivalent of
a gas thyratron. It is constructed by making both an
alloyed PN junction and a separate ohmic contact to a
diffused PNP silicon pellet. Schematic representation of
the SCR is shown in figure 1-26. With reverse voltage
(encircled polarities) impressed on the device (cathode
positive), it blocks the flow of current as in an ordinary
rectifier. With positive voltage applied to the anode
(uncircled polarities), the SCR blocks the flow of
current until either the forward breakdown voltage is
reached, or a suitable gate pulse is applied to the gate.
In practical application, the positive pulse applied to the
gate is used to control the firing of the SCR. At this point,
the SCR switches to a high-conduction state; the current
flow is limited only by the external circuit impedance
and supply voltage. The magnitude of gate impulse
needed to turn on an SCR varies with temperature and
30 kW CLOSELY REGULATED MOTOR
GENERATOR SET
The 30-kW 440/450-volts ac, 60/400-Hz, 3-phase
motor generator set (fig. 1-25) consists of a wound rotor
induction motor driving a synchronous generator.
Internal control circuits include voltage and frequency
regulating systems, a motor controller (magnetic
starter), and generator output circuit breakers. The unit
is designed for parallel operation with an identical unit.
Its housing is dripproof.
The wound rotor motor and generator is a
two-bearing unit with motor and generator rotors, plus
a self-cooling fan mounted on a single shaft. The single
row ball bearings are prelubricated, double sealed,
Figure 1-25.-Motor generator set with control equipment.
1-22
rotor, maintaining rated speed at an increased torque
demand.
Since the synchronous speed of the stator flux is
directly proportional to the input frequency of the supply
to the motor, a change is necessary in the rotor torque to
maintain constant speed for this variation also. The
frequency regulator supplies the proper triggering pulse
to the rotor SCRs controlling the current flow in the
rotor, hence controlling the speed/torque of the motor.
Figure 1-26.-Schematic symbol silicon controlled rectifier.
CONTROL EQUIPMENT
The motor control consists of an ac magnetic starter
containing overload protection, start and stop switches,
and a frequency-regulating system. The first two components are standard; however, the frequencyregulating system is further divided into a detector, a
preamp and trigger, a starter, a motor rotor control unit,
and a resistor unit (fig. 1-27).
type of SCR. Recise firing is attained by a short gate
pulse with an amplitude of at least 3 volts and is capable
of delivering the maximum firing requirements of the
SCR.
Short or delayed SCR firing time allows a small
rotor current to flow, thus limiting the torque developed
FREQUENCY REGULATOR
by the rotor required to maintain rated speed (necessary
for 400 Hz) at no-load or light loads. As generator load
The detector in the frequency-regulating system
is primarily a frequency-sensing transformer with a
is increased, a greater current is allowed to flow in the
Figure 1-27.-Block diagram of current flow.
1-23
voltage output that varies linearly with changes in
generator output frequency rather than generator output
voltage. The signal voltage obtained from the
frequency-sensing transformer is rectified, filtered, and
compared in a Zener reference voltage divider, all
contained within the detector circuit. This circuit
provides an interesting application of Zener diodes, as
shown in figure 1-28. The purpose of the Zener
reference bridge is to compare a high-supply voltage
with a reference voltage and to provide a low-voltage
amplitude output signal voltage to be used as a base
drive for a transistor.
Consider the input voltage
to be 22 volts; then
the output voltage will be 1 volt. Next, consider the input
voltage
to be 24 volts; then the output voltage will
be 2 volts. Although the input voltage is 22 volts to 24
volts, the output voltage is only 1 volt to 2 volts. Therefore, without adding additional components to lower the
voltage to the point where it can be used as abase drive
for a transistor, the output voltage of the bridge can be
used as abase drive for a transistor.
The Zener reference bridge consists of resistors R1,
R2, R3, and Zener diode D1, as shown in figure 1-28.
Resistors R1, R2, and R3 are equal, and the Zener diode
is equal
D1 has a breakdown rating of 10 volts. When
to or less than 10 volts, negligible current will flow
through R1, and the bridge is operating in mode I, as
shown on the graph in figure 1-28. As
rises above 10
volts, the voltage drop across D1 remains constant at 10
volts, and the current through R2 and R3 increases,
increasing the voltage drop across R2 and R3. When
equals 20 volts, the drop across resistors R1, R2, and R3
is 10 volts, so
is zero. When
is between 10 volts
and 20 volts, the bridge is in mode H, as shown on the
graph in figure 1-28. As
rises above 20 volts, the
voltage at point B will rise above 10 volts; however, the
voltage at point A will remain at 10 volts, and potential
differences between points B to A will increase. For
greater than 20 volts, the bridge is in mode III, which is
the normal operating mode.
The purpose of the preamp and trigger is to amplify
and convert the varying dc input voltage into controlled
pulses of sufficient amplitude to fire the SCRs.
The signal leaving the Zener bridge is amplified by
two dc transistor amplifiers, in the detector, before going
to the preamp and trigger (fig. 1-27).
In the trigger circuit, the signal (pulse) amplitude
controls the tiring point of the SCRs in the motor rotor
control circuit (which are in series with large, approximately 3,000-watt resistors). Thus, control is exerted
on the motor rotor.
VOLTAGE-REGULATING
SYSTEM
The voltage-regulating system is composed of the
voltage regulator and the static exciter (fig. 1-27). The
voltage regulator receives its signal from the generator
output. The static exciter receives its signal input from
the power section in the voltage regulator.
The operation of the detector in the voltage regulator is similar to that of the frequency regulator, in that
the detector senses a change in generator output; however, the change is in voltage rather than frequency. The
increase or decrease in voltage is rectified, faltered, and
compared prior to amplification. Again the comparison
is made on a Zener reference bridge before amplification
in dc amplifiers.
The preamp and trigger operate essentially as
described in the section under frequency regulation,
except that in this case the signal is fed to a power
section.
The power circuit provides an application of SCR
operation. This section (fig. 1-29) consists of three
diodes (D1, D2, and D3) and two SCRs (SCR1 and
SCR2). D2, D3, SCR1, and SCR2 are connected in the
normal full-wave rectifier bridge manner. No current
will flow out of the bridge (between points E and F) until
the SCRs receive a trigger pulse at the gates that will
turn the SCRs on. Assume that during the first half cycle
of applied ac voltage (time 0 to 1), SCR 1 has its anode
Figure 1-28.-Zener reference bridge.
1-24
Figure 1-29.-Power circuit.
positive with respect to cathode, and a trigger pulse is
applied to terminals A and B. SCR1 will conduct current,
and voltage spikes. Controlling the point during any
and SCR2 will block current like a normal rectifier bridge,
for the remainder of the applied half cycle, as shown in
applied to the gate of the SCRs makes it possible to
applied half cycle of ac voltage that the trigger pulse is
figure 1-29. Diode D1 and thyrector SP1 (a General
control the output power of the dc power supply.
The signal developed in the power section of the
Electric silicon controlled diode used for ac surge
voltage regulator (fig. 1-27) is used as dc control current
protection) are used to protect the circuit from transients
to the static exciter.
1-25
conjunction, excite the common secondary (3-4
windings of T1, T2, and T3) to provide generator field
excitation.
STATIC EXCITER
The static exciter (fig. 1-30), which derives its
operating power from the generator output, is designed
to supply the correct amount of field current to the
generator, to maintain a constant output voltage to a load
that varies in magnitude or has a lagging power factor.
During the motor-starting period, there is no generator
output, and the generator field current is supplied by the
field-flashing circuit. The field-flashing circuit derives
its operating power from the 60-cycle supply voltage.
his voltage is reduced to 30 volts by transformer T5,
rectified by diode D2, and faltered by capacitor C3. The
dc current then flows through dropping resistor R4 and
excites to the generator field.
When a load is applied to the output, current will
flow in the current primaries of T1, T2, and T3 of the
SCPT. A current transformer action will take place with
the common secondary 3 and 4 of T1, T2, and T3 of the
SCPT that will add to the field excitation current caused
in the secondary by voltage primary 1 and 2 of the SCPT.
This action is explained later. L1, L2, and L3 are chokes.
The field excitation current will rise in proportion
to the application of load and lagging power factor.
Adding a dc control winding on the SCPT will change
the coupling between primary and secondary windings.
This winding controls the generator output voltage. This
is accomplished by connecting the output of the voltage
regulator to the dc control winding.
The saturable current-potential transformer (SCPT,)
(fig. 1-30) has two sets of primary windings exciting a
common secondary. The primary windings of T1, T2,
and T3 in series with the load are current primaries.
Those primary windings in parallel (T1, T2, and T3)
are potential primaries. Both primaries, acting in
The signal developed in the power section of the
voltage regulator (fig. 1-27) is used as dc control to the
static exciter.
Figure 1-30.-Static exciter.
1-26
The use of the SCPT is relatively new to
motor-generator application. Since the basic operation
of each core in the SCPT is identical, only one core will
be explained.
The basic operation of the SCPT is explained with
the aid of figure 1-31. It consists of two voltage primary
windings
and
two current primary windings
and
two secondary windings
and
and
a dc control winding
In figure 1-31, these windings are arranged on a
three-legged E-type lamination. For simplicity, consider
and
the leg of the transformer with windings
The
winding and the secondary winding (Vs1)
function like a normal power transformer, and the
current primary winding
and secondary winding
function like a normal current transformer. When either
or ) induce a voltage into
of the primary windings
the secondary winding
(the secondary winding is
connected to a load), a current will flow in the secondary
winding
The SCPT is constructed in such a
manner that the current flow in the secondary is the sum
of the current that would be caused to flow by the
and
As can be seen in figseparate windings
ure 1-31, there is a voltage and current primary winding
and a secondary winding on each of the cores of the
SCPT The function of each is as described in the
previous paragraphs.
Figure 1-32.-Saturable potential transform.
core, no voltage is induced into the control winding.
When voltage is applied to the primary windings,
current flows in these windings, which are labeled in
figure 1-32. If the primary voltage is instantaneously
positive (+) at the start of winding
then the current
flowing through the turns of
and
should create
the flux; 01 and 02, following the left-hand rule, which
defines winding polarity.
To understand the principle of operation of the dc
control winding, refer to figure 1-32. The action that
takes place between the primary winding (either current
primary or voltage primary), the secondary winding,
and dc control winding is the same. Therefore, only a
voltage primary winding
is shown in figure 1-32.
The outer legs of the core are each wound with a primary
and a secondary winding. The control winding is wound
on the center leg. The primary and secondary windings
are connected so their flux oppose each other in the
center core. Thus, with the net flux of zero in the center
The flux caused by
is in an upward direction,
and the flux caused by
is in a downward direction.
These fluxes will close their loop through the center leg
of the laminated core because of the shorter path it
presents; but because the fluxes are of equal magnitude,
they cancel each other in the center leg and thus induce
no voltage in the control winding
Because the
fluxes, 01 and 02, link the secondary turns,
and
a voltage is induced in each of these with a sum of V
sec. The relationship that exists between the primary and
secondary windings when the core is not saturated is
identical to any voltage transformer with a core that is
not saturated. When a direct current flows through the
control winding
in the direction shown by a dc flux
is created, according to the left-hand rule, which is
in an upward direction opposing 01 and aiding 02. When
the magnitude of the dc flux becomes great enough,
it begins to force the core material into saturation.
Figure 1-31.-Saturable current-potential transformer.
1-27
30-kW load at unity power factor will result in a current
of only 38.5 amperes per line. The difference in the
output current with identical kilowatt loads is the result
of the flow of reactive current in the load circuit. This is
known as the reactive volt ampere component of the
load and is abbreviated VAR.
Saturation may be defined as the condition in the
magnetic material where an increase of magnetomotive
force causes no increase in flux. The coupling of the
primary and secondary voltage is accomplished only
when there is a flux change; consequently, when the core
material is forced into the condition where no flux
change can take place, the coupling of the primary and
secondary voltages becomes nonlinear, and the effect of
de- coupling the secondary winding is produced. Figure 1-31 indicates the path of dc flux when the start of
is positive. Naturally, when the applied voltage
polarity reverses itself, the fluxes, 01 and 02, also
reverse themselves; but the dc flux through the control
winding then forces 01 into saturation before 02 is
forced into saturation. Since the load on the saturable
potential transformer secondary is magnetically coupled
to the primary of the saturable potential transformer, the
variable control current through the winding
will
produce a variable secondary output voltage. The
control current versus the output voltage characteristic
of the saturable potential transformer is shown in figure 1-33. The saturable potential transformer is designed
to operate in the linear position of the characteristic
curve, as shown in figure 1-33.
This VAR component of the load is caused by the
current of the generator being out of phase with the
voltage. The mathematical relationship of power factor,
watts, VA, and VAR is shown in figure 1-34.
It is possible for the current to either lead or lag
behind the voltage, and, if it is lagging (for inductive
reactive loads), the power factor would be a lagging
power factor.
The phase angle of the current in relation to the
voltage of the generator output in combination with the
magnitude of the output current is used by the
power-sensing network to produce an output signal.
That signal will vary in magnitude in relation to the
useful output (kW) of the generator and will produce no
output when the generator load is entirely VAR. Any
combination of VAR and kW will produce an output
signal that is directly proportional to the kW load only.
The amount of power required by the motor to drive
the generator is also directly proportional to the kW
output of the generator. This makes it possible to use the
output signal of the power-sensing network with
changing load.
POWER-SENSING NETWORK
The power-sensing network functions to balance the
load between generators operating in parallel. In single
generator operation, the power-sensing network is not
used.
This network is designed to sense real power or the
kilowatt (kW) output of the generator only, as opposed
to kilovolt amperes (KVA) output.
This generating system has an output rating of 30
kW at 0.8 power factor, 37.5 KVA. The current in each
line with this load will be 48.5 amperes at 450 volts. A
Figure 1-33.-Characteristic curve of a saturable potential
transformer.
Figure 1-34.-Watt, VA, and VAR relationship.
1-28
rheostat A/R1, thus disabling the power-sensing system.
If the leads from current transformer A/CT1 to resistor
A/R1 are reversed, the phase relationship of the voltage
across resistor A/R1 would be 180° out of phase with
the secondary of transformer A/T1. Therefore, with
increasing load, the regulator would try to raise the
output frequency of the generator. This is known as
frequency compounding.
A power-sensing network has been provided in one
phase of the generator output (fig. 1-35) for simplicity;
consider first the power-sensing circuit of generator A.
This circuit consists of current transformer A/CT1 and
real power-sensing rheostat A/R1. Note that power
transformer A/T1 is connected from neutral to line C,
and, therefore, the voltage across the primary of
transformer A/T1 will be in phase with the current in line
C at unity power factor. Transformer A/T2, which is the
frequency-sensing transformer, is in parallel with power
transformer A/T1, and, therefore, the voltage output of
the secondary of transformer A/T2 is in phase with the
voltage in the primary of transformer A/T1. Then, at
unity power factor, the voltage across the secondary
windings A/T2 will be in phase with the current in line
C. Real power-sensing rheostat A/R1 is actually the load
resistor for current transformer A/CT1. Therefore, when
a load is applied to the output of generator A, a voltage
will be impressed across rheostat A/R1, and this voltage
will be in phase with the voltage across the secondary
winding of transformer A/T1. The voltage from
transformer A/T2 and the voltage across resistor A/R1
will add, and the sensed voltage will be an increased
voltage to rectifier A/RD1. This would represent an
increased output frequency; thus, the regulator would
decrease the speed of the motor and thus reduce the
output frequency of the generator. This is known as a
frequency droop. To eliminate this droop in singular
operation, a shorting bar or relay contact is placed across
PARALLEL OPERATION
Refer to figure 1-35 and note that generator B has a
real power-sensing system exactly as generator A. Note
also that not only is current transformer A/CT1
connected across its load rheostat A/R1, but when circuit
breaker CB3 is closed, it also is connected across real
power-sensing rheostat B/R1. Consider what would
happen if generator A were to supply the greater amount
of real power to the load. There would be a difference
in potential between current transformers A/CT1 and
B/CT1. Due to the difference in potential, a current will
flow in resistors A/R1 and B/R1 connected in parallel.
The current will be in phase with the voltage out of
secondary of transformer A/T1 and 180° out of phase
with the secondary voltage of transformer B/T1. Hence,
the regulator of generator A will decrease its output
frequency, and the regulator of generator B will raise its
output frequency. This will permit the generator to
Figure 1-35.-Power sensing.
1-29
operate in parallel without speed droop with changing
load and to divide the load (kW) evenly between them.
and the negative lead is connected to the cathode side,
the ohmmeter will indicate a low value (15 ohms or
less). With the ohmmeter leads reversed across the
diode, a higher reading will be obtained (Refer to
fig. 1-36) A front to back ratio of 10 to 1 is usually
considered a good diode.
SAFETY
The inherent dangers of rotating machinery are kept
to a minimum; however, it remains the responsibility of
supervisory personnel to ensure that personnel
performing preventive and corrective maintenance are
thoroughly acquainted with the possible hazards
involved. Except during supervised maintenance, all
doors and covers should be in place. Since considerable
semiconductor application is made here, test equipment
settings and proper soldering techniques must be
observed when maintenance is required.
Various test setups have been devised for transistors, and often they are included in the manufacturer’s
technical manual.
A key to good maintenance that should be stressed
is familiarity with the manufacturer’s technical manual.
STATIC INVERTER
The need for a highly dependable, static, 400-Hz
power supply led to the development of the 4345A static
inverter.
MAINTENANCE
The 3-M system provides adequately for preventive
maintenance on the motor generator. No corrective
maintenance should be attempted without a thorough
understanding of the pertinent sections of the
manufacturer’s technical manual. Troubleshooting
charts are of great value when employed with test
procedures in identification and isolation of problem
areas.
The model 4345A static inverter delivers a closely
regulated 400-Hz, 3-phase, 120-volt output from a
250-volt dc source. Two single-phase static inverters are
One test that may be of some assistance is that used
for silicon diodes. With this test, the silicon diodes may
be tested without removal from the circuit by the use of
a low-range (0-500 ohms) ohmmeter. The test is
performed by readings taken with the ohmmeter leads
connected across the diode in the opposite or reverse
direction. This means that the positive lead of the
ohmmeter will be connected to first one side of the diode
and then to the opposite side. Comparison of the reading
will indicate the condition of the diode. When the
positive lead is connected to the anode side of the diode
Figure 1-36.-Diode test.
Figure 1-37.-Static inverter.
1-30
operated with a controlled 90° phase difference. Pulse
width modulation is used for control of the output voltage of each static inverter. The outputs of the two
inverters are fed into two Scott “T’’-connected
transformers to provide a 3-phase output from a 2-phase
input.
generators, a frequency standard oscillator, a phase variable pulse width generator, two drive subassemblies, a
step change adjustment circuit, and two silicon control
rectifier power stages.
The power stage assembly contains capacitors,
transformers, and filters associated with the power stage
of the inverters.
The 4345A static inverter is enclosed in an aluminum cabinet (fig. 1-37), divided into three sections.
These are the meter panel assembly, the inverter module
assembly, and the power stage assembly. A resistor
subassembly is located on the back of the cabinet.
FUNCTIONAL DESCRIPTION
A simplified functional block diagram of the model
4345A static inverter is shown in figure 1-38. A brief
discussion of the various components and circuits
contained in the unit follows.
The meter panel assembly contains the instruments
and controls necessary for the operation of the equip
ment.
The inverter module assembly contains a control
circuit +30-volt dc power supply, a drive circuit
+30-volt dc power supply, an input sensing circuit, a
synchronizing subassembly, two variable pulse width
Oscillator Assembly
The oscillator (fig. 1-38) consists of a 1600-Hz
tuning fork controlled oscillator and a binary frequency
Figure 1-38.-Simplified block diagram of a static inverter.
1-31
A unijunction transistor is used to generate the drive
pulse trigger.
divider (countdown) circuit. The countdown circuit
reduces the 1600-Hz oscillator frequency to an 800-Hz
reference frequency required by the inverter control
circuits.
Power Stages
Variable Pulse Width Generators
Each power stage contains three power and three
commutating SCRs for each side of the power stage and
a transformer. The SCRs switch the dc source across the
primary of the transformer at a 400-Hz rate to produce
a 400-Hz square-wave output. The square-wave output
is filtered to produce a sine wave.
The inverter module contains one variable pulse
width generator (VPWG) for each inverter (main and
secondary VPWG) (fig. 1-38) and one VPWG for
controlling the phase angle between the inverters. Each
VPWG contains a monostable (one-shot) multi vibrator,
a modulator circuit, and an inverter output voltage errorsensing circuit.
The SCR is the semiconductor equivalent of the gas
thyratron tube. Once it is made to conduct, it will
continue to conduct for the remaining positive half cycle
(anode positive with respect to cathode). Neither the
removal of the gate voltage nor the reversal of the gate
voltage will stop the SCR from conducting. Conduction
may be stopped only by removing the positive anode to
negative cathode voltage completely or by applying a
slightly greater reverse negative anode to positive
cathode voltage.
The modulator circuit consists of a transistor and
resistors connected in the discharge path of a capacitor.
Varying the level of conduction of the transistor varies
the discharge time of the capacitor, which varies the time
the monostable multivibrator remains in the unstable
state. The time the monostable multivibrator remains in
the unstable state determines the width of the output
pulse.
The principle of operation of the power stages is
illustrated in the simplified schematic diagram in figure 1-39.
The monostable multivibrator used in the VPWG
can be triggered only on positive pulses.
The output voltage error-sensing circuit for each
VPWG receives an ac signal (via the feedback loop)
proportional to the output voltage of the inverter. The ac
signal is converted into a corresponding dc signal, compared with a reference signal, and the error (difference)
signal is used to control the level of conduction of the
transistor in the modulating circuit.
When the power SCR (Q1) is triggered on by an
output pulse from the driver, a rising current will flow
The secondary VPWG regulates the output voltage
of phase AB and the phase control, and the main VPWG
regulates the voltages of phases BC and CA. The phase
control VPWG also provides a delay in time between
triggering of the main and secondary VPWG to control
the phase angle between the power stages ( 1 and 2) of
the inverters.
The main and secondary VPWGs deliver one
NM-Hz input to each of the driver stages ( 1 and 2) and
another 800-Hz input to a binary countdown circuit that,
in turn, delivers two 400-Hz inputs 180° apart to each
of the driver stages.
Drivers
Each driver contains four drive pulse generators.
Two of the drive pulse generators generate the triggers
for the power SCRs (“turn on” SCRs), and the other two
generate the triggers for the commutating SCRs (“turn
off SCRs) in the power stages.
Figure 1-39.-Power stage, simplified schematic diagram.
1-32
network functions to reduce voltage transients in the
inverter 3-phase output.
through primary winding 3-4 of output transformer T1
(through Q1, L1, and the battery), inducing a voltage in
secondary 6-7 in one direction. By autotransformer
action, a voltage is also induced in winding 4-5. This
voltage charges capacitor C1 through Q1, CR 1, and R1.
When the commutating SCR (Q3) is triggered on by the
driver, the positive voltage from the right plate of Cl is
applied through Q3 (Q3 conducting) to the Q3-CR3
junction. This applies a reverse negative anode to
positive cathode voltage to Q1, causing Q1 to stop
conducting. Capacitor C 1 discharges through L1, CR3,
and Q3. With Q1 off, the current in winding 3-4 of T1
gradually drops to zero; and slightly later when the 3-4
current ceases, the voltage between secondary terminals
6-7 drops to zero. The voltage between terminals 4-5
also drops to zero. When C1 discharges to zero, Q3 stops
conducting. Because of the gradual drop of current in
the 3-4 winding, the voltage induced in the 6-7 winding
is of reversed polarity and low amplitude.
Drive Switch
The drive switch (fig. 1-37, S-1) has three positions:
OFF, START, and RUN. In the OFF position, power is
supplied to the standby indicator light to indicate the
inverter is in the standby mode. In the standby mode, a
+30-volt dc signal is supplied to the synchronizing
stage. Also, in the OFF position, the input dc voltage is
connected as a source of power for the control circuit
+30-volt dc power supply.
In the START position, power is removed from the
indicator light. Also, the +30-volt dc signal to the
synchronizing stage is removed, allowing signals to pass
to start the inverter properly.
When the drive switch is switched to the RUN
position, the input dc voltage for the control circuit
+30-volt dc power supply is disconnected and a bridge
rectified output from phase CA of the inverter is used.
On the other side of the power stage, power SCR
Q2 is then triggered on by the driver output, and
capacitor C2 charges in the same manner as C1 charged.
The operation of this side of the power stage is the same
as the side just discussed. However, the polarity of the
output is reversed, completing the square-wave output
on the secondary of T1.
Power Supplies
The power supplies in the inverter are the control
circuit +30-volt dc power supply and the drive circuit
+30-volt dc power supply. The control circuit +30-volt
dc power supply provides power for all control circuits
except the drivers and under-over voltage circuits. These
two circuits are supplied by the drive circuit +30-volt dc
power supply.
Filters
The filters (fig. 1-38) convert the square-wave outputs of power stages 1 and 2 to sine waves. Each filter
consists of one series and four shunt LC filters. The
series filter provides a low-impedance path for the
400-Hz fundamental frequency and a high-impedance
path for the odd harmonics in the output. The predominate odd harmonics are filtered out by individual
shunt filters. A shunt filter is provided for the third, fifth,
seventh, and ninth harmonic. Even harmonics are
negligible due to the balanced design of the push-pull
power stage.
The input power for the control circuit +30 volt
power supply comes from two sources. During the
START mode, power is obtained from the inverter input
dc source. In the RUN mode, the control circuit +30-volt
dc power supply receives its input from phase CA of the
inverter output.
The drive circuit +30-volt dc power supply provides
power for the drivers and the under-over voltage
circuits. This power is obtained from the inverter input
dc voltage.
Scott “T” Transformer
The Scott “T” transformer is a center-tapped
autotransformer. The output voltages from the main and
secondary inverter fibers combine in the Scott “T’
transformer to produce a 120-volt, 3-phase output.
Overload Circuit
The overload circuit turns the inverter off in case of
overload. An overload signal from the current-sensing
circuit produces a dc signal of sufficient amplitude to
trigger a unijunction transistor that, in turn, triggers a
bistable multivibrator. The bistable multivibrator output
is fed to the binary circuit in the SYNC stage, which
switches the inverter off.
Clipper
The 3-phase clipper network, consisting of
capacitors, resistors, and diodes, is connected across the
3-phase output of the Scott ‘T’ transform. The clipper
1-33
of the input signal. If the amplitude of the input signal
is above a specified level, the Schmitt trigger bistable
multivibrator will be in one state (one transistor conducting while the other is off); if the amplitude is below
a specified level, it will be in the other state.
Under-Over Voltage-Sensing Circuit
The under-over voltage-sensing circuit turns the
inverter off when the input dc source voltage is out of
the operating range (210 to 355-volts dc) of the inverter.
A modified Schmitt trigger circuit is used to supply
the interlock signal to the binary circuit in the SYNC
stage. The Schmitt trigger is a form of bistable multivibrator. It differs from the conventional bistable multivibrator, in that it is at all times sensitive to the amplitude
Dc Input Sensing
The dc input-sensing circuit compensates for
changes (step changes) in the input dc voltage source. A
Figure 1-40.-Waveforms.
1-34
voltage-sensing network composed of resistors and
capacitors is connected to the bus that supplies the de
input to the inverter. Positive and negative step changes
in the dc supply voltage produce positive and negative
pulse outputs from the voltage-sensing network. The
output pulses are fed to the pulse width modulator circuit
in the main and secondary VPWGs to compensate for
the voltage change.
composed of a transient and a steady-state condition.
The transient condition lasts for approximately
2 seconds. This 2-second time delay is provided by the
delayed B+ voltage interlock to allow the inverter
circuits to reach a steady state as mentioned previously.
During the standby mode, the 800-Hz countdown
circuit of the oscillator supplies an 800-Hz square-wave
voltage to the SYNC stage and the main VPWG (wave-
OPERATION CYCLE
form B, fig. 140, view A, and fig. 1-38). A+30-volt dc
signal is applied to the binary circuit in the SYNC stage
via the drive switch (S1, fig. 1-37) that keeps the bistable
When the main power circuit breaker is ON and
the drive switch is in the OFF position, the inverter is in
the standby mode of operation. The standby mode is
multivibrator in the SYNC stage in the “turnoff’ state.
Figure 1-40.-Waveforms–Continued.
1-35
should light. Turn the drive switch, S1, to the START
position. The power on light, I1, should light, and the
standby light, I2, should go out. After the output of the
inverter has reached a steady state (approximately 2
seconds), turn the drive switch, S1, to the RUN position.
Adjust the voltage, and adjust potentiometers R785,
R786, and R787 to the required output for each phase.
Use the voltage selector switch, S2, and meter, M1, to
read the voltage of each phase.
Turning the drive switch to the START position
removes the 30-volt dc signal from the binary circuit and
allows the first negative-going edge of the 800-Hz
square wave (waveform B) to reverse the bistable multivibrator in the SYNC stage. This allows the positivegoing edge of waveform B (at time 0, fig. 1-40, view A)
to trigger the monostable multivibrator in the main
VPWG (fig. 1-38).
The trailing edge of the first positive half of
waveform C (edge No. 1, fig. 1-40, view A) from the
main VPWG triggers the main 40-Hz countdown
circuit. The main 400-Hz countdown output (D) triggers
the pulse generator in the driver that generates the pulse
(E) to trigger the power SCRs for one side of the power
stage. The main 400-Hz countdown (D) and the leading
edge of the second positive half of waveform C (2,
fig. 1-40, view A) provide coincident gating for the
pulse generator in the driver that generates the pulse (F)
to trigger the commutating SCRs in this side of the
power stage.
The output voltages must be adjusted in the following sequence: phase CA, phase AB, and then phase BC.
To secure the inverter, turn the drive switch, S1, to
the OFF position, and then turn the power circuit breaker
CB1 to OFF.
MAINTENANCE
Maintenance of the static inverter should normally
be limited to simple replacement with a new or serviceable module. This will ensure rapid restoration of the
inverter into service without risking dangers of handling
high-test voltages.
The main 400-Hz countdown output(G) triggers the
pulse generator in the driver that generates the pulse (H)
to trigger the power SCRs in the other half of the power
stage. Waveform G and the leading edge of the next
positive half of waveform C (3, fig. 1-40, view A) gate
the pulse generator in the drive that generates the pulse
(J) to trigger the commutating SCRs in this half of the
power stage. The leading edge of waveform C controls
the duration of the ON time of the power stage.
Complete familiarization with the theory of operation must be obtained before troubleshooting is
attempted. Then follow the step-by-step procedures outlined in the manufacturer’s technical manual while
using the specified test equipment.
RECTIFIER POWER SUPPLY
The leading edge of the 180° signal (K) from the
main VPWG triggers the phase control VPWG. The
phase control VPWG provides a delay in time (N)
between the main and secondary VPWGs to control the
phase angle between the two power stages.
The rectifier power supply is a regulated dc power
supply. It is intended to furnish 120-volt dc power for
interior communication and fire control application. Its
input is 440-volts ±5 percent, 60 cycles ±5i percent,
3-phase. It will produce a dc output adjustable from
below 117 volts to above 126 volts at a load of 1 kW.
The output voltage is regulated within 5 percent against
the combined effects of load and line fluctuations,
The secondary VPWG is triggered by the trailing
edge of the phase control VPWG signal (waveform N,
fig. 140, view B). The trailing edge of waveform P from
the secondary VPWG triggers the secondary 400-Hz
countdown. The outputs from the secondary 400-Hz
countdown (U and R) and the leading edge of the
secondary VPWG output (P) trigger the pulse
generators in the secondary driver in the same manner
as just described for the main driver. The sequence of
operation for the secondary power stage is the same as
for the main power stage.
INSTALLATION
The equipment is bulkhead mounted in a drip-proof
cabinet. No switches, meters, or external controls are
provided. Two phase rotation lights are on the front of
the cabinet. One light is for correct phase rotation of
input 3-phase power and the other is for incorrect phase
rotation. Fast-acting fuses are provided for circuit
protection.
OPERATING PROCEDURE
Voltage checks are made at the load if incorrect
adjustments are made internally by repositioning a
potentiometer.
To operate the static inverter, turn the main power
circuit breaker CB1 (fig. 1-37) to ON. Turn the drive
switch, S1, to the OFF position. The standby light, I2,
1-36
NO-BREAK POWER SUPPLIES
PRINCIPLES OF OPERATION
A no-break power supply is designed to provide
uninterrupted electrical power by automatic takeover
should the normal supply fail or momentarily deteriorate
beyond the system demands. No-break power supplies
are provided for communication systems, computers,
navigational equipment, automated propulsion systems,
and related equipment where a momentary loss of power
would cause a permanent loss of information resulting
in the need to recycle or reprogram the equipment. Since
equipment requiring no-break power normally requires
closely regulated power, no-break power supplies are
designed not only to provide uninterrupted power, but
also to provide power that is regulated to meet the needs
of the equipment it serves.
The input 440-volt, 60-cycle, 3-phase power is
stepped down by transformers and applied to an SCR
(diode) 3-phase bridge. The output voltage of the bridge
can be controlled by varying the phase that the SCRs are
triggered. The output is then filtered and sent to the load.
The voltage across the load is compared with an
internally generated, temperature-compensated,
reference voltage. Any difference between the actual
load voltage and the desired load voltage, indicated by
the reference voltage, is amplified by the voltage control
circuit. This amplified voltage is combined with a
properly phased ac signal and applied to the trigger
circuit of the SCRs. The ac signal controls the time of
firing of the SCRs. By controlling the time of firing of
COMPONENTS
the SCRs, the output voltage is also controlled.
The SCRs are fired earlier if the output voltage is
The no-break “uninterrupted” power supply system
consists of two major assemblies plus the storage batteries. The control cabinet and motor-generator set are
shown in figure 1-41.
too low. They are fired later if the output is too high.
Special frequency-shaping circuits are used to ensure
stability and prevent oscillations or hunting.
Figure 1-41.-No-break “uninterrupted” power supply system components.
1-37
OPERATION
The control cabinet contains all the control and
monitoring equipments. The motor generator is a singleshaft unit. Either section of the motor generator can
perform as the motor with the other as the generator.
This permits two operational modes: NORMAL and
STOP GAP.
Normal ship’s power (fig. 1-42) is applied to the
voltage and frequency monitors. If the monitors sense
the normal power to be within the frequency and voltage
limits required relay action (relay #1) will allow the
normal power to be applied to the load and other circuitry. (It should be noted that the relay numbers in
fig. 1-41 refer to relay action sequence rather than relay
designations.) Power is applied to the relay control
power circuit from the battery.
NORMAL operation uses the normal supply (ship’s
generators). The motor generator is driven by the ac
motor from the ship’s supply, and the dc generator
charges the batteries.
In STOP GAP operation, the motor generator is
driven by the dc motor with power from the batteries.
Under this condition the ac generator provides power to
the critical load.
When the system is turned on, the motor generator
will accelerate to approximately synchronous speed
as an induction motor before a time delay relay is
Figure 1-42.-No-break “uninterrupted” power supply system, block diagram.
1-38
GAP when the input frequency drops below 56 Hz or
the input voltage falls below an adjustable limit (330 to
380 volts).
energized. When the delay relay energizes (relay #2), it
applies normal power to the ac field rectifier, via the ac
voltage regulator, for application as field excitation to
the ac motor to allow synchronous motor operation. At
the same time, the dc generator is rerouted to the dc
supply (relay #3) to prevent starting the motor-generator
set on dc and to charge the batteries. The system is now
operating in NORMAL mode.
The voltage monitor circuitry is basically the same
as the voltage-sensing and error voltage detector circuit
of the voltage regulator. The frequency monitor is
basically the same as the frequency discriminator and
error voltage detector circuits. These circuits will be
discussed later in this chapter. The big difference in the
circuits is the output application. The output of the
monitors is used for relay switching, since the other
circuit’s output is for regulation of either voltage or
frequency.
If the normal supply falls out of its limits in either
voltage or frequency, the respective monitor will sense
it, and relay action (relay #4) will shut down the motorgenerator set. At the same time, the dc generator field is
disconnected from the dc field rectifier #2 and connected directly to the battery supply (relay #5). The dc
motor speed regulator and the ac generator voltage
regulator are energized (relay #6 and #7) to maintain the
required motor speed and control the load voltage. The
system is now in the STOP GAP mode.
VOLTAGE REGULATOR
The function of the voltage regulator is to maintain
the output voltage at the preset value (2 percent) regardless of temperature or load variations. The basic circuitry for both the ac and dc regulators is similar except
that the dc regulator does not use the 6-phase rectifiers
in the sensing circuit. Constant generator voltage output
is obtained by having the regulating circuit change the
voltage feed in response to an error signal.
If the reason for switching modes had been a voltage
drop, the voltage would not have dropped below 317
volts, and the transition would have been accomplished
within 1 second. In the case of a frequency drop, the
change is made within 2 seconds and the frequency does
not drop below 54 Hz.
When the ship’s power returns to the specified
limits, the synchronizer will have the normal power at
one side and the ac generator power at the other. It will
automatically adjust the speed regulator to match the
generator frequency to the normal power. The matching
is accomplished in less than 1 minute, and the system is
transferred back to ac motor drive and battery charge
(NORMAL mode).
A differential amplifier is used in the error voltage
detector circuit (fig. 1-43) to compare the generator
output voltage, with a reference voltage, to produce the
error signal. The error signal, acting through the
modulator, modifies the timing of the pulse repetition
frequency of the unijunction trigger circuits. The
controlled pulses are fed to the respective field rectifier
to control the average power to the generator field. The
rate circuit modifies the error signal to stabilize the
voltage regulator.
MONITOR CIRCUITS
The frequency and voltage monitoring circuits are
designed to switch and set from NORMAL to STOP
Figure 1-43.-Voltage regulator, block diagram.
1-39
applied via R8, which is a factory set and locked
reference voltage adjustment.
Voltage-Sensing Circuit
The voltage-sensing circuit (fig. 1-44) steps down
the 3-phase generator 440-volt ac output through voltage-sensing transformer T1 to 25-volt ac. Each phase is
rectified by diodes CR1 through CR6 and filtered by C1
and C2. This dc voltage is proportional to the generator
output voltage. The dc voltage is applied to voltage
divider network R1 through R4 (R3 can be adjusted to
develop the amount of voltage desired as the
representative generator output) for comparison to the
reference voltage in the error voltage detector circuit.
Resistor R9 is the voltage dropping resistor for CR7,
and capacitor C3 reduces the ripple and noise voltages
across CR7 to provide a clean dc reference voltage.
Resistors R6 and R7 are load resistors for transistor Q2.
Any difference between the input voltage at the base
of Q1 and the reference voltage at the base of Q2 will
produce an error signal (a change in collector current).
If the input voltage is higher than the reference voltage,
Q1 conducts heavier than Q2 and vice versa when the
reference voltage is higher than the input. The voltage
drop across R6 is the error voltage that is applied to the
base of the modulator Q3.
Error Voltage Detector Circuit
Modulator Circuits
Transistors Q1 and Q2 (fig. 1-44) forma differential
amplifier to compare the base voltages of the two
transistors. The signal from the voltage-sensing circuit
is applied to the base of Q1, while the reference voltage
is applied to the base of Q2. The reference voltage is
The modulator circuit (fig. 1-44) modifies the time
constant of the RC circuit (C4, R10, and the Q3
collector-emitter resistance). (The collector-emitter
Figure 1-44.-Voltage regulator, simplified schematic.
1-40
resistance is controlled by the current through resistor
R6.) An increase in the error signal across R6 decreases
the collector-emitter resistance of Q3 and thus decreases
the charge time of C4. If the error signal increases, the
charge time of C4 is increased.
relaxation oscillator that initiates controlled rate pulses
to trigger the field rectifiers. Q4 turns on when the
voltage across C4 and the emitter current of Q4 reach
preset values. When Q4 conducts, trigger pulses are
applied to the trigger amplifier Q5.
Capacitor C4 discharges when the voltage across it
is approximately 9 volts (the peak point voltage of
unijunction transistor Q4).
Trigger Amplifier Circuit
A synchronizing circuit (discussed later) clamps C4
to ground, thus delaying the RC time cycle. A rate
feedback signal is also applied by the rate circuit to the
collector of Q2. This signal modifies the error signal,
thus stabilizing the voltage regulator.
The trigger amplifier (fig. 1-44) amplifies and
shapes the trigger pulses. The circuit is a common
emitter amplifier with RC input (R13 and C5) and
transformer output (T2).
Transistor Q5 is protected against the inductive
kickback voltage of T2 by diode CR8. Resistors R14 and
R15 with capacitors C6 and C7 include a pulse-shaping
network to prolong the life of the SCRs in the field
rectifier.
Rate Circuit
The function of the rate circuit is to dampen the
generator output voltage distortion about a set point.
Otherwise, the high gain of the voltage regulator would
cause the generator output voltage to hunt. The method
used for damping the voltage distortion is feeding back
an inverted signal (opposite to the error signal),
proportional to the rate of voltage change.
GENERATOR FIELD RECTIFIER
Both the ac and dc field rectifiers are similar in
operation. The function of the generator field rectifier is
to provide controlled dc power to the generator field to
regulate the generator input voltage with the field power
being proportional to the conduction line of the SCRs.
The rate circuit (fig. 1-44) consists of a common
emitter amplifier (Q6, R19, and R20) and an integrating
circuit (R16 and C8). Resistor R17 is a discharge resistor
for C8, and CR9 and CR10 are common rectifiers.
Transformer T3 (fig. 1-45) transfers voltage from
the generator that is rectified by the bridge rectifier
(CR11 through CR14). The conduction of the bridge is
controlled by SCRs, CR13, and CR14. One series
combination of diode and SCR (CR11, CR13, or CR12,
CR14) may conduct for alternate half cycles. The dc
output is the controlled generator field power.
The input is supplied by the generator field rectifier
(described later), integrated, and applied as forward bias
to the base of Q6. Any change in the base is amplified
and passed by C9 to the collector of the error detector,
Q2. As this signal is opposite to the error signal, it will
decrease conduction and stabilize the circuit.
Diode CR 15 is used as an inductive kickback diode
to provide a path for the current generated by the
collapsing magnetic field of the generator during the idle
portion of each cycle. The amount of field power can be
adjusted by R21.
Unijunction Trigger Circuit
The trigger function is performed by the unijunction
trigger circuit (fig. 1-44). Unijunction transistor Q4 is a
Figure 1-45.-Generator field rectifier, simplified schematic.
1-41
on for a greater or smaller portion of the half cycle.
Figure 1-46 shows how power can be increased as the
firing point is moved along the phase time axis.
The SCRs accomplish power control because they
are rectifiers and in an ac circuit conduct only during
half of each cycle and then only after being turned on
by a positive gate pulse (from the trigger amplifier).
The firing point is determined by the position (or
timing) of a spiked gate pulse. When applied to the SCR,
Power control is accomplished by switching the power
Figure 1-46.-Phase shift of gate pulse.
1-42
When the alternate bridge rectifier conducts, the
voltage across R23 permits C4 (fig. 1-44) to charge,
introducing the phase delay of the SCR gate pulse.
Firing of SCRs, CR13, and CR14 applies equal potential
at both ends of voltage divider R22 and R23. This
removes the voltage drop across R23 and thus allows
Q7 to turn off and Q8 to turn on. Thus, the timing
capacitor C4 is clamped until the start of the next half
cycle.
the pulse turns it on. By controlling the phase of the gate
pulse (with respect to the supply voltage), the firing
(delay) angle of the SCR gate may be delayed to any
point in the cycle up to approximately 180°. Through
control of the firing angle, the average power delivered
to the load can be adjusted.
Referring to figure 1-46, you can see that by applying a gate pulse at 0° of the phase time axis (view A),
output power will be applied during the complete half
cycle. View B shows that power is obtained for a half of
each half cycle by applying a pulse at 90° of the phase
time axis. The other extreme of no output when the
phase delay is 180° is represented in view C.
FREQUENCY DISCRIMINATOR
The speed/frequency regulator automatically maintains the motor speed and the generator frequency at a
preset value despite line variations or load changes.
SYNCHRONIZER
Constant output frequency is obtained by auto
matically adjusting the power to the motor control field
in response to a frequency discriminator. The frequency
discriminator converts the generator output frequency
to a voltage signal that is in direct proportion to the
speed/frequency of the motor generator.
The function of the synchronizer is to assure that the
firing angle is always reckoned from the instant the
supply voltage crosses the zero axis at each positive half
cycle (fig. 1-46, view A). As shown in figure 1-47, when
the SCRs are not conducting, an alternate bridge
rectifier circuit is. This alternate bridge consists of diode
CR12, resistor R21, the generator field, resistors R23
and R22, diode CR16, and the secondary of T3. During
the alternate half cycle, the patch (dashed arrows) is the
same except diodes CR 11 and CR 17 are used.
The speed/frequency regulator circuit is the same as
the voltage regulator previously discussed. The
operational difference is that the voltage regulator
required an increase in generator output voltage to cause
Figure 1-47.—Synchronizer, simplified schematic.
1-43
Before the trigger pulse is applied, C13 has been
charged to the collector voltage (Vcc) level through
resistor R25 with the other end clamped to ground
through diode CR27 and the base-emitter junction of
Q11. When C13 discharges due to the trigger pulse, it
turns Q11 off. The collector will rise to the collector
voltage level, and resistor R26 will apply base current
to Q10 to hold it saturated after the trigger pulse ends.
a decrease in generator field current; but, in the
frequency regulator, an increase infrequency causes the
field current to increase.
The discriminator circuit is shown in figure 1-48. It
essentially consists of a one-shot multivibrator that puts
out a constant width pulse whenever a trigger pulse is
applied. The trigger circuitry is designed so a pulse is
applied six times each output cycle to obtain a high
enough sampling rate to decrease the response time of
the circuit. The multivibrator output is integrated to
provide a dc voltage that is proportional and linear with
frequency.
This state (Q10 on, Q11 off) will exist until C13
charges through R27 to a voltage high enough to allow
Q11 to become forward biased again. At this time the
output pulse ends since Q11 saturates and the base drive
of Q10 is removed. The time duration of the output pulse
is controlled by C13 and R27 with CR27 in the circuit
to protect the base junction of Q11 from overvoltage.
The positive collector voltage input furnishes the
circuitry operating biases and 6-phase ac is used to
obtain the trigger pulses. The trigger circuitry consists
of three single-phase full-wave rectifiers (CR18 and
CR19, CR20 and CR21, and CR22 and CR21). Each is
driven from a winding of the T1 star secondary (fig.
1-44). The rectified voltages are clipped by the Zeners
(CR24, CR25, and CR26) to obtain a square pulse,
which is further shaped by the differentiating circuitry
of C10, C11, C12, and R24. The differentiated pulses
drive the trigger transistor Q9, which saturates whenever a positive pulse is applied.
The output pulse from the collector of Q11 is fed
through resistor R29 to integrating capacitor C14.
During the time no output pulse is present, C14 is
discharged through R29 and the collector-emitter
junction of Q11.
If the frequency of the generator increases, the ratio
of charge time to discharge time increases, which in turn
increases the discriminator output voltage proportional
to the frequency shift. A decrease in frequency does the
opposite. The output is applied to the error voltage
detector circuit (base of Q1, fig. 1-44) or its equivalent
in the frequency regulator.
Transistors Q10 and Q11 form a one-shot multivibrator with an output that is a 2-millisecond wide pulse
equal in amplitude to the collector voltage. Q11 is
normally held on through R25, CR27, and R28. Thus,
Q10 is held off as its base drive comes from the collector
of Q11. Since Q9 saturates when a trigger pulse is
applied, the collector voltage of Q10 is at ground
potential whenever a pulse is applied.
MAINTENANCE
Under normal conditions, the motor-generator set
and control equipment require inspection and cleaning
as designated by the PMS maintenance requirement
cards. When you inspect the motor generator, observe
Figure 1-48.—Frequency discriminator, simplified schematic.
1-44
Take care to ensure that the drying current does not
exceed 80 percent of the full-load rating. When drying
the field winding, remove the brushes to prevent
marking or pitting the collector rings (which can occur
if the brushes carry the drying current).
cleanliness, brush operation, condition of brushes and
commutator, bearing temperature, and vibration.
When necessary, remove dust from the wound
section with a vacuum cleaner, if available. If a vacuum
cleaner is not available, use either compressed air (30
psi maximum) or a hand bellows. Be certain that the
compressed air does not have any grit, oil, or moisture
content in it. Use compressed air with caution,
particularly if abrasive particles, such as carbon, are
present, since these may be driven into the insulation
and puncture it or may be forced beneath insulating
tapes or other possible trouble spots. If vibration exists,
check for loose parts or mounting bolts.
Check the insulation resistance at regular intervals.
Remember, when using the current method, the
resistance may drop temporarily as the moisture is
forced to the surface of the winding. Drying should
continue until the resistance is at least 1 megohm. The
drying process can take days in extreme cases. When the
windings are dried out, apply a coating of insulating
varnish.
When cleaning the control equipment, use a vacuum
cleaner or hand bellows. Accumulations of dust or dirt
around components can impair the natural flow and
cause overheating.
OIL-SOAKED WINDINGS
If oil enters the windings, insulation breakdown
may be imminent, and the winding will probably have
to be rewound. However, patches of oil should be
removed with a clean cloth soaked in an approved
solvent. Use the solvent sparingly, being careful that the
insulation is not saturated as this can cause softening of
the insulation. After cleaning with solvent, apply one of
the drying methods.
DAMP WINDINGS
Moisture in windings can soften the insulation and
reduce the dielectric strength. However, considerable
time is usually required before the moisture will harm
the windings. By checking the insulation resistance of
the winding, you can spot possible trouble and take
appropriate maintenance action.
SUMMARY
In this chapter, you were introduced to the
fundamentals of the various ac and dc motor and circuit
control devices to enable you to maintain, troubleshoot,
and repair the equipment successfully. You were given a
basic understanding of frequency regulators and the
troubleshooting and repair of them as well. Most
equipment installed will have a manufacturer’s
technical manual that should be used to adjust and repair
the equipment following the recommended
specifications. The Naval Ships’ Technical Manual
(NSTM), chapter 302, will provide additional
information of value to you.
If the insulation resistance falls below 1 megohm,
dry out the windings. Three recommended methods of
drying are oven drying, forced warm air drying, or
low-voltage current drying.
Oven drying is accomplished using a maximum
temperature of 85°. The forced warm air method is
simply using a fan to blow warm air across the damp
windings, The air must be dry and should be in a vacuum
with the temperature below 212°F.
The low-voltage current method requires
circulating a limited direct current through the windings.
1-45
CHAPTER 2
ANEMOMETER SYSTEMS
CHAPTER LEARNING OBJECTIVES
Upon completion of this chapter, you should be able to do the following:
Describe the two types of anemometer (wind
Describe the synchro signal amplifier and its
direction and speed indicating) systems.
principles of operation.
Describe the procedures in performing preven-
Identify the major components of anemometer
systems.
tive maintenance on anemometer systems.
Describe the procedures to follow in trouble-
Describe the purpose and operation of the major
components.
shooting and repairing the components in ane-
Describe synchros and the procedures for zeroing different types of synchros.
Describe the crosswind and headwind computer
mometer systems.
system
Detector
The anemometer (wind direction and speed indicator) system, circuits HD and HE, provides instantaneous
and continuous indication of wind direction and speed
relative to the ship’s heading and speed. Wind direction
and speed information is important for combat systems
operations, flight operations, and maneuvering.
Throughout this chapter we will use the term wind
direction and speed indicator systems interchangably
with the term anemometer systems.
The detector (fig, 2-1) is a dual-purpose instrument
employing two type 18CX4 synchros for transmitting
the instantaneous undamped signals representing wind
direction and speed to the transmitter and/or computers.
The detector should be mounted on a mast or yardarm where it will receive unobstructed wind flow from
all directions. Be careful not to submit the detector to
wind currents and eddies from nearby objects. Avoid a
location where flue gases or exhaust currents will strike
the detector. Equipment cannot be installed in the area
that will interfere with the detectors.
WIND DIRECTION AND SPEED
INDICATOR SYSTEMS
There are two types of wind indicating systems, type
F and type B. The type F system provides both 115-volt,
60- and 400-Hz outputs. The type B system provides
only 115-volt, 60-Hz outputs. Most ships have two
systems installed; one for the port side of the ship and
one for the starboard side of the ship.
The direction synchro in the detector is mounted in
a vertical support and is coupled to a plastic vane
assembly. A speed synchro enclosed in synchro housing
is mounted in the head of the vane and is geared to a
screw-type rotor assembly that senses wind speed. The
angular position of the vane and rotating speed of the
rotor assembly are sent to their respective synchros in
the transmitter. Electrical connections are made to the
speed synchro through the collector ring assembly and
brushes on the brush holder assembly.
MAJOR COMPONENTS
The major components of the system are the wind
direction and speed detector, the wind direction and
speed transmitter, and the wind direction and speed
indicator. Throughout this chapter we will refer to these
components as the detector, the transmitter, and the
indicator. The synchro signal amplifier is also a component of these systems.
Wind direction is determined by the position of the
vane and is shown as degrees off the bow of the ship.
The direction synchro is set to electrical zero when the
vane points directly to the bow. As the wind positions
2-1
Figure 2-1.—Wind direction and speed detector.
2-2
the vane, the rotor on the synchro (directly coupled to
the vane) moves angularly a like amount. The angular
position of the type 18CX4 synchro is sent electrically
to a 18CT4 synchro in the direction assembly of the
transmitter and/or to computers.
Windspeed is determined by the speed of the rotor
assembly. The rotor assembly is held directly into the
wind by the vane assembly. Speed of rotation of the rotor
assembly is proportional to the speed of the wind
striking the blades.
Transmitter
The transmitter consists of two plug-in assemblies,
a direction assembly and a speed assembly. The assemblies are housed in a common, dripproof case designed
for bulkhead mounting.
The direction assembly is essentially a servoamplifier circuit using a type 18CT4 synchro control
transformer as a receiver for angular displacement signals representing the position of the vane. The purpose
of the direction assembly is to receive a 400-Hz signal
equivalent to a change in the position of the vane as sent
by the detector and to send this change at a predetermined rate, in the form of 60-Hz and 400-Hz
synchro signals, to the indicators and/or recorders.
Figure 2-2.—Wind indicator.
with the exception of their graduated dials, and are
housed in a watertight case, therefore eliminating consideration of the elements when determining location.
The speed assembly consists of a servo-amplifier
circuit and a roller disc-type integrator. The servo amp
lifier uses a type 18CT4 synchro control transformer as
a receiver for signals from the detector representing the
rotating speed of the rotor assembly. The purpose of the
speed assembly is to receive a signal equivalent to a
change in rotational speed of the rotor assembly as sent
by the detector, to amplify the signal, and to transmit
this change at a linear rate, in the form of 60-Hz and
400-Hz synchro signals, to indicators and/or recorders.
The design of the wind indicating equipment, type
F, allows for the use of a type B indicator with the system
if so desired. The mounting for both types of indicators
are basically the same. The selected indicator should be
mounted on a bulkhead or stationary surface, according
to the applicable dimensions. The location selected will
depend upon the intended use of the indicator and the
convenience for wiring and servicing.
The direction assembly and the speed assembly are
basically a servo unit made up of a synchro control
transformer, a followup motor, and a synchro
transmitter.
The assemblies mount on individual baseplates. The
assemblies and baseplates are enclosed in a metal housing to form a complete wind direction and speed
indicator unit.
The transmitter should be mounted in a location that
is convenient for wiring and servicing. Consideration
for protection from the elements is important, as the case
is dripproof but not waterproof. Ensure the case is
grounded
The direction synchro receiver receives the angular
displacements from the synchro transmitter in the
direction assembly of the transmitter unit and indicates
these displacements on the direction dial. The direction
dial is graduated in 10° intervals from 0° to 360°.
Indicator
The speed synchro receiver receives the angular
displacements from the synchro transmitter in the speed
assembly of the transmitter unit and indicates these
displacements on the speed dial. The dial is graduated
The wind direction and speed indicator (fig. 2-2) is
a dual unit consisting of a wind direction assembly and
a windspeed assembly. The two assemblies are the same,
2-3
in 5-knot intervals from 0 to 100 knots, covering 360°.
A revolving pointer directly attaches to the shaft.
The dials and pointers are illuminated by red lights.
No lamps in parallel supplied from a 115/6-volt
transformer inside the housing provide dial illumination
for each assembly. A knob on the side of the case controls
a rheostat for varying the intensity of the illumination.
If the dials are indicating inaccurately, and you
decide to orient the speed and direction dials to a
different position, it will be necessary to zero the
synchros after the dials are repositioned. Zeroing
synchros is discussed later in this chapter.
Figure 2-4.—A simple synchro system.
Synchros (fig. 2-3) are used primarily for the rapid
and accurate transmission of information between
equipment and stations. Synchros are seldom used
singly. They work in teams, and when two or more
synchros are interconnected to work together, they form
a synchro system. Such a system may, depending on the
types and arrangement of its components, be put to
various uses. Figure 24 shows a simple synchro system
that can be used to transmit different types of data.
NOTE: The type B indicator does not have dials that
can be repositioned. Consider this fact when mounting
the component.
The synchros in the indicator, either a 18TRX6 or
18TRX4, electrically connect to the synchros in the
transmitter. The synchros in the indicator assume the
positions dictated by the transmitter synchros. The
pointers fastened to the rotor shafts of the synchros
indicate wind direction and windspeed on separate
circular dials.
STANDARD SYNCHRO CONNECTIONS
In systems in which a great many synchro units are
used, it is necessary to have a closely defined set of
standard connections to avoid confusion. The conventional connection is for counterclockwise rotation for an
increasing reading.
SYNCHROS
In performing the required PMS and maintenance
on wind direction and indicating systems and on synchro
signal amplifiers (discussed later in this chapter), you
should have an understanding of synchros. The following paragraphs will discuss synchros and the zeroing of
synchros.
The standard connections of a simple synchro
transmission system consisting of a synchro transmitter
and receiver is shown in figure 2-5. The R1 transmitter
and receiver leads connect to one side of the 115-volt ac
supply line. The R2 transmitter and receiver leads connect to the other side of the line. The stator leads of both
the transmitter and receiver connect lead for lead; that
is, S1 connects to S1, S2 to S2, and S3 to S3. Thus, when
sending an increasing reading over the transmission
system, the rotor of the synchro receiver will turn in a
counterclockwise direction.
When it is desired, the shaft of the synchro receiver
turns clockwise for an increasing reading. The R1 and
R2 transmitter and receiver leads connect as before. The
S1 transmitter lead connects to the S3 receiver lead, and
the S2 transmitter lead to the S1 receiver lead.
ZEROING SYNCHROS
If synchros are to work together properly in a
system, they must be correctly connected and aligned in
respect to each other and to the other devices with which
they are used. The reference point for alignment of all
Figure 2-3.—Phantom view of a synchro.
2-4
Figure 2-5.—Transmission system diagram; standard connections of a simple synchro.
Regardless of the synchro to be zeroed, there are
synchro units is electrical zero. The mechanical
reference point for the units connected to the synchros
depends upon the particular application of the synchro
system. Whatever the application, the electrical and
mechanical reference points must be aligned with each
other. The mechanical position is usually set first, and
then the synchro device is aligned to electrical zero.
Each type of synchro has a combination of rotor position
and stator voltages that is its electrical zero.
two major steps in each procedure. The first step is the
coarse or approximate setting. The second step is the
fine setting. The coarse setting ensures the device is
zeroed on the 0° position rather than the 180° position.
Many synchro units are marked in such a manner that
the coarse setting may be approximated physically by
aligning two marks on the synchro. On standard
synchros, this setting is indicated by an arrow stamped
on the frame and a line marked on the shaft, as shown
in figure 2-6. The fine setting is where the synchro is
precisely set on 0O.
There are various methods for zeroing synchros.
Some of the more common zeroing methods are the
voltmeter and the electrical lock methods. The method
used depends upon the facilities and tools available and
how the synchros are connected in the system. Also, the
method for zeroing a unit whose rotor stator is not free
to turn may differ from the procedure for zeroing a
similar unit whose rotor or stator is free to turn.
Voltmeter Method
The most accurate method of zeroing a synchro is
the ac voltmeter method. The procedure and the testcircuit configuration for this method vary somewhat,
depending upon which type of synchro is being zeroed.
Transmitters and receivers, differentials, and control
transformers each require different test-circuit configurations.
For the ac voltmeter method to be as accurate as
possible, an electronic or precision voltmeter having a
0- to 250-volt and a 0- to 5-volt range should be used.
On the low scale, this meter can also measure voltages
as low as 0.1 volt.
Figure 2-6.—Coarse eletrical zero markings.
2-5
NOTE: Many synchro systems energize by
individual switches. Therefore, be sure the synchro
power is off before working on the connections.
ZEROING TRANSMITTERS AND RECEIVERS (VOLTMETER METHOD).– A synchro
transmitter, CX or TX, is zeroed if electrical zero
voltages exist when the device whose position the CX
or TX transmits is set to its mechanical reference
position. A synchro receiver, TR, is zeroed if, when
electrical zero voltages exist, the device actuated by the
receiver assumes its mechanical reference position. In a
receiver or other unit having a rotatable stator, the zero
position is the same, with the added provision that the
unit to which the stator is geared is set to its reference
position. In the electrical zero position, the axes of the
rotor coil and the S2 coil are at zero displacement and
the voltages measured between terminals S1 and S3 will
be minimum. The voltages from S2 to S1 and from S2
to S3 are in phase with the excitation voltage from R1
to R2.
3. Energize the synchro circuit and turn the stator
or rotor until the meter reads about 37 volts (15 volts for
a 26-volt synchro). This is the coarse setting, and it
places the synchro at about electrical zero.
4. De-energize the synchro circuit and connect the
meter as shown in figure 2-7, view B, using the 0- to
5-volt scale.
5. Re-energize the synchro circuit and adjust the
rotor or stator for a null (minimum voltage) reading.
This is the fine electrical zero position of the synchro.
The common electrical zero position of a TX-TR
synchro system can be checked with a jumper. Put the
transmitter and receiver on zero and intermittently
jumper S1 and S3 at the receiver. The receiver should
not move. If it does, the transmitter is not on zero and
should be checked again.
The following method may be used to zero
transmitters and receivers:
1. Carefully set the unit whose position the synchro
transmits to its zero or mechanical reference position.
ZEROING DIFFERENTIAL SYNCHROS
(VOLTMETER METHOD).– A differential is zeroed
when it can be inserted into a system without introducing a change in the system. In the electrical zero
position, the axes of coils R2 and S2 are at zero
displacement. If a differential synchro requires zeroing,
the following method may be used:
2. De-energize the synchro circuit and disconnect
the stator leads. Set the voltmeter to its 0- to 250-volt
scale and connect it into the synchro circuit as shown in
figure 2-7, view A.
1. Carefully and accurately set the unit to be zeroed
to its zero or mechanical reference position.
Figure 2-8.—Zeroing differential synchros by the voltmeter
method.
Figure 2-7.–—Zeroing a transmitter or receiver by the voltmeter
method.
2-6
2. De-energize the circuit and disconnect all other
connections from the differential leads. Set the voltmeter on its 0- to 250-volt scale and connect as shown
in figure 2-8, view A. If a 78-volt supply is not available,
you may use 115 volts. If you use 115 volts instead of
78 volts, do not leave the unit connected for more than
2 minutes or it may overheat and may cause permanent
damage.
3. Energize the circuit, unclamp the differential’s
stator, and turn it until the meter reads minimum. The
differential is now approximately on electrical zero.
De-energize the circuit and reconnect it as shown in
figure 2-8, view B.
4. Re-energize the circuit. Start with a high scale
on the meter and work down to the 0- to 5-volt scale to
protect the meter movement. At the same time, turn the
differential transmitter until a zero or null (minimum
voltage) reading is obtained. Clamp the differential
stator in this position, ensuring the voltage reading does
not change, de-energize, and connect all leads for
normal operation. This is the fine electrical zero position
of the differential.
Figure 2-9.—Zeroing a control transformer by the voltmeter
method.
ZEROING A CONTROL TRANSFORMER
(VOLTMETER METHOD).– Two conditions must
exist for a control transformer (CT) to be on electrical
zero. First, its rotor voltage must be minimum when
electrical zero voltages are applied to its stator. Second,
turning the shaft of the CT slightly counterclockwise
produces a voltage across its rotor in phase with the rotor
voltage of the CX or TX, supplying excitation to its
stator. Electrical zero voltages, for the stator only, are
the same as for transmitters and receivers.
required to zero the CT, leave the S1 lead on, disconnect
the S3 lead on the CT, and put the S2 lead (from CX) on
S3. This is necessary since 78 volts exist only between
S1 and S2 or S2 and S3 on a properly zeroed CX. Now
energize the circuit and turn the stator of the CT to obtain
a minimum reading on the 250-volt scale. This is the
coarse or approximate zero setting of the CT.
4. De-energize the circuit, reconnect the S1, S2,
and S3 leads back to their original positions, and then
connect the circuit as shown in figure 2-9, view B.
To zero a CT by the voltmeter method, use the
following procedure:
1. Set the mechanism that drives the CT rotor to
zero or to its reference position. Also, set the transmitter
that is connected to the CT to zero or its reference
position.
5. Re-energize the circuit. Start with a high scale
on the meter and work down to the 0-to 5-volt scale to
protect the meter movement. At the same time, turn the
stator of the CT to obtain a zero or minimum reading on
the meter. Clamp down the CT stator, ensuring the
reading does not change. This is the fine electrical zero
position of the CT.
2. Check to ensure there is zero volts between S1
and S3 and 78 volts between S2 and S3. If these voltages
cannot be obtained, it will be necessary to rezero the
transmitter.
Zeroing Multispeed Synchro
Systems
NOTE: If 78 volts from the transmitter cannot be
used and an autotransformer is not available, use a
115-volt source. The CT should not be energized for
more than 2 minutes in this condition because it will
overheat and may cause permanent damage.
If multispeed synchro systems are used to
accurately transmit data, then the synchros within the
systems must be zeroed together. This is necessary
because these synchros require a common electrical
zero to function properly in a system.
3. De-energize the circuit and connect the circuit
as shown in figure 2-9, view A. To obtain the 78 volts
2-7
holes into its frame, NEVER use pliers on the threaded
shaft, and NEVER use force to mount a gear or dial on
the shaft.
First, establish the zero or reference position for the
unit whose position the system transmits. Then, zero the
most significant synchro in the system and work down
to the least significant. For example, zero the coarse
synchro, then the medium synchro, and finally the fine
synchro. When zeroing these synchros, consider each
synchro as an individual unit and zero accordingly.
In maintaining synchros, there are two basic rules
to apply:
1. IF IT WORKS, LEAVE IT ALONE.
There are a few 3-speed synchro systems. These
systems require zeroing in an identical reamer as the
dual-speed systems. First, zero the most significant
synchro in the system and then work down to the least
significant.
2. IF IT GOES BAD, REPLACE IT.
Shipboard synchro troubleshooting is limited to
determining whether the trouble is in the synchro or in
the system connections. You can make repairs to the
system connections, but if something is wrong with the
unit, replace it.
Remember that all synchros in a system must have
a common electrical zero position.
Electrical Lock Method
SYNCHRO SIGNAL AMPLIFIER
The electrical lock method (although not as accurate
as the voltmeter method) is perhaps the fastest method
of zeroing synchros. However, this method can be used
only if the rotors of the units to be zeroed are free to turn
and the lead connections are accessible. For this reason,
this method is usually used on the TR because, unlike
transmitters, the TR shaft is free to turn.
The reason for using synchro signal amplifiers is to
reduce the size of synchro transmitters. These smaller
synchro transmitters are used in wind indicators and
other sensing devices that are more accurate if there is
only a small load on their outputs.
You should already know the operating principle of
the synchro signal amplifier. The input to the amplifier
is from a small synchro transmitter or two small transmitters that give a coarse and a fine signal. The input
signal controls a small servomotor. This servomotor
drives one or more large synchros into a position corresponding to the position of the input synchro. The
output from the large synchros is then used as needed to
drive several synchro receivers.
To zero a synchro by the electrical lock method,
de-energize the unit, connect the leads, as shown in
figure 2-10, and apply power. The synchro rotor will
then quickly snap to the electrical zero position and lock.
As stated before, you may use 115 volts as the power
supply instead of 78 volts if the unit does not remain
connected for more than 2 minutes.
SYNCHRO MAINTENANCE AND
TROUBLESHOOTING
Synchro signal amplifiers must meet some or all of
the following operational requirements:
Synchro units require careful handling at all times.
NEVER force a synchro unit into place, NEVER drill
Accept a low-current synchro signal, amplify the
signal, and use the amplifier signal to drive largecapacity synchro transmitters.
Isolate oscillations in a synchro load that may be
reflected from the input signal bus.
Permit operation of a 60- or 400-Hz synchro load
from either a 60-or 400-Hz synchro bus.
Provide multiple charnel output transmission of
a single-channel input signal.
Permit operation of a synchro load independent
of the input synchro excitation.
A block diagram of a synchro signal amplifier is
shown in figure 2-11.
Figure 2-10.—Zeroing a synchro by the electrical lock method.
2-8
Figure 2-11.—Block diagram of a synchro signal amplifier.
GENERAL DESCRIPTION
1 speed
E- and F-type synchro signal amplifiers will be
discussed in this section of the chapter. The major
36 speed
2 speed
difference between the two types is that the type E
operates with 60-Hz supply and input. The type F
operates with 400-Hz supply and input signals. The
2 and 36 speed
The E- and F-type synchro signal amplifiers consist
of subassemblies housed in a dripproof case. These
cases are the same on both types of synchro signal
amplifiers. The internal subassemblies are similar in
design. The only differences are the ones previously
covered.
different supply and input frequencies require that the
E- and F-type units use different synchro control transformers, servomotors, synchro capacitors, and
amplifiers. Both types have provisions for four output
synchros: two for 60-Hz and two for 400-Hz transmission. Both types of synchro signal amplifiers are
The subassembly is easily accessible through a front
access door in the case that can be opened by loosening
screws in the door. The door has hinges and supporting
chains so it can be lowered and used as a service platform for the internal subassembly. An alarm switch, a
designed to provide for input and output transmission at
any of the following combinations of speeds:
1 and 36 speed
2-9
revolve in response to the same reading, a vernier effect
is achieved so that a higher accuracy is obtained
dial window, four indicator lights, and a double fuse
holder are mounted on the front access door. A
schematic diagram of the subassembly is provided on
the inside of the front access door.
Synchro Operation
Terminal boards on the inside bottom of the case
serve as a common junction for connecting the ship’s
wiring. Access plates on both sides of the synchro signal
amplifier provides for external cabling. Stuffing tubes
are mounted to these plates as required at installation,
and the external cabling is run through the stuffing tubes.
The synchro transmitter resembles a small bipolar
3-phase motor. The stator is wound with a three-circuit
Y-connected winding. The rotor is wound with a singlecircuit winding. Electrically, the synchro acts as a transformer; all voltages and currents are single phase. By
transformer action, voltages are induced in the three
elements of the stator winding, the magnitude depending upon the angular position of the rotor.
Speed changes from 1 speed to 2 speed and vice
versa are made by installing change gears. These gears
are not normally furnished with the synchro signal
amplifier. Both the E- and F-type units have a dial with
two scales, one on each side. One scale is calibrated
every degree from 0° to 360° and is driven at 1 speed,
when 1 speed is used. The other scale is calibrated 60°
either side of zero (300° to 0° and 0° to 60°), and this
scale is used when a 2-speed transmission is needed. The
dial turns over when changing from 1 speed to 2 speed
or vice versa.
The synchro receiver is constructed essentially the
same, both mechanically and electrically, except it is
provided with a mechanism for dampening oscillations.
Consider the simplest synchro transmission system,
where the transmitter and receiver units are connected
as shown on figure 2-5. If the receiver rotor were free to
turn, it would take a position where induced stator
voltages would be equal to the transmitter voltages.
Under such a condition there is no current flow. However, if the transmitter rotor was displaced by any angle,
the stator voltage balance would be altered and current
would flow in the stator windings. This current flow
would set up a two-pole torque, turning the receiver
rotor to a position where the induced stator voltages
would again be equal. Therefore, any motion given to
the rotor of one unit would be transmitted to the rotor of
the other unit where it is duplicated thereby setting up
a system of electrically transmitted mechanical motion.
When either unit is operating from a low 1- or
2-speed input, you must make some minor wiring
changes. Connections between the terminals on the
plug-in damping unit should be changed from those
shown for 1 and 2 speed and 36 sped to those shown
for 1 or 2 speed. This connects the normally disconnected low-speed synchro control transformer.
These connections also remove the antistickoff voltage,
which will be discussed later in this chapter.
The synchro signal amplifier transmission system
depends upon the type of transmitter described in the
previous paragraphs, but its receiver is a synchro control
transformer. The purpose of the synchro control transformer is to supply, from its rotor terminals, an ac
voltage whose magnitude and phase polarity depend
upon the position of the rotor and voltages applied to its
stator windings. Since its rotor winding is not connected
to the ac supply, it does not induce voltage in the stator
coils. As a result, the stator current is determined by the
high impedance at the windings and it is not affected
appreciably by the rotor’s position. Also, there is no
detectable current in the rotor and, therefore, no torque
striving to turn the rotor. The synchro control transformer rotors cannot on their own accord turn to a
position where the induced currents are once again of
balanced magnitude. The synchro amplifier cycle of
operation must take place to turn the rotor of the synchro
control transformer.
PRINCIPLES OF OPERATION
The synchro signal amplifier is actually a synchro
data repeater. It accepts synchro data from remote transmitters, aligns associated output synchros to electrical
correspondence with the remote transmitters, and retransmits the data to other equipment. Synchro transmission is increased by using larger output synchros
than the remote transmitter.
Since the output synchros are driven to electrical
correspondence with the remote transmitters by gearing,
a power supply of a different frequency may be used for
the output synchros. This gives the synchro signal
amplifier another attribute, as a frequency converter.
A higher accuracy is obtained from a synchro signal
amplifier with a 36-speed input than would be obtained
from a l-speed input. By virtue of the 36 speed revolving
36 times the angular distance that the 1 speed would
2-10
A synchro amplifier cycle of operation takes place
as follows:
1. A change occurs in the remotely transmitted
synchro data.
2. The signal received by the synchro control
transformers in the mechanical unit is, as an error voltage, amplified and used to operate the servomotor. The
servomotor, through gearing, turns the synchro control
transformer rotors until the error voltages are zero (or,
in the low-speed unit, matched to the stickoff voltage),
thereby stopping the turning or follow-up action.
3. Simultaneous with step 2, the servomotor also
drives the rotors of the output synchros into alignment
with the new input signal.
S2 to terminal block terminal B2
S3 to terminal block terminal B3
When the shaft of the synchro is to be driven clockwise
for an increasing reading, the connections to the
terminal bus should be as follows:
R1 to terminal block terminal B
R2 to terminal block terminal BB
S3 to terminal block terminal B1
S2 to terminal block terminal B2
S1 to terminal block terminal B3
For a synchro control transformer, these con- nections
will apply to the stator, but the rotor connections go to
the input of the servo amplifier.
Synchro Connections of a Synchro Amplifier
Cutover Circuit
The conventional connection is for counterclockwise rotation for increasing reading-an increasing reading is when the numbers associated with the action being
measured are increasing. The five wires of a synchro
system are numbered in such a way that the shaft of a
normal synchro will turn counterclockwise. When an
increasing reading is sent over the wires provided, the
synchro is connected as follows:
The purpose of the cutover circuit is to automatically select the error voltage from either the high
(36 speed) or low (1 or 2 speed) synchro control
transformer and feed it to the servo-amplifier input
terminals. The low-speed control transformer is
connected when the error is large (more than 2 1/20),
and the high-speed control transformer is connected
when the error is small (less than 2 1/20).
R1 to terminal block terminal B
The cutover circuit (fig. 2-12) consists of six diodes
(CR12A through CR17) and three resistors (R12, R13,
and R14). The circuit operates on the principle that
R2 to terminal block terminal BB
S1 to terminal block terminal B1
Figure 2-12.—Cutover circuit.
2-11
Servo Amplifier
diodes, connected back to back, act as nonlinear
resistances. When a high voltage appears across the
diodes, it appears as a low resistance or a short circuit.
When a low voltage appears across the diodes, it appears
as a high resistance or an open circuit.
The servo amplifier is a 10-watt plug-in amplifier
with a push-pull output stage that feeds the semomotor
control winding. The servo amplifier drives the servomotor, which, in turn, repositions the control
transformer rotors to null the error voltage to the servo
amplifier. The amplifier has an internal power supply
operating from 115 volts ac. It provides 12 volts dc and
unfiltered 40 volts dc for the amplifier stages. In
addition, the power supply power transformer supplies
reference voltage for the servomotor and antistickoff
voltage.
When control transformer error voltages are small,
diodes CR12A, 13A, 14, and 15 act as a high resistance
and block the low speed (1X) signal from the servo
amplifier. Diodes CR 16 and 17 act as a high resistance
and allow the lightspeed (36X) signal to pass to the
servo amplifier.
When the error voltages are high, diodes CR12A,
13A, 14, and 15 act as a low resistance and pass the
low-speed signal to the servo amplifier. Diodes CR16
and 17 act as a low resistance and short the high-speed
signal before it reaches the servo amplifier. Resistors
R12, 13, and 14 are current-limiting resistors.
The amplifiers for 60- and 400-Hz units are similar
except for the power transformers and capacitors.
Gear train oscillation, or hunting, is caused by overshoot as the servo reaches its null. To prevent this,
clamping circuits introduce a stabilizing voltage at the
amplifier input. This stabilizing voltage is proportional
to acceleration or deceleration of the unit.
Antistickoff
Alarm Circuit
The low-speed control transformer output winding
connects in series with a 2.7-volt winding of the power
transformer. This small, constant voltage (called the
antistickoff voltage) is added to the output voltage of the
low-speed control transformer. It, in effect, shifts the
angular position of the control transformer null, or
position of zero output. The antistickoff voltage is either
in phase or 180° out of phase with the low-speed control
transformer output.
The alarm circuits in the synchro signal amplifier
monitor the 60- and 400-Hz output excitation, servo
excitation, and follow-up error. With all power sources
present and a follow-up error of less than 2 1/2°, the four
indicator lights on the access door will light. If one of
these conditions fails, the appropriate light will go out,
indicating the problem area, and an alarm will sound.
With the equipment normally energized and the
alarm switch in the ON position, the alarm circuit will
be open. A loss of any of the three power sources, a
follow-up error of more than 2 1/2°, or putting the alarm
switch in the OFF position will close the alarm circuit,
causing an alarm to sound.
If the high- and low-speed control transformers
were set to electrical zero at the same position, there
would be a point at 0° and 180° where the error voltage
would equal zero. Within 2 1/2° of the 180° point, the
36-speed error signal would drive the servomotor to
synchronize the control transformers at the 180° point.
The control transformers would also synchronize at the
180° point if the synchro signal amplifier were
energized when the control transformers were within
2 1/2° of the 180° point.
Gear Train
The gear train consists of a series of tine pitch,
precision, spur gears. They link together the rotors of the
two control transformers, four output synchros, and the
servomotor.
To remove the chance of synchronization of the
control transformers at the 180° point, the low-speed
control transformer is rotated 2 1/2° from correspondence with the high-speed control transformer null,
or zero, position. An antistickoff voltage of constant
magnitude and phase is added to the single-speed
control transformer output. The resultant voltage is now
zero at the 185° point instead of the 180° point. At either
side of the 185° point, both the 36-speed and
single-speed voltage tend to drive the synchro
transmitters toward true zero.
MAINTENANCE OF SYNCHRO
SIGNAL AMPLIFIERS
The synchro signal amplifier should require little
attention in service, there being few parts inside the
amplifier unit or the synchros that need lubrication or
replacement under normal operating conditions.
2-12
while watching the indicator and comparing the readings, you can determine if there is a problem with a
detector. Every 90 days and after exposure to high
winds, inspect the detector mounting and tighten the
The alarm circuit takes the place of many routine
checks, since failure of the synchro signal amplifier
output to follow the input or loss of input excitation
automatically completes the alarm circuit. The only
routine checks that are required are a monthly check of
the alarm circuit and yearly inspection of the gearing.
mounting bolts if necessary. The rotor and vane also
should be inspected every 90 days. Turn the rotor by
hand to confirm that it turns freely. Rotate the vane
through 360° in both directions to assure it rotates freely.
If friction or binding of the vane is suspected, perform
When inspecting the gearing, if dirt is found, clean
the gears. If a gear shows excessive wear, replace it.
Turn the gears manually, with the equipment deenergized, noting whether the gears mesh smoothly.
the friction test. Every 6 months, the detector should be
inspected, lubricated, and, if conditions warrant,
cleaned. Refer to the technical manual for specific procedures.
Under normal conditions, the synchro signal
amplifier will require no lubrication. All rotary devices,
such as synchros, gear teeth, ball bearings, and so on,
are factory lubricated for the life of the equipment.
TRANSMITTER
TROUBLESHOOTING ANEMOMETER
SYSTEMS
Every 6 months, the transmitter should be inspected,
lubricated, and, if warranted, cleaned. When inspecting
Troubleshooting wind direction and indicating
systems is simple once you have identified that you have
a problem. Many potential problems can be avoided by
careful preventive maintenance. If the trouble is not
avoided, you can at least identify it by following the
Planned Maintenance System (PMS) procedures. The
principles of operation of the various components of the
systems were included in this chapter to aid you in
troubleshooting.
the transmitter, you should inspect the following:
All moving parts for freeness.
Gears for excessive wear and broken teeth.
Bearings, gears, and other moving parts for
gummed oil, dust, and so on.
When troubleshooting the systems, you should refer
to the troubleshooting tables given in chapter 4 of the
technical manual Operation and Maintenance Instruction - Wind Indicating Equipment, Type F, NAVSHIPS
0965-108-9010. These troubleshooting tables can be
very useful in that they enable personnel to locate malfunctions and take the necessary corrective action. They
are also a quick reference guide.
Sensitive switches; turn them over and replace if
worn.
Driving discs for wear.
INDICATOR
MAINTENANCE OF ANEMOMETER
SYSTEMS
Watch the indicator periodically for uneven
movement of the pointer as this indicates a possible
Preventive maintenance for the system consists of
periodic inspections, cleaning, and lubrication. You
should refer to the appropriate technical manual for
specific procedures to follow. Many potential troubles
in the system can be avoided by careful preventive
maintenance.
problem. By comparing the pointer movement of one
indicator with another, you can determine if the trouble
is in a single indcator or in the system. Erratic indications, resulting from excessive friction, often can be
avoided by cleaning and oiling of the units. Other causes
of excessive friction may be discovered during periodic
maintenance inspection. When beginning a periodic
inspection, observe the indicators when there is enough
wind to act on the vane and rotor. The indicator requires
no lubrication.
DETECTOR
Most ships have a detector mounted port and starboard on the mast. By switching from one to the other
2-13
corresponding voltage that is proportional to the speed
of the wind. This windspeed voltage is then applied to
the wind direction circuit where the crosswind and
headwind components are developed.
CROSSWIND AND HEADWIND
COMPUTER
An elaborate development of a transmission system
is the crosswind and headwind computer system, designed for use aboard CVAs. Although this system is
not at present intended for use aboard other vessels, its
design should be interesting to you as an application of
synchro and servomechanism basics.
The windspeed synchro signal input is applied to the
stator of the control transformer in the windsped
circuit. The output of the control transformer is an error
voltage representing the difference between the
electrical angle of the synchro signal and the mechanical
angle of the stator in the control transformer. This error
voltage feeds to the servo amplifier through a
transformer, not shown in the functional diagram. The
purpose of the transformer is to compensate for the
phase shift caused by the inductance of the windings of
the control transformer rotor. The signal fed to the
amplifier is either 0° or 180° from correspondence with
the line voltage. The amplifier is a push-pull type, and
applies an output voltage to the second coil of the
servomotor, thereby controlling the direction and speed
of the motor.
The crosswind and headwind computer receives
relative wind direction and speed information from a
wind direction and speed indicator system, as shown in
figure 2-13. The output from the computer is in the form
of variable voltages. These voltages represent the
factors of windspeed from dead ahead, across the beam,
and parallel to and across the angled deck of the carrier.
These voltages are applied to indicators that provide
direct reading of crosswind and headwind speeds in
knots. The crosswind and headwind computer assembly
is shown in figure 2-14, and a functional diagram of the
computer assembly is shown in figure 2-13. In figure 2-13, the heavy lines represent signal flow and the
dashed lines represent mechanical linkages that make
the system self-synchronous.
The servomotor drives a gear train that positions the
rotor of the control transformer, driving it until it
corresponds with the input signal. The gear train also
positions the arm of the precision potentiometer that
regulates the dc power supply input. The position of the
arm of the potentiometer determines the amount of
voltage applied to the sine-cosine potentiometer in the
wind direction circuit. This voltage is proportional to the
WINDSPEED CIRCUIT
The windspeed circuit takes the synchro signal
from the windspeed transmitter and converts it to a
Figure 2-13.—Computer system, functional diagram.
2-14
40.133
Figure 2-14.–Cross and headwind computer assembly.
which the windspeed voltage from the other circuit is
applied.
speed of the wind. The function of components is the
same as in the synchro amplifier just described,
except that this mechanism positions a potentiometer
instead of a synchro transmitter.
The sine-cosine potentiometer contains four
stacked sections, one for each of the desired
components
of windspeed. The signals from the angled deck
sections lag the signals from the straight deck
sections by 10°
WIND DIRECTION CIRCUIT
The wind direction circuit converts the synchro
signal output of the wind direction transmitter into
volt-ages proportional to the desired crosswind and
head-wind components of windspeed. This is done
with a mechanism similar to the one used in the
windspeed circuit, which positions a sine-cosine
potentiometer, to
The dc power supply is a highly regulated unit
that converts 115-volt, 60-Hz power to a 40-volt dc
output.
2-15
INDICATOR
working with transistors and that they follow the
instructions in the proper technical manual. The
manufacturer has specified the use of certain meters
for analyzing the condition of the components of the
unit, and, where possible, these should be used.
The crosswind component signals are applied to
the crosswind indicator of the indicator assembly
(shown in fig. 2-15). The headwind component signal
is applied to the other indicator in the assembly. The
indicators have microammeter movements. The
headwind indicator is calibrated for 50 microampere
full-scale deflection, which corresponds to 60 knots.
The dial reads from 0 to 60 knots in 1-knot
increments. The crosswind indicator is calibrated for
±25 microampere for full-scale deflection left and
right. The crosswind scale reads from 30 knots port to
30 knots starboard in 1-knot increments. The
rheostat on the assembly connects in series with the
secondary of the line transformer and the
illuminating lamps, and is used to control their
intensity.
SYNCHRO SIGNAL CONVERTER AND
SYNCHRO SIGNAL ISOLATION
AMPLIFIER
Another of the recent developments in the use of
synchro signals is in the synchro signal converter and
synchro signal isolation amplifier shown in figure 216.
The problem of retransmitting accurate wind
information devoid of error and unwanted feedback to
the transmitter has existed for some time. The
additional problem of conversion of a 60-Hz signal for
use in computers is also not new. The synchro signal
isolation amplifier receives its signal from the wind
system and prepares it for the converter, allowing the
exact signal to be converted to 400 Hz.
MAINTENANCE AND
TROUBLESHOOTING
The maintenance of this unit is outlined in the
appropriate PMS documents. The technical manual
for
the
equipment
contains
an
adequate
troubleshooting chart. Therefore, there should be no
difficulty in keeping the unit running. You should be
sure that personnel trying to repair the amplifier
units are familiar with the proper techniques for
ISOLATION AMPLIFIER
The amplifier contains two chassis that are the
same, one for direction and one for speed. The
principles of
40.135
Figure 2-15.–Indicator assembly.
2-16
40.137
Figure 2-16.—Synchro signal converter and synchro signal isolation amplifier.
the input transformer. The signal is stepped down
and fed into a transistor amplifier operating in the
class B push-pull configuration.
one apply to the other. Each chassis consists of three
channels that are the same in circuitry and
operation; thus, the principles of operation of only one
channel will be explained. (See fig. 2-17.)
The input impedance of the amplifier is high, and
the output impedance is low. This condition prevents
any torque feedback from the output synchro (due to
The sine-wave output from the stator winding of an
external synchro is applied to the primary winding of
Figure 2-17—-Simplified amplifier block diagram (direction or speed).
2-17
Figure 2-18.—Simplifled converter block diagram (direction or speed).
direct current at a level dependent upon the amplitude
of the signal voltage from the synchro stator.
phase differences between the input and output
synchros) from being reflected into the converter. The
amplified signal is transformed into sufficient amplitude
and is applied with the outputs of the two other channels.
The dc signal is then fed into a ring-modulator stage
that is excited by the voltage from a 400-Hz excitation
transformer. The output of the ring modulator is a
400-Hz sine wave with an amplitude proportional to the
magnitude of the dc signal. Two power transistors
operating in the class B push-pull amplifies the 400-Hz
signal.
CONVERTER
The converter also contains two chassis that are the
same, one for direction and one for speed. The principles
of operation of one apply to the other. Each chassis
consists of three channels that are alike in circuitry and
operation; thus, the principle of operation of only one
channel is discussed. (See fig. 2-18.)
The amplified 400-Hz signal is sent through an
output transformer that steps up the amplitude to 90
volts, the required level for excitation of a type 15CT4
synchro control transformer.
MAINTENANCE
The sine-wave output from one stator winding of an
external synchro or the synchro isolation amplifier is
applied to the primary winding of the input transformer
of the converter. The stepped down signal is sent to the
ring-demodulator stage. The ring-demodulator stage is
excited by the voltage from a 60-Hz excitation
transformer. The sine wave from the synchro is either in
phase or 180° out of phase with the excitation voltage.
If the sine wave is in phase, the demodulated signal is a
positive, pulsating dc voltage. If the sine wave is out of
phase, the demodulated signal is a negative, pulsating
dc voltage. The pulsating dc voltage enters a low-pass
filter network. The output of the filter network is pure
Once initially set up for proper operation, the
synchro signal converter and isolation amplifier unit
requires a minimum of maintenance. As with all
transistorized units, heat can be a problem, and careful
selection of location is necessary.
Preventive maintenance should be limited to cleaning all units periodically.
Corrective maintenance requires the use of specific
metering, outlined in the manufacturer’s technical manual
2-18
CHAPTER 3
STABILIZED GLIDE SLOPE INDICATOR SYSTEM
CHAPTER LEARNING OBJECTIVES
Upon completion of this chapter, you should be able to do the following:
Describe the stabilized glide slope indicator
Describe the procedures to follow when
(SGSI) system and its associated components.
troubleshooting the SGSI system
Identify the purpose and principles of operation
Describe the procedures to follow when
of the components of the SGSI system.
performing maintenance on the SGSI system
The stabilized glide slope indicator (SGSI) system
consists of a GSI cell mounted on top of an electrohydraulic stabilized platform. The GSI cell is an optical
viewing system used to indicate to a pilot the aircraft
approach angle to a landing platform or ship. The GSI
system is an electrohydraulic optical landing aid designed for use on ships equipped for helicopter operations. By use of the SGSI, a helicopter pilot may visually
establish and maintain the proper glide slope for a safe
landing. The system is self-contained, relying on the
ship for 115 volts ac 400-Hz and 440 volts ac 60-Hz
power.
indicates to the pilot of the approaching aircraft whether
the aircraft is above (green), below (red), or on (amber)
the correct glide slope. By varying the aircraft altitude
to keep the amber light bar visible, the pilot maintains
the correct glide path to the ship’s landing pad. The bar
of light is formed by the combined actions of source
light, Fresnel lens, and lenticular lens.
To steady the GSI with respect to the pitching and
rolling motions of the ship, the light cell is mounted on
an electrohydraulic stabilized platform. This equipment
uses a local gyro for reference and develops electronic
error signals that, in turn, control hydraulic cylinders
that move the platform in the opposite direction to the
ship’s pitch and roll axis. The system incorporates a
failure detection circuit that turns off the lights in the
event of stabilization failure.
The GSI, which is mounted on a stable platform,
provides a single bar of light either green, amber, or red
(fig. 3-1). The cell face acts as a window through which
the pilot views the light. The color of the light bar
F’igure 3-1.—Glide slope indicator and light beam.
3-1
electrical and electronic components required to control
the major components of the system.
SGSI SYSTEM COMPONENTS
The assemblies that comprise the SGSI system are
as follows (fig. 3-2):
To understand the system operation, you must understand feedback control systems. A feedback control
system compares an input signal with a reference signal
and then generates an error signal. This error signal is
then amplified and used to drive the output in a direction
to reduce the error. This type of feedback system is often
referred to as a servo loop. A gyro, mounted on the
stabilized platform, acts as the reference of the system.
Since the gyro is stable, synchro transmitters located on
the gimbals will sense any motion of pitch or roll. As the
ship begins to pitch or roll, an error signal is developed
by the synchro transmitter stators. Look at the block
diagram in figure 3-4 and follow the path of the error
signal through the electronic enclosure assembly. (The
block diagram represents either the pitch or the roll
control loops. They are identical electrically.)
Electronic enclosure assembly
Remote control panel assembly
Hydraulic pump assembly
Transformer assembly
GSI assembly
Stabilized platform assembly
ELECTRONICS ENCLOSURE ASSEMBLY
The electronics enclosure assembly (fig. 3-3) is the
signal processing distribution and control center for the
system. It contains the circuits, amplifiers, and other
Figure 3-2.—Stabilized glide slope indicator system.
3-2
Figure 3-3.—Electronics enclosure assembly.
From the transmitter stators the error signal is sent
to the gyro demodulator, where the signal is changed
from ac to dc. The signal then goes through a stab-lock
relay (described later) and is amplified as it moves
through the servo amplifier, which in turn operates the
servo valve. The servo valve opens and allows hydraulic
Figure 3-4.—Stabilization circuits, block diagram.
3-3
fluid to enter the hydraulic actuator (fig, 3-5), thereby
leveling the platform and thus canceling the error signal.
When this occurs, a READY light is actuated on the
remote control panel. If the system develops a malfunction and the error signal is not canceled, an errorsensing circuit will light the NOT READY light on the
remote control panel and turn off the GSI.
In the previous paragraphs, we discussed the normal
mode of operation in the electronics portion of the
system. The stabilization lock feature (stab-lock relay)
tests and aligns the GSI. Referring to figure 3-6, you will
see internal gyro stab-lock and ship gyro stab-lock push
buttons and two test switches, one of which is pitchoff-roll.
As previously mentioned, the error signal in the
normal mode goes through a stab-lock relay. When the
stab-lock button is pushed, the normal error signal
supplied from the gyro is stopped at this point (see
Figure 3-5.—Stabilized platform assembly, functional diagram.
Figure 3-6.—Compenents panel assembly (P/O electronics enclosure-F100) controls and indicators.
3-4
fig. 3-7). When the stab-lock button is pushed, the error
signal comes from the linear voltage differential transformer (LVDT) when the test switch is in the off
position. The core of the LVDT is mechanically attached
to the hydraulic actuator, which levels the platform. As
the actuator moves, the core also moves, thereby
supplying a signal proportional to the amount of roll or
pitch. These signals can be measured to aid in the
maintenance and alignment of the system. Revisions
are also made to drive the platform manually using the
test switches and the manual drive potentiometer.
REMOTE CONTROL PANEL ASSEMBLY
The remote control panel (fig. 3-8) is located in the
flight operations control room. TM panel provides
Figure 3-7.—Stabilization control circuit–signal flow.
Figure 3-8.—Remote control assembly.
3-5
HYDRAULIC PUMP ASSEMBLY
control and indicators for operating and monitoring the
SGSI system from a remote location. It contains the
READY and NOT READY lights deseribed previously.
The panel also contains an OVERTEMP light to indicate
when the hydraulic fluid is heated to a temperature
The hydraulic pump assembly (fig. 3-9) is a selfcontained medium-pressure, closed-loop system used
to supply hydraulic pressure for the stabilized platform.
This assembly consists of an electric pump motor, a
coupling unit, a hydraulic pump reservoir, valves,
piping, and an electrical system. All components are
mounted on a steel base and comprise a complete selfcontained 1400-psi hydraulic power supply.
higher than 135°F±5°, a source failure light to indicate
that one or more of the GSI source lights are burned out,
a variable transformer to control the intensity of GSI
light, and a panel illumination control. A standby light
will be energized when the main switch on the electronic
Hydraulic fluid is stored in a reservoir and piped to
a motor-driven pump. The output is pressurized by the
enclosure assembly is on.
Figure 3-9.—Hydraulic pump assembly.
3-6
area. This assembly contains a local gyro, gimbaled
platform, hydraulic cylinders, and electrically operated
servo valves. More information on the stabilized platform is given later in this chapter.
pump to 1400 psi, filtered, and piped to the power supply
output line where it is available to the external system
through a shutoff valve. On the return line, fluid is
returned from the external system to the reservoir at a
reduced pressure of 75 psi. A shutoff valve is also used
in this low-pressure line. Electrical power is obtained
from ship’s power system and connected through the
motor controller and junction box. This assembly is
located as close as possible to the stabilized platform. It
provides hydraulic fluid at 1400 psi to the hydraulic
actuator on the stabilized platform. The motor and controller operate on 440-volt, 3-phase received from
normal ship’s power supply. The temperatures witches
(not shown) operate the OVERTEMP light on the
remote control panel. Also, a pressure switch in the
hydraulic pump discharge line will close at 1200 psi. If
not closed, the pressure switch will de-energize the
electronic panel assembly on low oil pressure.
Hydraulic fluid heaters in the oil reservoir maintain the
temperature at approximately 70°F±5°.
PRINCIPLES OF LENSES USED IN THE
GSI SYSTEM
There are two types of lenses used in the optical
portion of the GSI system: the Fresnel lens and the
lenticular lens. A discussion of the principles of the
piano-convex lens is provided so the physical characteristics of this type of lens may be compared with the
physical characteristics of the Fresnel lens.
PLANO-CONVEX LENS
A piano-convex lens has a plane, or flat, surface and
a spherical surface. This type of lens is a positive, or
collective, lens; that is, a lens in which the light rays are
collected at a focus to form an image. The radius of the
spherical surface of the lens is known as the radius of
curvature.
TRANSFORMER ASSEMBLY
The transformer assembly is a weathertight
enclosure mounted within 3 feet of the stabilized platform. An interconnecting cable, which is part of the
transformer assembly, connects the transformer
assembly to the GSI. This assembly is located as close
as possible to the stabilized platform. Its purpose is to
step down the voltage for the source light (GSI) from
115 volts ac to 18.5 volts ac.
FRESNEL LENS
The Fresnel lens is a lightweight and relatively thin
sheet of transparent Lucite material. The refraction of
light rays by the Fresnel lens is collective, as in a
piano-convex lens; however, the Fresnel lens differs
from a piano-convex lens, as shown in figure 3-10. One
surface of the Fresnel lens consists of a number of
stepped facets. These facets are circular, concentric
grooves that extend from the center of the lens to the
edges. The slope of each facet is independent of the
slope of all other facets. These slopes are designed to
provide a perfect focus of the light rays that pass through
the lens. Thus, the Fresnel lens provides an advantage
over a piano-convex spherical lens in that the planoconvex spherical lens causes spherical aberration of
GLIDE SLOPE INDICATOR
ASSEMBLY
The GSI assembly consists of two major subassemblies: the mounting base assembly and the
indicator assembly. The indicator assembly is supported
in the mounting base assembly, which is mounted on the
stabilized platform. The incoming system cable connects at the rear of the right-hand heater compartment.
The mounting base assembly provides the means to
accurately position the indicator assembly in relation to
the landing pad. The mounting base is then secured in
this position by the retractable plunger. Indicator elevation is controlled by the elevation adjustment knob. The
GSI sits in the trunnions of the mounting base assembly.
STABILIZED PLATFORM
ASSEMBLY
Figure 3-10.—Comparison of the physical characteristic of
piano-convex lens and Fresnel lens.
The stabilized platform assembly is mounted to the
ship’s deck in close proximity to the helicopter landing
3-7
The second effect that will be observed is that the
motion of the bar of light from the cell center to the
transition line does not appear to be smooth. At higherthan-design temperature, the bar of light disappears in
the observed cell before it starts to appear in the adjacent
cell. At lower-than-design temperatures, the bar of light
disappears into the transition line before a bar of light
starts to appear in the adjacent cell. At extreme temperatures, it is possible to get blank areas or double bars
of light at or near the transition line.
light rays, as illustrated in figure 3-11. When the rays of
light, parallel to the principal axis of a convex spherical
lens, pass through zones near the edge of the lens, the
principal focus occurs at a point that is closer to the lens
than the focus for rays that pass through the lens near
the principal axis. Therefore, the light rays from a planoconvex spherical lens tend to scatter. The Fresnel lens
also can be formed around a suitable radius to minimize
astigmatism. Astigmatism of a lens is the inability of the
lens to bring all the light rays from a point on an object
to a sharp focus to form the image.
The last effect that will be observed is that the
vertical field angle (angle of the lens from top to bottom
as viewed from the front) is larger when the ambient
temperature is higher than design temperature and
smaller when the ambient temperature is lower than the
design temperature. To maintain design characteristics
of the Fresnel lens, the lens-heating compartments are
maintained at a temperature that is relatively constant.
The Fresnel lenses are each enclosed in a separate
compartment in which a lenticular lens serves as the
front and an optical glass serves as the back of the
compartment. Hot air is circulated in the compartment
under thermostatic control.
The optical characteristics of the Fresnel lens will
vary appreciably with a change in temperature. If the
lens temperature is allowed to vary beyond operational
limits, three effects will be observed. First, the size of
the bar of light near the center of the lens is different
from that which is seen near the center of the lens when
the lens is at design temperature. Also, as the observer
moves up or down, the size of the bar of light appears
to change as the image moves from the lens center to the
transition line between cell assemblies. The transition
line is defined as the physical break between the cells.
If the ambient temperature is higher than design temperature, the bar of light at the center appears smaller
than the design bar of light, and it blooms to a largerthan-design bar of light at the transition line between
cells. If the ambient temperature is lower than design
temperature, the opposite conditions occur.
LENTICULAR LENS
A lenticular lens is placed in front of each Fresnel
lens. Each lenticular lens consists of many long, convex,
cylindrical lenses placed side by side, as shown in
figure 3-12. Each individual lens has the same short
focal length. The area in which the light source (the
object) can be viewed is spread by the short focal length
of the lenticular lens. If the object consists of a multiplelight source with spacing between the lights, the object
appears to an observer looking into the lens as a continuous band of light that fills the width of the lens. In
the GSI system, the arrangement of the lenses with
respect to the source lamps and the physical properties
of the lenses cause the source lamps to appear as a single
light image 12 inches wide and approximately 1/2 inch
high. The object appears as a continuous band of light
regardless of the observer’s position in the azimuthal
range of the lenticular lens. The azimuthal range is the
angular position (expressed in degrees) in a horizontal
plane in which a pilot of an approaching aircraft can
observe the band of light. The azimuthal range of the
lenticular lens used in the Fresnel system is 40° (see
fig. 3-12). The appearance of the height of the object is
not affected by the lenticular lens.
The lenticular lens in the GSI assembly is manufactured with three different color segments to eliminate
the need for filters and their subsequent light
Figure 3-11.—Comparison of optical characteristics of
piano-convex lens and Fresnel lens.
3-8
junction point for various cables of the system, as are all
junction boxes that are a part of the system.
SYSTEM OPERATION,
TROUBLESHOOTING, AND
MAINTENANCE
The following paragraphs provide information on
operating, checking-out, troubleshooting, and maintaining the SGSI system. We will discuss some of the
things that can be done to keep the SGSI operating
efficiently.
When troubleshooting the SGSI system, you should
refer to the troubleshooting charts in the Stabilized Glide
Slope Indicator (SGSI) Mk 1 Mod 0 (Incorporating
Gyro Failure Alarm) for Air Capable and Amphibious
Assault Ships, NAVAIR 51-5B-2, technical manual. By
using the charts/tables in the technical manual for overall system checkout procedures, you will know what
controls must be set during the performance of the
checkout procedure. These tables also list the location
of each control, the necessary instructions for the proper
use of these controls, and the normal indications that
should be observed during the operation of these controls. When an abnormal indication is observed during
the checkout procedures, certain additional procedures
must be performed that use the controls available within
the equipment to establish conditions that enable maintenance personnel to isolate malfunctions with a minimum use of test equipment. By using these procedures,
Figure 3-12.—Optical characteristics of the lenticular lens.
attenuation. The top segment is colored green, the
middle segment is amber, and the large bottom segment
is colored red. When projected, the resulting glide path
has the viewing zone as shown in figure 3-13. The GSI
cell was designed so 1 inch on its face is equal to 1° of
arc. Thus, the 1° amber is 1 inch on the cell face.
The stowlock assembly provides a means of
securing the source light indicator in a fixed position
when the system is not in operation. The stowlock
assembly is located directly below the source light
indicator assembly and is secured to the deck-edge
boom. The shipbuilder’s junction box is used as a
Figure 3-13.—Viewing zone of glide slope indicator.
3-9
you can locate the cause of the specific malfunction and
perform the recommended corrective maintenance.
Maintenance is an ongoing process to keep the
equipment operating effciently and consists of preventive and corrective maintenance. For all maintenance requirements for the SGSI system, you should
refer to the maintenance requirement cards (MRCs).
There are maintenance items to be performed weekly,
quarterly, semiannually, and annually. System maintenance must be performed on a regular basis regardless
of use cycle. Deterioration and/or damage to equipment
may result if system maintenance is not performed
regularly. The information given in the following paragraphs is not intended to replace preventive maintenance cards or the applicable technical manuals. This
information should familiarize you with some of the
requirements and procedures to keep the equipment in
top notch operating condition.
Figure 3-14.—Vertical gyro, simplified schematic.
GYRO ALARM OFF
When the flywheel of the gyroscope is rotating at
high speed, its inertia is greatly increased. This causes
the flywheel to remain stationary within the gyro gimbal
structure. To align the gyroscope flywheel to the local
earth gravity vector (downward pull of gravity), a
pendulum sensor is attached under the spinning flywheel. In operation, the pendulum is held suspended
within a magnetic sensor with the magnetic sensor
measuring the difference between the pendulum axis
and the spin motor axis. The sensor output is amplified
and used to drive a torque motor that causes the gyro
flywheel to rotate in a direction to reduce the sensor
output. In actual operation, the pendulum sensor is
affected by lateral accelerations that cause it to oscillate
about true position. To correct for this oscillation, the
gyro circuits time constants are long. The long time
constants cause the gyros flywheel to ignore periodic
variations of the pendulum and align itself to the average
pendulum position. Figure 3-15 shows the essential
elements of the gyro.
If a failure occurs in the error sensing circuitry or if
the ship’s gyro information or gyro reference voltage is
not being sent to the SGSI, a ready light cannot be
obtained. This will keep the lamp relay de-energized and
not allow the source lamps to illuminate. Operation in
the internal gyro mode is still possible through the
activation of the gyro alarm off switch-indicator on the
component panel assembly. Since the gyro alarm off
switch-indicator disables the independent failure detection circuit, a gyro alarm off indicator is automatically
illuminated in both the electronic enclosure and the
remote control panel. Servo error sensing is not affected
by activation of gyro alarm off. Depressing the gyro
alarm off push button will activate the ready light and
allow the source lamps to illuminate if no other system
problems exist.
GYRO FAILURE ALARM CIRCUIT TESTS
These tests are to be performed once a week when
the SGSI is being used for air operations. These tests
will ensure that all failure monitoring circuits are
operational.
CELL ALIGNMENT
For a pilot to use the SGSI for an accurate landing,
the cell must be properly aligned. There are two adjustments necessary for this alignment. One adjustment is
focusing the cell and the other is setting the beam angle
in reference to the GSI base plate.
VERTICAL GYROSCOPE
The vertical gyroscope is basically a mechanical
device. The essential element of the gyroscope is a
flywheel rotating at high angular velocity about an axis.
The flywheel is mounted within gimbals that allow it
two degrees of freedom as shown in figure 3-14.
Cell Focusing
As shown in the simplified cell schematic, figure 3-16, you can see that by moving the light mask into
3-10
Figure 3-15.—Vertial gyro, schematic diagram.
Figure 3-16.—Simplifled cell schematic.
or away from the colored filter changes the sensitivity
of the cell. The sensitivity can be defined as how fast the
light bar will appear to move in the cell as an observer
traverses from the bottom to the top of the cell. If the
light mask is close to the colored filter, the sensitivity is
decreased and the angle that a viewer would move
through in going from the bottom to the top of the cell
is increased. If the light mask is moved away from the
colored filter, the sensitivity is increased and the angular
coverage of the window decreases.
3-11
At the same time the cell is focused it can
be calibrated for proper glide slope. Referring to figure 3-19, you can see that the same screen arrangement
can be used for measuring the angle of the red/amber
inter- face.
Thus, the cell can be focused and the sensitivity set
by moving the light source and slots in relation to the
colored filter (fig. 3-17). In the GSI cell, the distance
from the slots to the Fresenel lens is 16.8 inches. The
cell is calibrated so the 1-inch amber section of the
lenticular lens is exactly 1 degree of arc. A typical cell
calibration setup is shown in figure 3-18.
Set the baroscope supplied with the system on top
of the level plate and mark off a reference mark on each
screen. Adjust the cell glide angle using the knurled
knob under the lamp housing until the difference between the reference mark on the red/amber interface on
To focus the cell, it must be placed on a level plate
and two screens 10 feet (±1/8 inch) apart must be set up
in front of the cell (see fig. 3-18). Turn the cell on and
measure the height of the amber at screen one and
subtract it from the height of the amber at screen two
(fig. 3-19). If the cell is properly focused, the difference
should be 2-3/32inch±1/8 inch. A dark band will appear
between each of the colors due to light scattering at the
interface; this band should be split evenly to obtain
height measurements.
screen two is equal to 6-9/32 inches ±7/32 inch. Drill
and pin the degree plate so it indicates three degrees.
In this measurement, the cell should project the
beam on the two screens and the center of the dark band
between the red and amber filter should be used for all
measurements.
The slot through which the light bar is formed
determines the size of the light bar as it is viewed
through the cell face. In this system, it is not adjustable.
Beam Angle
The angle of the light beam to the horizon must be
accurate and remain constant so a pilot may maintain a
fixed rate to the ship. The glide slope angle is set using
the degree plate on the right side of the cell and is
checked on-the platform by means of pole checks to
ensure the proper settings.
THERMAL CONTROL
Temperature control of the GSI includes cooling
of the projection lamp compartment and temperature
Figure 3-17.—Gulide slope indicator, simplified functional diagram.
3-12
Figure 3-18.—Typical cell calibration setup (overhead view).
Figure 3-19.—Cell focusing measurements.
maintaining a weather seal to keep moisture, dirt, and so
on from entering. Cool air is drawn in through the rear
louver by the blower fan, and exhausts through the side
louver after absorbing heat radiated by the projection
lamps.
regulation in the lens compartment. These are discussed
in the following paragraphs.
Projection Lamp Compartment Cooling
The three projection lamps used in the GSI generate
large amounts of heat when they are operated at full
intensity. Cooling of this compartment is accomplished
by a blower/louver arrangement. A special design louver
assembly is located on each side of the projection lamp
shroud This design allows entry of cooling air while
Lens Assembly Temperature Control
Temperature control of the Fresnel/lenticular lens
assemblies is important to prevent lens distortion fogging, or other environmental reactions. In the GSI, lens
3-13
TRANSFORMER
temperature control is achieved by blowers, heaters, and
thermal switches.
are set at 100 +10°F. To keep this temperature constant,
The GSI uses three 21-volt 150-watt projection
lamps for its light source. This is about 21 amps of
current and would cause considerable voltage drop if
long cables were used, thus the transformer assembly is
mounted close to the GSI light and uses a fixed length
of cable (10 feet) from the transformer secondary to
the GSI cell connector. The system autotransformer
supplying the primary voltage to the transformer is
located in the remote control panel. A simplified
schematic is shown in figure 3-21.
S1 and S2 open and close as the temperature rises and
STABILIZED PLATFORM SYSTEM
The temperature control circuits (see figs. 3-20 and
3-21) are used to regulate operating temperatures in the
GSI assembly. When power is applied at the remote
control panel, voltage is applied to the heaters and
blowers to the left and right of the lens assemblies.
Blower motors B1 and B2 begin to operate as soon as
voltage is applied. Control thermoswitches S1 and S2
falls in the GSI assembly. As the thermoswitches open
The stabilized platform system is an electrohydraulic served platform used to stabilize the GSI
against the ship’s pitch and roll. This keeps the tricolored
GSI light at a fixed angle to the horizon. The
stabilization is termed a one-to-one stabilization system.
This means that for each degree of pitch or roll of the
and close, power is removed from or applied to heaters
H1 and H2. If S1 and S2 fail to open, backup thermoswitches S3 and S4 will open, preventing damage to the
lenses. A simplified schematic of the cell wiring appears
in figure 3-20.
Figure 3-20.—GSI cell, simplified schematic.
3-14
Figure 3-21.—Cell power.
be set to internal gyro for internal stab-leek operation.
ship, the platform pitches or rolls an equal amount in the
opposite direction. Thus, the platform remains level to
the horizon or more precisely perpendicular to the local
earth gravity vector.
While in this mode, the test switches and manual drive
potentiometer can be operated to enable insertion of
signals independent of the local gyro. This mode enables
the operator to isolate and test various parts of the system
Operational Modes
while disabling other parts.
SHIP GYRO STABILIZATION MODE.- Ship
The system has four operational modes: internal
gyro, internal gyro stabilization lock ship gyro, and ship
gyro stabilization leek.
gyro stabilization is provided as an alternative to platform-mounted internal gyro stabilization. The system
should be operated in the internal gyro mode unless
SGSI SYSTEM NORMAL OPERATING
PROCEDURE.- Stabilization from the internal gyro
is the normal mode of system stabilization and is
preferred to ship gyro mode because of higher system
accuracy and addition of the gyro failure alarm. The
system should always be operated in this mode as
opposed to ship gyro operation unless a system failure
prevents it. Operating control is normally conducted
from the remote control panel from which the operator
can turn the system on and vary the intensity of the
source light. The system may also be turned on at the
electronics enclosure assembly when the POWER
ON/OFF push button is depressed. Adjustment of the
source light intensity, however, can only be adjusted
at the remote control panel. The normal mode is the
interred gyro mode, where the gyro acts as the system
sensor detecting any eviations from platform level. In
this mode the platform will always remain level and
cannot be offset.
component failure disables that portion of the circuitry
since switching to the ship’s gyro reduces system
accuracy. The internal gyro/ship gyro switch-indicator
is on the component panel assembly. A ship gyro indicator on the remote control panel serves to remind
system operators when the alternative stabilization
source is in use.
SHIP GYRO STABILIZATION LOCK
MODE.- The ship gyro stabilization leek mode disconnects the ship’s gyro signals at the input to the gyro
signal card assembly and replaces them with ground
reference or manual drive potentiometer signals. This
permits check-out and troubleshooting of ship gyro
stabilization and stabilization error detecting circuitry.
The internal gyro/ship gyro switch-indicator on the
component panel assembly should be placed in the ship
INTERNAL GYRO STABILIZATION LOCK
MODE.- The internal gyro stab-leek mode disconnects
internal gyro signals from the stabilization loop and
locks the platform in a neutral position for test, alignment, and troubleshooting purposes. The system must
gyro position to enable the stabilized platform to track
manual drive signals. The lamp control relay
extinguishes GSI source lamps while operating in this
stab-leek mode.
3-15
and used to drive the output in a direction to reduce the
error.
Platform Configuration
The stable platform consists of a flat top plate to
which the GSI is affixed. The top plate is attached to the
base plate through a universal joint and a center post and
is moved by two hydraulic actuators that are coupled to
the top plate with two axis rod ends. The universal joints
and rod ends allow the platform to tilt in two axes. These
are designated pitch and roll to match ship motions for
which the platform compensates. Figure 3-22 illustrates
a platform compensating for a roll motion, showing the
major components of the platform.
Assuming the input and output pots are initially
equal, then the difference in voltage is zero and there
is no error. If the input command pot is moved, then
an error is generated. The amplifier amplifies the error
and drives the power actuator that moves the output
pot in a direction to reduce the error. Thus, in a
feedback system, the output can be made to follow the
input. This type of feedback system is often referred
to as a servo loop.
The GSI stable platform uses two servo loops in
each axis, the gyro loop and the LVDT loop. In the gyro
loop, the gyro is used as an error detector sensing the
downward pull of gravity at its particular location. his
is termed earth’s local gravity vector. The gyro lines
itself up with this downward pull and any difference
between the gyro case and its internal reference provides
an output. This output is used as an error signal to correct
the platform top to earth level.
SERVO LOOPS
To understand the system operation, you need to
have an understanding of feedback control systems. A
feedback control system is a system where an input
signal is compared with the system output and an error
signal is generated. This error signal is then amplified
Figure 3-22.—Functional diagram of the stabilized platform assembly.
3-16
Figure 3-23.—LYDT servo loop.
Figure 3-24.—Stabilization circuits, block diagram.
The LVDT loop is quite similar to the gyro feedback
loop, only the sensor is changed Figure 3-23 shows that
the LVDT is mechanically connected to the actuator to
sense its position pot. The feedback signal from the
LVDT is connected to the error detector. The LVDT has
as its input either zero (stab-lock) or a signal from the
manual position pot. With the manual position pot
switched out of the circuit, the input to the error detector
is zero (ground). The LVDT is adjusted so its output is
zero when the platform top is level to its base, thus errors
are only generated when the LVDT has an output and
these are amplified and drive the output to zero.
In operation, any voltages measured in the servo
loops are small and are proportional to the system
error.
The complete system servo feedback loop (single
channel) is shown in figure 3-24. This incorporates both
the gyro and stab-lock loops and the switching between
them.
3-17
The op-amps used in this system are integrated
circuit types using a configuration as shown in figure 3-26.
Figure 3-25 shows the signal flow in the servo loop.
For example, in gyro normal mode, the gyro is powered
through the gyro power switch and the gyro erection
amp. The gyro synchro signal is converted to dc in the
gyro demodulator and goes through the stab-lock relay
into the servo amplifier. The servo amplifier drives the
servo valve that moves the cylinder to correct platform
position. Any servo errors are compared in the error
circuit and trigger the error relay if the errors are large
enough. The error relay will turn on the NOT READY
light and turn off the GSI light. Stab-lock mode is similar
and can also be followed on figure 3-25.
An op-amp is a very high gain device, whose output
is the amplified difference between the inverting and
noninverting inputs. If feedback is added, the op-amp
will try to keep the voltage difference between the two
inputs near zero.
The most common form of op-amp is the inverting
amplifier, as shown in figure 3-27. With the noninverting input tied to ground, the inverting input will be
close to ground and is referred to as a virtual ground.
The higher the amplifier gain, the closer the point will
be to ground and for all computations it is assumed to
be ground. If an input voltage (Vin) is applied to the
circuit of figure 3-27, a current will flow in R in. The
amplifiers will amplify and invert the current and provide an output voltage. The output voltage will cause a
current to flow in RF that will exactly cancel that flowing
through Rin. If the currents do not cancel, the difference
between them will be amplified until they do.
OPERATIONAL AMPLIFIERS
Operational amplifiers (op-amps) are used throughout the stable platform system as amplifiers, oscillators,
and comparators. To understand the different circuits,
you need to have a basic understanding of op-amps. An
operational amplifier is a high gain (10,000 or greater),
highly stable, dc amplifier. It is used most often to
perform analog computer functions such as summing
and integration.
Multiple input circuits are similar to the inverting
amplifier circuit. The gain of each input is controlled by
Figure 3-25.—Stabilization control-signal flow.
3-18
Servo amplifiers
Dither oscillator
Error circuit
Gyro alarm circuits
Gyro signal card
Source light failure detector
Power distribution circuits
Gyro Demodulator
The gyro demodulator is a nonrepairable item. The
gyro demodulator receives 115-volts ac, 400-Hz
reference signals from stator leads S1 and S3 of the pitch
and roll synchros in the gyro. The demodulator converts
the ac synchro signals to dc with the in-phase ac signal
positive and the out-of-phase signal being negative. This
type of demodulator is called a phase-sensitive rectifier.
For an in-phase signal, the device behaves as a bridge
rectifier with a capacitor falter to remove ripple.
Figure 3-27.—Inverting amplifier diagram.
The internal gyro synchros that feed the demodulator are excited with 26 volts ac, 400 Hz and have a
maximum output between S1 and S3 of 11.8 volts ac at
±90° rotation. When the signals are demodulated by the
gyro demodulator, the output is ±10 volts dc at ±90° of
rotation from horizontal.
its input resistor and the feedback resistor with the inputs
added.
No voltage greater than 15 volts should be applied
to any pin of an op-amp or damage will result. The
op-amps output is short-circuit protected; thus, shorting
the op-amps outputs will not damage them. Op-amps
exhibit three common types of failures: no output,
saturated positive, and saturated negative. A saturated
voltage is one that is maximum for a particular op-amp
usually greater than 11 volts. Any op-amp whose output
is greater than 11 volts and does not change with varying
inputs may be defective. Check for large inputs and open
feedback resistors before replacing the op-amp.
Linear Voltage Differential Transformer
The LVDT is an ac electromechanical transducer
that converts physical motion into an output voltage
whose amplitude and phase are proportional to position.
In operation, an ac excited primary winding is
coupled to two secondary windings by a moveable core
placed between them (fig. 3-28). Displacement of the
SYSTEM ELECTRONICS
The GSI system electronics is divided into 13
fictional areas as follows:
Gyro demodulator
LVDT
LVDT demodulator card
LVDT oscillator
Figure 3-28.—LVDT aimplified schematic
LVDT demodulator
3-19
charged positive. The noninverting integrator IC3-1 will
charge C1 so its output goes positive. This positive
voltage will cause the inverting integrator IC3-2 to
charge its capacitor C2 and its output will go negative.
This negative voltage will discharge C3. This will continue until C3 is charged negative and then reverse,
causing the circuit to oscillate. The zener diodes clamp
the output and stabilize the amplitude so the output
voltage is a stable 6.5 volts ac.
core from its null position causes the voltage in one
winding to increase, while simultaneously reducing the
voltage in the other winding. The difference between the
two voltages varies with linear position.
LVDT Demodulator Card
The LVDT demodulator card supplies a constant
voltage ac excitation to the LVDT primaries and converts the pitch and roll LVDT amplitude and phase
signals to a variable dc voltage. This is accomplished in
three separate circuits: the LVDT oscillator and the pitch
and roll demodulators.
LVDT Demodulator
The pitch and roll LVDT demodulator are identical
except for their gains. They are called phase sensitive
demodulators. The input to the demodulator is a variable-voltage, variable-phase signal from the LVDT. This
signal is full-wave rectified and filtered and its output
polarity is positive for signals out of phase with the
reference and negative for signals in phase.
LVDT Oscillator
The LVDT oscillator consists of a quadrature oscillator and a power amplifier. The quadrature oscillator is
used to generate a constant-amplitude, constantfrequency sine wave. The power amplifier is a lowoutput-impedance driver used to power the LVDT
primaries and the pitch and roll demodulator diode
switches.
Servo Amplifiers
The pitch and roll servo amplifier circuit cards are
identical except for the gains and servo compensation.
Three inputs are summed into amplifier A1: LVDT,
To understand the operation of the quadrature
oscillator, assume capacitor C3 of figure 3-29 is initially
Figure 3-29.—LVDT quadrature oscilitator.
3-20
reference voltage that represents the maximum allowed
system error. If it is exceeded the system will go from
ready to not ready and turn out the GSI light. System
errors existing during turn-on would trigger a false not
ready light. To prevent this, a delay is included in the
error circuit.
gyro/manual control, and rate gyro. In normal operation,
only gyro signals are used. In stab-lock mode, the LVDT
signal is the input with manual control being used for
testing.
The zero adjustment on the two amplifiers are used
to reduce any offsets in the amplifiers to zero. The
compensator circuit (R3-C1) is used to reduce the system gain at higher frequencies. At high frequencies, the
capacitor will act as a short circuit and the op-amp gain
will be cut in half. Amplifier A2 is used as a voltage-to-current driver. This is necessary because the
servo valve is current controlled. The current driver
(A2) circuit is similar to the voltage amplifier previously
described.
A schematic of the error circuit is shown in figure 3-31. Errors may be of either polarity; thus the
op-amp A3 accept signals on both its inverting and
noninverting inputs. If the servo error is positive and on
the roll axis, it will pass through diode CR7 and resistor
R12. This voltage will be added to the reference voltage
set on pot R8. If the reference is greater than the error,
the output of op-amp A3 will be positive. Its amplitude
will be 3.25 times the difference of the error voltage
minus one half the reference.
When a voltage is applied to the amplifier input, a
current flows in the servo valve coil and through resistor
R12. The current in R23 causes a voltage drop across
itself. This voltage is provided as feedback to the input
through R11. If 1 volts dc is applied to TP-B, a current
will flow through R12 to generate 1 volt across it since
R11/R8 = 1.R12 is 105 ohms, so the current in R12
for 1-volt input is approximately 10 ma (fig. 3-30). The
other input to A2 is from the dither oscillator and is
attenuated by a voltage divider.
Servo error gain is 7.5. Capacitor C5 averages out
the varying error signals so short-term errors (spikes) do
not trigger errors. The output of op-amp A3 drives
transistor switch Q1, which turns on the error relay. In
its energized state, the error relay turns on the remote
panel READY lamp and actuates the GSI lamp control
relay.
The delayed start circuit is charged when the system
first goes into ready. Capacitor C7 keeps the system in
ready (error relay energized) for about 6 seconds to
allow the system errors to settle out.
Dither Oscillator
The dither oscillator provides a high-frequency
(compared to system response) signal to the servo valves
to keep them in constant motion to prevent sticking at
null.
Gyro Alarm Circuits
The SGSI system incorporates an independent failure detection circuit that detects any failure that will
result in a loss of stabilization. It does this by comparing
an input from the ship’s gyro with the output of the
platform LVDT. When the system is operating correctly
in the internal gyro mode, the output of the LVDTs is
directly proportional to the ship’s motion. If the ship’s
motion from the LVDTs is out of phase (reverse polarity)
to the ship motion from the ship’s gyro, the two will
cancel. Any voltage left over from the summation will
be the error between the ship gyro and the platform. The
error is compared against a preset limit, and if it exceeds
this limit the platform error relay is tripped. The ship
gyro input is required for the gyro alarm and is also used
for ship gyro stabilization and for the rate lead. The rate
lead circuits are used to reduce velocity lag of the
platform and increase system dynamic accuracy. In the
ship gyro stabilization mode, the system operates at a
reduced accuracy due to null errors and LVDT linearity
error. Therefore, the ship gyro mode is to be used as a
backup mode only.
The dither oscillator is a phase shift oscillator. It
depends on the phase shifts inherent in RC networks to
shift the phase of the amplifier feedback 180°. This will
cause a sustained oscillation if the amplifier gain is high
enough. The gain also determines the quality of the sine
wave.
Resistor R5 (amplifier gain control) is adjusted
until the amplifier starts oscillation and has a clean sine
wave with no flattening of the tops. The zener diode acts
as an upper limit for the amplitude. The relay on the
dither oscillator is parallel to the stab-lock relay, which
controls the rate gyro information.
Error Circuit Card
The error circuit card is used to monitor the pitch
and roll servo errors. It allows monitoring of the gyro’s
internal pendulum reference for test purposes. Since the
system is not perfect, servo errors are present. Voltages
representing system errors are compared with a
3-21
3-22
3-23
The gyro alarm failure alarm circuit can be disabled
by pushing the gyro alarm OFF push button. This
supplies +15 volts dc to one side of the error relay and
effectively disconnects the gyro failure alarm circuits.
In addition an interlock circuit prevents unwanted platform oscillation when the alarm circuit is not actuated.
A simplified signal flow diagram of the gyro alarm
circuits is shown in figure 3-32. The switches are shown
in the normal mode of operation; namely, internal gyro
operation with the failure alarm armed The gyro alarm
circuit is only tied to the system in this mode by the
system supplies and the error relay. In operation, the ship
gyro signal is converted to a dc signal in the linear
synchro to dc converter (F110/F111). This signal goes
through the ship gyro stab-lock switch, is amplified in
the F106 card and is summed with a scaled voltage from
the platform LVDTs and an offset voltage that makes up
for alignment differences between the ship gyro and the
platform base. This summed signal (error voltage) is
applied to the F110/F111 card, full-wave rectified,
faltered and compared against a preset threshold. If
the error voltage exceeds the preset threshold, the
comparator trips and removes the +15 volts from the
error relay. This turns off the SGSI cell and gives a not
ready indication at the remote panel. The comparators
on the F110/F111 cards are electrically latching relays.
If the error is removed, these relays can be reset by
pushing the gyro alarm reset button to remove latching
voltage.
Gyro Demodulator Board
The gyro demodulator board contains a synchro to
dc converter and a gyro error detector circuit. The F110
and F111 are identical cards: one is used in the pitch
channel and the other in roll. The synchro to dc converter
is a sealed module not repairable by shipboard personnel.
Gyro Error Detector Circuit
The gyro error detector circuit consists of a precision N-wave rectifier, a filter, a voltage comparator,
a transistor, and a relay. The input signal to this card is
the summation of the ship’s gyro and the platform
LVDTs.
Figure 3-32.—Cyro alarm circuits—signal flow.
3-24
pressurized with dry nitrogen to 700 psig for the high-pressure accumulator and 38 psig for the low-pressure
accumulator.
Gyro Signal Card Assembly
The gyro signal card (F106) amplifies and sums the
demodulated pitch and roll synchro signals from the
ship’s gyro with the platform LVDT outputs. It also
provides offset adjustments to make up for any
difference in alignment between the ship’s gyro and
platform. In addition, rate lead signals are derived by
differentiating the ship gyro signals.
When hydraulic pressure is applied, the accumulator falls with fluid and the bladder is compressed until
the dry nitrogen charge pressure equals that of the
hydraulic system. In this system, it is 1400 psig. Because
of the bladder compression, the accumulator will absorb
pressure fluctuations and prevent hydraulic hammer. If
the system momentarily requires a higher flow than the
pump will supply, the accumulator will provide it and
be recharged when the demand has passed.
Source Light Failure Detector
The source light failure detector is a circuit that
monitors the voltage and current going to the three
source lights. When one or more of the source lamps
fail, the source light failure indicator on the remote panel
is illuminated
Hydraulic Cylinder
The hydraulic cylinders used in this system are
linear actuators. Hydraulic fluid gaited by the servo
valve will push the piston in either direction. The
hydraulic pressure exerted by the piston is 1400 psig in
extension and 700 psig in compression. Extreme care
must be exercised when working on the system due to
the amount of force available.
Power Distribution Circuits
The system requires two power sources from the
ship 440-volts ac, 60-Hz, 2.7-amp power for the pump
and 115-volts ac, 60-HZ, 15-amp power for the rest of
the system. In standby (system circuit breaker on), the
system heaters and standby lights are on. When the
POWER ON push buttons are depressed, the internal
power supplies are energized except for the ±15 volts
The cylinder is an inherently reliable device requiring little maintenance in normal use. However, the only
required maintenance is cleaning dirt and grit off the
actuator rod and tightening the packing gland nut if a
leak develops. Do not overtighten the gland nut or the
packing will bind on the rod, causing the cylinder to
chatter in operation. If cylinder replacement becomes
necessary, the defective cylinder must be returned
through supply charnels for overhaul.
dc. The ±15 volts dc supply is energized after the time
delay relay has timed out, the hydraulic pump is running,
and system hydraulic pressure is normal. Then, the
hydraulic pressure switch is actuated.
HYDRAULIC COMPONENTS
System low-amplitude vibration, or chatter in some
cases, may be traceable to cylinder internal binding; in
which case the cylinder should be replaced.
The SGSI system uses hydraulic pressure for
motive power. A constant-pressure, variable-delivery
hydraulic pump supplies hydraulic pressure. Pressure
fluctuations are dampened by accumulators. The fluid
is gaited by servo valves into either side of the hydraulic
cylinders. The fluid pressure then causes the cylinders
to move the platform.
Servo Valve
Servo valves are commonly used in closed-loop
servo systems. They control the flow of fluid to or from
the load actuator in proportion to the impact current
signal to the valves’ torque motor.
The hydraulic system is sensitive to dirt and other
contaminants. Therefore, care must be used when
adding fluid or opening any part of the hydraulic system.
Hydraulic Pump
Refer to the hydraulic pump assembly shown in
figure 3-9 when studying the following paragraphs.
The hydraulic pump used in this system is a constant-pressure, variable-delivery pump. It is similar to a
constant voltage source in which current will vary upon
demand. Referring to figure 3-9, hydraulic fluid is
gravity fed from the reservoir to the pump unit through
the pump case fill piping to ensure that the pump case is
full at all times, thus keeping air out of the line. The
motor-driven pump draws fluid through a suction
Hydraulic Accumulator
The hydraulic accumulators used in this system are
steel cylinders with internal rubber bladders. Before
putting the accumulators in service, the bladders are
3-25
Hydraulic Fluid Heater
strainer, located in the reservoir, into the pump where it
is pressurized to 1400 psi and applied to the hydraulic
pressure line. A fluid flow filter removes solid impurities
greater than 3 microns in size. In the event the filter
becomes clogged, it is bypassed. The filter output then
flows past the pressure gauge, the pressure switch, and
the bypass valve. The pressure gauge should indicate
1400 psi in normal operation, and the pressure switch
should be closed for pressures above 1200 psi. The
bypass valve is normally closed and will open only if
the pressure exceeds 1800 psi.
The fluid heater is a 175-watt immersion-type
heater. The fluid must be kept at approximately 70°F or
greater to prevent it from becoming too viscous and
causing servo errors. The heater is a Calrod type with a
built-in thermostat. The thermostat is normally factory
set but may be adjusted if necessary. To adjust the heater,
unscrew the cover plate by turning counterclockwise
and use the internal screwdriver adjustment to set the
temperature. It will take about a half hour for the temperature to stabilize.
If the pump is operating normally, the bypass valve
will be closed and the fluid will flow through the check
valve and out the gate valve to the system. The check
valve is a one-way valve. The fluid returning from the
system flows through the return gate valve and check
valve into the reservoir. The return check valve only
allows fluid to flow in one direction and requires 75 psi
of pressure before it will open. This maintains the return
line pressure at 75 psi.
Overtemperature Switch
The overtemperature switch is a mechanically
adjustable immersion-type thermoswitch. It is used to
indicate overheating of the pump oil. It does not indicate
a direct failure. In a warm environment of approximately 85°F the oil temperature will be about 120°F. An
increase in oil temperature will most likely be due to
increased fluid viscosity or a clogged pump falter. If this
is the case, the pump should be drained and flushed with
warm water, and the fluid and filter replaced.
For the pump, heater, and overtemperature switch
to operate properly, the fluid reservoir must be properly
filled. Too little fluid may actually cause the pump to
overheat.
The overtemperature switch is adjusted by prying
the cap off the protruding stem and inserting a screwdriver in the stem.
Pump Motor Contactor
The motor controller usually has 440 volts ac
applied to it. The pump is actuated by applying 115 volts
ac to the motor controller relay. The pump motor is
protected by thermal overloads, located in the motor
controller. A thermal overload is a relay that is actuated
by heat. Motor current flows through a low-value
resists, generating a small amount of heat. If the current
increases beyond a specified value (3.7 amps), the heat
generated will melt a solder bond on a ratchet wheel,
which holds back a spring-loaded relay. This will cut the
pump power by opening the circuit to the motor control
relay. The thermal relay should then be allowed to cool
before pushing the reset button on the pump controller.
Hydraulic Pressure Switch
The hydraulic pressure switch is a single-pole,
double- throw, pressure-actuated switch. It is used to
turn on the system electronics when there is enough
pressure to stabilize the system. It is normally set to
actuate at 1200 psi.
The pressure switch is adjusted by turning the label
until the inner body is exposed. It can be turned with a
screwdriver or other instrument inserted in the inner
body holes. The pressure switch setting is decreased by
turning the inner body counterclockwise as viewed from
the connector end.
The pump motor is factory wired for 440-volts ac
operation and should not be changed as the motor controller current limits are set for 440-volts ac operation.
The hydraulic pressure switch is a nonrepairable
item that must be replaced if it is not operating properly.
3-26
CHAPTER 4
TECHNICAL ADMINISTRATION
CHAPTER LEARNING OBJECTIVES
Upon completion of this chapter, you should be able to do the following:
ibration.
Recognize the procedure to follow for requesting
calibration of equipment.
Identify the calibration echelons established for
Describe the different calibration statuses of
equipment.
Describe the system used for equipment cal-
calibrating equipment.
Describe the procedures in updating equipment
calibration schedules.
Describe the Metrology Automated System for
Uniform Recall and Reporting (MEASURE)
program.
Recognize the procedures used to instruct IC
watch standers.
As an IC Electrician Second Class, your administrative responsibilities will include updating various
forms and schedules concerning equipment calibration.
You will also be responsible for instructing your personnel on IC watch standing. This will include ensuring that
your personnel are informed of safety precautions and
procedures to follow when they are standing the various
IC watches. Therefore, this chapter will give you some
background on the Navy Metrology and Calibration
(METCAL) program, the Metrology Automated System
for Uniform Recall and Reporting (MEASURE) program, and IC watch standing, which will include
electrical safety.
success of our Navy depends on the use of accurate and
reliable measuring instruments, and the best way to
assure continued accuracy is by periodic calibration
performed by skilled technicians.
The increased complexity of ship systems
(especially weapons, propulsion, and navigation) has
made it necessary to improve the quality and accuracy
of measurements. Problems existed in measurements
because the measurements of one activity did not agree
with those of another activity even though identical
items were being measured. In such cases, there was a
tendency to “write off” the discrepancies as variations
in the measuring instrument. But, in fact, most of any
discrepancy was due to the lack of standardized
measurements. It was the purpose of standardizing
instrument measurements that the Navy METCAL
program was established. This program emphasizes the
need to complete measurement standardization
throughout the Navy.
THE NAVY METROLOGY AND
CALIBRATION PROGRAM
Metrology is the science and art of measurement for
the determination of conformance to technical requirements. It includes the development of standards and
systems for absolute and relative measurements. Although measurement methods have changed considerably since ancient times, the basic concept of using
calibration to maintain the accuracy of tools and
measuring devices to manufacture quality products and
maintain quality performance has not changed.
The Navy has established the METCAL program to
ensure traceability and accuracy of instrument
calibration to the National Institute of Standards and
Technology (NIST). To operating personnel, this means
that any instrument used aboard ship for quantitative
measurement must be calibrated and that the standards
used are more accurate than the shipboard instruments.
The accuracy of a standard must be traceable, through
documentation by each higher calibration activity, to the
Calibration assures us that our weapon systems are
working right and that the parts obtained from different
manufacturers will fit together as they should. The
4-1
STANDARD
NIST. Each instrument calibrated (including standards)
must bear evidence that it is in calibration. This evidence
is in the form of a calibration label affixed to the
instrument. This label provides the date and place of
calibration and the next due date for calibration. The
METCAL program provides for periodic calibration of
most instruments. The responsibility for assignment of
these periodic calibration intervals has been given to the
Metrology Engineering Center (MEC).
A standard is a laboratory-type device that is used
to maintain continuity of value in the units of measurement. Its accuracy is ensured through periodic comparison with higher echelon or national standards. A
standard may be used either to calibrate a standard of
lesser accuracy or to calibrate test and measurement
equipment directly.
The calibration of all measuring devices is based on,
and is dependent upon, the basic international and
national standards of measurement. Since we cannot
rush off to the NIST every time we need to measure a
length, a mass, a weight, or an interval of time, the NIST
prepares and issues a great many practical standards that
can be used by government and industry to calibrate
their instruments. Government and industry, in turn,
prepare their own practical standards, which are
applicable to their own requirements. Thus, there is a
continuous linkage of measurement standards that
begins with the international standards, comes down
through the national standards, and works all the way
down to the rulers, weights, clocks, gauges, and other
devices that we use for everyday measurement.
TRACEABILITY
Traceability is the unbroken chain of properly
conducted and documented calibration of equipment
from the fleet through higher echelons to the National
Bureau of Standards (NBS).
TEST AND MONITORING SYSTEMS
Test and monitoring systems (TAMS) are the
instruments used for all quantitative measurements
except metrology standards. TAMS can also be referred
to as precision measurement equipment (PME), test and
measuring equipment (T&ME), or test, measuring, and
diagnostic equipment (TMDE).
For further information and detailed assignment of
the METCAL program, refer to NAVMAT Instruction
4355.67.
OPERABLE EQUIPMENT
Operable equipment is equipment that before being
submitted to calibration is found by review of its performance history and by cursory electrical and physical
examinations to be operational in all its required
functions.
CALIBRATION TERMS AND
DEFINITIONS
Before proceeding, it is necessary for us to discuss
some of the commonly used terms associated with the
instrument calibration program used by the Navy. It is
important that you understand the meaning of these
terms and use them correctly. Many of these terms will
be used throughout this text. Other very important terms
are listed in the glossary, appendix II. Refer to it as often
as necessary.
INCIDENTAL REPAIRS
Incidental repairs are those repairs found necessary
during calibration of an operable equipment to bring it
within its specified tolerances. These include the
replacement of parts that, although worn sufficiently to
prevent calibration, do not otherwise render the
equipment inoperative. This repair work is normally
performed incidental to the calibration of standards.
CALIBRATION
Calibration is the act of comparing a measurement
system or device of unverified accuracy to a
measurement system or device of known and greater
accuracy to detect and correct any variation from
required performance specifications.
TRACEABILITY OF STANDARDS
The U.S. Department of Commerce, National
Institute of Standards and Technology, located at
Gaithersburg, Maryland, is the focal point in the federal
government for maintaining and advancing standards
and technology for the physical and engineering
sciences. NIST provides the common reference for
Navy scientific measurements and certifies the
The calibration process involves the use of
approved instrument calibration procedures (ICPs). It
includes any adjustments or incidental repairs that are
necessary to bring a standard or an instrument being
calibrated within specified limits.
4-2
NAVY CALIBRATION LABORATORIES
(SHORE)
standards used by the type I Navy Standards Laboratory
(NSL). Figure 4-1 is a flow chart of the traceability of
test measuring and diagnostic equipment.
Navy calibration laboratories (NCLs) obtain
calibration services from higher echelon laboratories.
The capabilities of these laboratories vary. Their mission
is twofold: (1) to maintain standards of measurement
within the activity, and (2) to calibrate and repair
standards and to calibrate and accomplish incidental
repair on fleet and shore activity test and measuring
equipment.
TYPE I NAVY STANDARDS LABORATORY
The type I NSL is located at the Western Standards
Laboratory, Naval Air Rework Facility, North Island,
San Diego, California. A detachment is located at the
Naval Station, Navy Yard Annex, Washington, D.C. The
operation of the laboratory and its detachment is under
the cognizance of the Naval Air Systems Command. The
NSL maintains and disseminates the most accurate
units of measurement within the Navy METCAL
program and obtains calibration services from and
maintains traceability to the NIST. In performing its
functions, the NSL provides services for the systems
commands,
cognizant
laboratories,
and
project
managers.
MECHANICAL INSTRUMENT REPAIR
AND CALIBRATION SHOPS
Mechanical instrument repair and calibration shops
(MIRCS) are located on board tenders (other than FBM),
repair ships, and specified shore activities. Their
function is to calibrate and repair mechanical and
electromechanical measuring devices installed aboard
ships and submarines. Standards used by MIRCs are
submitted to a higher echelon laboratory for calibration.
TYPE II NAVY STANDARDS
LABORATORIES AND REFERENCE
STANDARDS LABORATORIES
FLEET MECHANICAL CALIBRATION
LABORATORIES
Type II NSLs and reference standards laboratories
(RSLs) provide the second highest echelon of calibration
services within the Navy. Type II NSLs obtain standards
calibration services from type I NSLs and calibrate
standards from lower echelon laboratories. RSLs are
similar in capability and operation to the type II NSLs.
In addition, shipyard RSLs provide calibration support
for mechanical instrumentation.
NATIONAL
INSTITUTE OF
STANDARDS AND
TECHNOLOGY
Fleet mechanical calibration laboratories (FMCLs)
are on board FBM submarine tenders to provide
calibration services for FBM submarine mechanical, test,
and measurement equipment. Standards from these
laboratories arc submitted to higher echelon laboratories
TMDE FLOW
NAVY STANDARDS
LABORATORY
(TYPE I)
REFERENCE
STANDARDS
LABORATORIES
(SHIPYARDS & SRF’S)
NAVY CALIBRATION
LABORATORIES
(SHORE)
FIELD CALIBRATION
ACTIVITIES
(SHORE)
SHORE TMDE
(INCLUDING)
SHIPS IN YARDS)
MIRCS
OVERFLOW
MECHANICAL
INSTRUMENT REPAIR &
CALIBRATION SHOPS
FLEET MECHANICAL
CALIBRATION
LABORATORIES
FIELD CALIBRATION
ACTIVITIES (FCA’S)
(FLEET)
FIELD CALIBRATION
ACTIVITIES
(FLEET)
FLEET
TMDE
(NON-FBM)
FLEET
TMDE
(FMB)
Figure 4-1.—Test measuring and diagnostic equipment traceability flow chart.
4-3
Several documents are used to update the database
of the MEASURE system. These documents will be
discussed in the following paragraphs.
for calibration. The FMCLs are operated by IM
personnel with an 1821 NEC. The basic difference
between the MIRCs and the FMCL is that the FMCL
has the additional capability for optical calibration.
The MEASURE system is a tool for your use. It is
only as good as the information that is put into it. It is
important that all information be thoroughly legible,
accurate, and consistent.
FIELD CALIBRATION ACTIVITIES
Navy field calibration activities (FCAs) make up the
next lower echelon. These activities have been set up to
enable user activities to calibrate locally such specific
types of instruments as pressure gauges, temperature
gauges, and electrical meters, rather than send them to
a laboratory. Calibration is performed by specially
trained personnel. Most ships in the fleet have
designated FCAs.
INVENTORY REPORT FORMS
The MEASURE Test Measuring and Diagnostic
Equipment (TMDE) Inventory Report Form and the
MEASURE Calibration Standards Inventory Report
Form provide the initial input of data pertaining to
TAMS equipment and calibration. This information,
when stored in a computer, establishes a data base for
all MEASURE forms and reports.
SUPPORT FOR CALIBRATION
STANDARDS
N O T E : Since computers cannot think,
completeness and accuracy of information is essential
to make the program effective.
To receive calibration support for standards, you
should take the following steps:
1.
Inventory report forms are submitted to an
intermediate level activity of FCA for screening. This
activity determines whether or not it has the capabilities
for the calibration of the equipment listed in the
inventory. Items that are outside the capability of this
activity are noted on the inventory report form. The
report forms are forwarded to a METCAL
representative for validation. They are then forwarded
to the MEASURE Operational Control Center (MOCC)
in Concord, California, and are entered into the data
bank. The customer is provided with an automated
inventory and a set of preprinted METER cards.
Request funds from the type commander.
2. Request calibration services, by official
message, from the supporting laboratory.
3.
Makeup a recalibration schedule with the help
of the supporting laboratory. This schedule will
minimize the delay in getting your standards
recalibrated and back in service.
METROLOGY AUTOMATED SYSTEM
FOR UNIFORM RECALL AND
REPORTING
Normally, the inventory forms are only used for the
initial input of data. However, if 10 or more items are to
be added to the inventory, an appropriate inventory
report form can be used. This form is prepared in the
same manner as the initial inventory report except that
the words Add-On-Inventory are entered above the
customer activity code block at the top center of the
form.
In an effort to ensure that all equipment requiring
calibration and/or servicing is maintained at maximum
dependability, the Chief of Naval Material implemented
the MEASURE program. It is the Navy’s single data
reporting system for the TAMs and the Navy METCAL
program.
As an IC Electrician Second Class, you will be
required to update calibration schedules. Therefore, you
should have a thorough understanding of the
MEASURE program and be familiar with the forms and
reports used with this system. You will be required to
check documents for completeness and accuracy and to
assist customers in the completion of these documents.
Information on how to use this program effectively and
how to complete the necessary documents accurately is
provided in the latest edition of the Measure Users
Manual, OP43P6.
METER CARD
The METER card (fig. 4-2) is a five-part,
color-coded form to which the equipment identification
(ID) and receipt tag is attached. It is filled out by either
the customer or the calibrating activity and is used to
report information and transactions pertaining to TAMS
and calibration standards.
The METER card, either preprinted by the MOCC
or handprinted by the customer activity, contains all
4-4
Figure 4-2.—Metrology Equipment Recall and Report Meter Card.
equipment. Every item should have a label affixed to it
that indicates the calibration status of that item. All
labels must be attached in a conspicuous place, so as to
be readily seen by all interested persons, and all tags
must remain attached to the instruments as long as the
information on the tag is pertinent.
information necessary to identify a single piece of
TAMS equipment and to update the data base.
This card is used to record a calibration action, to
add or delete equipment in the inventory, to reschedule
equipment for calibration at other than the prescribed
time, to transfer custody of equipment from one activity
to another, or strictly to record man-hours for a
completed calibration.
In the following sections we will discuss the labels
and the tags, and the criteria for their use.
The white copy of the completed METER card is
forwarded to the MOCC where the information is
keypunched into a computer to update the MEASURE
data base. The new information is then printed on
another METER card and sent to the customer activity
to be used the next time another transaction is to be
completed.
CALIBRATED
This label (black lettering, white background),
which comes in three different sizes, is the most
commonly used label in the METCAL program. It
indicates that an instrument is within its applicable
tolerance on all parameters.
Accurate data, completeness, and legibility in filling
out the METER card are essential.
CALIBRATED - REFER TO
REPORT
EQUIPMENT IDENTIFICATION AND
RECEIPT TAG
This label (red lettering, white background), which
comes in two sizes, is used when actual measurement
values and associated uncertainties must be known for
the instrument to be used.
The receipt and identification tag, attached to the
METER card, bears the same control number as the
METER card. Like the METER card, it is a five-part,
color-coded form.
SPECIAL CALIBRATION
Blocks A, B, C, D, and E of this form contain the
same information that is contained in blocks 1, 3, 4, 9,
and 11 of the METER card. This information is used to
identify the equipment being calibrated. Both block T of
the ID tag and block 5 of the METER card identify the
customer; however, this information is abbreviated on
the METER card.
One copy of the ID tag is given to the customer as
a receipt. The other four copies are kept by the
calibrating facility. Unlike the METER card, no part of
the ID tag is sent to the MOCC. The MOCC
automatically enters this information when it preprints
the METER card.
There are two Special Calibration labels (black
lettering, yellow background). They differ in size and
content. There is also a Special Calibration tag that is
used with the smaller of the two labels. The Special
Calibration label is used when some unusual or special
condition in the calibration should be known to the user
and/or the calibrator. These special conditions may be
deviations from usual calibration tolerances, multiple
calibration intervals, or requirements for in-place
calibration. All conditions requiring special calibration
are described either directly on the large label, or on the
tag, when the small label is used. The following
information amplifies these special calibrations.
MEASURE REFERRAL CARD
USER CALIBRATION
The MEASURE referral card is used to forward
questions, recommendations, and comments pertaining
to MEASURE to concerned authorities. Instructions
regarding the preparation of the referral card are found
in the Measure Users Manual.
Some TAMS may be calibrated by the user and the
instrument does not need to be sent to a calibration
facility. For example, some instruments are provided
with their own standards and must be calibrated either
each time they are used or very frequently. Some
instruments, such as oscillographic recorders, may
require calibration before, during, and after each use.
Some automatic test equipments require self-calibration
tests to be performed each time they are used. Still other
instruments are calibrated as part of checkout
CALIBRATION CATEGORIES
When you are updating equipment calibration
schedules, you need to know the calibration status of the
4-6
procedures performed daily or weekly. The requirement
for calibration by the user and the calibration interval
(each Use, daily, weekly, every 100 hours, each overhaul,
and so on) is indicated in the METRL. The User
Calibration label (black lettering, white background)
must be used when the calibration is performed by the
user. This label is not replaced at each calibration. When
the label is first affixed to the instrument, a notation is
made about the appropriate calibration interval. Records
of calibrations performed, when other than each time
used, are maintained in conformance with normal
maintenance practices; that is, maintenance log and
maintenance action form.
the label should bear the notation “Not used for
quantitative measurements.”
REJECTED
In the event an instrument fails to meet the
acceptance criteria during calibration and cannot be
adequately repaired, a Rejected label (black lettering,
red background) must be placed on the instrument. All
other servicing labels must be removed. In addition to
the Rejected label, a Rejected tag giving the reason for
rejection and any other pertinent information is affixed
to the instrument. The Rejected label and tag remain on
the instrument until it is repaired and recalibrated. The
instrument MUST NOT be used while bearing a
Rejected label.
INACTIVE
If an individual instrument due for recalibration is
not expected to be used for some time in the future,
recalibration may be indefinitely postponed by affixing
an Inactive label (green lettering, white background) to
the instrument. The Inactive label must remain on the
instrument until the instrument is recalibrated, and the
instrument will NOT be used while bearing the Inactive
label. It must be calibrated before it can be used.
CALIBRATION VOID IF SEAL BROKEN
This label (black lettering, white background) is
placed over readily accessible (usually exterior)
adjustments to prevent tampering by the user when such
tampering could affect the calibration. The label must
not cover any adjustments or controls that are part of the
normal use and operation of the instrument. This label
is also used to prevent removal and/or interchange of
plug-in modules, subassemblies, and so on, when such
removal or interchange can affect the calibration.
CALIBRATION NOT REQUIRED
Standards and TAMS not requiring calibration are
shown as NCR in the METRL. The No Calibration
Required label (orange lettering, white background) is
affixed to and should remain on the instrument until its
calibration requirements change. When an instrument is
not listed in the METRL as NCR, the following criteria
must be used for placing the instrument in the No
Calibration Required category:
WATCH STANDING
Shipboard personnel stand a variety of watches, all
important to the ship and to the ship’s company. In
particular, your personnel stand the IC and gyro room,
telephone switchboard, damage control central, and
sounding and security watches. The IC and gyro room
watch is long and usually uneventful until a gyro alarm
sounds or until the electrical supply is shifted. At this
time, the person on watch must be alert. There are
always minor repairs needed, such as to sound-powered
telephones, which can be used to keep the person alert,
but “skylarking” should be outlawed. The telephone
switchboard operator should be well indoctrinated, and
then periodically checked to make sure he/she is
rendering good service to the ship. Personal calls require
specific permission, and your operator should require
adherence to regulations in this regard. The damage
control central and sounding and security watches are
independent watches and are under limited supervision.
1. The instrument does not make quantitative
measurements nor does it provide quantified outputs.
2. The device is “fail-safe” in that any operation
beyond specified tolerances will be apparent to the user.
3. All measurement/stimulus circuits are either
monitored by calibrated instruments during their use or
are dependent on external, known or calibrated, sources
for performance within required limits.
When it is determined that an instrument falls into
the Calibration Not Required category, the label is
annotated as to the authority on which the decision was
based, such as METRL, technical manual, letter, or
message from higher authority. In the case of
instruments that normally require periodic calibration
but are not used to perform quantitative measurements,
You should make sure your personnel are
performing their watch standing duties properly and
alertly. When problems occur, take immediate action.
Only through careful counseling, adequate instructions,
4-7
and periodic checks can you assure the watch standing
of your personnel.
Their responsibilities for security
The importance of security and the penalties for
violating security regulations
The usual means of training watch standers is by an
apprentice program where the person stands watches
under instruction and supervision until he/she is
qualified to do the job on his/her own. Whether or not
the person is qualified depends on the judgment of the
person assigned to instruct and supervise him/her. This
system is not always dependable for the following
reasons:
The techniques used by foreign intelligence
agents and agencies
Their responsibilities for reporting any attempt
or suspected attempt of foreign intelligence
activities to gain U.S. defense information
1. The person in training may learn bad practices
as well as good from the instructor. This problem can be
partially remedied by rotating the person’s watch so
he/she receives indoctrination from more than one
watch stander.
Any IC personnel having duties in a telephone
exchange should be aware that although interior
communications within a ship are fairly secure, once
telephone conversations get to the beach, they are very
easily intercepted by taps on land lines and interceptions
of microwave telephone transmissions.
2. A person can stand numerous watches without
experiencing a casualty, and without being exposed,
through simulation, to all the possible casualties the
watch stander may experience.
As part of security training, personnel having access
to classified information should be briefed periodically.
The following points should be emphasized:
1. Divulge classified information only to personnel
who have the necessary security clearance and who
must have the information to perform their official
duties.
By recognizing the potential for these problems you
can compensate for them by preparing watch-station
qualification checkoff sheets and by supervising the
indoctrination of watch standers to the extent necessary
to ensure that they become fully qualified. By these
means you can be sure that the inservice training of
watch standers is delivering the qualified personnel that
you need.
2. Personnel who have classified information have
the responsibility for protecting it.
3. Personnel must be alert and ready to defend
themselves against any possible espionage or
subversion.
SECURITY TRAINING
4. Discussing any classified information over a
telephone is prohibited.
As a supervisor, you will have responsibilities in the
security area, both in safeguarding information you
possess and in indoctrinating your personnel in proper
procedures for handling classified information. Your
security training responsibilities are part of an overall
security, orientation, education, and training program
that is the responsibility of your commanding officer
and directed to all hands.
In addition to routine briefings, personnel who have
access to classified information should be briefed before
traveling to or through communist countries where there
may be an attempt to subvert, or obtain, information
from them. If any of your subordinates have close
relatives living in communist controlled countries, they
should receive a special briefing, which your command
will arrange.
The object of security training is to develop in all
hands a sense of personal responsibility for protecting
classified information and equipment. This training is
done either through use of group lessons, using lectures
and films, or by having personnel study the Information
Security Program Regulation Manual, OPNAV
Instruction 5510.1H, or other printed information on
security. In and near areas where classified material is
used and stored, posters are placed to remind personnel
of their duties in respect to security.
TEAM TRAINING
The following procedure, recommended for
training a team and its members, is especially applicable
to engineering casualty control training:
1. Analyze the duties of each person in the team.
2. Permit the team (or individual) to perform a
rehearsal or “dry run” of the operation slowly and
without pressure.
The following list contains some of the things
personnel should be taught about security:
4-8
3. Drill for greater speed and accuracy.
Emphasize correct procedures in early drills and
increase emphasis on speed as drills progress.
The introduction explains the use of the
qualification standard in terms of what it will mean to
the user as well as how to apply it.
4.
Allow the team (or individual) to perform the
actual operation.
The theory (100 series) section specifies the
knowledge of theory necessary as a prerequisite to the
study of the specific equipment or system for which the
PQS was written.
5.
Evaluate and discuss the performance with
your personnel.
The system (200 series) section breaks down the
equipment or systems to be studied into functional
sections. PQS items are constructed as clear, concise
statements/questions according to a standard format.
The answers must be extracted from the various
manuals covering the equipment or systems for which
the PQS is written. This section asks the user to explain
the function of the system, to draw a simplified version
of the system from memory, and to use this drawn
schematic or the schematic provided in the maintenance
manual while studying the system or equipment.
Emphasis is given to such areas as maintenance management procedures, components, component parts,
principles of operation, system interrelations, numerical
values considered necessary to operation and maintenance, and safety precautions. A study of the items in
the system section provides the individual with the
required information concerning what the system or
equipment does, how it does it, and other pertinent
aspects of operation.
PERSONNEL QUALIFICATIONS
STANDARDS
The Personnel Qualification Standards (PQS)
program is another element in the Navy’s overall
training program. It is used to help develop in personnel
the skills necessary to perform their assigned duties.
The Personnel Qualification Standard (PQS)
Management Guide, NAVEDTRA 43100-1D, provides
information on the PQS concept and describes its
implementation into the training program of operational
units of the Navy.
The purpose of the program is to assist in qualifying
trainees to perform their duties. It is recommended that
trainees carry their qualification cards with them so they
can take advantage of training “targets of opportunity”
that may occur during their daily routine. Individuals are
allowed to progress at a pace that fits their individual
learning ability. This progress, of course, is contingent
upon time periods established by department heads and
division officers. Although designed for a different
purpose, the PQS program helps to prepare personnel
for advancement. When studying theory questions,
trainees are referred to applicable training manuals and
other sources of information.
The watch stations (300 series) section includes
questions regarding the procedures the individual must
know to operate and maintain the equipment or system.
In this section, the questions advance the qualification
process by requiring answers or demonstrations showing the ability to use the knowledge covered in the
system section and to maintain the system or equipment.
Areas covered include normal operation; abnormal or
emergency operation; emergency procedures that could
limit damage and/or casualties associated with a
particular operation; operations that occur too
frequently to be considered mandatory performance
items; and maintenance proeedures/instructions such as
checks, tests, repairs, replacements, and so on.
To determine what equipment or watch station is in
the PQS program and to obtain the stock number for a
particular PQS booklet, refer to NAVSUP 2002 or
CNET Notice 3500.
Each qualification standard has four main subdivisions in addition to a preface, introduction, glossary,
bibliography, and feedback form. These subdivisions
are as follows:
The qualification cards (400 series) section covers
the accounting documents used to record the individual’s satisfactory completion of items. A complete PQS
package should be given to each person being qualified
so he or she can use it at every opportunity to become
fully qualified in all areas of the appropriate rating and
the equipment, system, or watch station for which the
PQS was written. At what point to begin a PQS booklet
will depend on the individual’s assignment within an
100 Series—Theory
200 Seris—System
300 Series—Watchstations (duties, assignments, or
responsibilities)
400 Series—Qualification cards
4-9
when new safety posters or precautions are received,
supervisors are responsible for interpreting the
messages correctly. In this way, they will ensure all
personnel interpret and observe the approved safety
rules and procedures correctly. It is essential that all
repair and maintenance work be accomplished without
personnel injury or damage to equipment.
activity. Upon transfer to a different activity, each
individual usually must requalify.
As a Petty Officer Second Class, you will be able to
use the required watch station PQS to help train the
personnel assigned to your watch section. It will also
give you a way of documenting the progress of each
person in qualifying as an IC Electrician watch stander.
SAFETY
Enforcing Safety
Safety is the responsibility of all personnel.
Personnel injury or death due to electric shock and
damage to equipment require that all personnel adhere
strictly to applicable safety precautions. With electrical
and electronic equipment, safety violations could result
in immediate equipment damage and severe personnel
injury.
Safety precautions, as all rules, laws, or regulations,
should be enforced. It is your duty to take appropriate
action any time you see any person disregarding a safety
precaution. You should require that all jobs be done
according to applicable safety precautions.
Doing a job the safe way in some cases may take a
little longer or may be a little more inconvenient;
however, there is no doubt as to the importance of doing
it this way.
If you are in doubt about applicable electrical or
electronic safety precautions, refer to NSTM, chapters
300 and 400, the Standard Organization and
Regulations of the U.S. Navy (SORM), ONNAVINST
3120.32B, and NAVOSH Program Manual for Forces
Afloat, OPNAVINST 5100.19B. Remember, safety is
paramount!
Safe Electrical/Electronic
Maintenance
Electrical/electronic maintenance is, to some extent,
hazardous due to the nature of the work. Safety must
rank as a prime concern because of the inherent danger
of electrical shock.
Safety Responsibilities
U.S. Navy Regulations, article 0712 states: “The
Commanding Officer shall require that all persons
concerned are instructed and drilled inapplicable safety
precautions and procedures, that these are complied
with, and that the applicable safety precautions, or
extracts therefrom, are posted in appropriate places, In
any instance where safety precautions have not been
issued, or are incomplete, he shall issue or augment such
safety precautions as he deems necessary, notifying,
when appropriate, higher authorities concerned.”
EFFECTS OF ELECTRICITY.— The factors that
determine whether you receive a slight or fatal shock are
(1) the amount and duration of current flow, (2) the parts
of the body involved, and (3) the frequency of the
current if it is ac. Generally, the greater the current flow
and the length of time one is subjected to it will
determine the damage done. The extent of the current
through you to vital nerve centers and organs may
determine whether or not you survive the electric shock.
The frequency of the current is also a determining factor,
with 60- and 400-Hz current flow being more dangerous
than dc.
Navy Regulations also spells out specific
responsibilities of the executive officer, engineer
officer, division officer, and engineering officer of the
watch. These regulations are intended to make safety a
prime responsibility of supervisors. Commanding
officers cannot delegate their safety responsibilities, but
they can delegate their authority to officers and petty
officers to ensure safety precautions are understood and
enforced.
The ability to resist an electrical shock will vary
from person to person and day to day. The Naval Sea
Systems Command (NAVSEA) has summarized the
relationship of current magnitude to degree of shock:
1. At about 1 milliamp (0.001 ampere), shock is
perceptible.
As a supervisor, you must be aware of the safety of
personnel and ensure they receive the necessary training
and information in regards to safety. The most important
step in maintaining safe working conditions is a
thorough indoctrination of all personnel. For example,
2. At about 10 milliamps (0.01 ampere), shock is
sufficient to prevent voluntary control of muscles.
3. At about 100 milliamps (0.1 ampere), shock is
usually fatal if it lasts for 1 second or more.
4-10
12. Never use your finger to test a “hot” line. Use
approved meters or other indicating devices.
SAFE PRACTICES.— When working on electrical
or electronic circuits, you must observe applicable
safety precautions and follow approved procedures.
These precautions should be scrupulously followed by
both yourself and the person working with you.
It is the responsibility of every person connected
with equipment maintenance to discover and eliminate
unsafe work practices.
1. Electrical and electronic circuits often have
more than one source of power. Take time to study the
schematics or wiring diagrams of the entire system to
ensure that all power sources are secured and tagged out.
Sources of Safety Information
Included among the available sources of safety
information are directives, instructions, and notices
issued by the Chief of Naval Operations, the NSTMs,
manufacturers’ technical manuals, safety notices, and
bulletins published periodically.
2. If pertinent, inform the remote station
regarding the circuit on which work will be performed.
3. Use one hand when you turn switches on or off.
Keep the doors to switch and fuse boxes closed, except
when working inside or replacing fuses.
SAFETY DIRECTIVES AND PRECAUTIONS.— The items in the various safety directives and
publications are designed to cover usual conditions in
naval activities. Commanding officers and others in
authority are authorized and encouraged to issue special
precautions to their commands to cover local conditions
and unusual circumstances. Guidance for the promotion
of accident prevention aboard ship is contained in the
Navy Occupational Safety and Health (NAVOSH)
Program Manual for Forces Afloat, OPNAVINST
5100.19B, and the Navy Occupational Safety and
Health (NAVOSH) Program Manual, OPNAVINST
5100.23B. Safety directives and precautions should be
followed to the letter in their specific application.
Should any occasion arise in which any doubt exists as
to the application of a particular directive or precaution,
the measures to be taken are those which will achieve
maximum safety. The safety officer is available to assist
in interpreting and suggesting ways of implementing
safety directives and precautions.
4. After frost making certain that the circuit is
dead, use a fuse puller to remove cartridge fuses.
5. All supply switches or cutout switches from
which power could possibly be fed should be secured in
the off or open (safety) position and tagged with a red
danger tag (NAVSHIPS 9890/S(REV)).
6. Keep clothing, hands, and feet dry if at all
possible. When it is necessary to work in wet or damp
locations, use a dry steady platform to sit or stand on,
and place a rubber mat or other nonconductive material
on top of the platform. Use insulated tools and insulated
flashlights of the molded type when required to work on
exposed parts. In all instances, repairs on energized
circuits must be made with the primary power not
applied except in case of emergency, and then only after
specific approval has been given by the commanding
officer. When approval has been obtained to work on
equipment with the power applied, keep one hand free
at all times (behind you or in your pocket).
NAVAL SHIPS’ TECHNICAL MANUAL.—
Chapter 300, “The Electrical Plant General,” gives clear
and concise electrical safety precautions that should be
“required study material for all hands.” Although some
areas may need explanation to nonrated personnel,
many items of common sense are stressed. This material
should be included in the training of all personnel, with
heavy emphasis placed on the correct procedure for
artificial respiration.
7. Never short out, tamper with, or block open an
interlock switch.
8. Keep clear of exposed equipment; when it is
necessary to work on it, wear approved, tested rubber
gloves and work with one hand as much as possible.
9. Avoid reaching into enclosures except when
absolutely necessary; when reaching into an enclosure,
use rubber gloves to prevent accidental contact with the
enclosure.
Other chapters of the NSTM, including chapter 430,
“Interior Communications,” give specific precautions
related to specific areas.
MANUFACTURERS’ TECHNICAL MANUALS.— Applicable safety precautions are written in all
equipment technical manuals. Generally speaking, most
training underscores the Principle of Operation and the
Maintenance sections of these manuals, yet fails to place
10. Make certain that equipment is properly
grounded.
11. Turn off the power before connecting alligator
clips to any circuit.
4-11
type and in good condition. In addition to ensuring good
performance and long equipment service life, careful
workmanship will help prevent fires. A badly made
connection that vibrates loose or a conductor that carries
high voltages too close to another can cause an arc.
Pulling fuses on energized circuits should be avoided
since an arc can result. When it comes to fire prevention,
the fewer sparks the better.
proper emphasis on safety items. Often the precautions
are located in the front of the manual before the table of
contents, where they are easily overlooked.
Senior petty officers should ensure that each person
sent out on a maintenance action is instructed on the
precautions to be observed. Too often high voltage
sources and alternate power sources mentioned in the
Safety section of the technical manual are overlooked
or forgotten by junior electricians until the screwdriver
is in place.
If a fire or overheated condition occurs in electrical
equipment, the circuit should be de-energized as quickly
as possible. Carbon dioxide (CO2) is to be used in
fighting electrical fires because it is nonconductive and
thereby the safest to use in terms of personnel safety, and
because it offers the least likelihood of doing equipment
damage. However, if the discharge horn is allowed to
touch an energized circuit, the horn may transmit a
shock to the handler, due to frost on the horn.
MAINTENANCE REQUIREMENT CARDS.—
Each maintenance requirement card (MRC) used in the
Navy has a section devoted to safety precautions to be
observed by the person who performs the maintenance
action prescribed on the card. Sometimes, this section
contains only a reminder to observe standard safety
precautions. But, whatever they are, the leading petty
officer responsible for the maintenance action should
ensure that each person in his/her work group is
instructed in the safety precautions and observes them
while performing his/her tasks.
Outside Safety
IC Electricians perform maintenance on equipment
located throughout the ship. A leading petty officer may
have personnel working simultaneously on the bridge,
in the engine room and fireroom, and in several other
spaces. It is imperative that all of these personnel be
aware of the general and specific safety precautions
involved in their work. The person who neglects to
secure the power to the salinity system (circuit SB) when
cleaning it is just as likely to be injured or killed as the
one who doesn’t properly use a safety harness when
aligning the anemometer (circuits HD, HE).
PERIODICALS.— Many sources of safety information are distributed on a monthly or quarterly basis
by various naval activities. The Naval Safety Center
publishes the Ships Safety Bulletin and Fathom, a
quarterly surface ship and submarine safety review.
Fathom presents accurate and current information on
the subject of nautical accident prevention. Safety
Review, published monthly by the Chief of Naval
Material (CHNAVMAT), contains information on the
safe storage, handling, or other use of products and
materials. Articles dealing with safety appear often in
Electronics Information Bulletin, Deckplate, and
Surface Warfare magazine.
Live Circuits
More often than not, it is impossible to align
de-energized equipment. Gyro repeaters, engine order
telegraphs, and other synchro systems require
adjustment “hot”; therefore, several precautions must be
observed whenever the work is being done on energized
electrical equipment.
Fire Safety
The best way to control any fire is not let it happen.
When working on equipment, personnel should always
be aware that circuit protective devices, such as fuses
and circuit breakers, are frost-line insurance against
overheating and must be in good condition. The filter is
an important part of filtered ventilating systems. If the
filter is clogged, the equipment will run hot and may
bum out. If the filter is not in place or has holes in it,
dust will get into the system and present a possible fire
hazard. When falters are replaced, the replacement filter
must be the same type as the original. When equipment
is opened, components and wiring insulation should be
inspected for signs of overheating. To avoid dangerous
short circuits, electrical insulation must be of the correct
1. Provide ample illumination.
2. Do not wear a wrist watch, rings, watch chain,
metal articles, or loose clothing that might make
accidental contact with live parts or that might
accidental] y catch and throw some part of the body into
contact with live parts. Clothing and shoes should be as
dry as possible.
3. Insulate the worker from ground by means of
insulating material covering any adjacent grounded
metal with which he/she might come in contact. Suitable
insulating materials are rubber mats, dry canvas, dry
4-12
can occur from even a small spark drawn from a charged
piece of metal or rigging. Although the spark itself may
be harmless, the “surprise” may cause the worker to let
go his grasp involuntarily. There is also shock hazard if
nearby antennas are energized, such as those on stations
ashore or aboard a ship moored alongside or across a
pier.
phenolic material, or even heavy dry paper in several
thicknesses. Be sure any such insulating material is dry,
has no holes in it, and has no conducting materials
embedded in it. Cover sufficient areas so adequate
latitude is permitted for movement by the worker in
doing the work
4. Use insulated hand tools.
Danger also exists from rotating antennas that might
cause personnel working aloft to fall by knocking them
from their perch. Motor safety switches controlling the
motion of antennas must be tagged and locked open
before anyone is allowed aloft close to such antennas.
5. Insofar as practicable, provide insulating
barriers between the work and any live metal parts
immediately adjascent to the work to be done.
6. Use only one hand in accomplishing the work
if practical. Wear a rubber glove on the hand not used
for handling tools. If the work being done permits, wear
rubber gloves on both hands.
Personnel working near a stack must wear the recommended oxygen breathing apparatus. Among other
toxic substances, stack gas contains carbon monoxide.
Carbon monoxide is too unstable to buildup to a high
concentration in the open, but prolonged exposure to
even small quantities is dangerous.
7. Have personnel stationed by circuit breakers or
switches, and telephone manned if necessary, so the
circuit can be de-energized immediately in case of
emergency.
Each time a person goes aloft to work he/she must
follow established procedures listed here:
8. Have immediately available a person qualified
in mouth-to-mouth respiration and cardiac massage for
electric shock.
1. Get permission of the communications watch
officer (CWO) and the OOD.
Tagging Procedure
2. Check with the engineer officer to ensure that
the boiler safety valves are not being set.
For many years the Navy has recognized the value
of tagging circuits upon which personnel are working,
but a good tagging procedure is worthless unless it is
backed up by the petty officers in charge. Often junior
personnel tend to take tags lightly—a tendency that could
prove fatal. Then too, there have been cases where
personnel have long since left the ship and the tags they
installed remain in place. When this happens, the entire
circuit must be checked for grounds and shock hazards
before the tags are removed and the circuit energized.
3. Get the assistance of another person along with
a ship’s Boatswain’s Mate who is qualified in rigging.
4. Wear a safety harness. To be of any benefit, the
best harness must be fastened securely as soon as the
place of work is reached. Some workers had complained
on occasion that a safety harness is clumsy and interferes
with movement. True as this maybe, it is also true that
a fall from the height of an antenna is usually fatal.
5. Keep both hands free for climbing. Tools are not
to be carried in hand; an assistant can lift them to the
work site.
Recently there has been a tendency to supply power
to certain nonvital circuits, such as the wardroom buzzer
system, from local lighting panels. Since power is taken
from a lighting panel, the repairing IC Electrician must
tag the circuit using a red danger tag before working on
it.
6. Secure tools with preventer lines to keep them
from dropping on a shipmate.
7. Keep a good footing and firm grasp at all times.
The nautical expression HOLD FAST serves as a good
memory device, in case one is needed.
If more than one repairman is engaged in repairing
apiece of equipment, each person should tag the circuit
and, upon completion of work, each should remove
his/her own tag.
Shore Connections
The connection of the ship’s service telephone
system to a shore exchange is a frequent evolution
carried out by junior IC Electricians. There are two
possible hazards: the 48-volt dc power supply and the
90-volt ring current used in telephones.
Working Aloft
When radio or radar antennas are energized by
transmitters, workers must not go aloft until steps have
been taken to ensure that no danger exists. A casualty
4-13
When operating circuit breakers or switches, use
only one hand if possible. Use judgment in replacing
blown fuses. Only fuses of 10 ampere capacity or less
should be removed or replaced in energized circuits.
Fuses larger than 10 ampere ratings should be removed
or replaced only when the circuit is de-energized. Do not
work on any energized circuit, switchboard or other
piece of electrical equipment unless absolutely
necessary. Do not undertake any work on energized
switchboards without first obtaining the approval of the
commanding officer. When you have received
permission to work on a live circuit, DO NOT attempt
to do so by yourself; have another person (safety
observer), qualified in first aid for electrical shock,
present at all times. The person stationed nearby should
also know the circuits and the location of switches
controlling the equipment and should be given
instructions to pull the switch immediately if anything
unforeseen happens. The worker within the enclosure
must always be aware of the nearness of other live
circuits. Use rubber gloves where applicable and stand
on approved rubber matting.
Any hazard due to the ship’s telephones can be
avoided by keeping the manual switchboard
de-energized during connection. In making the shore
connection, the IC Electrician must assume the circuit
is energized (as is the practice in some ports) and act
accordingly.
Connection at some piers is made by plug-in-type
plugs and the hazards are minimized; however, where
lug and screw connections are made, emphasis must be
placed on live circuit precautions.
On many ships, IC Electricians assist in connecting
and disconnecting ship’s service power to shore power.
The applicable guidelines are contained in Electrician’s
Mate 1&C, NAVEDTRA 10547-E.
IC Room Safety
Since a major portion of the IC Electrician’s time is
spent working in the IC room or IC workshop, it is
important that supervisory personnel examine the
personnel hazards present in these areas. It is mandatory,
of course, that the area be initially laid out with the
proper rubber matting and that the workbench and test
switchboard be installed with maximum safety for
personnel as a prime consideration.
Circuits or equipment to be worked on should be
de-energized by opening all switches through which
power could be supplied and then testing the circuit with
a voltmeter or voltage tester. These switches should then
be tagged with danger tags. In case more than one party
is engaged in repair work on a circuit, a danger tag for
each party should be placed on the supply switches.
Maintenance and Repair
As an IC Electrician Second Class, you will be
expected to supervise and train personnel when standing
watch. Most commands have a trouble-call log in either
DC central or in the IC/gyro room. There is usually one
to three personnel on watch in the IC/gyro room
depending on the size of the command. If not, there is
always someone with the duty of responding to
casualties when they occur. You, as a supervisor, will be
expected to train your watch personnel on how to
respond to these calls and the hazards they may
encounter.
A cardinal, yet often violated, rule regarding
enclosed equipment is never override or disable an
interlock. The Navy designed the interlock in the circuit
and no one should be allowed to violate it.
Dirt, dust, lint, and excessive oil must be removed
from IC equipment. Junior personnel should, before
they begin a cleaning evolution, be instructed in and take
adequate precautions for their safety. Two general
cleaning rules are as follows:
SWITCHBOARDS AND ENCLOSED EQUIPMENT.— The hazards involved to the operator and the
repairman regarding switchboards have been greatly
reduced in recent years by the installation of dead-front
service-type switchboards. These and other enclosed
equipments, however, require specific care in servicing
and cleaning.
1. Loose dust and dirt should be removed with a
vacuum cleaner or clean rags. Low-pressure
compressed air may be used provided the air is free of
foreign particles and moisture. Normal ship’s service air
is 100 psi and must be reduced to approximate y 30 psi
before it is used.
2. Oil or hard dirt may require a cloth dampened
with inhibited methyl chloroform for adequate cleaning.
Extreme care must be used on steel and varnish.
Switches should be operated with the safety of both
the operator and other personnel in mind. Before closing
any switch, be sure the circuit is ready in all respects to
be energized. Make sure all personnel working on the
circuit are notified that it is to be energized.
IN-SHOP REPAIRS.— Many repairs made in the IC
room involve equipment normally used in other parts of
4-14
the ship. To make these repairs, it is often necessary to
use hand and portable electric tools.
Other safe practices in the use of portable electric
power tools include the following:
Safe Practices for Hand Tools.— Normally, you
should have no problems when working with hand tools.
In all likelihood, however, you have seen some
dangerous practices in the use of hand tools that should
have been avoided. One unsafe practice involves the use
of tools with plastic or wooden handles that are cracked,
chipped, broken, or otherwise unserviceable. This
practice is sure to result in accidents and personnel
injuries, such as cuts, bruises, and foreign objects being
thrown in the eyes. If these unserviceable tools are not
repairable, discard or replace them.
–Inspect the tool cord and plug before using the tool.
Do not use the tool if its cord is frayed or its plug is
damaged or broken. Do not use spliced cables except in
an emergency that warrants the risk involved.
–Before using the tool, lay all portable cables out so
you and others cannot trip over them. The length of
extension cords used with portable tools should not
exceed 25 feet. Extension cords of 100 feet are
authorized on flight and hangar decks. Extension cords
of 100 feet are also found in damage control lockers, but
are labeled for “Emergency Use Only.”
Safety with Portable Electric Tools.— Portable
electric tools should be clean, properly oiled, and in
good repair. Before they are used, inspect the tool for
proper grounding. The newer double insulated, plastic
case tools have a two-conductor cord and a two-prong
plug.
–Do not use jury-rigged extension cords that have
metal “handy boxes” for receptacle ends of the cord. All
extension cords must have nonconductive plugs and
receptacle housings.
–Connect the tool cord into the extension cord
(when required) before inserting the extension cord into
a live receptacle. After using the tool, unplug the
extension cord (if any) from the live receptacle before
unplugging the tool cord from the extension cord. Do
not unplug the cords by yanking on them.
If a tool is equipped with a three-prong plug, it
should be plugged into a grounded-type electrical outlet.
Never remove the third prong from the plug. Make
absolutely sure the tool is properly grounded according
to NSTM, chapter 300. Observe safety precautions and
wear rubber gloves when plugging in and operating
portable electric tools under particularly hazardous
conditions. Examples of particularly hazardous
conditions are wet decks, bilge areas, or working over
the side in rafts or boats.
–Stow the tool in its assigned place after you are
through using it.
Nonstandard Equipment.— The practice of having
unauthorized or jury-rigged electrical equipment on
board is a hazard and must be dealt with as such. The
only way to ensure that jury-rigged and unauthorized
equipment is not being used is for you personally to
make checks for such installations.
Before issuance of any portable electrical
equipment, the attached cable with plug (including
extension cords, when used) should be examined
visually to assure it is in satisfactory condition. (Tears,
chafing, exposed insulated conductors, and damaged
plugs are causes for cable or plug replacement.) Any
portable electrical equipment with its associated
extension cords should be tested before to issue with an
approved tool tester or plugged into a dummy (or
de-energized) receptacle and tested for resistance from
equipment housing to ship’s structure with an ohmmeter
(the resistance of the grounding circuit must be less than
1 ohm). Move or work the cable with a bending or
twisting motion. A change in resistance will indicate
broken strands in the grounding conductor. If this is
found, replace the cable. It is further suggested that, at
the discretion of the commanding officer, a list be
established of portable equipment requiring testing
more or less often than once a month depending on
conditions in the ship. Where the Planned Maintenance
System (PMS) is installed, tests should be conducted
according to the MRCs.
Alterations
Naval regulations provide that no alterations are
permitted to be made to ships until authorized by
NAVSEA. Some of the reasons for this regulation that
are particularly applicable to IC systems are as follows:
1. NAVSEA is responsible for the design and
maintenance of IC systems in all naval ships. Therefore,
it is necessary that NAVSEA have accurate information
as to all existing installations.
2. In the interests of standardization, it is necessary
that all requests for alterations be forwarded to
NAVSEA so the alteration may be authorized for all
ships in which similar conditions exist.
3. In the interests of conserving funds, NAVSEA
weighs the importance and necessity of all alterations so
available funds may be most wisely used.
4-15
you always follow the safety precautions outlined
4. Many alterations that seem desirable to the ships
may have unsuspected defects or disadvantages not
immediately apparent to ship’s personnel. In this respect
NAVSEA acts as a clearing house for information from
numerous sources, including other bureaus and offices
of the Naval Establishment.
earlier, you can minimize the risk. But remember, the
possibility of electric shock is always present. If you are
at the scene of an accident, you will be expected to help
the victim as soon as possible.
Additional information on watch standing and
Electric Shock
safety can be found in Basic Military Requirements,
NAVEDTRA 10054-F, and in the military requirements
As an IC Electrician, you will be working in areas
and on equipment that pose a serious shock hazard. If
training manuals.
4-16
APPENDIX I
GLOSSARY
ALARM ACKNOWLEDGE– Push button that must
be depressed to silence an alarm horn.
COMPONENT PARTS– Individual units of a subassembly.
ALARM LOG– Record of quantities that are in an
alarm condition only.
COMPONENTS– Any electrical device, such as a coil,
resistor, transistor, and so forth.
ANALOG DATA– Data represented in continuous
form, as contrasted with digital data having discrete
values.
COMPUTER– A data processor that can perform substantial computation, including numerous arithmetic or logic operations, without the intervention
by a human operator during the run.
AND GATE– (1) An electronic gate whose output is
energized only when every input is in its prescribed
state. An AND gate performs the function of the
logical “AND”; also called an AND circuit. (2) A
binary circuit, with two or more inputs and a single
output, in which the output is a logic 1 only when
all inputs are a logic 1 and the output is a logic 0
when any one of the inputs is a logic 0.
CONDITION– State of being of a device, such as ONOFF, GO-NO GO, and SO forth.
CONTINUOUS DISPLAY– Electrical instrument
giving a continuous indication of a measured
quantity.
CONTROL MODE– Method of system control at a
given time.
ANNUNCIATOR– A device that gives an audible and
a visual indication of an alarm condition.
CONTROL POWER– Power used to control or operate
a component.
ASSEMBLY– A number of parts or subassemblies, or
any combination thereof, joined together to perform
a specific function.
CONTROL TRANSMITTER (CX)– A type of
synchro that converts a mechanical input, which is
the angular position of its rotor, into an electrical
output signal. The output is taken from the stator
windings and is used to drive either a CDX or CT.
BELL LOG– A printed record of changes in the ship’s
operative conditions, such as speed or point of
control.
BINARY UNIT– One of the two possible alternatives,
such as 1 or 0, YES or NO, ON or OFF.
CONTROL TRANSFORMER (CT)– A type of
synchro that compares two signals: the electrical
signal applied to its stator and the mechanical signal
applied to its rotor. The output is an electrical volt-
BLOCK DIAGRAM– Drawing of a system using
blocks for components to show the relationship of
components.
age, which is taken from the rotor winding and is
used to control a power-amplifying device. The
phase and amplitude of the output voltage depends
on the angular position of the rotor with respect to
the magnetic field of the stator.
CALIBRATION ACTIONS– The number of
calibrations performed by the related calibration
activity (laboratory) during the reporting period.
CARD– See PRINTED CIRCUIT BOARD.
CONTROL SIGNAL– Signal applied to a device that
makes corrective changes in a controlled process.
CASUALTY– An event or series of events in progress
during which equipment damage and/or personnel
injury has already occurred. The nature and speed
of these events are such that proper and correct
procedural steps will only serve to limit equipment
damage and/or personnel injury.
CONTROL DIFFERENTIAL TRANSMITTER
(CDX)– A type of synchro that transmits angular
information equal to the algebraic sum or difference
of the electrical input supplied to its stator, and the
mechanical input supplied to its rotor. The output is
CLOCK– An instrument for measuring and indicating
time, such as a synchronous pulse generator.
an electrical voltage taken from the rotor windings.
AI-1
CONVERTER– A device for changing one type of
signal to another; for example, alternating current
to direct current.
CORRECTIVE MAINTENANCE– Includes location
and repair of equipment failures.
CORRESPONDENCE– The term given to the positions of the rotors of a synchro receiver when both
rotors are on 0 degree or displaced from 0 degree by
the same angle.
DAMPING– (1) The process of smoothing out
oscillations. (2) In a meter, this process is used to
keep the pointer of the meter from overshooting the
correct reading. (3) A mechanical or electrical
technique used in synchro receivers to prevent the
rotor from oscillating or spinning. Damping is also
used in servo systems to minimize overshoot of the
load.
EMERGENCY– An event or series of events in
progress that will cause damage to equipment unless
immediate, timely, and correct procedural steps are
taken.
ERROR DETECTOR– The component in a servo
system that determines when the load has deviated
from its ordered position, velocity, and so on.
ERROR SIGNAL– (1) In servo systems, the signal
whose amplitude and polarity or phase are used to
correct the alignment between the controlling and
the controlled elements. (2) The name given to the
electrical output of a control transformer.
EXCITATION VOLTAGE– The supply voltage
required to activate a circuit.
FAIL– Loss of control signal or power to a component.
Also breakage or breakdown of a component or
component part.
DATA TRANSMISSION– The transfer of information
from one place to another or from one part of a
system to another.
FAIL POSITION– Operating or physical position to
which a device will go upon loss of its control signal.
FEEDBACK– A value derived from a controlled
function and returned to the controlling function.
DEAD BAND– The range of values over which a
measured variable can change without affecting the
output of an amplifier or automatic control system.
FREQUENCY– (1) The number of complete cycles per
second existing in any form of wave motion, such
as the numbers of cycles per second of an alternating
current. (2) The rate at which the vector that
generates a sine wave rotates.
DEMAND– To request a log printout or data display.
DEMODULATOR– A circuit used in servosystems to
convert an ac signal to a dc signal. The magnitude
of the dc output is determined by the magnitude of
the ac input signal, and its polarity is determined by
whether the ac input signal is in or out of phase with
the ac reference voltage.
FUNCTION– To perform the normal or characteristic
action of something, or a special duty or
performance required of a person or thing in the
course of work.
DIGITAL– Pertaining to data in the form of digits.
GATE– As applied to logic circuitry, one of several
types of electronic devices that will provide a
particular output when specified input conditions
are satisfied. Also, a circuit in which a signal
switches another signal on or off.
DIGITAL CLOCK– A device for displaying time in
digits.
DIRECT CURRENT– An electric current that flows in
one direction only.
GENERATOR– A machine that converts mechanical
energy to electrical energy by applying the principle
of magnetic induction. A machine that produces ac
or dc voltage, depending on the original design.
DRIFT– A slow change in some characteristics of a
device, such as frequency, current, and direction.
ELECTRICAL ZERO– A standard synchro position,
with a definite set of stator voltages, that is used as
the reference point for alignment of all synchro
units.
GYRO– Abbreviation for gyroscope.
GYROSCOPE– A mechanical device containing a
spinning mass mounted so it can assume any
position in space.
ELECTRICAL-LOCK– A synchro zeroing method.
This method is used only when the rotors of the
synchros to be zeroed are free to turn and their leads
are accessible.
HERTZ– A unit of frequency equal to one cycle per
second.
AI-2
HYDRAULIC ACTUATOR– A device that converts
hydraulic pressure to mechanical movement.
calibration activity (laboratory) during the reporting
period.
INACTIVE CODE– An asterisk (*) preceding the
customer/laboratory code indicating that the
activity is inactive (not currently accepted by
MEASURE), and no updating occurs. (formats 100
& 105)
MODIFICATION ACTIONS– The number of
modifications performed by the related calibration
activity (laboratory) during the reporting period.
MODULE– Subassemblies mounted in a section.
MONITOR– One of the principal operating modes of a
data logger that provides a constant check of plant
conditions.
INTERLOCK– A device that prevents an action from
taking place at the desired time, but that allows the
action when all required conditions are met.
MONITORING POINT– The physical location at
which any indicating device displays the value of a
parameter at some control station.
JACKING GEAR– An electric motor-driven device
that rotates the turbine shaft, reduction gears, and
line shaft at a low speed.
NO-BREAK POWER SUPPLY– A device that
supplies temporary power to the console during
failure of the normal power supply.
LINEAR– Straight line relationship where changes in
one function are directly proportional to changes in
another function.
NORMAL MODE– Operating condition at normal
ahead speeds, differing from maneuvering, where
certain functions, pumps, or valves are not required,
while others are for proper operation of ship and
machinery.
LOGIC– The basic principles and applications of truth
tables, interconnections of off-on circuit elements,
and other factors involved in mathematical
computation in automatic data processing systems
and other devices.
NULL POSITION— Condition where the output shaft is
positioned to correspond to that which the input
shaft has been set.
LOGIC DIAGRAMS– In computers and data processing equipment, a diagram representing the
logical elements and their interconnections without
necessarily expressing construction or engineering
details.
ONE-LINE SCHEMATIC– A drawing of a system
using only one line to show the tie-in of various
components; for example, the three conductors
needed to transmit 3-phase power are represented
by a single line.
LOGIC INSTRUCTION– Any instruction that
executes a logic operation that is defined in
symbolic logic, such as AND, OR, NAND, or NOR.
ONE-LINE SKETCH– A drawing using one line to
outline the general relationship of various
components to each other.
MAINTENANCE– Work done to correct, reduce, or
counteract wear, failure, and damage to equipment.
MANUAL THROTTLE CLUTCH– Means of
mechanically disconnecting the throttle handwheels, mounted on the engine-room console, from
the reach rods that are connected to the throttle
valves.
OPEN LOOP– System having no feedback.
OPERATING CHARACTERISTICS– Combination
of a parameter and its set point.
OR GATE– A gate that performs the logic OR function.
It produces an output 1 whenever any or all of its
inputs is/are 1.
METRL CYCLE– The number of months established
as the optimum period of time the corresponding
equipment can be used before recalibration is
required.
PARAMETER– A variable, such as temperature,
pressure, flow rate, voltage, current, or frequency
that may be indicated, monitored, checked, or
sensed in any way during operation or testing.
MFR– A five-character alpha/numeric or threecharacter alphabetical code representing the
specific manufacturer for the corresponding
equipment model number.
PERIPHERAL– Existing on or new the boundary of a
surface or area.
PILOT MOTOR– A small dc motor that drives the
input shaft of an actuator.
MODIFICATION MAN-HOURS– The total manhours expended on modifications by the related
AI-3
SERVO AMPLIFIER– Either ac or dc amplifiers used
in servo systems to build up signal strength. These
amplifiers usually have relatively flat gain versus
frequency response, minimum phase shift, low
output impedance, and low noise level.
POWER SUPPLY– A module that converts the
115-volt 60-hertz incoming power to ac or dc power
at a more suitable voltage level.
PRINTED CIRCUIT BOARD– Devices usually
plugged into receptacles that are mounted in
modules.
SERVO SYSTEM– An ac or dc motor used in servo
systems to move a load to a desired position or at a
desired speed. The ac motor is usually used to drive
light loads at a constant speed, while the dc motor
is used to drive heavy loads at varying speeds.
PRIORITY– Order established by relative importance
of the function.
PROTECTIVE FEATURE– Feature of a component
or component part designed to protect a component
or system from damage.
SET POINT– Numerical value of a parameter at which
an alarm is actuated.
RECEIVER– (1) The object that responds to the wave
or disturbance. Same as DETECTOR. (2) Equipment that converts electromagnetic energy into a
visible or an audible form. (3) In radar, a unit that
converts rf echoes to video and/or audio signals.
SIGNAL– A general term used to describe any ac or dc
of interest in a circuit; for example, input signal.
SILICON CONTROLLED RECTIFIER PACKAGE– A device that furnishes controlled dc power
to a device.
REFERENCE POINT– A point in a circuit to which all
other points in the circuit are compared.
SINE WAVE– (1) The curve traced by the projection on
a uniform time scale of the end of a rotating arm, or
vector. Also known as a sinusoidal wave. (2) The
basic synchronous alternating waveform for all
complex waveforms.
REFERENCE SIGNAL– Command signal that
requests a specific final condition.
RELAY– An electromagnetic device with one or more
sets of contacts that change position by the magnetic
attraction of a coil to an armature.
SOLID STATE– Class of electronics components, such
as transistors, diodes, integrated circuits, silicon
controlled rectifiers, and so forth.
ROTOR– The rotating member of a synchro that
consists of one or more coils of wire wound on a
laminated core. Depending on the type of synchro,
the rotor functions similar to the primary or
secondary winding of a transformer.
SPAN– Distance between two points.
SPECIAL FUNCTION– Unique service performed by
a system; usually above and beyond the direct
designed intent of the system.
SCALING– Applying a factor of proportionality to data
or signal levels.
STANDARD PRINT– Standard drawing, schematic, or
blueprint produced in the applicable technical
manual or other official technical publication.
SCAT CODE– The subcategory (SCAT) code assigned
to the equipment, if applicable.
SEB NUMBER– The number of the support equipment
change that contains the modification implemented
on the corresponding equipment by the related
calibration activity (laboratory).
STATOR– The stationary member of a synchro that
consists of a cylindrical structure of slotted
laminations on which three Y-connected coils are
wound with their axes 120° apart. Depending on the
type of synchro, the stator’s functions are similar to
the primary or secondary windings of a transformer.
SELSYN– Self-synchronizing device or synchromotor.
SENSING POINT– Physical and/or functional point in
a system at which a signal may be detected or
monitored in an automatic operation.
STATUS LOG– Record of the instantaneous values of
important conditions having analog values.
SENSOR– A device that is sensitive to temperature,
pressure, position, level, or speed.
SUBASSEMBLY– Consists of two or more parts that
form a portion of an assembly or a unit.
SERVICING LABEL (SL)– A label attached to the
equipment to indicate the status of the equipment
after servicing.
SWITCH– (1) A device used to connect, disconnect, or
change the connections in an electrical circuit. (2)
A device used to open or close a circuit.
AI-4
TRANSFORMER– A device composed of two or more
coils, linked by magnetic lines of force, used to
transfer energy from one circuit to another.
SYNCHRO– A small motorlike analog device that
operates like a variable transformer and is used
primarily for the rapid and accurate transmission of
data among equipments and stations.
TROUBLE INDICATORS– Signal lights used to aid
maintenance personnel in locating troubles quickly.
SYNCHRO SYSTEM– Two or more synchros
interconnected electrically. The system is used to
transmit data among equipments and stations.
TROUBLE TABLES– Tables of trouble symptoms and
probable causes, furnished by many manufacturers
to help technicians isolate problems.
SYNCHRO TROUBLESHOOTING– The locating or
diagnosing of synchro malfunctions or breakdowns
by means of systematic checking or analysis.
TROUBLESHOOTING– The process of locating and
diagnosing faults in equipment by means of
systematic checking or analysis.
SYNCHRONIZER– A circuit that supplies timing
signals to other radar components.
TURNING GEAR– See JACKING GEAR.
SYNCHRONOUS– A type of teletypewriter operation
where both transmitter and receiver operate
continuously.
UNIT– (1) An assembly or any combination of parts,
subassemblies, and assemblies mounted together.
Normally capable of independent operation. (2) A
single object or thing.
SYSTEM– A combination of sets, units, assemblies,
subassemblies, and parts joined together to form a
specific operational function or several functions.
UNIT IDENTIFICATION CODE (UIC)– A
three-character alpha/numeric code representing
the Naval Aviation Maintenance Program (NAMP)
3-M organization code for the respective
customer/laboratory.
SYSTEM INTERRELATION– Specific individual
operations in one system affecting the operation in
another system.
TACHOMETER GENERATOR– A device for converting rotational speed into an electrical quantity
or signal.
VOLT– The unit of electromotive force or electrical
pressure. One volt is the pressure required to send 1
ampere of current through a resistance of 1 ohm.
TEST POINT– A position in a circuit where
instruments can be inserted for test purposes.
WATCH STATION– Duties, assignments, or
responsibilities that an individual or group of
individuals may be called upon to carry out; not
necessarily a normally manned position with a
watch bill assignment.
THRESHOLD– The least value of current or voltage
that produces the minimum detectable response.
TOLERANCE– An allowable deviation from a
specification or standard.
TRACKING– One object or device moving with or
following another object or device.
WAVEFORM– The shape of the wave obtained when
instantaneous values of an ac quantity are plotted
against time in rectangular coordinates.
TRANSDUCER– A device that converts a mechanical
input signal into an electrical output signal.
ZEROING– The process of adjusting a synchro to its
electrical zero position.
AI-5
APPENDIX II
REFERENCES USED TO DEVELOP
THE TRAMAN
Chapter 1
Electrician’s Mate 3 & 2, NAVEDTRA 10546-F, Naval Education and Training
Program Management Support Activity, Pensacola, Fla., 1988.
IC Electrician 3, NAVEDTRA 10559-A, Naval Education and Training Program
Management Support Activity, Pensacola, Fla., 1989.
IC Electrician 2 & 1, NAVEDTRA 10561-1, Naval Education and Training
Program Management Support Activity, Pensacola, Fla., 1985.
Service Manual, Motor Generator Set 30 kw, 440/450 Vac, 60/400 Cycle, 3 Phase
with Control Equipment, NAVSHIPS 363-1112, Department of the Navy,
Bureau of Ships, Washington, D.C., April 1964.
Chapter 2
Military Handbook, Synchros Description and Operation, MIL-HDBK-225A,
Naval Air Systems Command, Washington, D.C., March 1991.
Navy Electricity and Electronics Training Series, NAVEDTRA 172-15-00-85,
Module 15, Principles of Synchros, Servos, and Gyros, Naval Education and
Training Program Management Support Activity, Pensacola, Fla., 1985.
Technical Manual, Operation and Maintenance Instruction, Wind Indicating
Equipment, Type F, NAVSEA 0965-LP-108-9010, Naval Sea Systems
Command, Washington, D.C., December 1973.
Chapter 3
Stabilized Glide Slope Indicator (SCSI) Mk 1 Mod 0 (Incorporating Gyro Failure
Alarm) for Air Capable and Amphibious Aviation Ships, NAVAIR 51-5B-2,
Naval Air Systems Command, Washington, D.C., January 1991.
Chapter 4
IC Electrician 2 & 1, NAVEDTRA 10561-1, Naval Education and Training
Program Management Support Activity, Pensacola, Fla., 1985.
Instrumentman 3 & 2, NAVEDTRA 10193-D, Naval Education and Training
Program Management Support Activity, Pensacola, Fla., 1986.
Instrumentman 1 & C, NAVEDTRA 12202, Naval Education and Training Program
Management Support Activity, Pensacola, Fla., 1990.
Metrology Automated System for Uniform Recall and Reporting (MEASURE),
OP43P6A, Chief of Naval Operations, Washington, D.C., November 1984.
AII-1
INDEX
A
G
Anemometer systems, 2-1 to 2-18
Glide slope indicator assembly, 3-7
crosswind and headwind computer, 2-14 to 2-16
Gyroscope, vertical, 3-10
detector, 2-1 to 2-3
H
indicator, 2-3 to 2-4
maintenance of, 2-13
Hydraulic pump assembly, 3-6 to 3-7
major components, 2-1 to 2-4
L
synchro signal amplifier, 2-8 to 2-13
synchro signal converter and synchro signal
isolation amplifier, 2-16 to 2-18
synchros, 2-4 to 2-8
Lenticular lens, 3-8 to 3-9
M
transmitter, 2-3
Manual bus transfer switches, 1-1
troubleshooting of, 2-13
Manual bus transfers, motor controllers, and frequency
regulators, 1-1 to 1-45
types of, 2-1
frequency regulators, 1-22 to 1-45
C
manual bus transfer switches, 1-1
Calibration, 4-1 to 4-7
motor controllers, 1-1 to 1-21
calibration categories, 4-6 to 4-7
laboratories and activities, 4-2 to 4-4
terms and definitions, 4-2
MEASURE inventory report forms, 4-4
METCAL program, 4-1 to 4-4
Calibration laboratories and activities, 4-2 to 4-4
METER card, 4-4 to 4-6
Calibration standards, support for, 4-4
Metrology Automated System for Uniform Recall and
Reporting (MEASURE), 4-4 to 4-6
Crosswind and headwind computer, 2-14 to 2-16
euipment identification and receipt tag, 4-6
indicator, 2-16
inventory report forms, 4-4
maintenance and troubleshooting of, 2-16
MEASURE referral card, 4-6
wind direction circuit, 2-15
METER card, 4-4 to 4-6
windspeed circuit, 2-14
Motor controllers, 1-1 to 1-21
E
dc controllers, 1-10 to 1-15
Electric brakes, 1-15 to 1-17
magnetic across-line controllers, 1-6 to 1-10
Electronics enclosure assembly, 3-2 to 3-5
overload relays, 1-3 to 1-5
F
troubleshooting of, 1-18 to 1-21
Frequency regulators, 1-22 to 1-45
types of master switches, 1-3
Fresnel lens, 3-7 to 3-8
types of motor controllers, 1-2 to 1-3
INDEX-1
N
Stabilized Glide Slope Indicator (SGSI) SystemContinued
Navy Metrology and Calibration (METCAL) Program,
4-1 to 4-4
operational modes, 3-15 to 3-16
principles of lenses, 3-7 to 3-9
system electronics, 3-19 to 3-25
O
system operation, troubleshooting, and maintenance, 3-9 to 3-26
Operational amplifiers, 3-18 to 3-19
Stabilized platform assembly, 3-7
Overload relays, 1-3 to 1-5
Synchro signal amplifier, 2-8 to 2-13
description of, 2-9 to 2-10
P
maintenance of, 2-12 to 2-13
Personnel qualifications standards (PQS), 4-9
principles of operation, 2-10 to 2-12
Plano-convex lens, 3-7
Synchro signal converter and synchro signal isolation
amplifier, 2-16 to 2-18
R
Synchros, 2-4 to 2-8
maintenance and troubleshooting of, 2-8
Remote control panel assembly, 3-5 to 3-6
standard synchro connections, 2-4
synchros, zeroing of, 2-4 to 2-8
S
Synchros, zeroing of, 2-4 to 2-8
Safety, 4-10 to 4-16
electrical lock method, 2-8
alterations, 4-15
voltmeter method, 2-5 to 2-7
electric shock, 4-16
enforcing safety, 4-10
T
fire safety, 4-12
Technical administration, 4-1 to 4-16
IC room safety, 4-14
Transformer assembly, 3-7
live circuits, 4-12 to 4-13
maintenance and repair, 4-14 to 4-15
W
outside safety, 4-12
safe electrical/electronic maintenance, 4-10 to 4-11
Watch standing, 4-7 to 4-16
safety responsibilities, 4-10
personnel qualifications standards (PQS), 4-9 to
4-10
shore connections, 4-13 to 4-14
sources of safety information, 4-11 to 4-12
safety, 4-10 to 4-16
tagging procedure, 4-13
security training, 4-8
working aloft, 4-13
team training, 4-8 to 4-9
Stabilized Glide Slope Indicator (SGSI) System, 3-1 to
3-26
Wind direction and speed indicator systems, 2-1 to 2-18
crosswind and headwind computer, 2-14 to 2-16
components of, 3-2 to 3-7
detector, 2-1 to 2-3
hydraulic components, 3-25 to 3-26
indicator, 2-3 to 2-4
INDEX-2
Wind direction and speed indicator systems—Continued
Wind direction and speed indicator systems-Continued
maintenance of, 2-13
synchros, 2-4 to 2-8 transmitter, 2-3
major components, 2-1 to 2-4
synchro signal amplifier, 2-8 to 2-13
troubleshooting of, 2-13
synchro signal converter and synchro signal
isolation amplifier, 2-16 to 2-18
types of, 2-1
INDEX-3
Assignment Questions
Information: The text pages that you are to study are
provided at the beginning of the assignment questions.
ASSIGNMENT 1
Textbook Assignment:
“Manual Bus Transfer, Motor Controllers, and Frequency Regulators,”
chapter 1, pages 1-1 through 1-32.
1-4.
A. Manual controller
B. Magnetic controller
C. Across-the-line controller
D. Dc resistor controller
E. Ac primary resistor
controller
F. Ac secondary resistor
controller
G. Static variable-speed
controller
H. Autotransformer controller
J. Reactor controller
1. D
2. C
3. B
4. A
1-5.
IN ANSWERING QUESTIONS 1-1 THROUGH 1-8,
REFER TO FIGURE 1A.
1-6.
In what controller are resistors
inserted in the secondary circuit
of a wound-rotor ac motor for
starting or speed control?
What controller throws the
connected load directly across the
main supply line?
In what controller are resistors
inserted in the primary circuit of
the motor to control both starting
current and speed?
1. A
2. B
3. C
4. D
1. E
2. F
3. G
4. H
1-7.
1-3.
What controller has its contacts
closed or opened by electromechanical devices operated by
local or remote master switches?
1. H
2. F
3. D
4. B
1. B
2. C
3. E
4. F
1-2.
What controller is operated by hand
directly through a mechanical
system?
1. A
2. C
3. G
4. J
Figure 1A
1-1.
What controller has a resistor in
series with the armature circuit of
the motor?
What controller consists of solidstate and other devices that
regulate motor speeds in indefinite
increments through a predetermined
range?
1.
2.
3.
4.
1-8.
What controller starts the motor at
a reduced voltage and then connects
the motor to the supply line?
1. C
2. D
3. F
4. H
H
G
F
E
1
1-9.
Manual bus transfer switches are
most commonly used for what class
of equipment or circuit?
1.
2.
3.
4.
1-15.
Emergency
Nonvital
Vital
Casualty
Which of the following is a
disadvantage of an open-transition
compensator?
1.
2.
3.
1-10.
Motor controllers are used aboard
ship to start large motors because
the starting current is lower than
the running current.
1.
2.
1-11.
4.
3.
4.
Drum
Selector
Toggle
Pressure
1-17.
Electromechanical devices
A remote control master switch
A locally controlled master
switch
Each of the above
2.
3.
4.
1-18.
A dc resistor motor controller
A static variable-speed
controller
An across-the-line controller
An autotransformer controller
4.
2
The circuit through
contacts
The circuit through
switch
The circuit through
fuse element
The circuit through
operating coil
the main
the master
the control
the main
Which of the following is a coarse
adjustment to the thermal overload
relay?
1.
2.
3.
An ac secondary resistor
A dc secondary resistor
An ac primary resistor
An autotransformer
Local
Remote
Momentary
Maintaining
In a magnetic controller, what
circuit is opened by an overload
relay?
1.
In the secondary circuit of a
wound-rotor motor, what type of
controller is used to insert
resistance?
1.
2.
3.
4.
A master switch that is mounted in
the controller is classified as
what type of switch?
1.
2.
3.
4.
What type of controller is used to
start a 1/4-hp dc motor?
1.
2.
1-14.
1-16.
The contactors of a magnetic
controller are operated by which of
the following means?
1.
2.
3.
1-13.
True
False
Which of the following is NOT a
manually operated master switch?
1.
2.
3.
4.
1-12.
4.
The motor may slip into phase
during transition
The resistor dissipates too
much heat
The wound rotor has a tendency
to overspeed
The motor may slip out of phase
during transition, causing an
overload
Changing the heater element
Changing the magnetic air gap
Increasing the distance between
the heater and the sensitive
unit
Decreasing the distance a
bimetallic strip has to move to
open the circuit
1-22.
A.
Dashpot
B.
Bimetal
C.
Induction
D.
Solder pot
E.
Single metal
In the instantaneous and time-delay
magnetic overload relays, how
should you adjust the current
settings?
1.
2.
3.
4.
Figure 1B
IN ANSWERING QUESTIONS 1-19 THROUGH 1-21,
REFER TO THE TYPES OF OVERLOAD RELAYS
LISTED IN FIGURE 1B.
1-19.
1-23.
Which relay is NOT a type of
thermal overload relay?
1-24.
1-20.
A heat-sensitive element that
lengthens when heated to open the
contacts is used in which type of
relay?
1.
2.
3.
4.
1-21.
Which of the following types of
overload relays requires a time
delay before it is reset?
1.
2.
3.
4.
1. A
2
B
3. C
4. D
B
C
D
E
1-25.
1. A
2. C
3. D
4. E
Low-voltage
Low-voltage release
Overload
Each of the above
A reversing type of controller that
protects a 3-phase induction motor
against low voltage and overload
causes the motor to stop running
due to line voltage failure. After
line voltage is restored, how is
the motor restarted?
1.
2.
3.
4.
3
Dashpot
Magnetic
Solder pot
Each of the above
A controller protecting a motor is
able to disconnect it from the
power supply, keep it disconnected,
and then restart it automatically
when conditions return to normal.
What form of protection is the
controller providing?
1.
2.
3.
4.
Which type of relay is manufactured
for exclusive use in ac circuits?
By replacing the heating unit
By changing the distance of the
air gap between the armature
and the coil
By changing the distance
between the induction coil and
the tube
By changing the distance
between the heater and the
heat-sensitive unit
By automatic means
By the operator pressing the
forward push button or the
reverse button
By reversal of any two of the
three leads to the motor
By the operator resetting the
circuit breaker on the power
panel
1-26.
One type of ac motor speed
controller regulates the speed of
an ac motor by performing which of
the following actions?
1.
2.
3.
4.
1-27.
1-29.
Which symbol represents an OR logic
symbol?
1. A
2. B
3. C
4. D
Increasing and decreasing
stator current
Switching from one set of
stator windings to another
Increasing and decreasing the
voltage of the power source
Shunting different values of
resistance across the stator
windings
A 3-phase autotransformer is used
in starting 3-phase induction
motors and synchronous motors
because of its ability to perform
what function?
1.
2.
3.
4.
Furnish variable voltage
Reverse the direction of
rotation of the motor rotor
Switch motor stator connections
from wye to delta
Switch motor stator connections
from delta to wye
Figure 1D
IN ANSWERING QUESTIONS 1-30 THROUGH 1-33,
REFER TO THE DC CONTROLLER WITH ONE STAGE
OF ACCELERATION SHOWN IN FIGURE 1D.
1-30.
If the start button is pressed,
what action will cause line
contacts LC1 and LC2 to close?
1.
2.
3.
4.
1-31.
Figure 1C
IN ANSWERING QUESTIONS 1-28 AND 1-29,
REFER TO THE SYMBOLS SHOWN IN FIGURE 1C.
After closing contacts LC1, LC2,
and LC3, the controller accelerates
the motor. The controller connects
the motor across the line in what
manner?
1.
2.
1-28.
Which symbol represents an AND
logic symbol?
3.
1. A
2. B
3. C
4. D
4.
4
Closing of line contacts LC4
Operation of contactor coil LC
Operation of overload relay
coil OL
Current flowing through
armature A and contacts LC3
By the SR contact completing
the circuit to coil AC
By contact AC2 shorting out the
starting resistor
By allowing coil SR to restore,
closing the SR contact
Each of the above
1-32.
1-37.
After the motor is connected
directly across the line, what
should you do to interrupt the
circuit?
In a series dc motor, how is
dynamic breaking usually
accomplished?
1.
1.
2.
3.
4.
1-33.
Press the
Press the
button
Short out
Short out
stop button
start-emergency
2.
the series relay coil
the starting resistor
3.
4.
To vary the speed of the motor, how
should you change the controller
circuitry?
1.
2.
3.
4.
1-38.
Disconnect the SR relay
Disconnect the shunt field
winding
Connect a rheostat in series
with the SH winding
Connect a rheostat in parallel
with the AC coil
A dc motor is slowed by dynamic
braking when its turning armature
generates a countervoltage that
forces current through a connected
braking resistor. This resistor is
connected in what manner for (a) dc
series-wound motors and (b) dc
shunt-wound motors?
1.
1-34.
Magnetic blowout coils quench the
arc across contacts by which of the
following actions?
2.
3.
1.
2.
3.
4.
1-35.
4.
1-39.
Why are shaded coils used in an ac
solenoid brake?
1.
2.
3.
4.
1-36.
They increase the contact
separation
They provide a magnetic flux
that blows out the arc
They oppose the current flow
They pull the arc toward the
contacts
To
To
To
To
2.
3.
4.
In the operation of the torque
motor brake, what action applies
the brake shoes to the brake wheel?
1.
2.
3.
4.
(a)
(b)
(a)
(b)
(a)
(b)
(a)
(b)
Across the armature;
in series with the field
In series with the field;
across the armature
Across the armature;
across the armature
In series with the field;
in series with the field
When dynamic braking is used with a
dc shunt-wound motor, when, if
ever, does the generated
countervoltage equal zero?
1.
overcome eddy currents
reduce eddy currents
make magnetic pull constant
reduce vibration
The motor is disconnected from
the line
The armature and field are
connected in series with a
resistor to form a loop
Both 1 and 2 above
The field is disconnected from
the line
When the motor armature stops
turning
When the motor armature is
turning and lifting a heavy
load
When the brake is energized
Never
IN ANSWERING QUESTION 1-40, REFER TO TABLE
1-1 IN YOUR TEXTBOOK.
The torque motor advances the
jack screw upward
The torque motor acts to
increase the pressure in the
torque spring
The torque motor stalls,
permitting the brake to act
The torque motor circuit opens,
releasing the spring
1-40.
If controller contact tips
overheat, what action(s) should
maintenance personnel take?
1.
2.
3.
4.
5
Replace the blowout coil
Clean and adjust the contacts
Instruct the operator In the
correct operation
Replace the shading coil
1-43.
With the start button depressed,
what voltage will be present
between points B and D?
1.
2.
3.
4.
1-44.
IN ANSWERING QUESTIONS 1-41 THROUGH 1-43,
REFER TO THE 3-PHASE MAGNETIC LINE STARTER
SHOWN IN FIGURE 1E.
1-47.
1-41.
If a voltage is read at position A,
and no voltage is present at
position B, which of the following
statements is true?
1.
2.
3.
4.
1-42.
1-48.
After the start button is released,
which of the following conditions
will cause the motor to stop?
1.
2.
3.
4.
The
The
not
The
not
OL1
6
Voltage
Resistance
Temperature
Amperage
1V
2V
3V
4V
Which of the following is/are NOT a
part of the control equipment for a
motor generator?
1.
2.
3.
4.
holding relay is open
power contacts on L1 did
close
holding relay contacts did
close
is defective
SCR
Transistor
Diode
Mosfet
What is the minimum required
voltage of the gate pulse for
precise firing of an SCR?
1.
2.
3.
4.
The voltmeter is defective
All fuses are good
L1 fuse is defective
L2 fuse is defective
voltage
amperage
speed
resistance
Which of the following factors can
vary the magnitude of the gate
impulse needed to turn on an SCR?
1.
2.
3.
4.
Figure 1E
Constant
Constant
Constant
Constant
Which of the following
semiconductors is equivalent to a
gas-filled thyratron tube?
1.
2.
3.
4.
1-46.
V
V
V
V
Which of the following factors is a
requirement of a 30-kW-m-g set to
maintain a constant frequency?
1.
2.
3.
4.
1-45.
440
220
110
0
Overload protection
Start and stop switches
Frequency-regulating system
Motor
1-55.
IN ANSWERING QUESTIONS 1-49 THROUGH 1-52
REFER TO FIGURE 1-28 OF YOUR TEXTBOOK.
1-49.
What is the breakdown rating of the
Zener diode D-1?
1.
2.
3.
4.
5
10
15
20
1.
2.
3.
4.
V
V
V
V
1-56.
1-50.
When voltage in is 10 volts or
less, negligible current will flow
through R-1. The bridge is
operating in what mode?
1.
2.
3.
4.
1-51.
1-52.
0
5
10
15
1-57.
V
V
V
V
1-58.
I
II
III
IV
R1 and R2 only
R1 and D1 only
R1, R2, and R3 only
R1, R2, R3, and D1
The operation of the detector in
the voltage regulator is similar to
that of the frequency regulator
except that the detector senses
which of the following changes in a
generator?
1.
2.
3.
4.
Current rather than frequency
Speed rather than frequency
Voltage rather than frequency
Each of the above
IN ANSWERING QUESTION 1-59, REFER TO
FIGURE 1-29 IN THE TEXTBOOK.
One
Two
Three
Four
To amplify
To convert
Both 1 and
To convert
Which components form the Zener
reference bridge?
1.
2.
3.
4.
1-59.
What is the purpose of the preamp
and trigger?
1.
2.
3.
4.
Resistance measuring device
Voltage-sensing transformer
Linear frequency-sensing
transformer
Nonlinear frequency-sensing
transformer
IN ANSWERING QUESTIONS 1-57, REFER TO
FIGURE 1-28 IN THE TEXTBOOK.
How many dc amplifiers are used to
amplify the output from the Zener
bridge before going to the preamp
and trigger?
1.
2.
3.
4.
1-54.
4.
If the voltage in is greater than
20 volts, the bridge is operating
in what mode?
1.
2.
3.
4.
1-53.
I
II
III
IV
Supply voltage
External circuit impedance
Gate impulse magnitude
External circuit impedance and
supply voltage
The detector in the frequencyregulating system is what type of
device?
1.
2.
3.
When voltage in is 20 volts, the
drop across resistors R-1, R-2, and
R-3 is 10 volts. What is the
voltage out equal to?
1.
2.
3.
4.
When an SCR is in a high state of
conduction, the output current is
limited only by what factor?
What components form the power
circuit?
1.
2.
3.
4.
the varying dc input
the varying dc input
2 above
varying ac input
7
D1, D2, and D3 only
D1, D2, D3, SCR1, SCR2, and SP1
SCR1 and SCR2 only
SCR1, SCR2, and SP1 only
IN ANSWERING QUESTION 1-60, REFER TO
FIGURE 1-30 IN THE TEXTBOOK.
1-60.
1-64.
The field-flashing circuit consists
of which of the following
components?
When is the saturation point of the
magnetic material reached?
1.
2.
1.
2.
3.
4.
1-61.
D3,
D2,
T2,
D2,
T5,
R4,
and
D3,
and C3
and C3
T3
and T1
3.
What component is added to the
saturable current-potential
transformer to change the coupling
between the primary and secondary
windings?
1.
2.
3.
4.
1-62.
T3,
T5,
T1,
L3,
4.
1-65.
A dc control winding
An ac control winding
A filter capacitor
A resistor
1.
2.
3.
4.
Voltage windings Vp1 and Vs1
Current windings Ip1 and Ip2
Windings Vp1, Vp2, and Nc
Windings Vp1 and Ip2
1-66.
2.
3.
4.
causes an
causes an
Kilowatt load
Kilovolt ampere output
Unity power factor
VAR component of the load
The load current-sensing
transformer for generator A is
represented by which alpha/numeric
designation?
1.
2.
3.
4.
Assume that the core is not
saturated and the voltage of the
saturable potential transformer is
positive at the start of winding
NP1.
What will happen to the flux
01 and 02 in the center leg of the
transformer?
1.
causes no
flux
IN ANSWERING QUESTIONS 1-66 THROUGH 1-68,
REFER TO FIGURE 1-35 IN THE TEXTBOOK.
IN ANSWERING QUESTION 1-63, REFER TO THE
TRANSFORMER IN FIGURE 1-32 IN THE
TEXTBOOK.
1-63.
causes no
flux
When two generators are operating
in parallel, the power-sensing
network functions to balance which
of the following factors?
1.
2.
3.
4.
What windings on the saturable
current-potential transformer
function as a power transformer?
When an increase in
magnetomotive force
further increase in
When a decrease in
magnetomotive force
further decrease in
When an increase in
magnetomotive force
increase in flux
When a decrease in
magnetomotive force
increase in flux
1-67.
When will a shorting bar be placed
across CB3 contacts to eliminate
frequency droop?
1.
Flux 01 will cause an increase
in flux 02
Flux 02 will cause flux 01 to
increase
Flux 01 and 02 will cancel each
other
Flux 01 will cause a decrease
in flux 02
2.
3.
4.
8
A/T1
A/T2
A/CT1
B/CT1
When A and B are operating in
parallel
When A or B is operating by
itself
When A is carrying more load
than B
When A is carrying less load
than B
1-68.
1.
2.
3.
4.
1-69.
1-72.
The power-sensing system functions
to keep generators A and B
operating in parallel under which
of the following conditions?
1.
2.
3.
4.
When circuit breaker CB3 is
open
When transformer A/CT1 is
connected across rheostats A/R2
and B/R2
When transformer B/CT1 Is
connected across rheostats B/R1
and A/R2
When circuit breaker CB3 is
closed
1-73.
1-74.
1-70.
to
to
to
to
1
5
10
1
1-75.
The 4345A static inverter develops
a 400-Hz, 3-phase output. What is
the input voltage?
1.
2.
3.
4.
220
120
120
250
volts
volts
volts
volts
ac
ac
dc
dc
9
Hz
Hz
Hz
HZ
Front
Back
Side
Bottom
What assembly contains the controls
of the static inverter?
1.
2.
3.
4.
90°
180°
270°
360°
1600
800
400
60
On the 4345A static inverter, where
on the cabinet is the resistor
subassembly located?
1.
2.
3.
4.
The model 4345A static inverter has
two single-phase static inverters
that are operated with how many
degrees of controlled phase
difference?
1.
2.
3.
4.
1-71.
5
1
1
10
Oscillator assembly
Variable pulse width generator
Scott T-connected transformers
Power stage
What is the reference frequency
used in the 4345A static inverter
control circuits?
1.
2.
3.
4.
What front-to-back ratio is usually
an indication of a good diode?
1.
2.
3.
4.
What component(s) enables the
inverter to convert a 2-phase input
to 3-phase power?
Power stage assembly
Inverter module assembly
Resistor subassembly
Meter panel assembly
ASSIGNMENT 2
Textbook Assignment:
2-1.
“Manual Bus transfers, Motor Controllers, and Frequency Regulators,”
chapter 1, and “Anemometer Systems,” chapter 2, pages 1-32 through
2-18 .
2-4.
The level of conduction in the
modulating circuit is controlled by
which of the following signals?
1.
2.
3.
4.
An ac feedback signal
A synchronous pulse from the
oscillator
The output of driver stages
The dc voltage level input
The Scott T-connected transformer
will produce a 3-phase, 120-volt
output from which of the following
inputs?
1.
2.
3.
2-2.
What is the only way to stop an SCR
from conducting once it has already
started conducting?
1.
2.
3.
4.
4.
Remove the gate voltage
Reverse the gate voltage
Apply a slightly greater
reverse negative anode to
positive cathode voltage
Apply a slightly greater
reverse positive anode to
negative cathode voltage
2-5.
2-3.
What component in the inverter
reduces voltage transients in the
inverter 3-phase output?
1.
2.
3.
4.
IN ANSWERING QUESTION 2-3, REFER TO FIGURE
1-39 IN THE TEXTBOOK.
2-6.
When Q1 stops conducting, what
action causes the induced voltage
in the 6-7 winding to reverse
polarity?
1.
2.
3.
4.
A sudden drop to zero of
current in the 3-4 winding of
T1
A gradual drop to zero of
curent in the 3-4 winding of T1
A sudden rise of current in the
3-4 winding of T1
A gradual rise of current in
the 3-4 winding of T1
3.
4.
2-7.
Shows that the static inverter
is on standby
Supplies a +30-volt dc signal
to the synchronizing stage
Enables the input dc voltage to
be the power source for the
control circuit +30 volt dc
power supply
Each of the above
During the RUN mode, the control
circuits receive power from which
of the following sources?
1.
2.
3.
4.
10
Drive switch
Filters
Scott “T” transformer
Clipper network
When the main power circuit breaker
is in the OFF position, the drive
switch performs which of the
following functions?
2.
1.
A 3-phase, 120-volt filtered
input
A 3-phase, 120-volt unfiltered
input
A single-phase 0° controlled
input
Two single-phase, 90°
controlled inputs
+30-volt
Input dc
CA phase
Inverter
dc power source
power source
of the inverter
dc input voltage
2-8.
2-12.
In the STANDBY mode, a +30-volt dc
signal is applied to the binary
circuit in the sync stage via the
drive switch. This keeps the
bistable multivibrator in the sync
stage in what state?
What is used to control the bridge
circuit output voltage of the
rectified power supply?
1.
2.
1.
2.
3.
4.
Turn on
Turn off
Free running
Saturation
3.
4.
2-13.
IN ANSWERING QUESTION 2-9, REFER TO FIGURE
1-40 IN THE TEXTBOOK.
2-9.
The duration of the ON time of the
power stage is determined by which
of the following control signals?
1.
2.
3.
4.
2-10.
2-11.
2-14.
The output voltages of the static
inverter must be adjusted in what
phase sequence?
1.
2.
3.
4.
AB,
BC,
CA,
AB,
BC,
CA,
AB,
CA,
CA
AS
BC
BC
2.
3.
4.
Meter indications
Field excitation
Regulator controls
Relay switching
The voltage-sensing circuit steps
down the 3-phase generator 440-volt
ac output to what voltage?
1.
2.
3.
4.
50
50
25
25
volts
volts
volts
volts
ac
dc
ac
dc
IN ANSWERING QUESTIONS 2-15 AND 2-16,
REFER TO THE MODULATOR CIRCUIT SHOWN IN
FIGURE 1-44 IN THE TEXTBOOK.
Voltage checks on the rectifier
power supply are made at the load.
If incorrect, how are the voltages
adjusted?
1.
In the no-break power supply
system, the outputs of the voltage
and frequency monitors are
primarily used for what purpose?
1.
2.
3.
4.
Leading edge of waveform C
Trailing edge of waveform C
Leading edge of waveform P
Trailing edge of waveform P
A variable voltage SCR trigger
pulse
A variable polarity SCR trigger
pulse
A variable SCR firing time
A variable number of SCRs that
can be triggered
2-15.
Internally by repositioning a
lead on a trapped transformer
Internally by positioning a
potentiometer
Externally by positioning a
potentiometer
Externally by a switch that
changes leads on a tapped
transformer
What will happen to capacitor C4
when voltage peaks at the
unijunction transistor Q4?
1.
2.
3.
4.
2-16.
will
will
will
will
short
open
charge
discharge
What is the purpose of connecting
CR8 across the primary of T2?
1.
2.
3.
4.
11
It
It
It
It
To shunt out the self-induced
voltage of T2
To develop collector voltage on
Q5
To control the firing point of
Q5
To bypass T2 when Q5 is
conducting
2-17.
The SCRs of the generator field
recifier control power by varying
which of the following factors?
1.
2.
3.
4.
2-18.
2-22.
Voltage of the trigger pulse
Timing of the gate pulse on
each half cycle
Current of the gate pulse
Resistance of the generator
field
1.
2.
2-23.
When the generator output voltage
decreases, the voltage regulator
will increase the generator field
How can you cause the
current.
frequency regulator to increase
this field current?
2.
3.
4.
2-19.
2-20.
2-25.
One
Two
Three
Four
2.
3.
4.
Wind direction
detector
Wind speed and
transmitter
Wind direction
Wind speed and
indicator
What component in the speed
transmitter subassembly of the wind
transmitter changes linear
displacement to angular
displacement?
2-26.
1.
direction
2.
and gyro compass
direction
3.
4.
115 V, 60 Hz
115 V, 400 Hz
Both 1 and 2 above
220 V, 60 and 400 HZ
to
to
to
to
100 in 5-knot intervals
99 in 10-knot intervals
190 in 1-knot intervals
360 in 10-knot intervals
0 to 360
intervals
0 to 360
intervals
0 to 360
intervals
0 to 360
intervals
degrees in 1-degree
degrees in 5-degree
degrees in 10-degree
degrees in 15-degree
The conventional connection for
synchros is for a counterclockwise
rotation with an increasing
reading.
1.
2.
12
0
0
0
0
How is the dial of the direction
indicator marked?
and speed
2-27.
The synchronous integrator
The differential assembly
The magnetic amplifier
The friction disk and roller
assembly
How is the speed dial of a wind
indicator numbered?
1.
2.
3.
4.
The type F wind indicating system
provides what output(s)?
1.
2.
3.
4.
The direction transmitter
subassembly of the wind transmitter
contains what total number of
control transformers?
1.
2.
3.
4.
Which of the following is NOT a
major component of the wind
indicating system?
1.
2-21.
By increasing the generator
frequency
By decreasing the generator
frequency
By increasing the generator
voltage
By keeping the generator
voltage constant
What total number of mounted
anemometers are there on most
ships?
1.
2.
3.
4.
True
False
1. One
2. Two
3. Three
4. Four
2-24.
1.
The graduated dials in a type B
indicator are different than those
in a type F indicator.
True
False
2-28.
When it is desired for the shaft of
the synchro receiver to turn
clockwise for an increasing
reading, the leads should be
connected in which of the following
ways?
1.
2.
3.
4.
2-29.
When the synchro is at zero, which
windings will have minimum voltage
between them?
1.
2.
3.
4.
Mechanical
Electrical
Mechanical
Electrical
2-35.
zero
zero
null
null
The
The
The
The
dc voltmeter method
ac voltmeter method
synchro tester method
electric lock method
2-36.
2.
3.
To ensure a setting of zero
degrees rather than 180°
To prevent the voltmeter from
being overloaded
To keep the synchro device from
overheating
To correct the fine setting
to
to
to
to
S2
S3
S3
R2
S1
R1
R2
S1
and
and
and
and
S2
S1
S3
S3
A differential synchro is at
electrical zero if the axes of
which of the following coils are at
zero displacement?
1.
2.
3.
4.
S1
S2
R2
S1
and
and
and
and
S2
S3
S2
R1
If a synchro receiver is properly
zeroed, when do the stator windings
have electrical zero voltages?
When a 115-volt source is used
during the zeroing of a
differential synchro, what is the
maximum time the circuit can be
energized without causing damage to
the synchro?
1.
2.
3.
4.
1.
2.
3.
4.
4.
2-37.
S1
S2
S1
R1
The electrical zero position of a
TX-TR synchro system can be checked
by intermittently jumping which of
the following windings at the
receiver?
1.
2.
3.
4.
During synchro alignment, what is
the purpose of the coarse setting?
1.
2-32.
2-34.
What is the most accurate method of
zeroing a synchro?
1.
2.
3.
4.
2-31.
In the electrical zero position,
the axes of the rotor coil and what
other coil(s) are at zero
displacement?
1. S1
2. S2
3. S1 and S2
4. S3
What is the reference point for the
alignment of all synchros?
1.
2.
3.
4.
2-30.
S1 transmitter lead to S3
receiver lead
S2 transmitter lead to S1
receiver
Both 1 and 2 above
R1 transmitter lead to R2
receiver lead
2-33.
When the rotor is moving
When the rotor is stopped
When the rotor is at 270°
When the rotor is at its
reference position
13
1
2
15
30
minute
minutes
minutes
minutes
2-38.
On a properly zeroed CT, what
voltage exists only between S1 and
S2 or S2 and S3?
1.
2.
3.
4.
2-39.
2-45.
Both E- and F-type synchro signal
amplifiers have provision for what
total number of output synchros?
V
V
V
V
True
False
What method of zeroing a synchro is
the fastest but NOT the most
accurate?
1.
2.
3.
4.
2-41.
Synchro signal amplifiers used with
shipboard equipment are designed to
perform all except which of the
following functions?
1. Feed signals originating in the
synchro loads back to the input
bus, in phase with the input
2. Operate two synchro loads from
one input source
3. Operate large capacity synchro
transmitters with low current
inputs
4. Operate 400-Hz synchro loads
with 60-Hz inputs
If multispeed synchro systems are
used to accurately transmit data,
then the synchros within the system
must be zeroed separately.
1.
2.
2-40.
115
110
90
78
2-44.
The
The
The
The
1.
2.
3.
4.
dc voltmeter method
ac voltmeter method
electrical lock method
synchro tester method
2-46.
The electrical lock method of
zeroing a synchro requires
accessible leads and which of the
following conditions?
The major difference between the
type E- and type F-synchro signal
amplifiers is that the type E is
designed for operation on (a) what
input and the type F is designed
for operation on (b) what input?
1.
1.
2.
3.
4.
A rotor free to turn
A stator free to turn
A supply voltage to the stators
A zero-volt potential between
S1 and S2
2.
3.
4.
2-42.
The electrical lock method is
normally used to zero which type of
synchro?
2-47.
1. CT
2. TX
3. TR
4. CX
2-43.
1.
2.
3.
4.
To reduce the size of synchro
transmitters
To provide quicker information
To provide feedback to the
synchro transmitter
To match the impedance of the
system
14
(a) 400 Hz only;
(b)
60 Hz only
(a)
60 Hz only;
(b) 400 Hz only
(a)
60 and 400 Hz;
(b) 400 Hz only
(a)
60 Hz only;
(b)
60 and 400 HZ
What total number of scales is
provided on the dial of both the
type E- and type F-synchro signal
amplifiers?
1.
2.
3.
4.
What is the purpose of the signal
synchro amplifier?
One
Two
Three
Four
One
Two
Three
Four
2-48.
Speed changes from 1
speed and vice-versa
the type E- and type
signal amplifiers by
following actions?
1.
2.
3.
4.
2-49.
2.
3.
4.
A synchro amplifier cycle of
operation takes place during which
of the following conditions?
1.
Making wiring changes
Turning the dial over
Installing change gears
Both 2 and 3 above
2.
When the type E- or type F-synchro
signal amplifier is operated from a
low 1- or 2-speed input, it is
necessary to make some minor wiring
changes. What do these minor
wiring changes accomplish?
1.
2-50.
2-51.
speed to 2
can be made in
F-synchro
which of the
3.
Disconnect the low-speed
synchro control transformer
only
Connect the antistickoff
voltage only
Connect the low-speed synchro
control transformer and
disconnect the antistickoff
voltage
Disconnect the low-speed
synchro control transformer and
connect the antistickoff
voltage
4.
2-52.
When the shaft of a synchro is to
be driven clockwise for an
increasing reading, to which
terminal on the terminal block
should the S3 lead be connected
when standard synchro connections
are used?
1.
2.
3.
4.
How is the stator of a synchro
transmitter wound?
2-53.
With a two-circuit, parallelconnected winding
2. With a two-circuit, seriesconnected winding
3. With a three-circuit, deltaconnected winding
4. With a three-circuit, Yconnected winding
1.
2.
3.
4.
To serve as the preamplifier
for the servo amplifier
To switch from fine to coarse
data
To detect out-of-alignment
conditions between fine and
coarse data
To drive the relay-signaling
circuit
To prevent the synchro amplifier
system from locking in at 180° out
of phase, an antistickoff voltage
is applied to what component?
1.
2.
3.
4.
15
B1
B2
B3
BB
What is the purpose of a cutover
circuit?
1.
2-54.
When a change occurs in the
remotely transmitted synchro
data
When the signal received by the
synchro control transformers in
the mechanical unit is, as an
error voltage, amplified and
used to actuate the servomotor
which, through gearing, turns
the control transformer rotors
until the error voltages are
zero
When the servomotor drives the
rotors of the output synchros
into alignment
Each of the above
The fine synchro generator
The coarse synchro generator
The low-speed control
transformer
The high-speed control
transformer
2-55.
Gear train oscillation, or hunting,
is prevented in a synchro signal
amplifier by introducing a
stabilizing voltage at what
component?
2-59.
The phase shift that is inherent in
each control transformer of the
crosswind and headwind computer is
compensated for by what means?
1.
1.
2.
3.
4.
The
The
The
The
servo amplifier input
servo amplifier output
low-speed CT
high-speed CT
2.
3.
4.
2-56.
The external alarm of a synchro
amplifier will be energized under
all except which of the following
conditions?
1.
2.
3.
4.
2-60.
When the input and output
synchros are excited and the
alarm switch is off
When the input and output
synchros are excited and the
alarm switch is on
When the alarm switch is on and
one or more of the input or
output synchros are not excited
When the servo unit fails to
follow the input signal, within
2.5°
What is the phase relationship
between the straight deck crosswind
signal, A, and the angled deck
crosswind signal, B?
1.
2.
3.
4.
2-61.
The crosswind and headwind computer
system is designed for use aboard
which of the following vessels?
2.
3.
1.
2.
3.
4.
2-58.
PFs
DLGs
CLGs
CVAs
4.
2-62.
The crosswind and headwind computer
receives its input (a) in what form
and (b) from what source?
1.
2.
3.
4.
4.
16
leads B by 10°
lags B by 10°
leads B by 30°
lags B by 30°
Elimination of unwanted
feedback
Retransmission of accurate
information without error
Conversion of 60-Hz signals to
400-Hz signals
Each of the above
What feature of the synchro signal
isolation amplifier prevents torque
feedback from the output synchro
from being reflected into the
converter?
1.
2.
3.
(a) Relative wind direction;
(b) speed from HD and HE
circuits
(a) True wind direction;
(b) speed from CIC
(a) Relative wind direction;
(b) speed from CIC
(a) True wind direction;
(b) speed from HD and HE
circuits
A
A
A
A
Which of the following is a purpose
of the synchro signal converter and
the synchro signal isolation
amplifier?
1.
2-57.
An inductor in parallel with
the error signal
A transformer
Negative feedback in the servo
amplifier
Positive feedback in the servo
amplifier
Low amplification factor
High amplification factor
High input impedance, low
output impedance
Low input impedance, high
output impedance
2-63.
The output signal from the low-pass
filter network in the synchro
signal converter can be described
by which of the following phrases?
1.
2.
3.
4.
It is a
It is a
current
It is a
current
It is a
current
pure direct current
pulsating direct
60-Hz alternating
400-Hz alternating
17
ASSIGNMENT 3
Textbook Assignment:
3-1.
“Stabilized Glide Slope Indicator System,” chapter 3, pages 3-1
through 3-26
Which of the following information
in reference to a landing platform
or ship does the GSI indicate to a
pilot?
1.
2.
3.
4.
3-6.
1.
2.
3.
4.
Distance
Location
Approach speed
Approach angle
What does the failure detection
circuit do in case of stabilization
failure?
1.
1.
2.
3.
4.
115 volts ac 400 Hz and 440
volts ac 60 Hz
115 volts ac 60 Hz and 220
volts ac 400 Hz
115 dc and 440 volts ac 400 Hz
115 volts dc and 115 volts ac
160 HZ
2.
3.
4.
3-8.
3-3.
The light bar of the GSI contains
which three colors?
1.
2.
3.
4.
3-4.
3-9.
Red
Amber
Yellow
Green
The bar of light is formed by the
combined actions of which of the
following lights/lens?
1.
2.
3.
4.
It automatically switches to a
standby stabilization
It switches all three colors in
the light bar to red
It turns off the lights
It switches to a standby GSI
The feedback control system is
essentially a servo loop.
1.
2.
Yellow, red, and green
Red, orange, and green
Green, amber, and red
Yellow, amber, and red
If the pilot is on the correct
glide path, which of the following
colors will he see?
1.
2.
3.
4.
3-5.
115 volts ac
115 volts dc
Internal gyro
Local gyro
What is the source of power of the
GSI system?
3-7.
3-2.
The stabilized platform uses what
reference to develop electronic
error signals?
True
False
When the GSI is operating normally,
the LVDT generates the error
voltage that determines the
position of the stable platform.
1.
2.
True
False
A.
B.
C.
D.
E.
F.
Electronic enclosure assembly
Remote control panel assembly
Hydraulic pump assembly
Transformer assembly
GSI assembly
Stabilized platform assembly
Figure 3A
Source light, Fresnel lens, and
lenticular lens
Source light, Fresnel lens, and
collector lens
Fresnel lens, lenticular lens,
and colored lens
Source light, lenticular lens,
and contact lens
IN ANSWERING QUESTIONS 3-10 THROUGH 3-15,
REFER TO FIGURE 3A.
18
3-10.
3-16.
What assembly is the signal
processing distribution and control
center for the system?
1.
2.
3.
4.
1. A
2. C
3. B
4. D
3-11.
3-17.
What assembly is a self-contained,
medium-pressure, closed-loop system
used to supply hydraulic pressure
for the stabilized platform?
3-18.
What assembly steps down the
voltage for the source light from
115 volts ac to 18.5 volts ac?
3-19.
3-13.
What assembly is mounted to the
ship’s deck in close proximity to
the helicopter landing area?
2.
3.
4.
3-20.
3-14.
What assembly is made up of the
mounting base assembly and the
indicator assembly?
3-15.
3-21.
What assembly provides control and
indicators for operating and
monitoring the SGSI system from a
remote location?
4.
19
Gyro transmitter
Failure detection circuit
Servo amplifier
Stab-lock relay
What is the location of the remote
control panel?
1.
2.
3.
1. A
2. B
3. C
4. D
Hydraulic fluid enters the
actuator
An error signal is generated
The READY light is lighted
The NOT READY light is lighted
What FEATURE tests and aligns the
GSI?
1.
2.
3.
4.
1. A
2. B
3. E
4. F
Stab-lock relay
Power transformer
Servo amplifier
Gyro demodulator
When the platform becomes level,
what action occurs?
1.
1. A
2. C
3. E
4. F
Synchro transmitters
Synchro receivers
Synchro resolvers
Levels
The error signal is changed from an
ac signal to a dc signal by what
component?
1.
2.
3.
4.
1. B
2. C
3. D
4. F
Feedback control system
Reference signal system
Servo loop control system
Gyro signal system
What components mounted on the
gimbals senses any motion of pitch
and roll?
1.
2.
3.
4.
1. A
2. B
3. C
4. D
3-12.
The error signal from the
electronic enclosure assembly is
generated by what system?
In the engineering log room
On the bridge
In the flight operations
control room
On the flight deck
3-22.
The overtemp light comes on when
the hydraulic fluid heats to what
minimum temperature?
1.
2.
3.
4.
3-23.
±5°
±5°
±5°
±5°
3.
4.
The purpose of the transformer
assembly is to step-down the
115-volt ac source voltage to what
voltage?
1.
2.
3.
4.
When the stab-lock button is
pushed, the error signal is caused
by what component?
1.
2.
3-24.
115
125
135
145
3-28.
3-29.
The gyro
The linear differential
transformer
The potentiometer
The gyro signal synchro
amplifier
4.
3-30.
3-25.
3-27.
2.
What is the operating pressure of
the GSI hydraulic system?
1.
2.
3.
4.
3-26.
The hydraulic pump assembly
The transformer assembly
The remote control assembly
The glide slope indicator
assembly
1400
1300
1200
1000
3.
psi
psi
psi
psi
4.
3-31.
Hydraulic fluid heaters in the oil
reservoir maintain the temperature
at approximately what value?
1. 80° ±5°
2. 85° ±5°
3. 70° ±5°
4. 75° ±5°
3-32.
The three colors run together
vertically to form one solid
color
The size of the bar of light
near the center of the lens is
different from that which is
seen near the center of the
lens
The motion of the bar of light
from cell center to transition
line does not appear to be
smooth
The vertical field angle is
either larger or smaller
20°
30°
40°
50°
What is the color of the lenticular
lens in the (a) top segment and (b)
bottom segment?
1.
2.
3.
4.
20
Form an astigmatism
Converge all at one point
Pass through the lens near the
principle axis
Scatter
What is the azimuthal range of the
lenticular lens used in the Fresnel
system?
1.
2.
3.
4.
The pressure switch in the
hydraulic pump discharge line will
close at what pressure?
1. 1400 psi
2. 1200 psi
3. 1300 psi
4. 1000 psi
dc
dc
ac
ac
Which of the following effects is
NOT a characteristic of operating
the Fresnel lens outside specific
temperature limits?
1.
1.
2.
3.
4.
volts
volts
volts
volts
What do the light rays from a
piano-convex spherical lens tend to
do?
1.
2.
3.
What system consists of the
electric pump motor, a coupling
unit, a hydraulic pump reservoir,
valves, piping, and an electrical
system?
24.0
18.5
24.0
18.5
(a)
(a)
(a)
(a)
Green; (b) red
Amber; (b) red
Green; (b) amber
Red;
(b) Green
3-33.
3-39.
When the Fresnel system is not
operating, what component secures
the source light indicator assembly
in a fixed position?
1.
2.
3.
4.
1.
2.
3.
4.
Junction box
Stowlock assembly
Deck-edge boom
Roll power drive assembly
3-40.
3-34.
What is the essential element of
the vertical gyroscope?
1.
2.
3.
4.
3-35.
3-41.
One
Two
Three
Four
15.0
15.8
16.0
16.8
in.
in.
in.
in.
3-43.
1.
2.
3.
4.
3-38.
One
Two
Three
Four
3-44.
1.
2.
3.
4.
Blowers
Heaters
Thermal switches
All of the above
Ship gyro
Ship gyro stab-lock
Internal gyro stab-lock
Internal gyro
Ship gyro
Internal gyro
Internal gyro stab-lock
Ship gyro stab-lock
Electronic enclosure assembly
Transformer assembly panel
Remote control panel
Stabilized platform assembly
The LVDT loop is exactly the same
as the gyro feedback loop.
1.
2.
21
ft
ft
ft
ft
From what assembly/panel does the
operator control the intensity of
the source light?
1.
2.
3.
4.
In the GSI, lens temperature
control is achieved by which of the
following devices?
10
7
5
4
What mode of operation enables the
operator to isolate and test
various parts of the system while
disenabling other parts?
1.
2.
3.
4.
What total number of projection
lamps is used in the GSI?
+10°F
+10°F
+10°F
+10°F
Unless a system failure prevents
it, the GSI should always be
operated in what mode?
1.
2.
3.
4.
3-42.
110°
100°
98°
96°
The transformer assembly uses what
fixed length of cable from the
transformer secondary to the GSI
cell connector?
1.
2.
3.
4.
In the GSI cell, what is the total
distance from the slots to the
Fresnel lens?
1.
2.
3.
4.
3-37.
pendulum
thermal switch
projection lamp
flywheel
When performing the cell alignment
of the GSI, what total number of
adjustments must you make?
1.
2.
3.
4.
3-36.
A
A
A
A
In the GSI, control thermoswitches
S1 and S2 are set to operate at
what temperature?
True
False
3-45.
The universal joints and rod ends
allow the platform to tilt in what
total number of axes?
1.
2.
3.
4.
3-46.
3-50.
One
Two
Three
Four
1.
2.
3.
4.
The GSI stable platform uses what
total number of servo loops in each
axis?
When the output of the LVDT is
zero, what is the position of the
platform top in relation to the
base?
1.
2.
3.
4.
3-48.
3-49.
Above
Below
Level
Fluctuating
FIGURE 3B
IN ANSWERING QUESTIONS 3-51 THROUGH 3-61,
REFER TO FIGURE 3B.
Which of the following is NOT a way
in which op-amps are used in the
stable platform system?
1.
2.
3.
4.
Saturated positive
Saturated negative
No output
Output changes with varying
inputs
A. Gyro demodulator
B. LVDT
C. LVDT demodulator card
D. LVDT oscillator
E. LVDT demodulator
F. Servo amplifier
G. Dither oscillator
H. Error circuit
I. Gyro alarm circuits
J. Gyro signal card assembly
K. Source light failure detector
L. Power distribution circuits
1. One
2. Two
3. Three
4. Four
3-47.
Which of the following is NOT a
common type of failure for an opamp?
3-51.
Amplifiers
Demodulators
Comparators
Oscillators
An electromechanical transducer
that converts physical motion into
an output voltage whose amplitude
and phase are proportional to
position.
1.
2.
3.
4.
What will happen if feedback is
added to the amplified inverting
and noninverting inputs of an opamp?
3-52.
The voltage difference between
the inputs will increase
2. The voltage difference between
the inputs will remain the same
3. The voltage difference between
the Inputs will decrease
slightly
4. The voltage difference between
the inputs will be close to
zero
B
C
D
E
Consists of a quadrature oscillator
and a power amplifier.
1.
1. A
2. B
3. D
4. G
3-53.
Supplies a constant voltage ac
excitation to the LVDT primaries
and converts the pitch and roll
LVDT amplitude and phase signals to
a variable dc voltage.
1. A
2. C
3. H
4. J
22
3-54.
3-60.
Has three inputs summed into
amplifier A1.
1. L
2. K
3. J
4. I
1. E
2. F
3. J
4. K
3-55.
3-61.
Has a signal that is full-wave
rectified and filtered, whose
output polarity is positive for
signals out of phase with the
reference and negative for signals
in phase.
3-57.
3-62.
3-63.
L
K
H
G
1. A
2. B
3. H
4. I
3-58.
3-64.
Detects any failure that will
result in a loss of stabilization.
1. G
2. H
3. I
4. J
3-59.
1. A
2. J
3. K
4. L
23
38 psig; (b)
(a)
(a) 700 psig; (b)
70 psig; (b)
(a)
(a) 380 psig; (b)
700
38
380
70
psig
psig
psig
pslg
The hydraulic cylinders used in the
SGSI are linear actuators. The
hydraulic pressure exerted by the
piston is 1400 psig in extension.
What is the pressure exerted in
compression?
1.
2.
3.
4.
Amplifies and sums the demodulated
pitch and roll synchro signals from
the ship’s gyro with the platform
LVDT outputs.
True
False
The hydraulic accumulators used in
the SGSI are steel cylinders with
internal rubber bladders. The
bladders are pressurized with dry
nitrogen to what pressure for the
(a) high-pressure end (b) lowpressure accumulators?
1.
2.
3.
4.
Monitors the pitch and roll servo
errors.
L
J
G
A
The SGSI system uses hydraulic
pressure for motive power.
1.
2.
Provides a high-frequency signal to
the servo valves to keep them in
constant motion to prevent sticking
at null.
1.
2.
3.
4.
Provides two sources of power to
the system.
1.
2.
3.
4.
1. J
2. H
3. F
4. E
3-56.
Monitors the voltage and current
going to the three source lights.
700
500
400
200
psig
psig
psig
psig
ASSIGNMENT 4
Textbook Assignment:
4-1.
Administration,” chapter 4, pages 4-1 through 4-16.
The science and art of measurement
is known by what term?
1.
2.
3.
4.
4-2.
“Technical
4-5.
Meteorology
Traceability
Metrology
Physics
Each instrument calibrated must
bear evidence that it is in
calibration. This evidence is in
what form?
1.
2.
What is the calibration of all
measuring devices based on?
3.
4.
1.
2.
3.
4.
4-3.
The basic international and
national standards of
measurements
The advanced national standards
of measurement
The 16 principles of
calibration procedures
The American standards of
measurement
4-6.
1.
2.
3.
4.
To ensure traceability and
accuracy of instrument
calibration to NIST
To ensure traceability and
accuracy of instrument.
calibration to the CNO
To ensure traceability and
accuracy of medical equipment
To ensure traceability and
accuracy of periscopes
4-7.
The accuracy of a standard must be
traceable, through documentation by
each higher calibration activity,
to what activity?
1.
2.
3.
4.
NSL
MEC
RSL
NAVSEA
The common reference for Navy
scientific measurements is provided
by what activity?
1.
2.
3.
4.
4-8.
4-4.
The METCAL program provides for
periodic calibration of most
instruments.
The responsibility
for assignment of these periodic
calibration intervals has been
given to what activity?
1.
2.
3.
4.
What is the purpose of the METCAL
program?
A stamp on the instrument
A color coding on the
instrument
A letter from NIST taped to the
instrument container
A calibration label affixed to
the instrument
NIST
MEC
NAVSEA
OPNAV
What activity certifies the
standards used by the type I NSL?
1. MEC
2. NAVSEA
3. NIST
4. OPNAV
NAVSEA
NSL
NIST
RSL
24
4-14.
A.
B.
C.
D.
E.
F.
STANDARD
CALIBRATION
TEST AND MONITORING SYSTEM
TRACEABILITY
INCIDENTAL REPAIR
OPERABLE EQUIPMENT
1.
2.
3.
4.
4-15.
FIGURE 4A
IN ANSWERING QUESTIONS 4-9 THROUGH 4-14,
REFER TO FIGURE 4A.
4-9.
Equipment used for quantitative
measurement.
1.
2.
3.
4.
4-11.
B
C
E
F
4-17.
4-18.
A laboratory device used to
maintain continuity of value in the
units of measurement.
4-13.
4-19.
A piece of equipment that is
performing satisfactory before
being submitted for calibration.
25
Type I NSLs
Type II RSLs
Type III NSLs
MEC
What activities have been set up to
enable user activities to calibrate
locally such specific types of
instruments as pressure gauges,
temperature gauges, and electrical
meters?
1.
2.
3.
4.
1. A
2. C
3. E
4. F
First
Second
Third
Fourth
Type II NSLs obtain standards
calibration services from which of
the following activities?
1.
2.
3.
4.
1. F
2. C
3. D
4. A
Air Force personnel
Civil engineers
Safety supervisors
Project managers
What echelon of calibration is
provided by the reference standard
laboratories?
1.
2.
3.
4.
B
C
E
F
NAVSEA
NAVAIRSYSCOM
TYCOM
SECNAV
In performing its function, the NSL
provides services for the systems
commands, cognizant laboratories,
and what personnel?
1.
2.
3.
4.
The comparison of a measurement
device of unverified accuracy to a
device of known and greater
accuracy.
1.
2.
3.
4.
4-12.
4-16.
F
E
D
B
The operation of the type I NSL and
its detachment is under the
cognizance of what command?
1.
2.
3.
4.
The unbroken chain of properly
conducted and documented
calibration.
1. F
2. E
3. D
4. B
4-10.
Replacement of parts that prevent
calibration, but do not render the
equipment inoperative.
NSLs
FCAs
RSLs
NCLs
4-20.
To receive calibration support for
standards, you should take which of
the following steps?
1.
2.
3.
4.
4-21.
4-23.
Request funds
Request calibration services
Make up a recalibration
schedule
Each of the above
4-25.
Format 350
Inventory report form
METER card
Format 310
4-26.
4-27.
One
Five
Seven
Ten
1. MEC
2. METCAL rep
3. MOCC
4. MIRCS
A
B
E
F
Provides the initial input of data
pertaining to TAMS equipment and
calibration.
1.
2.
3.
4.
4-28.
A
B
C
E
Contains information on how to use
the MEASURE program.
1.
2.
3.
4.
The inventory report form
information is entered into the
data bank by what person/activity?
A.
B.
C.
D.
E.
F.
Used to report information and
transactions pertaining to TAMS and
calibration standards.
1.
2.
3.
4.
After the initial inventory report
form has been submitted, what
minimum number of items being added
to the inventory would allow the
use of the inventory report form
again?
1.
2.
3.
4.
Attached to the METER card.
1. A
2. B
3. C
4. D
The initial data input for the
MEASURE program is submitted on
what form?
1.
2.
3.
4.
4-22.
4-24.
A
D
E
F
Contains all information necessary
to identify a single piece of TAMS
equipment and calibration.
1. A
2. C
3. D
4. F
TMDE INVENTORY REPORT FORM
OP43P6
METER CARD
EQUIPMENT ID AND RECEIPT TAG
NAVSUP 4500
OP4700
4-29.
Bears the same control number as
the METER card.
1. A
2. B
3. C
4. D
FIGURE 4B
IN ANSWERING QUESTIONS 4-24 THROUGH 4-29.
REFER TO FIGURE 4B.
26
4-30.
4-35.
What document is used to forward
questions, recommendations, and
comments pertaining to MEASURE to
concerned authorities?
1.
2.
3.
4.
1.
2.
3.
4.
A MEASURE referral card
A METER card
A TMDE inventory report form
An equipment ID and receipt tag
4-36.
IN ANSWERING QUESTIONS 4-31 and 4-32,
REFER TO FIGURE 4-2 IN THE TEXT.
4-31.
4-32.
4-33.
1
11
19
4
and
and
and
and
E
D
E
D
CALIBRATED--REFER TO REPORT
CALIBRATION VOID IF SEAL BROKEN
CLEANED FOR OXYGEN USE
INACTIVE
What does block 65 identify?
The overall security, orientation,
education, and training program is
the responsibility of what person?
1.
2.
3.
4.
1.
2.
3.
4.
4-37.
Rejected piece of equipment
Calibration lab standard
Phase/level standard
Accessories
Which, if any, of the following
copies of the receipt and ID tags
are sent to the MOCC?
1.
2.
3.
4.
4-38.
White
Pink
Green
None of the above
1.
A calibrated label is used when
which of the following conditions
is met?
1.
2.
3.
4.
3.
A specific tolerance is
requested by the user
A specified condition requested
cannot be met
The instrument fails at more
than one test point within its
range
All parameters to be tested are
within tolerance
4.
4-39.
commanding officer
executive officer
security officer
engineer officer
Stressing the importance of
security and the penalties for
violating security regulations
Relating the techniques that
enemies have used to acquire
classified information
Using posters in appropriate
places as reminders of an
individual’s duties concerning
security matters
All of the above
What is the best means of
developing individuals and teams
into efficient working units?
1.
2.
3.
4.
27
The
The
The
The
Ways by which you can help make
personnel security conscious
include which of the following
methods?
2.
4-34.
USER CALIBRATION
CALIBRATED
SPECIAL CALIBRATION
NO CALIBRATION REQUIRED
Which of the following labels
requires that an instrument must be
calibrated before it can be used?
1.
2.
3.
4.
What blocks describe an item?
1.
2.
3.
4.
What label/tag must be used when
certain conditions must be known to
the user and/or the calibration
technician?
Teaching by the show-and-tell
method
Drilling and practicing on the
job
Showing technical films and
closed-circuit television
programs
Conducting classroom lectures
and informal group discussions
4-40.
The PQS program is designed to help
you train your personnel for which
of the following reasons?
1.
2.
3.
4.
4-41.
To qualify for advancement
To discharge their leadership
responsibilities
To perform their assigned
duties
To become familiar with offship IC equipment and systems
Doors to switch and fuse boxes
should be closed except under which
of the following conditions?
1.
2.
3.
4.
4-47.
Each qualification standard has
four main subdivisions. What
series is for watch standers?
1.
2.
3.
4.
4-42.
4-46.
What individual must give approval
to work on energized circuits?
1.
2.
3.
4.
100
200
300
400
4-48.
What section (series) of PQS breaks
down the equipment or systems to be
studied into functional sections?
4-43.
100
200
300
400
2.
3.
What section of the PQS is used to
record the individual’s
satisfactory completion of an item?
4.
4-49.
1.
2.
3.
4.
4-44.
2.
3.
4.
Amount and duration of current
flow
Parts of the body involved
Frequency of current
Each of the above
4-50.
1.
2.
3.
4.
1 mA
10 mA
50 mA
100 mA
28
555
430
300
None of the above
What piece of software, used in
PMS, has a section devoted to
safety precautions?
1.
2.
3.
4.
What amperage is usually fatal if
it lasts for 1 second or more?
Those that will achieve maximum
safety
Those that will achieve minimum
safety
Higher authority should be
contacted
Division officer’s advice
should be followed
Which, if any, of the following
NSTM chapters gives clear and
concise electrical safety
precautions that should be required
study material for all hands?
1.
2.
3.
4.
Which of the following factors
determines whether you receive
either a slight or fatal shock?
1.
4-45.
Theory
Qualification
Watchstation
System
Executive officer
Engineer officer
Commanding officer
Division officer
Should a situation arise where a
doubt exists as to the application
of a particular directive or
precaution, what measures should be
taken?
1.
1.
2.
3.
4.
When replacing fuses
When the area around the box is
not manned
During battle stations
After knock-off of ship’s work
Weekly schedule
Work center PMS manual
Maintenance requirement card
Quarterly schedule
4-51.
1.
2.
3.
4.
4-52.
2.
3.
4.
4-56.
PKP
CO2
Water
AFFF
4-57.
Removing rings, watches, and
loose clothing before starting
work
Wearing rubber gloves on both
hands
Using insulated hand tools
All of the above
2.
3.
4.
4-59.
ac
ac
ac
ac
and
and
and
and
220
48
90
48
volts
volts
volts
volts
ac
dc
ac
dc
Live front
Semi-dead front
Dead front
None of the above
10 amperes only
15 amperes only
25 amperes only
Any rating
What is the purpose of having an
on-the-scene observer when you are
working on a live circuit?
1.
2.
3.
4.
29
volts
volts
volts
volts
Fuses of what maximum rating may be
removed from a circuit before it is
de-energized?
1.
2.
3.
4.
Only one repairman tags the
supply and removes the tag when
the work is completed
At least two repairmen tag the
supply; one repairman removes
the tags when the work is
completed
Each repairman tags the supply
and removes only his/her tag
when his/her work is completed
Each repairman tags the supply;
the repairman completing
his/her work last removes the
tags
115
220
115
90
Which, if any, of the following
switchboards has greatly reduced
hazards to operators and repairmen?
1.
2.
3.
4.
4-58.
Officer of the deck
Engineer officer
Commanding officer
Command duty officer
What two hazardous voltages may be
encountered when the ship’s service
telephone system is connected to a
shore exchange?
1.
2.
3.
4.
When more than one repairman is
working on circuits that have a
common supply, what procedure
should be used for tagging circuits
and removing tags?
1.
What individual must grant
permission before a person can go
aloft?
1.
2.
3.
4.
A technician working on a live
circuit can help avoid accidents by
taking which of the following
precautions?
1.
4-54.
Use a 1 1/2-inch fire hose
Use a CO2 fire extinguisher
Use a PKP fire extinguisher
Do not let the fire happen
Which of the following agents
should be used to fight electrical
fires?
1.
2.
3.
4.
4-53.
4-55.
What is the best way to control any
fire?
To ensure that all safety
precautions are followed and to
run errands
To ensure that all safety
precautions are followed and to
give first aid if necessary
To deliver messages and to
locate specifications in NSTM,
chapter 300
Each of the above
4-60.
4-61.
Extension cords used with portable
electric tools should NOT exceed
what maximum length?
1.
2.
3.
4.
25
50
100
200
ft
ft
ft
ft
Naval regulations provide that no
alterations are permitted to be
made to ships until authorized by
what command or individual?
1.
2.
3.
4.
30
Type commander
Commanding officer
Naval Sea Systems Command
Chief of Naval Operations
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