inverter beginner course

inverter beginner course
INVERTER SCHOOL TEXT
INVERTER BEGINNER COURSE
INVERTER SCHOOL TEXT
INVERTER BEGINNER COURSE
MODEL
MODEL
CODE
HEAD OFFICE : TOKYO BUILDING, 2-7-3 MARUNOUCHI, CHIYODA-KU, TOKYO 100-8310, JAPAN
NAGOYA WORKS : 1-14 , YADA-MINAMI 5-CHOME , HIGASHI-KU, NAGOYA , JAPAN
When exported from Japan, this manual does not require application to the
Ministry of Economy, Trade and Industry for service transaction permission.
Specifications subject to change without notice.
SAFETY PRECAUTIONS
(Always read these instructions before the exercise.)
When designing a system, always read the relevant manuals and give sufficient consideration to
safety.
During the exercise, pay full attention to the following points and handle the equipments correctly.
[Precautions for Exercise]
!
WARNING
● Do not touch the terminals while the power is on, to prevent an electric shock.
● When opening the safety cover, turn the power off or conduct a sufficient check of safety before
operation.
!
CAUTION
● Follow the instructor’s directions during the exercise.
● Do not remove the units of a demonstration machine or change wirings without permission.
Doing so may cause a failure, malfunction, injury and/or fire.
● Turn the power off before installing or removing a unit.
Failure to do so may result in a malfunction of the unit or an electric shock.
● When an error occurs, notify the instructor immediately.
Introduction
Thank you very much for joining the FATEC school today. Also, thank you very much for choosing the
Mitsubishi products.
Before taking a course in this school, please read the following brief explanation on the contents and
purpose of this school.
The targets of this “Inverter introduction course” are from those who have never used an inverter before to
those who have some experience of using an inverter but want to know the basic principle, etc. This course
especially describes the techniques, motor-related and power circuit-related contents that are common to
inverters in an understandable way. This course also gives a simple account of the contents that are good to
know for using an inverter including basic operations of an actual machine.
For the requests to know more details or to use selection software, the other schools are also available.
School name
Inverter practice course
Description
Explains the inverter principle, the precautions for using an
inverter, etc. in an understandable way. You can understand
the functions, performance, etc. of an inverter by using an
actual machine.
Period
2 days
---------------- INDEX ----------------
1 BASICS OF MOTOR .................................................................................................. 1-1
1.1 Type of Motor ...................................................................................................... 1-1
1.1.1 Overview ....................................................................................................... 1-1
1.1.2 Classification of motor ................................................................................... 1-2
1.2 Principle of Motor Operation ................................................................................ 1-3
1.2.1 Overview ....................................................................................................... 1-3
1.2.2 Three-phase motor (induction type) ............................................................... 1-4
1.2.3 IPM motor (synchronous type) ....................................................................... 1-4
1.3 Performance of Motor .......................................................................................... 1-5
1.3.1 Heat-resistant classes and temperature rise .................................................. 1-5
1.3.2 Rated torque ................................................................................................. 1-6
1.3.3 Relationship between motor speed and generated torque .............................. 1-7
1.3.4 Slip................................................................................................................ 1-8
1.4 Installation ........................................................................................................... 1-9
1.4.1 Installation environment................................................................................. 1-9
1.4.2 Outer sheath form of motor............................................................................ 1-10
1.4.3 Mechanical specifications of main motors ...................................................... 1-11
1.4.4 Movement direction of motor load .................................................................. 1-12
2. BASICS OF INVERTER ............................................................................................ 2-1
2.1 Basic Configuration ............................................................................................. 2-1
2.1.1 Inverter.......................................................................................................... 2-1
2.2 Principle of Converter Operation .......................................................................... 2-2
2.2.1 Method to create DC from AC (commercial) power supply ............................. 2-2
2.2.2 Input current waveform when capacitor is used as load.................................. 2-3
2.2.3 Inrush current control circuit .......................................................................... 2-3
2.2.4 Principle of smoothing circuit operation.......................................................... 2-4
2.3 Principle of Inverter Operation ............................................................................. 2-5
2.3.1 Method to create AC from DC ........................................................................ 2-5
2.3.2 Method to change frequency.......................................................................... 2-6
2.3.3 Method to change voltage.............................................................................. 2-6
2.3.4 Three-phase AC ............................................................................................ 2-7
2.3.5 Switch element .............................................................................................. 2-7
2.3.6 V/F pattern .................................................................................................... 2-8
2.4 Regenerative Brake ............................................................................................. 2-9
2.5 Control ................................................................................................................ 2-10
2.5.1 Difference between general-purpose inverter and vector inverter ................... 2-10
2.5.2 Control method.............................................................................................. 2-11
3. DEMONSTRATION MACHINE OPERATION ............................................................. 3-1
3.1 Inverter (FR-A720) ........................................................................................................ 3-1
3.1.1 Representative connection wiring diagram............................................................. 3-1
3.1.2 Main parameter settings and setting method ......................................................... 3-3
3.1.3 Operating method................................................................................................... 3-7
4. PRECAUTIONS ........................................................................................................ 4-1
4.1 Environment ........................................................................................................ 4-1
4.1.1 Power supply harmonics................................................................................ 4-1
4.1.2 Leakage current ............................................................................................ 4-3
4.1.3 Noise............................................................................................................. 4-4
4.1.4 Compliance to standards ............................................................................... 4-6
4.2 Capacity Selection ............................................................................................... 4-8
4.2.1 Before selecting a capacity ............................................................................ 4-8
4.2.2 Selecting a motor according to driving force................................................... 4-8
4.2.3 Selecting the most suitable capacity in consideration of acceleration/
deceleration .................................................................................................. 4-9
4.2.4 Software for capacity selection using a personal computer ............................ 4-13
4.2.5 Software for starting up an inverter ................................................................ 4-17
4.3 Application Examples .......................................................................................... 4-19
4.3.1 Inverter application examples ........................................................................ 4-19
4.3.2 Vector inverter application examples .................................................................. 4-20
4.4 Maintenance and Inspection ................................................................................ 4-21
4.4.1 Motor............................................................................................................. 4-21
4.4.2 Inverter.......................................................................................................... 4-22
4.5 Troubleshooting ................................................................................................... 4-23
4.5.1 Alarm display................................................................................................. 4-23
4.5.2 Wiring precautions and others ....................................................................... 4-24
APPENDICES............................................................................................................... App-1
Appendix 1. Glossary ................................................................................................ App-1
1 BASICS OF MOTOR
1.1 Type of Motor
1.1.1 Overview
A motor is a device which converts the electrical energy to the rotating mechanical energy.
Many motors are used for various industrial machines to home appliances or bicycle in daily
use.
The types of motors can be classified by the performance, usage environmental condition,
applications, etc. These are shown below.
The motor driven by the inverter is a mainly three-phase squirrel-cage motor, and the motor
driven by the vector inverter is three-phase type motor with encoder which detects a position
and speed. In addition, there is an energy-saving drive high-efficiency magnetic motor (IPM)
for further energy saving.
Classification
by power
supply category
Classification by
principle of
operation
Classification
by structure
DC motor
DC (direct current
type) servo motor
Wound-rotor
motor
Induction type
motor
Motor
1-phase
motor
Squirrel-cage
motor
For
indoor
use
AC motor
3-phase
motor
SM
(synchronous
type) servo
motor
Synchronous
type motor
Deviation phase
strating motor
Condenser motor
Repulsion starting
motor
Drip-proof
protection type
Totally-enclosed
-fan type
IM (induction type)
servo motor
Motor for specific
environment
(outdoor, waterproof,
corrosion-proof,
explosion-proof, etc.)
IPM motor
Stepping motor
Pole number
conversion motor
Linear motor
Geared motor
Submersible motor
Eddy current with joint
Commutator motor
1-1
1 BASICS OF MOTOR
1.1.2 Classification of motor
The following table shows the values for when a motor is used in combination with a
controller which can adjust the speed of a motor.
Rated output
Maximum
Variable speed
range
motor speed
range
(kW)
(r/min)
(with inverter)
Motor types
Positioning accuracy
Encoder
0.01
0.1
1
10
100
100
1000
10
General-purpose
three-phase
motor
100
(guide)
of torque
(mm)
control
1:
General-purpose
three-phase
motor
Availability
1/1000 1/100 1/10
1000
Without
Not
available*
With
Not
available*
With
Available
Without
Not
available
1
Use the limit
switch.
with encoder
Vector inverter
dedicated motor
IPM motor
Use the limit
switch.
* Available for FREQROL-A700 series.
1-2
10
1 BASICS OF MOTOR
1.2 Principle of Motor Operation
1.2.1 Overview
Current
Force
Magnetic flux
The principle of operation is same for all
motors regardless of the size, and a torque
is occurred according to the "Fleming’s
left-hand rule" by which the current is
Force to a conductor
Current
applied to a conductor in a magnetic field
Magnetic flux
and a force acts to the conductor.
Current
Fig. 1.1 Fleming’s left-hand rule
The principle of induction motor operation is as below.
If the magnet is moved in the A direction when not touched with the disk, the disk also turns
in the same direction.
At the same time as the movement of magnet, the electromotive force is induced in the disk,
and the eddy current (induced current) is applied. The relationship between the eddy current
induced in the disk and the magnetic flux by the magnet (Fleming's left-hand rule) causes an
electromagnetic power, and the disk is turned in the arrow f direction.
Magnetic flux
A
Rotation direction
of the magnet
N
Permanent magnet
S
1) This phenomenon that the disk turns was proved
by an Italian called Arago and was named .
Arago’s disk
Copper disk
Eddy current i
B
Magnetic line
Torque direction f
which works to
the disk
Fig. 1.2 Arago’s disk
1-3
2) The eddy current i is generated
by the Fleming’s right-hand rule.
3) The electromagnetic power is
generated in the direction by
the Fleming’s left-hand rule,
and the disk moves.
1 BASICS OF MOTOR
1.2.2 Three-phase motor (induction type)
The cross section view of the three-phase motor
Cylindrical
stator core
(induction type) is shown on the right.
It consists of stator core, stator winding, gap and
Stator winding
(3-phase coil)
Cylindrical
rotor core
rotor core.
The current is applied to the winding part, and the
rotating magnetic field is generated. This rotating
magnetic field is equivalent of Fig. 1.2. For this
vector inverter dedicated motor used with the
three-phase motor, the method, in which the
Rotor groove
(aluminum die-casting)
Fig. 1.3 Cross section of 3-phase motor (induction type)
current creating a magnetic field with the current
applied to the stator winding (current for magnetic
field) and the orthogonal current generating a
torque
(current
for
torque)
are
electrically
controlled, is used. The control performance
equivalent to a direct-current machine is ensured
in principle. In addition, the vector inverter
dedicated motor is widely used because of its
constant torque control from low speed to high
speed and good response.
1.2.3 IPM motor (synchronous type)
The rotor of the IPM motor (synchronous type)
has permanent magnets embedded, and the
stator consists of the winding which applies the
Stator
winding
N
S
S
N
current. The cross section view is shown in Fig.
S
1.4. The current according to the movement of the
N
rotor is applied to the stator winding.
S
N
S
N
N
S
By detecting the magnet position at a start, the
magnetic flux of these rotor magnets and the
Permanent
magnet (rotor)
current applied to the stator winding are controlled
at right angles to each other.
Fig. 1.4 Cross section of PM motor
1-4
1 BASICS OF MOTOR
1.3 Performance of Motor
1.3.1 Heat-resistant classes and temperature rise
Various insulants with high heat resistance are used for general-purpose motors due to the
significant development of insulating materials to be used.
Currently, the motors have four types of heat-resistant class, E, B, F and H, and each
maximum permissible temperature is as shown in Table 1.1. The rise of temperature
severely shortens the life of motor.
It is necessary to set as (Ambient temperature + Motor temperature rise limit) < Maximum
permissible temperature.
Motors are designed for the ambient temperature of 40 .
For example, the motor temperature is designed to fit into the temperature rise limit
standardized in Table 1.1 when the motor is operated with the rated torque in the rated
voltage of 50Hz.
Table 1.1 Heat-resistant class, maximum permissible temperature and temperature rise limit
Heat-resistant class
Maximum permissible
Temperature rise limit
temperature
E
120
75K
B
125
80K
F
155
105K
H
180
125K
Example In the case of E type
40 (ambient temperature) + 75K (motor temperature rise limit)
< 120
155
(maximum permissible temperature)
< 120
* The temperature rise of insulants is measured in a resistance method.
1-5
1 BASICS OF MOTOR
1.3.2 Rated torque
The values of guaranteed output limit and designated voltage, current (torque), motor speed,
frequency, ambient temperature, etc. by the motor manufacturer are collectively called a
rating. These data are called rated output, rated current (rated torque), rated motor speed
and so on. For the rating of output, there are constant rating, short-time rating and repeat
rating (duty rating).
The constant rating is a constant output which can output continuously for a long time.
For the short-time rating, one hour rating, for instance, is a constant output which
continuously outputs only for one hour after a motor is cooled down.
The repeat rating (duty operation) indicates the output at the load if the load changes
periodically.
Motor rated output P [kW]
[N
Rated torque TM = 9550
m]
Rated motor speed N [r/min]
(Formula 1.1)
These values are indicated on the name plates of motors or in test reports.
Example
What is the rated torque of 3.7kW 4P rated motor speed 1730 [r/min]?
3.7 [kW]
Rated torque TM = 9550
= 20.4
1730[r/min]
1-6
[N
m]
1 BASICS OF MOTOR
1.3.3 Relationship between motor speed and generated torque
The torque characteristics are shown in Fig. 1.5 and the current characteristics in Fig. 1.6
when a three-phase squirrel-cage motor is directly started.
After the motor speed
passes this point,
the torque starts to reduce.
Torque
[N m]
Maximum
torque
Tm
Approx. 2 to 3 times
of the rated torque
Torque
Start
torque
Ts
Approx. 2
times of the
rated torque
Balancing point of load torque
and motor generated torque
Torque increase with
rotation rise
Torque required for
operating a machine
Rated
torque
Load
torque
TL
Motor speed
[r / min]
Fig. 1.5 Relationship of motor speed and torque
Area to be a generator
Current
Current decrease
with rotation rise
Current
[A]
Start
current
Is
Rated
current
IL
Motor current
at load torque TL
N
Motor speed
[r / min]
Synchronous motor
speed N0
The motor turns at a balancing point
of the load torque and the motor
generated torque.
Fig. 1.6 Relationship of motor speed and current
1-7
Slip S
3 to 5%
1 BASICS OF MOTOR
Here, the motor speed is determined by the relationship between the load torque TL and the
motor generated torque according to the figure on the previous page, it can be expressed
with the following formula.
120
Frequency f (Hz)
Motor speed =
(1 - S)
[r/min]
(Formula 1.2)
Pole number P
Determined by the
specification of the motor.
This magnitude is called
Synchronous speed N0.
Determined by the magnitude of
the load (load torque).
The control with an inverter is widely used in a method which changes this frequency f as a
control of the motor speed.
1.3.4 Slip
The motor speed becomes a speed mismatched with the synchronous speed when the load
is applied as shown in Fig. 1.5 and 1.6. The indicated degree of the gap with the
synchronous speed is called "Slip".
The slip is derived by the following formula.
Synchronous motor speed N0
- Motor speed N
Slip S =
(Formula 1.3)
Motor speed N0
At a start, the "slip" is 100% since the motor speed is 0.
When operating in the rated torque, the "slip" is generally 3 to 5%.
When the load torque increases, the motor speed slows down, the "slip" increases and the
motor current also increases.
In the case of the rotation linked with outside, the motor speed becomes faster than the
synchronous speed and the slip will be a minus value.
1-8
1 BASICS OF MOTOR
1.4 Installation
1.4.1 Installation environment
The motor driven with a general-purpose inverter is a general-purpose motor which does not
generally operate a feedback control.
On the contrary, the motor driven with a vector inverter requires the feedback control and has
a built-in encoder (sensor) behind the motor. For the encoder, a semiconductor and electronic
components are installed.
In addition, there are restrictions in the motor such as the environment and the lives of
internal winding insulating material, bearing material, grease material inside the bearing and
so on. The following environmental conditions are mainly defined.
Environment
General-purpose inverter motor
-20
Vector inverter dedicated motor
to 40
-10
to 40
Ambient
temperature
Ambient
humidity
Drip-proof
protection type
motor
Totally-enclosed-fan
type motor
Squirrel-cage induction motor
Squirrel-cage induction motor
85% RH or less
No dripping to be
generated
Elevation
95% RH or less
No dripping to be
generated
Special
1000m
or less
above
sea
level
Totally-enclosed-fan type motor
Standard
90% RH or less
No dripping to be generated
The installation height of a motor is 1000m or
less above sea level. If the atmospherical
pressure is low, the heat dissipation gets worse.
The motor temperature, insulation, grease life,
etc. during the operation cannot be guaranteed if
the elevation is over 1000m, a special dealing is
required.
Without
Oil mist
Corrosive gas
Dust and dirt
Ambiance
Without
Indoor, without direct sunlight
flammable gas
(excluding outdoor,
totally-closed-fan motor)
Restrictions of the vibration passed on to the motor during the operation
X
Vibration
resistance
Y
Both X and Y directions
2
4.9m/S
(0.5G) or less
The motors are designed with reference to the above environmental conditions.
1-9
1 BASICS OF MOTOR
1.4.2 Outer sheath form of motor
An outer sheath form for motor must be selected according to the installation condition and
environment. Selecting an inappropriate motor may cause a trouble or shorten the motor life.
Although the outer sheath forms (protection forms) are commonly classified into the
classification by JIS, the motors expressed in the classification by the international standard
IEC are recently manufactured as well. The classifications by JIS and IEC are as below.
(2) Classification by IEC
(1) Classification by JIS
Symbols for the protection types of motors
Symbols for the protection forms of
are indicated by putting the first and second
motors are indicated by putting the first and
reference numbers corresponding to the
second reference numbers corresponding
following table after IP.
to the following table after JP.
Example) IP 6 5
Example) JP 4 4
Second reference number
Second reference number
First reference number
First reference number
Upper: Classification by JIS
First reference number: Grade for the solid foreign
matter entrance protection
Lower: Classification by IEC
are indicated.
Nonprotected type
0
Unprotected
3
Half-protected type
1
Protection to avoid
the entrance of solid
foreign matter of
50mm or more such
as a hand
2
4
Protection to avoid the
entrance of solid
foreign matter of
diameter 1.0mm or
more such as a cable
or a flake
Dust-proof type
5
Second reference number: Grade for the water
entrance related protection
Protection from
powder dust, no
entrance of the
powder dust that
disturbs a normal
operation
Upper: Classification by JIS
Lower: Classification by IEC
Nonprotected type
Rainproof type
Unprotected
Protection against the
water spray within the
range of 60 from the
perpendicular
0
Absolute dust-proof
structure, totally
free from the
entrance of powder
dust
6
Totally-enclosed type
Protected type
Protection to avoid
the entrance of solid
foreign matter of
diameter 12mm or
more such as a
one-yen coin
Protection to avoid the
entrance of solid
foreign matter of
diameter 2.5mm or
more such as an edge
of tool or a wire
3
Ocean waves
protection type
Protection against
strong jet water as
ocean waves, no
water immersion
which disturbs a
normal operation
6
4
Drip-proof type
2
Protection against
the dripping within
the range of 15
from the
perpendicular
7
Protection against the
splash from all directions
Jetproof type
5
8
Protection against the
jet water from all
directions
1 - 10
Immersion
protection type
No water immersion
which disturbs a
normal operation
even if submerged
in 150mm to 1m
Underwater type
Under water
Protection against
the dripping that
vertically drops such
as condensed water
1m
Splash-proof type
1
are indicated.
Usable in water,
usable for a long
time below water
1 BASICS OF MOTOR
1.4.3 Mechanical specifications of main motors
Generally, for general-purpose inverters and vector inverter motors, leg installed type (with
legs) motors are used in relatively large numbers.
The following shows the point for the main mechanical specifications of these motors.
Leg installed
type
Installation
method
Leg installed type
Flange installed type
Frame number
C
(Frame number)
Flange installed
type
Open type
Open type
Totally-enclosed
type
Separate-cooling
type
Standard type
Cooling
method
Totally-enclosed
type
Suitable for adverse
environment with
dust, dirt, humidity, etc.
Separate-cooling
type
Adopted with large
capacity in a forced
cooling system
Direct connection
driving
Direct
Table
connection
Machine
on other end
Belt
Machine
on other end
Motor
Motor
Power
transmission
Gear
Belt driving
Motor Directly connected
to a machine
Gear driving
Set at right angle
Set at right angle
Parallelize the center
of shafts
Parallelize the center
of shafts.
Excitation open brake
Motor speed
Safety brake
Brake
Brake installation position for
the inverter motor
Excitation open brake
Brake current
Coasting time
Sudden stop time
Total braking time
Non-safety brake
When turning the brake power off separately
Excitation brake
1 - 11
1 BASICS OF MOTOR
1.4.4 Movement direction of motor load
There are many types of mechanical drive systems by motors, and they can be used
depending on the purpose (such as desired accuracy, positioning accuracy, travel distance
and details of machine operation at work). For classifying these drive system mechanical
sections and considering the relationship with the motor, the following indicates the
categories of the mechanical movement directions. "mm" is used for the linear motion as a
command unit, and an angle or the number of partitions is used for the rotational motion.
Category of movement direction
Horizontal direction
Vertical direction (ascent and descent)
Moving table
Chain
Ballscrew
Linear motion
Ballscrew
Motor
PLG
Reduction gear
Motor
B
•
Counterweight
Most common drive pattern •
which is used for a table feed of
each machine or a transfer
machine with a ballscrew, rack &
pinion, belt, etc.
Reduction
W
gear
Electromagnetic brake
Drive pattern which is used for a
lifting shaft of transfer machine or a
robot up-and-down shaft. As shown
in the figure, the counter weight for a
load balance is often mounted, and
the motor with the electromagnetic
brake is used for avoiding a slip down
at a power failure.
Rotational motion
Timing belt
Motor
Worm wheel
Bevel wheel
Motor
(Example 1. Connection with gear)
•
(Example 2. Connection with belt)
Drive pattern which is used for a rotary shaft of the index table, etc.
The motor speed of load shaft (table rotary shaft) is generally slow and
often used by being reduced the speed according to the teeth number ratio
of a gear or pulley.
Types of motor direction
1 - 12
2. BASICS OF INVERTER
2.1 Basic Configuration
2.1.1 Inverter
The basic configuration of an inverter is as follows.
AC
Commercial
supply
power
DC
DC
Converter
AC
General-purpose squirrel-cage
(induction) motor
Inverter
Smoothing circuit
IM
Control circuit
VR
Frequency
command
The inside of this frame is
generally called inverter.
Fig. 2.1 Basic configuration of inverter
Each part of an inverter has the following function.
Converter
Circuit to change the commercial power supply to the DC
Smoothing circuit
Circuit to smooth the pulsation included in the DC
Inverter
Circuit to change the DC to the AC with variable frequency
Control circuit
Circuit to mainly control the inverter part
2-1
2. BASICS OF INVERTER
2.2 Principle of Converter Operation
2) Inrush current control circuit
The converter part consists of
1) Converter
the following parts as Fig. 2.3 shows:
D1
D2
D3
R
P +
NFB
1) Converter
2) Inrush current control
AC
power
supply
V
C
3)
Smoothing
capacitor
E
circuit
D4
3) Smoothing circuit
D5
D6
N -
Fig. 2.3 Converter part
2.2.1 Method to create DC from AC (commercial) power supply
A converter is a device to create the DC from the AC power supply. See the basic
principle with the single-phase AC as the simplest example.
Fig. 2.5 shows the example of the method to convert the AC to the DC by utilizing a
resistor for the load in place of a smoothing capacitor.
Diodes are used for the elements. These diodes let the current flow or not flow
depending on the direction to which the voltage is applied as Fig. 2.4 shows.
+
-
-
+
Not flowable (Non conducting)
Flowable (Conducting)
Fig. 2.4 Diode
This diode nature allows the following: When the AC voltage is applied between A and
B of the circuit shown in Fig. 2.5, the voltage is always applied to the load in the
same direction shown in Table 2.1.
That is to say, the AC is converted to the DC.
(To convert the AC to the DC is generally called rectification.)
Table 2.1 Voltage applied to the load
A
B
AC voltage
Load
AC flowing direction
Voltage applied to load
Direction of solid line
Same
direction
Direction of dotted line
Fig. 2.5 Rectifying circuit
E
Fig. 2.6 (Continuous waveforms of the ones in Table 2.1)
2-2
1
2. BASICS OF INVERTER
For the three-phase AC input, combining six diodes
to rectify all the waves of the AC power supply
allows the output voltage as shown in Fig. 2.7.
R phase S phase T phase
Input voltage V
(3-phase)
Converter part
output voltage E1
2 V
Fig. 2.7 Converter part waveform
2.2.2 Input current waveform when capacitor is used as load
The principle of rectification is explained with a resistor. However, a smoothing capacit
or is actually used for the load. If a smoothing capacitor is used, the input current
waveforms become not sine waveforms but distorted waveforms shown in Fig. 2.8
since the AC voltage flows only when it surpasses the DC voltage.
Converter
E
2V
D1
Voltage
D2
I
AC power
supply V
Current I
C
E
Inverter
part
t1
(Load)
t2
D3
D1
D4
D3
Conduction
D2
Conduction
D4
Principle of converter
2.2.3 Inrush current control circuit
The principle of rectification is explained with a resistor. However, a smoothing
capacitor is actually used for the load. A capacitor has a nature to store electricity.
At the moment when the voltage is applied, a large inrush current flows for charging
a capacitor.
To prevent rectifying diodes from being damaged by this large inrush current, make
a forcible series connection to capacitors for approximately 0.05 second from the
power on to control the inrush current value. After that, short the both ends of these
resistors with a magnetic switch to configure a resistor-bypassed circuit.
This circuit is called an inrush current control circuit.
Without inrush current
control circuit
P
R
Control resistor
With inrush current control circuit
I
I
I
The circuit makes the
peak value smaller and
prevents the converter
module from being damaged.
Peak values are large.
Charging current
C
Smoothing capacitor
t
N
Fig. 2.9 Inrush current
2-3
Approx.50ms
t
[V]
2. BASICS OF INVERTER
2.2.4 Principle of smoothing circuit operation
The smoothing circuit creates the DC voltage E2 with little pulsation from the rectified
DC voltage E1 using a smoothing capacitor.
Pulsation waveform
(ripples)
E1
Output voltage
(Without smoothing capacitor)
E2
Smoothed DC voltage
Fig. 2.10 DC smoothed waveform
2-4
2. BASICS OF INVERTER
2.3 Principle of Inverter Operation
2.3.1 Method to create AC from DC
An inverter is a device to create the AC from the DC power supply. See the basic
principle with the single-phase DC as the simplest example.
Fig. 2.11 shows the example of the method to convert the DC to the AC by utilizing
a lamp for the load in place of a motor.
When four switches, S1 to S4, are connected to the DC power supply, S1 and S4
and also S2 and S4 are respectively paired and the pairs are alternatively turned ON
and OFF, the AC flows as shown in Fig 2.12.
Switch
Switch
S1
S3
+
Lamp
DC power
supply
E
+
+
-
A
L
-
Switch
S2
A
A
S1 S4 ON
S2 S3 ON
B
+
-
Switch
B
S4
Fig. 2.11 Method to create AC
When the switches S1 and S4 are turned ON, the current flows in the lamp
in the direction of A.
When the switches S2 and S3 are turned ON, the current flows in the lamp
in the direction of B.
If these operations are repeated by a certain period, the AC is created since the
direction of the current flowing in the lamp alters.
2-5
2. BASICS OF INVERTER
2.3.2 Method to change frequency
The frequency changes by changing the period to turn ON and OFF the switches S1
to S4.
For example, if the switches S1 and S4 are turned ON for 0.5 second and S2 and
S3 for 0.5 second and this operation is repeated, the AC with one alternation per
second, i.e., the AC with a frequency of 1[Hz] is created.
0.5 second
0.5 second
S1,S4 ON
t
S2,S3ON
Figure 2.13 1Hz AC waveform
Generally, if S1/S4 and S2/S3 are respectively turned ON for the same period and the total
time for one cycle is t0 second(s), the frequency f becomes f=1/t0 [Hz].
S1,S4 ON
S1,S4 ON
S2,S3 ON
t
t
S2,S3 ON
0
Fig. 2.14 Frequency
2.3.3 Method to change voltage
The voltage changes by turning ON and OFF the switches with a shorter period.
For example, if the switches S1 and S4 are turned ON for the half period, the output
voltage is E/2, half of the DC voltage E.
To obtain a higher voltage, turn ON for the longer period. To obtain a lower voltage, t
urn ON for the shorter period.
S1,S4 ON
S2,S3 ON
Voltage - High
Voltage - Low
Output voltage
E
E
E
2
E
Output
voltage
Fig. 2.16 Method to change voltage
Figure 2.15
Voltage
waveform
of E/2
Figure
2.15
Voltage
waveform
of E/2
This control method is generally used and called PWM (Pulse Width Modulation)
since it controls pulse width. The frequency to be referenced to determine the time
for pulse width is called a carrier frequency.
2-6
2. BASICS OF INVERTER
2.3.4 Three-phase AC
The basic circuit of the three-phase inverter and the method to create the three-phase
AC are shown in Fig. 2.17 and 2.18.
0
60
120 180 240 300 360 420 480 540
S1
S2
S3
S4
DC power
supply
S1
S3
S5
U
S5
S6
+
E
U -V
S4
S6
V
S2
W
V -W
Motor
W- U
Fig 2.17 3-phase inverter basic circuit
Fig. 2.18 Method to create 3-phase AC
To obtain the three-phase AC, connect the switches S1 to S6 to the circuit and
simultaneously turn ON/OFF all the six switches at the timing shown in Fig. 2.18.
If the order of turning ON/OFF six switches is changed, the phase order is changed
between U-V, V-W and W-U and the rotation direction can be changed.
2.3.5 Switch element
For the switch element in the explanation above, a semiconductor called IGBT
(Insulated Gate Bipolar Transistor) is used.
2-7
2. BASICS OF INVERTER
2.3.6 V/F pattern
Changing the motor speed is enabled by changing the frequency as shown in
Formula 1.2. When the output frequency of an inverter is changed, the output voltage
must be changed.
The output torque of a motor is expressed as the product of the magnetic flux inside
the motor (Φ) multiplied by the current flowing in the coil (I). (Refer to the
principle of induction motor operation and the Fleming’s left-hand rule.)
V
F
Torque TM
The relationship between the magnetic flux (Φ), the voltage applied to a motor
(V) and the frequency (F), is expressed as Φ=V/F. If the voltage is fixed
(e.g. 200V) and only the frequency is decreased, the increased magnetic flux (Φ)
causes the iron core to be magnetic saturation and then the increased current causes
overheat and burnout.
Changing the voltage applied to a motor (V) and the frequency (F) with their
relationship kept constant allows the motor output torque to be constant even if the
motor speed is changed. For these two reasons, the output voltage must be controlled
low when the inverter output frequency is low, and controlled high when the
frequency is high.
This relationship between the output frequency and the output voltage is called V/F
pattern.
Torque
Voltage
Constant torque
Voltage proportional
to frequency
Decreasing torque
(Constant output)
Constant voltage
Frequency
Fig. 2.19 V/F pattern and motor output torque
2-8
2. BASICS OF INVERTER
2.4 Regenerative Brake
When the motor speed surpasses the inverter output frequency (speed command from
an inverter) such as the situation where an elevator goes down, a motor works as a
generator and the generated electricity (energy) returns to an inverter. This status is
called regeneration.
When the electricity returns to an inverter, the DC voltage of the inverter (Fig. 2.20
E1) increases. If this DC voltages surpasses a certain specified value (370VDC for
200V class), rectifying diodes or IGBT of the inverter part are damaged.
To prevent this, insert a resistor and a power capacitor for a switch element in series
in the DC voltage circuit (between P and N) as shown in Fig. 2.20. This prevents the
DC voltage increase by turning ON the power transistor to consume the current as
heat when the DC voltage surpasses a certain specified value. See Fig. 2.21.
This resistor is called a regenerative brake resistor and this power capacitor a
regenerative brake capacitor.
For a large capacity inverter that needs a large regenerative brake resistor, the power
return system, which returns the regenerative energy to the power supply side, is
adopted to prevent the heat influence to the ambience.
P
E
When TR is not turned ON
1
R
E1
Rectifying
circuit
When TR is turned ON
TR
t
N
ON
TR
Fig. 2.21 DC voltage (between P and N)
Fig. 2.20 Regenerative brake circuit
2-9
2. BASICS OF INVERTER
2.5 Control
2.5.1 Difference between general-purpose inverter and vector inverter
Although the same main circuit is used between a general-purpose inverter and a
vector inverter, the following differences exist in outline according to the used control
circuit or the presence/absence of an encoder, which depends on the applied motor.
Table 2.2 Difference between general-purpose inverter and vector inverter
Type
General-purpose inverter
Output
Transmission gear ratio (approx.)
Speed fluctuation
percentage (%)
100W to 560kW
1:10 to 1:20 to 200
3 to 4%
(1% or less for advanced
magnetic flux vector
control and real
sensorless vector
control)
Low 1 to 19Hz
Vector inverter
Item
Frequency
response
Guideline of
start/stop frequency
Positioning
accuracy
Torque
characteristics
Remarks
(Mitsubishi inverter main series)
30 to 125Hz
Approx. 15 times/min.
Approx. 100 times/min.
Approx. 1 to 5mm
Approx. 10 m to 100 m
Constant torque
(Torque decreased for
a base frequency or
more)
General-purpose motor
(Induction motor)
Main series
FR-E500
FR-A024
FR-A700
FR-A500
FR-F700
FR-F500
FR-S500
Applied motor
1.5 to 250kW
1:1000 to 1:1500
0.03%
(Load fluctuation
between 0 to 100%)
Constant torque
(0 to rated speed)
Dedicated motor
(Motor with encoder)
Main series
FR-V500
10000
1000
Response
Vector inverter
(rad/s)
100
General-purpose inverter
10
Response
10
100
Speed control range
2 - 10
1000
10000
+
2. BASICS OF INVERTER
2.5.2 Control method
There are three methods to control an inverter: speed control to control the motor
speed mainly with the analog voltage, position control to control the motor rotation
amount with simple limit switches, a high accuracy encoder or others and torque
control to control the current flowing into a motor for a constant torque value.
The detailed account is given below.
(1) Speed control
1) Open loop control
This control method does not feed back the speed as general-purpose inverters
adopt it.
The command system is analog voltage command, which is used for many
applications such as the conveyor speed control, fan wind amount control, pump
flow amount control, etc. The slip at the rated torque depends on the characteristics
of a motor. Approximately 3 to 5% speed fluctuation occurs.
The recent inverters are resistant to temperature
drifts for the digital control that allows setting the
speed data internally and for the digital command
Pulley
(pulse train, parallel data and communication). In
addition, the inverters of advanced magnetic flux
Belt
vector control or real sensorless vector control
Motor
are available with the speed fluctuation of 1%
or less.
This speed control method is used for almost
all general-purpose inverters.
2 - 11
Inverter
2. BASICS OF INVERTER
2) Closed loop control
To ensure the change of the motor speed, an encoder must be installed to detect
the actual speed and feed it back to a control circuit. This method is called a
closed loop control.
To detect the speed, TG (tachogenerator), encoder, etc. are used. Encoders are
mostly used these days. For the closed loop control too, the analog voltage or
current is used for the speed command. However, inputting pulse trains or using the
digital input allows a high accuracy speed control for the draw operation or
continuous speed control operation.
0 to ±10V
Vector dedicated motor
Vector inverter
(2) Position control
The position control allows not only the control of the motor speed but also the
control to stop at the target stop position. There are many control methods from
the simple method to stop at the target position by taking the external sensor signals
into the stop signal, to the method to perform a high accuracy positioning with an
encoder installed to the motor, and to the advanced method to perform a positioning
to always-changing target stop positions by tracking or synchronization.
1) Open loop control
This control is used for the applications
that do not need high accuracy for stop.
LS Middle speed signal
The motor decelerates to stop with
signals from the limit switches installed
LS Low speed signal
before the target stop position for
Speed V
deceleration command. This is the
LS Stop signal
simplest and most reasonable method
although the fluctuation of the
deceleration points affects the stop
High speed
positions in accuracy.
2 - 12
Middle speed
Low speed
2. BASICS OF INVERTER
2) Semi-closed loop control
An encoder installed to a motor performs
feedback. For example, a vector
dedicated motor operates for the command
Vector
dedicated
motor
Ballscrew
Moving part
input to a vector inverter when the
feedback is looped back. At this moment,
Vector
inverter
the speed command is calculated to
zero the difference between the input
PC QD75
command amount and the feedback
Moving distance
amount for rotating the motor.
3) Full-closed loop control
This control is performed by the feedback from a linear scale or encoder installed
to the machine side.
Installing a linear scale or encoder to the final machine edge allows a high
accuracy positioning free from backlashes or mechanical system errors. Instead,
it is required to heighten the machine rigidity. This control is sometimes used for
machine tools part of which requires a high accuracy control.
»°
Î Þ
Position detection
Table
Positioning
controller
Linear scale
(3) Torque control
The torque control indicates controlling the torque (current) output from a motor and
it must be distinguished from the torque limit. However, both of them are available
depending on the application. The most appropriate method should be selected. The
torque control performs a control of the torque (current) against the torque command
value. Therefore, the speed automatically increases when the load torque is smaller
and decreases when larger. If the load torque is equal to the torque command value,
both torque values are balanced and the speed becomes zero. That is to say, the
motor stops. In short, the same principle as a tug of war is working.
On the other hand, the torque limit is used when a machine can be damaged for
unnecessary torque to control the position or speed, when the stop is performed by
pressing the machine, or when the mechanical lock is performed.
For the torque control, the current flowing in the motor must be detected and
controlled. Therefore, the torque control can be supported by the vector inverter or
the inverter of real sensorless vector control, which perform current detection.
2 - 13
2. BASICS OF INVERTER
1) Open loop control
This control is used for the applications that do not require high torque accuracy
such as an unwinding or winding axis. The analog command is generally used for
the torque command.
For this control, it must be taken into account that the torque accuracy
(temperature drift) varies depending on the temperature and machines have losses.
Winding part
Reduction gear
Command
2) Closed loop control
This control is used for the applications that require high tension accuracy such as
an unwinding or winding axis (for paper, film, etc.).
This control feeds back the tension applied to the actual products to a tension
control device.
Tension encoder
Winding part
Reduction gear
Tension control device
Command
2 - 14
3. DEMONSTRATION MACHINE OPERATION
3.1 Inverter (FR-A720)
3.1.1 Representative connection wiring diagram
(1) The following shows a wiring connection example as a minimum requirement to operate
the inverter FR-A720.
Inverter
NFB
Power supply
200~230VAC
Motor
R
S
T
U
V
W
IM
External brake resistor
FR-ABR
Forward rotation
STF
Reverse rotation
STR
Reset
RES
PR
P
N
SD
Frequency setting
potentiometer
1/2 W 1k
B characteristic
A1
B1
10 (5V)
Alarm output
(operation at alarm)
C1
Scale
calibration
resistor
2
5
FM
SD
3-1
Multi-functional
indicator output
(1mA full-scale)
A
3. DEMONSTRATION MACHINE OPERATION
(2) Connection diagram of school demonstration machine
The following shows the connection diagram of the demonstration machine to be used in
this school.
Inverter
NFB
Power supply
100VAC
50/60Hz
Emergency stop
TR
MC
Motor
R
S
T
U
V
W
MC
Forward rotation
Reverse rotation
High speed
Middle speed
Low speed
Output stop
Second acceleration/
deceleration
IM
5V
STF
STR
RH
RM
RL
MRS
RT
SD
Motor speed
r/mi display
PG
RUN
FU
SE
Load setting
device
10 (5V)
Frequency setting
potentiometer
2W, 1k
FM
2
5
SD
AM
5
Compensation input
2W, 1k
1
3-2
FM output
Hz display
AM output
% display
3. DEMONSTRATION MACHINE OPERATION
3.1.2 Main parameter settings and setting method
(1) Parameters
An inverter has various settings for adjusting it to the operation conditions and machine
specifications, which are called parameters.
The following shows the minimum required parameters to operate an inverter.
Factory default
Param
Name
Description
value
eter
(7.5kW or less)
No.
0
Manual torque boost Heightens the motor torque at a start.
6/4/3 %
1
Maximum frequency Sets the maximum value of the inverter output
120 Hz
frequency.
2
Minimum frequency Sets the minimum value of the inverter output frequency.
0 Hz
3
Base frequency
Sets the base frequency of the motor to be used.
60 Hz
4
3 speed setting
Sets the frequency to operate the motor at high speed.
60 Hz
(high speed)
5
3 speed setting
Sets the frequency to operate the motor at middle
30 Hz
(middle speed)
speed.
6
3 speed setting
Sets the frequency to operate the motor at low speed.
10 Hz
(low speed)
7
Acceleration time
Sets the time taken to accelerate the motor up to the
5 sec.
reference frequency.
8
Deceleration time
Sets the time taken to decelerate the motor from the
5 sec.
reference frequency to 0.
9
Electronic thermal
Sets the permissible motor current value to protect the Rated current
O/L relay
motor.
The inverter can be operated with the factory default values for the above parameters.
Set
only the necessary parameters to the optimum value in accordance with the operation
specifications of the machine.
(Note) Pr. is an abbreviation of Parameter.
1) Pr 0 Manual torque boost
This parameter makes output voltage compensation
100%
in the low speed area under the V/F control and
Output
voltage
improves the decrease of the motor torque at low
speed.
It is used with the increased setting value when the
distance to the motor is long or the motor torque in
the low speed area is insufficient. However, if the
setting value is increased too much, an overcurrent
trip occurs.
The factory default values differ depending on the
inverter capacity.
3-3
Pr.0
Setting
range
Output
frequency(Hz)
Base frequency
3. DEMONSTRATION MACHINE OPERATION
2) Pr1 Maximum frequency, Pr2 Minimum frequency
100%
These parameters determine the upper and lower
limits of the inverter output frequency.
The inverter clamps to prevent the frequency
Minimum
frequency
from exceeding the upper limit and dropping
Frequency
setting signal
below the lower limit.
Factory default value
Maximum
frequency
Output
frequency
Pr.1
Pr.2
5V(10V)(20mA)
Pr1: 120Hz
Pr2:
0Hz
Inverters are normally used with the initial values.
3) Pr3 Base frequency
Setting range of base frequency
This parameter is used to adjust the reference
frequency of the inverter to the rating of the
Output
voltage
motor.
Factory default value
100%
Pr. 19 *
Base
frequency
voltage
Pr3: 60Hz
When operating a standard three-phase motor,
Base
frequency
Pr.3
normally set this parameter to 60Hz.
400Hz
*If Pr.19 is set to 9999 (factory default), theaximum
m
output
voltage will be the same as the power supply voltage.
4) Pr4, Pr5, Pr6 Multi-speed settings
These parameters determine a frequency at
each operation speed when the frequency at the
operation with external signals is switched by
Output
frequency
1 speed
(high
speed)
2 speed
(middle
speed)
(Hz)
three speed levels of high, middle and low.
Factory default value
3 speed
(low
speed)
Pr4: 60Hz (High speed)
Pr5: 30Hz(Middle speed)
Pr6: 10Hz (Low speed)
Set these parameters depending on the
specification of the machine operation.
3-4
Between
RH and SD
Between
RM and SD
Between
RL and SD
Between STF
(R) and SD
ON
ON
ON
ON
3. DEMONSTRATION MACHINE OPERATION
5) Pr7 Acceleration time, Pr8 Deceleration time
These parameters determine the acceleration
Pr.20
time and deceleration time when the motor is
Operation
frequency
started and stopped.
Factory default value Pr7: 5 seconds
Time
Pr8: 5 seconds
Set these parameters depending on the
Acceleration
Pr.7
specification of the machine operation.
6) Pr9 Electronic thermal
This parameter sets the electronic thermal for the motor protection.
Set the current value to protect the motor.
Normally set the rated current value of the connected motor at 50Hz.
3-5
Deceleration
Pr.8
3. DEMONSTRATION MACHINE OPERATION
(2) Parameter setting operation method
Parameter settings are performed by the operation of the
parameter unit (PU) at an operation stop.
1) Press the PU key and select the PU operation mode.
2) Press the PrSET
SETTING MODE
0~9:Ser Pr.NO.
key to switch to the setting mode.
The
display
on
the
left
appears.
Select Oper
3) Set the predetermined parameter number with the
numeric keys.
SETTING MODE
Pr.NO.
1
When setting the numerical
key 1 .
<READ>
4) Press the
1
READ
key to read the parameter settings of the selected parameter number.
MAXf
120H Z
The current setting value is displayed.
0~120
5) Set the predetermined parameter value with the numeric keys.
When setting 6 0 with the numerical keys
1
MAXf
120H Z
60
0~120
6) Press the
1
WRITE
key to write the set parameter.
MAXf
60H Z
Completed
The parameter setting value is changed from 120 to 60 by the above operation.
3-6
3. DEMONSTRATION MACHINE OPERATION
3.1.3 Operating method
There are two types of inverter operating method, parameter unit operation (PU operation)
and external operation.
For the PU operation, an inverter can be easily operated only by the parameter unit operation
when a machine is test-operated at a startup of the machine.
For the external operation, an inverter is operated with the control signal from outside the
inverter according to the specification of the machine operation, and normally operated with a
signal from a machine control panel or a PLC.
(1) Parameter unit operation (PU operation)
Operate an inverter with the key operation of the parameter unit.
1) Press the PU key and select the PU operation.
2) Press the keys of 6 , 0 and
WRITE in order and
adjust the parameter unit display to the frequency to be
operated.
Freq Set
SET 60.00Hz
Completed
3) Press the FWD or REV
60. 00 H
STF FWD
REV key to start the motor.
Z
PU
4) When changing the operation frequency
Press
PU
,enter the operation frequency directly with the numeric keys, and
press WRITE
5) Press the
STOP
RESET
.
key to stop the operation.
Confirm the change of the motor speed for the frequency setting by performing the PU
operation above repeatedly.
3-7
3. DEMONSTRATION MACHINE OPERATION
(2) External operation
Operate an inverter with the operation switch of a
demonstration machine.
1) Select the external operation with the parameter unit.
0. 00 H
STOP
Z
EXT
2) Set the frequency setting potentiometer to the
predetermined frequency (60Hz) on the operation
panel of a demonstration machine.
60. 00 H
STF FWD
Z
EXT
3) When the operation panel switch "正転 (Forward)" is
turned ON, the motor starts to rotate in the forward
direction.
When "正転 (Forward)” is turned OFF, the rotation
stops.
4) Change the frequency as desired with operating the frequency setting potentiometer
on the operation panel during the rotation and check that the motor rotation is freely
changed by the inverter control.
5) The motor is rotated in the reverse direction with the operation panel switch “逆転
(Reverse)”. Check the movement of the motor with the changed frequency (rotation)
as described above.
6) By turning ON/OFF the operation switches, “ 高 速 (High speed)", “ 中 速 (Middle
speed)” and “ 低 速 (Low speed)”, the multi-speed operation is performed at the
frequency of the inverter parameter setting.
The frequency of the frequency setting potentiometer gives priority to that of the
multi-speed selection.
7) Change the acceleration/deceleration time setting in parameter Pr7 and 8 to check the
movement of the acceleration and deceleration.
3-8
4. PRECAUTIONS
4.1 Environment
4.1.1 Power supply harmonics
(1) Harmonics and its effects
(a) What is harmonics?
The sine wave of a commercial power supply provided from a power company is called a
fundamental wave. The sine wave which has an integral multiple frequency of this fundamental
wave is called harmonics. The power supply waveform becomes a distorted waveform when
the harmonics are added to the fundamental wave. (Refer to the following figure.)
When a rectifying circuit and a smoothing circuit with a capacitor are provided in the circuit of
equipment, the input current waveform becomes distorted and the harmonics are generated.
1)
2)
3)
+
=
Harmonic current
Fundamental wave
current
(Severalfold frequency)
Distorted current
(b) Principle of harmonic generation
The AC input current supplied from the inverter power supply side is rectified with a bridge
rectifier, smoothed with a capacitor, converted to the DC and then supplied to the inverter part.
To charge this smoothing capacitor, the AC input current becomes a distorted waveform with
the harmonics.
Inverter
Bridge commutator
Power supply
Motor
Smoothing
+ capacitor
M
Inverter part
4-1
4. PRECAUTIONS
(c) Effects of harmonics
The harmonics generated by equipment may give the following effects to the facilities or other
equipments through cables.
(1) Unusual noise, vibration, burnout, etc. caused by the influx of the harmonic current to
equipments
(2) Malfunction, etc. caused by the harmonic voltage applied to equipments.
(2) Target models
Input
Capacity of target
power
motor
Measures
Make a judgment based on “Harmonic suppression guideline for
1-phase
customers who receive high voltage or special high voltage” issued by
100V
the Japanese Ministry of Economy, Trade and Industry (formerly
1-phase
200V
Ministry of International Trade and Industry) in September 1994 and
3-phase
take measures if necessary. For calculation method of power supply
200V
harmonics, refer to materials below.
Full capacity
Reference material (The Japan Electrical Manufacturers' Association
(JEMA) )
· “Harmonic suppression related measure brochure”
3-phase
· “Calculation method of harmonic current of the general-purpose
400V
inverter used by specific consumers”
· JEM-TR201 (revised in December, 2003)
(3) Harmonic current suppression measures
As a harmonic current suppression measure for inverters, connect a power factor improving
reactor as shown in the figures below.
DC reactor
Inverter
AC reactor
Power supply
Inverter
+
Motor
M
AC reactor
Power supply
+
Motor
DC reactor
Even for consumers to whom the guideline is not applied, it is recommended to connect a power
factor improving reactor in the same manner to avoid possible troubles due to the harmonic
current.
4-2
M
4. PRECAUTIONS
4.1.2 Leakage current
In I/O cables and motors of an inverter, the stray capacitances C are present. High-speed
switching in the main circuit lets the leakage current flow from the stray capacitances C to the
ground. The amount of the leakage current differs depending on the stray capacitances C,
carrier frequency, etc. Accordingly, the low-noise type inverters generate the larger leakage
current.
(1) Effects of leakage current
1) The leakage breaker or leakage relay may operate unintentionally due to the leakage
current between grounds.
The leakage current includes many high frequency components that have a relatively
small influence on human body.
2) The external thermal relay may operate unintentionally due to the leakage current
between cables.
NV1
Inverter
Motor
Power supply
C
Leakage breaker
C
NV2
Motor
Leakage breaker
C
Undesirable current path of leakage current
Measures
· Decrease the carrier frequency of the inverter.
(Note that doing so causes a louder motor noise.)
· Install leakage breakers designed for the harmonics and surge
suppression to the inverter's own system and other system.
(Switching speed does not have to be decreased.)
· Decrease the stray capacitances between grounds.
(Use cables or wires that are insulated with materials of low relative
permittivity.)
(2) Selecting a leakage breaker
Select a leakage breaker designed for the harmonics and surge suppression.
4-3
4. PRECAUTIONS
4.1.3 Noise
Most inverters employ the PWM control method (refer to Section 2.3.3).
Inverters generate the AC by switching the main circuit elements.
This principle of operation can be referred to as the noise source.
(Note) The noise mentioned here and the harmonics mentioned previously are
sometimes thought of as interchangeable. This is because both of them affect
other electrical equipment. Generally, however, the harmonics commonly refer
to waves with a frequency between 40th and 50th (2.4 to 3kHz) whereas noise
commonly refers to waves with a frequency of tens of kilohertz or higher.
(1) Noise types and propagation paths
Noises generated from an inverter are broadly classified into the following types: those
radiated from the cables connected to the inverter and inverter main circuits (I/O), those
electromagnetically and electrostatically induced from the signal cables of the peripheral
devices close to the main circuit power supply, and those transmitted through the power
supply cables.
5
7
Telephone
7
2
7
1
Instrument
Receiver
2
4
Motor
Sensor power supply
Inverter
3
6
IM
8
3
Noise types and paths
(a). Air-propagated noise (Paths 1) to 3))
This noise is generated by an inverter and radiated to the air. The paths of this noise can
be classified into the following three types.
1) Radiated from inverter
2) Radiated from input cables
3) Radiated from motor connection cables
(b). Electromagnetic induction noise (Paths 4) and 5))
This noise is generated and transmitted when power cables or signal cables of peripheral
devices cross a magnetic field generated by the current that is input to or output from an
inverter.
(c). Electrostatic induction noise (Path 6))
This noise is combined capacitances that are generated by the principle of electrostatic
induction and transmitted through I/O cables of an inverter.
4-4
4. PRECAUTIONS
(d). Cable-propagated noise (Path 7))
This noise is a high-frequency noise that is generated inside the inverter and transmitted
to peripheral devices through cables on the power supply side.
These noises tend to gain the lower noise level as the noise frequency band is higher.
Generally, the noise level is low enough not to be problematic in frequencies of 30MHz or
higher.
(2) Measures against noise
Although there are many noise propagation paths, noise sources can broadly be classified
into the following three types:
1) Propagation, induction or radiation from an input power supply cable
2) Induction or radiation from motor connection cables
3) Radiation from an inverter
(a) Reducing noises transmitted to the power supply cable
An effective method is to install a filter between an inverter and
the power supply cable.
1) Radio noise filter FR-BIF (200V class), FR-BIF-H (400Vclass)
2) Line noise filter FR-BSF01, FR-BLF
NFB
As short
as possible
3) Combination of FR-BIF(-H) and
FR-BLF/FR-BSF01
R
Power supply
4) Noise-cutting transformer
S
(b) Reducing noises radiated from cables between an inverter
Metal case
Installing the FR-BLF or FR-BSF01 line noise filter to the
Metal pipe
output side of the inverter is a method to reduce the radiated
noises. Generally, however, a metal pipe is used.
T
Line noise filter
FR-BLF
FR-BSF01
and motors
Inverter
Power supply
Inverter
IM
Earth (Ground)
(c) Reducing noises radiated from an inverter
Noises generated from this inverter are relatively small and
Noise filter
less problematic. However, when an inverter is installed
close to devices easily affected by noises, it is required to
house the inverter in a metal case and install a noise filter
Power supply
Metal pipe
Inverter
Earth (Ground)
on the power supply side. Also, for the output side,
connect a metal pipe to the case.
Good to know
For 55kW or less of the FREQROL-A700 and F700 series, functions equivalent to the line
noise filter and radio noise filter on the input side are provided.
4-5
IM
4. PRECAUTIONS
4.1.4 Compliance to standards
Inverters are compliant to non-Japanese standards that are UL standard, cUL standard and
EN (European Norm).
● cUL standard
Refers to an American standard equivalent to CSA, a
Canadian standard. Products compliant to cUL
standard are also compliant to CSA standard.
TUV Rheinland
● UL (Underwriter’s Laboratories Inc.) standard
: An American standard
UL is a nonprofit product testing organization founded by the
National Board of Fire Underwriters, providing conformity
assessment for industrial products. Safety standards defined
by UL are exceptionally strict and cover virtually all possible
cases that may occur while products are in use. This has
brought the UL mark up to a position with extremely high
authority and reliability. In many of provinces or cities of the
United States, conforming to UL standards is obligated by
state laws or ordinances.
● EN (European Norm)
Refers to a European safety standard.
(Refer to the following.)
● EN (European Norm)
In the process of uniting Europe, EC (the European Commission) has been making an effort
to establish balanced rules that are adopted beyond countries. The intention of these rules
is to realize borderless and free exchange of people, goods and services as well as free
sales of goods and services. As one of these rules, EC proposed the integrated standard
for technologies involving human health and safety as a form of 13 directives. The nations
are currently seeking legislation based on these directives. The rules state that
the-directive-targeted products must have the CE mark, which is the indication that
approves exportation, free exchange and sales of the product across the Europe area. The
directives involving driving products are the following three:
(1) Directive of Machinery
This directive defines safety requirements for machinery.
This directive basically requires that the health and safety of
both man and animals and the safety of any objects should
not be endangered under the condition that proper
installation, maintenance and operation are conducted.
4-6
4. PRECAUTIONS
(2) EMC Directive
This directive defines electromagnetic compatibility.
This directive basically requires that an inverter should not
adversely affect other equipment by electromagnetic
interferences and that an inverter should have sufficient
noise resistance. (EMC directive compliant filters are
prepared for the requirement.)
(3) Low Voltage Directive
This directive defines safety
requirements for electrical
equipment. This directive basically
requires that the health and safety
of both man and animals and the
safety of any objects should not be
endangered under the condition
that proper installation,
maintenance and operation are
conducted.
4-7
Enclosure
Power
supply
Inverter
EMC
noise filter
Motor
4. PRECAUTIONS
4.2 Capacity Selection
4.2.1 Before selecting a capacity
Before selecting a capacity, it is necessary to generally know the operating environment, the
target work and if the performance and functions are satisfied. Based on this information,
select a motor, and an inverter or a vector inverter to control the motor. In terms of the
hardware basics, the same concept can be applied to both inverters and vector inverters.
4.2.2 Selecting a motor according to driving force
The formula to obtain the driving force differs depending on horizontal or vertical (up-down)
movement.
(1) Horizontal movement
When the total weight of the traveling object is W [Kg], the speed is V [m/min] and the friction
factor is , the required motor driving force P is calculated as follows:
Travel resistance
W[N]
P=
WV
6120
Speed V[m/min]
W[kg]
[kW] ········ (Formula 4.1)
Example 1
Under the condition that the mass is 80kg, the object speed is 80m/min, the friction
resistance is 0.2 and the machine efficiency is 0.8, the driving force required for the
motor is:
P= 80× 0.2 × 80 / (6120 × 0.8)
= 0.26kW
4-8
4. PRECAUTIONS
(2) Vertical movement
When an object with the mass of W [kg] is
hoisted at the speed of V [m/min], the required
Hoisting speed
Vm/min
motor driving force P is as follows:
P=
WV
6120
[kW]········ (Formula 4.2)
 : Machine efficiency
W kg
Example 2
Under the condition that the mass is 50kg, the object speed is 60m/min and the machine
efficiency is 0.8, the driving force required for hoisting is:
P = 50 × 60 / (6120×0.8)
= 0.61kW
4.2.3 Selecting the most suitable capacity in consideration of acceleration/deceleration
Vector inverters frequently perform acceleration/deceleration. Select the most suitable
capacity in accordance with the movement of the machine.
To make this selection, check data on the machine side and the operation pattern
beforehand. The following shows the steps of the selection.
(1) Find the load torque of the machine.
Load torque: Force that is required to move a load.
(2) Find the inertia moment (J) of the machine.
J: Value that indicates how much difficult to move or stop an object.
It can be compared to a load on the back of a truck.
4-9
4. PRECAUTIONS
(3) Find the operation pattern of the machine.
Operation pattern: One cycle of machine operation status derived from travel time and
stop time. The gray area below indicates travel amount.
Top speed V
Travel amount L
speed
Acceleration
tpsa
Constant speed
Deceleration
tpsd
Stop
Time
t
When the top speed is V [mm/s], travel time is t [s], acceleration and deceleration times are
respectively tpsa [s] and tpsd [s], travel amount is L [mm], and tpsa=tpsd, their relation is
as shown in the following formula.
L = V [mm/s] × ( t - tpsa) [mm] ········ (Formula 4.3)
(4) Tentatively select a motor.
Tentative selection: Selecting a motor that
I won!
can be the most suitable in reference to
Oh,
no…
the load torque and J.
1) The rated torque of the motor must be
larger than the load torque.
d
Rate
e
torqu
Loa
4 - 10
d to
rqu
e
4. PRECAUTIONS
(5) Calculate a torque with the motor tentatively selected.
Torque calculation: Calculation that is basically made in accordance with the following
four conditions. (Most typical pattern)
1) Torque required for accelerating to a constant speed from the start
Constant speed
J
Load torque
This torque must not
exceed the maximum
torque of the motor!
Torque to accelerate J
Motor acceleration torque
TMa
Load torque
TL
Ta
2) Torque required for keeping the load moving at a constant speed
Load
torque
Motor torque
Load torque
TML
TL
3) Torque required for decelerating to the stop
This man represents a load torque.
(He is supportive of braking operation.)
Braking (regenerative brake)
is used to prevent J from rolling
down.
J
Makes a negative value smaller.
Torque to decelerate J
Makes a negative value smaller.
-Ta
TMd
4 - 11
Load torque
TL
4. PRECAUTIONS
4) Judge the heat availability of the motor.
Using the motor current values obtained in 1) to 3) and the period of one cycle, obtain
the equivalent current with the following formula to compare with the rated current. The
selected motor must have the equivalent current that does not exceed the rated current.
Motor equivalent current =
(In2
tn)
(Cn
tn)
········ (Formula 4.4)
Cn:Cooling factor
Example. V/F control
6Hz f 60Hz
C
0.4
( 60f )
(Complement) When, as a feature of inverters, driving multiple motors with one
inverter, select motors so that a value of “(total current of motors)
multiplied by (approximately 1.05 to 1.1)” does not exceed the
rated current of the inverter.
INV
(6) Check the necessity of a brake resistor for the regenerative brake.
Calculate the braking electric power from the energy generated by the use of the
regenerative brake in a deceleration operation. Check if the calculated power is within the
permissible range of the performance specifications. Install an external brake resistor
(optional) if the power is outside the range
Regenerative energy
Hmm...
Its tough.
It could be better installing
a brake resistor.
Clearing (1) to (6) completes the steps of a motor selection.
4 - 12
4. PRECAUTIONS
4.2.4 Software for capacity selection using a personal computer
The software is available, which automatically selects a capacity. The user’s task is just to
select a machine and input each data into the software. The software provides various
efficient tool functions such as inertia calculation and unit conversion.
(1) For inverter use (FR-SW1-SEL-WJ)
1) Specifications
Item
Types of machine
components
Item
Result
output
Print
Data save
Inertia moment
calculation function
Specifications
Ballscrew for horizontal use
· Ballscrew for vertical use
· Rack & pinion
· Rotating table
· Cart
· Elevator
· Conveyor
· Others (inertia direct input)
Selected inverter model name
· Selected motor model name
· Selected braking unit
· Control method
The following items are printed out: input data, operation pattern,
calculation process, motor speed (feed speed), torque graph and
selection result.
The following data are saved in a named file: input data, operation
pattern, selection result, and FAX form.
Cylinder
· Rctangular column with declination axis
· Speed change
· Linear motion
· Suspension
· Circular cone
· Circular truncated cone
2) Input screen (with an example of a ballscrew for horizontal use)
4 - 13
4. PRECAUTIONS
4 - 14
4. PRECAUTIONS
3) Examples of other input screens
Cart
Elevator
Conveyor
Others
4 - 15
4. PRECAUTIONS
4) Calculation example
The detailed results of calculations can be confirmed. The results also can be printed out.
4 - 16
4. PRECAUTIONS
4.2.5 Software for starting up an inverter
(1) FR Configurator (FR-SW2-SETUP-WJ)
The software is available, which supports
starting up a Mitsubishi general-purpose
inverter from the screen of a personal
computer connected to the inverter.
Using this software allows the following:
monitoring and diagnosing an inverter and
also setting parameters on the personal
computer screen; measuring frequency and
current waveform of an inverter and then
displaying them as a graph; and saving and
diverting data.
In
addition,
the
software
automatically
converts parameters of the conventional
models
(FREQROL-A500,
V500/F500)
to
those of FREQROL-A700/F70 series.
1) Supported general-purpose inverter models
FREQROL-A700 series
FREQROL-F700 series
2) Functions
· Monitor: Indicator needle display, waveform display, etc.
· Alarm: Alarm display, alarm history, etc.
· Diagnosis: Operation diagnosis, error diagnosis, service life diagnosis
· Parameter: Parameter setting, list display, converting function, etc.
· Test operation: Test operation, auto tuning, etc.
· File-related operation: Open, save, print
4 - 17
4. PRECAUTIONS
3) Connection
Mouse
FR Configurator
USB connector used*2*3
USB connector
RS-232C
PU connector used*2
Converter*1
Connection cable
Connector: RJ45 connector
Example: Tyco Electronics AMP K.K.
5-554720-3
Cable: Cable compliance with EIA56B
(e.g. 10BASE-T cable)
Example: Mitsubishi Cable Industries, Ltd.,
SGLPEV-T 0.5mm&drcross4P
(Twisted pair cable, 4 pairs)
RS-485 terminal used*2
Commercially available printer
(ESC/P compatible)
Connection cable
RS-485/RS-422
Multidrop link system
RS-485 terminals
RS-485 terminals
RS-485 terminals
RS-485 terminals
RS-485 terminals
PU connector
Inverter
Inverter
USB connector
Inverter
Inverter
Inverter
Inverter
*1: A commercially available converter is required when the personal
computer uses the RS-232C port.
<Example of commercially available products> (As of April, 2004)
1) Model: FA-T-RS40? Converter (A model with connectors and a
cable is also available.)
2) Model: DINV-CABV (with connectors and a cable)
*2: The PU connector, RS-485 terminal or USB connector (FREQROL-A700
series only) can be used to make communication.
*3: The communication using the USB connector (FREQROL-A700 series
only) cannot connect two or more inverters. (A personal computer and
an inverter are connected on a 1:1 basis)
The communication using a USB HUB cannot be made.
4 - 18
4. PRECAUTIONS
4.3 Application Examples
4.3.1 Inverter application examples
Inverters are used in various fields.
Features
Inverters realize energy saving and automation.
●Useful for air flow control (flow amount control)
●Automatic control over air flow (pressure or
flow amount)
●Necessary amount can be changed according
to seasons and day/night.
Application examples
· Pump
· Fan, blower
· Ventilation fan
Cooling tower
· Drying machine
(Furnace fan)
Damper control
Switch
Damper
Motor
Fan, Blower
Inverter control
Inverter
Damper
Motor
Fan, Blower
Higher machine efficiency and downsizing of
machines
●Conventionally, the rotation speed of a main
spindle was controlled by changing the speed
of a pulley, etc., according to the size of a
workpiece. Using inverters makes such speed
change system simpler, allowing downsized
machines.
●The most suitable machining conditions are
easily obtained.
· Drive for a main spindle
of a machine tool
· Table of a machine tool
Spindle stock feed
· Drive for a cutter
· Rice mill
Workpiece
Inverter
Motor
Higher machine efficiency, defined position stop,
automatic operation
●The operation efficiency can be improved and
carts can be stopped at the defined
position.
●The conveyor speed can be changed to
the most suitable value according to the
workpiece.
· Cart
· Belt conveyor
· Wood working machine
· Weighing machine
· Packaging machine
Pulley
●The soft start and stop realizes preventing
products from falling down and wobbling.
●Shocks to machines are absorbed and
Belt
the acceleration and deceleration without
shocks are realized.
Motor
Inverter
4 - 19
4. PRECAUTIONS
4.3.2 Vector inverter application examples
Features
High starting torque, small speed
fluctuation
●Accurate control over extrusion
pressure according to the material
extruded
●Even for loads that change (increase)
their
viscosity
as
the
speed
decreases,
operations
continue
without torque shortage.
· Extruder
· Molding machine
· Wiredrawing
machine
Application examples
· Agitator
· Roller driving
· Testing machine
Motor
Agitator
Vector inverter
Inverter
Mill roller
Motor
Conveyor
Cutting machine
Motor
Motor
Inverter
Higher machine efficiency and accurate
torque control
●Accurate torque control over
Inverter
· Various winding
· Unwinding line
Pinch roll
winding and unwinding
M
Feed motor
Power supply
200VAC
Vector
inverter
Higher machine efficiency, fixed position
stop, automatic operation
●Higher machine speed enables higher
machine efficiency.
●Carts can be stopped at the fixed
· Multilevel car parking towers
· Automated warehouse
· Cargo elevator
· Conveyer
PLG
MC
Electromagnetic brake
position.
●Multilevel car parking towers with a
circulating system may need a large
starting torque depending on the
imbalance amount of the automobiles
parked. The vector control is suitable
for such application.
A negative load may be generated
depending on the number of
automobiles parked, requiring a large
brake torque. In such cases, use a
Motor
M
Vector inverter
NFB
Power supply
B
IM
FR-V
Motor
PLG
FR-CV
Power regeneration
common converter
vector inverter with the power
regeneration common converter
FR-CV (optional) to construct an
efficient driving system.
Parking facility with
a circulating system
4 - 20
4. PRECAUTIONS
4.4 Maintenance and Inspection
4.4.1 Motor
General-purpose motors and vector inverter dedicated motors are three-phase induction
motors. These motors mainly consist of a rotary shaft, bearings, stator winding and
connection terminals. Vector inverter dedicated motors have an encoder at the rear of their
rotary shaft. These components must be inspected periodically to prevent any fault from
occurring due to the adverse effects from the operating environment, such as temperature,
humidity, dust, dirt and vibration, changes in the parts with time, service life, and other
factors.
(1) Inspection items for a motor
It is recommended to check the following items periodically.
1) Check if screws of the terminal block are securely tightened. Retighten if the screws
are loosened.
2) Check if there is no unusual noise generated from the bearings or brake of motors.
3) Check if there are no damages or cracks in cables. Especially for operated motors,
perform an inspection periodically in accordance with the operating environment.
4) Check if the load connecting shaft has its axis without declination.
(2) Service life
A service life of each part is as shown below. Note that the service lives shown below may
differ depending on the operating conditions or environmental conditions. Replace faulty
parts if found. For part replacement, contact a Mitsubishi service center or service station.
Generalpurpose
motor
Part Name
Standard replacement
interval
Bearing
20,000 to 30,000 hours
Grease
20,000 to 30,000 hours
Bearing
10,000 to 30,000 hours
(2 to 3 years)
20,000 to 30,000 hours
Encoder
20,000 to 30,000 hours
Oil seal
5,000 hours
10,000 to 30,000 hours
(2 to 3 years)
Forced cooling fan
Vector
inverter
dedicated
motor
Forced cooling fan
4 - 21
Remarks
Standard replacement
intervals are for
reference.
Replace faulty parts if
found regardless of
the standard
replacement interval.
4. PRECAUTIONS
4.4.2 Inverter
An inverter is a static unit mainly consisting of semiconductor devices. Daily inspection must
be performed to prevent any fault from occurring due to the adverse effects from the
operating environment, such as temperature, humidity, dust, dirt and vibration, changes in
the parts with time, service life, and other factors.
Caution
For some time after the power is switched off, a high voltage remains in
the smoothing capacitor. When accessing the inside of an inverter for
inspection, wait until the charge lamp is turned off, and then make sure
that the voltage across the main circuit terminals P-N is not more than
30VDC using a tester, etc.
· Inverter
Inspection items
(1) Daily inspection
Basically, a daily inspection is to check for the following faults during operation.
1) Check if the motor operates properly as set.
2) Check for unusual vibration and noise.
(2) Periodic inspection
Check the areas inaccessible during operation and those which require periodic
inspection.
1) Check if there are no abnormal signs in the cooling system ······ Clean the air filter,
etc.
2) Tightening check and retightening ······ Screws and bolts may become loose due to
vibration, temperature changes, etc. Check
and retighten them.
3) Check the conductors and insulating materials for corrosion and damages.
4) Measure the insulation resistance.
5) Check and replace the cooling fan, smoothing capacitors and relays.
(3) Service life
A service life of each part is as shown below. Note that the service lives shown below may
differ depending on the operating conditions or environmental conditions. Replace faulty
parts if found. For part replacement, contact a Mitsubishi service center or service station.
FREQROL-A700, F700 series
Components
Cooling fan
Main circuit smoothing
capacitor
On-board smoothing
capacitor
Relays
Standard Replacement Interval
10 years
10 years
10 years
-
4 - 22
Remarks
Standard replacement intervals
are for reference.
Replace faulty parts if found
regardless of the standard
replacement interval.
4. PRECAUTIONS
4.5 Troubleshooting
4.5.1 Alarm display
An inverter provides various protective functions that prevent semiconductors (main circuit
elements) from being damaged due to errors that may occur on the power supply side, load
side of the inverter or external sequences.
· Inverter ···· The protective functions of an inverter are largely classified into those to
protect the inverter and those to protect a motor from overheat. In addition to the
protective functions, an inverter is equipped with warning functions to inform that the
operation status is abnormal.
Item
Description
Display
example
Inverter
· When an alarm occurs, a code assigned to
the alarm status is displayed on the
operation panel (parameter unit), and the
alarm output (contact signal) is turned on.
· When the operation stops due to an alarm,
refer to the displayed alarm code to identify
the error source.
· The inverter holds the error status until the
alarm is canceled (reset).
Parameter unit
Display area
インバータトリップ
カソクジ カデンリュウ
(Example of overcurrent shut-off)
Protection
Useful
software
· Overcurrent shut-off (during
acceleration, low speed operation,
deceleration)
· Regenerative overvoltage shut-off
· Instantaneous power failure protection
· Overload shut-off (electronic thermal relay)
· Undervoltage protection
· Output side earth (ground) fault
overcurrent
etc.
Installing the inverter setup software on a
personal computer allows displaying alarms
and warnings, setting various parameters, and
monitoring the operation status.
(Note) How alarms are displayed and what alarms display differ depending on the inverter series.
4 - 23
4. PRECAUTIONS
4.5.2 Wiring precautions and others
Switch the control power supply on at the
same time as or before switching the main
circuit power supply on.
Power
supply
Use a shielded cable or twisted cable
to connect to the control circuit
terminal.
Use two parallel micro-signal contacts
or twin contacts to prevent contact
faults when using contact inputs since
the control circuit input signals are
micro-currents.
Operation signal
Control
power
supply
Do not connect the power
supply cables to the output
terminals (U, V, W).
Doing so may damage the
inverter.
R S T
Connect the thicker cable to
the dedicated earth (ground)
terminal
for
earthing
(grounding) the inverter.
Inverter
Wire the cable connected to the
analog input terminal fully away from
high voltage power lines such as
200V
(400V)
without
bundling
together.
Do not earth (ground) the common
terminals used for control purpose.
Setting
potentiometer
U V W
Earth (Ground)
Motor
A long wiring distance causes the
decreased motor torque for a cable
voltage drop at the low-speed
operation.
Use a fully thick cable.
Encoder
4 - 24
An encoder is required for
vector inverters.
Make
sure
to connect
properly.
APPENDICES
Appendix 1. Glossary
· Absolute (absolute position) encoder <Antonym; Incremental encoder>
This is an encoder which can output the angle data within one rotation of the encoder to the
outside, and the one which can take out 360
in 8 to 12-bit data is generally used.
If using the encoder as a servo motor encoder, the position within one revolution of the
motor is identified. Therefore, this is used when the absolute positioning system is
configured with a rotation amount counter.
The following figure shows the common structure of the absolute position encoder. In this
case, the absolute position signal of 7 bits is output.
Rotary shaft
Sensor
Rotary glass disk
slits are
( 7-stage
)
radially provided.
Structure example of absolute position encoder
· Absolute (absolute position) positioning
This is a positioning method in which the absolute coordinate based on the home position is
set in the range of machine movement and specified in the positioning data.
· Acceleration
This is a change of the motor speed, which is expressed with ratio to the acceleration time,
and is a slope to the time of motor speed change.
· Acceleration time
This is a time which is taken to reach from the current motor speed to the next motor speed
when the motor speed is changed.
· Acceleration time constant
This is a time which is taken from start to end of the acceleration when the motor is
accelerated from the stop status to the certain motor speed (rated motor speed, parameter
limit speed, etc.).
For the acceleration pattern of the primary delay function, it indicates the time taken when
the actual speed reaches to 63.5% of the target speed.
N0
N0
N0
N1
0.632N 0
N2
T
t
Primary delay time
Acceleration pattern with primary delay constant
Acceleration time andacceleration time constant
t2
t1
t0
t 0:Acceleration time up to the reference speed = Acceleration time constant
t 1:Acceleration time up to the motor speed N1
t 2:Acceleration time up to the motor speed N2
App-1
APPENDICES
· All digital control (Digital control)
This is a system which is controlled by a micro computer or a circuit configured with the
peripheral LSI and logic IC.
· Analog control <Antonym; Digital control>
This is a control system which is realized with a control circuit comprised of analog devices
such as an operational amplifier.
· Angular frequency (ω)
The number of cycles per second is expressed in Hz (hertz) as a unit to express the
continuous sine wave, and it is called angular frequency when expressed in angle (radian). It
is converted to 2лf [rad/sec] at frequency f [Hz].
· Auto tuning (Offline auto tuning/Online auto tuning)
The offline auto tuning is a function with which an inverter itself measures and stores a
necessary motor constant.
The online auto tuning is a function with which the status of the motor is quickly tuned at a
start. Therefore, the high accuracy operation unaffected by the motor temperature and stable
operation with high torque down to ultra low speed can be performed.
· Auto tuning (Real time auto tuning)
The performance (especially response and stability) of a machine driven by the servo motor
depends on the characteristics (inertial moment and rigidity) of the machine. Consequently,
an adjustment operation is necessary to raise the machine performance to the best condition,
and this operation is called tuning.
The auto tuning is a function with which automatically operates the tuning mentioned above
and normally indicates a function with which automatically adjusts the speed and position
loop gains to be set by a servo amplifier.
The real time auto tuning indicates a function with which a tuning is automatically performed
by always tracking, especially when the machine characteristics are changed during
operation.
· Capacitor regeneration
This is a method to perform a regenerative operation by charging the regenerative energy in
the capacitor of the main circuit.
Since the heat is not generated, the capacitor can be repeatedly used when the regenerative
energy is smaller than the energy charged in the capacitor. However, the method is only
applied to small capacity models since the energy, which can be charged in the capacitor, is
small.
· Differential transmission system
This is a system in which one signal is simultaneously transmitted in pair with a signal of
reversed polarity. Since the logic of the signals can be evaluated at the same time on the
receiving side, this system has superior noise resistance and is used for a signal
App-2
APPENDICES
transmission at high speed such as the input and output of pulse trains. Generally, the
sending side is called driver and the receiving side receiver, and a dedicated IC is used.
Sending side
A
Receiving side
B
Receiver
Driver
· Digital control <Antonym; Analog control>
This is a control system which is realized with a control circuit comprised of digital devices.
In these days, a system, in which an operation is processed with software using a micro
computer or micro processor for the increase of the calculation amount, has become
common.
The merits of the digital control system are that there is no temperature drift and the
performance is stable and has a high-repeatability.
· Droop pulses and stop settling time
Droop pulses represent the gap between the command pulses counted with the deviation
counter of a servo amplifier and the feedback pulses of a position encoder.
A constant amount of the droop pulse exists in the deviation counter during the operation at
a constant speed. As the speed varies, the number of the droop pulses also varies.
Since the servo motor rotates with a delay behind a command for the amount of the droop
purses of the servo amplifier, it stops a little bit behind the command completion. This delay
time is called stop settling time.
Command
pulse
frequency
Command pulse Droop pulse
f
Feedback pulse
ts
Droop pulses and stop settling time
Time
· Dynamic brake
This is a break function to be used for stopping a machine rapidly at a power failure or a
servo amplifier failure, and a large break torque is obtained from an electromagnetic brake.
However, there is no holding torque during stop.
This function is not provided for the IM servo with an induction motor.
· Electronic gear
This indicates that the feedback pulse ratio to a command pulse is changed. However, the
position resolution is not changed since it is determined with an encoder. The ratio change
can be made using fractions with parameters.
Unlike a mechanical gear, the motor torque is not increased even if the ratio magnification is
App-3
APPENDICES
increased.
· Error excessive
This means that droop pulses exceed the capacity of the deviation counter.
When an overflow occurs on the deviation counter in the positioning system, an accurate
positioning cannot be made. In this condition, a servo amplifier or positioning module stops
the machine with outputting the error excessive error.
· Feed forward control
This is a control which outputs a speed command before droop pulses increase when a
pulse command is input in the position loop control.
· Feedback control
This is a control which detects a gap between a command and an actual speed with a closed
loop and compensates the command value to reduce this gap.
· Frequency response (characteristic)
This expresses the speed response quantitatively. The frequency to which the actual motor
can respond is indicated in ωc [rad/sec] or fc [Hz] when the speed command is changed into
a sine wave pattern as a extremely low-speed command of approximately 10r/min. This
frequency response can be enhanced by increasing the speed loop gain. However, if it is
increased too much, a vibration or stability easily occurs due to the rigidity of a mechanical
system.
· Gain search
A personal computer searches the value of the shortest settling time with little overshoot or
vibration while automatically changing the gain.
This function exhibits the best performance when a high-level adjustment is required.
· Grounding
This indicates a condition in which either a cable (P or N after a diode rectification) of the
main power supply circuit of the servo amplifier or a power line (U, V or W) of the motor is
short-circuited with the earth.
· IGBT(Insulated Gate Bipolar Transistor)
Compared to the existing transistor, IGBT is available for high-speed switching and is better
for the current, pressure resistance, etc.
· Impact drop
This expresses the temporal response characteristic as a value indicating the fluctuation
range of the output to the input command in the feed back control. The value is indicated
with the size and duration time of the temporary movement amount for when the load is
changed in a staircase pattern.
Especially, it will be effective when including an integral operation.
· Incremental (relative position) positioning
This is a relative positioning in the machine movement. In the positioning data, the
App-4
APPENDICES
positioning is executed by specifying the travel from the current position as a reference
(home position). This positioning system is used for the fixed-feed of the roll feed, etc.
· Inertia (Inertia moment)
Refer to “· Inertia moment” on App-4.
· Inertia moment (Inertia)
This is the amount which indicates the rotation gravity of a rotator and is equivalent to the
mass of the linear operation.
Definitional equation
J = m · r2
Here, J: Inertia moment [kg · cm2]
M: Mass [kg]
r: Rotation radius [cm]
In addition, GD2 is usually used as the amount to indicate the inertia moment. The r (radius)
of the equation above is expressed in 2r (diameter), and there is a relationship as shown
below.
GD2=m · (2r)2=4J
· Instantaneous power failure
The servo amplifier and inverter keep the control when the power failure is very short
(normally, 15msec or less). However, if the power failure is longer than 15msec, they stop
the control with outputting an instantaneous power failure error.
If the power failure continues (normally, several 100msec or more), as in the case of power
off, they are recovered to the same condition as at power on by power restoration.
The power failure, which is 15msec or more and several 100msec or less as described
above, is normally called instantaneous power failure, and the instantaneous power failure
error is hold.
· Machine analyzer
By connecting to a servo motor, this automatically vibrates the servo motor and analyzes the
frequency characteristic of the mechanical system.
Although this analysis varies depending on the performance of personal computer, it can be
completed in approximately 30 seconds.
· Model adaptive control
This is a control system which is used for the servo amplifiers of MR-H, MR-J2, MR-J2S,
MR-J2-03A5, and MR-C series. It has an ideal servo amplifier and load (high rigidity and no
backlash, etc.) as an ideal model on the software and exhibits the best performance at the
actual load with always adapting the actual operation.
· Motor electromagnetic brake
The electromagnetic brake, which is installed on the motor with the electromagnetic brake, is
a no-excitation operation brake to be used in a up-and-down drive, etc. for preventing a drop
at power failure or servo error occurrence or for keeping during a stop.
App-5
APPENDICES
· Motor frame number
The installation dimension, shaft diameter and shaft length, etc. of general-purpose motor are
standardized by JIS standards as shown below.
The size of the electric motor can be checked with the frame number.
For the display method of the frame number, the C dimension is indicated in mm, and the
size of the frame length is shown after that.
The additional letter such as S, M, L, and LL is applied.
S
M
L
LL
: short machine
: medium machine
: long machine
: long long machine
L
R
Q
H
C
E
Example:3 1 5
E
F
C(Centerheight)
Height to the shaft center
(indicated in mm)
F
S
Represents the shortest frame of the 315 frame (L dimension)
Center height 315mm
· Open loop
This system is a positioning by the stepping motor, etc. Since this is a system which does not
use an encoder, the control system is simple and reasonable. Therefore, it is often used for a
relatively rough positioning or applications which do not really need a torque of small
capacity at high speed.
· Position loop gain
This indicates the response to a command in the position control. The following shows the
block diagram of the position control indicating the speed control system as Gv(s).
Position control
Here, the position loop gain is
expressed as follows
Position
command
+
–
Kp
Speed loop
Machine
Gv(s)
1/S
Position loop gain = Kp · Gv(s)
= Kp
The speed control is assumed as Gv(s)
1 since the response to the position control is
sufficiently high.
The position loop gain will be KP=ωP[rad/sec] expressed as a position response.
· Power rate
For the rated torque motor with the output rise ratio that can be output by the motor, this
indicates the speed when the motor itself accelerates. The definition is expressed with the
following formula.
App-6
APPENDICES
Q=
T R2
×10 [kW/s]
JM
TR : Motor output torque [N · m]
JM : Motor inertia moment [kg · cm2]
· Power regeneration
This is a system to return the regenerative energy to the power supply side via the bus of the
amplifier. A dedicated unit for returning the regenerative energy to the power supply side is
required. However, since there are merits that the heat generation is less than that in the
resistance regenerative system and the installation dimension becomes smaller with the
large regenerative energy, this system is mainly used for the operation to be a continuous
generation such as large-capacity models and an up-and-down shaft.
· Primary delay time constant
This is a time constant of exponential function, which is a time taken to reach 63% of the
final value.
· Proportional control
The proportional control is also called P control and expressed as Y=ε×Kp since the
operation amount Y is proportional to the deviation ε. After the positioning is completed,
even if the mechanically locked motor is turned in the amount of one pulse, the large current
flows into the motor, and an attempt is made to compensate the position declination. To
prevent this, the proportional control is set to decrease the torque gain at the same time as
the positioning completion, and then the current is suppressed. Also, the vibration during
servo lock can be suppressed by setting to the proportional control. Here, the proportional
control immediately starts to eliminate the deviation for a sudden disturbance. However, the
deviation cannot be completely eliminated for a continuous disturbance. It is because the
control system continues the operation to correct the deviation for the continuous
disturbance. Therefore, some amount of the deviation has to exist.
· Regeneration
This is a condition that the power flows from the motor side to the power supply (servo
amplifier or inverter) side. For instance, when the motor speed is faster than the speed
command, the difference of the rotation energy flows to the power supply side. The servo
amplifier or inverter stores this energy in a capacitor or consumes it in a resistor if it is large.
· Regenerative brake
Normally the power is supplied from an amplifier to a motor when a load is driven with the
motor. This condition is called driving. On the contrary, the rotation energy of the motor and
load flows to the amplifier when the load speed is decelerated at motor deceleration or
descent load drive. This status is called regeneration.
The servo amplifier obtains the regenerative brake torque with consuming the regenerative
energy in a capacitor and resistor.
The regenerative brake torque is automatically adjusted depending on the deceleration
App-7
APPENDICES
pattern. However, the regenerative brake option is used when the regenerative frequency is
high.
· Regenerative overvoltage
This is a condition that the converter bus voltage exceeds the permissible value due to the
regenerative energy which flows to the servo amplifier or inverter during regenerative
operation. In this case, since the breakdown of the capacitor, etc. may occur, the control
function is stopped with the regenerative overvoltage error.
This condition may occur when the regenerative energy is extremely large or the capability of
regenerative brake resistor is low.
· Resistance regeneration
This is a system in which a breaking torque is obtained by applying the regenerative energy
to the resistor connected to the bus of the amplifier and consuming it with heat.
· Response
The servo system has the position, speed and current loops. They indicate the trackability in
response to each command and generally the speed response.
· Speed fluctuation percentage
This is a fluctuation percentage of the motor speed generated when an inverter is used as a
speed servo, and the ratio to the rated motor speed of the fluctuated motor speed is
indicated in percentage.
The speed fluctuation percentage by load fluctuation is shown in the following formula.
Speed
fluctuation =
percentage
×100 [%]
· Speed loop gain
This indicates the response to a command on the speed control. When the constant to be
determined by a motor is assumed as K1,
Speed
+
command
ω
-
Kv
Speed control
K1
1
(JL+JM) S
Speed
ω
Speed loop gain
the speed loop gain is expressed with the following formula.
Speed loop gain=
Kv : Speed amplifier gain
K1×Kv
JL : Load inertia
J M+ J L
JM : Motor inertia
· Stop settling time
The servo motor moves holding a constant deviation to the position command. Therefore,
there is a delay time from when a stop-time command is completed until the servomotor
stops.
This delay time is called stop settling time, and approx 3 Tp is assumed in the time of ts in
the figure of the droop pulses described above. (Tp: Position loop time constant)
App-8
APPENDICES
When the operation pattern of the servo motor is examined, this stop settling time must be
considered.
· Torque linearity
This indicates the relationship of a torque command and the torque generated by a motor.
Especially in the torque control, there is a dead band around the torque zero. In addition, the
magnetic force of the magnet used for the motor is changed due to the temperature, and the
torque linearity is affected as a result.
· Undervoltage
When the power supply voltage becomes lower than a specified value in a servo amplifier or
an inverter, the control is stopped for a device protection and an external error signal is
output. This specified value is normally about 160V for a device used at 200V, and the
voltage level at or below the specified value is called undervoltage level.
· Uneven rotation
This is a fluctuation of instant motor speed to a command. The unevenness generally
increases at low speed and decreases at high speed.
· V/F control
This is a control system in which the ratio of frequency to the output voltage is constant
when the frequency is changed.
In this system, if the voltage to be actually valid decreases due to a voltage drop in a wiring
or the primary coil of a motor, enough amount of torque cannot be output (the slower the
speed is, the more this phenomenon affects.). Therefore, the amount of voltage drop
estimated in advance is set higher (torque boost) to cover the shortage of the torque at low
speed.
· Vector control
Detect a motor speed with an encoder and calculate a motor slip to identify the load
magnitude.
This control is a system which divides the inverter output current into an excitation current (a
current necessary to generate a magnetic flux) and a torque current (a current proportional to
the load torque) by vector calculation and controls a frequency and voltage optimally to flow
a necessary current individually according to this load magnitude.
App-9
INVERTER SCHOOL TEXT
INVERTER BEGINNER COURSE
INVERTER SCHOOL TEXT
INVERTER BEGINNER COURSE
MODEL
MODEL
CODE
1A2P20
SH(NA)-060011ENG-A(0609)MEE
HEAD OFFICE : TOKYO BUILDING, 2-7-3 MARUNOUCHI, CHIYODA-KU, TOKYO 100-8310, JAPAN
NAGOYA WORKS : 1-14 , YADA-MINAMI 5-CHOME , HIGASHI-KU, NAGOYA , JAPAN
When exported from Japan, this manual does not require application to the
Ministry of Economy, Trade and Industry for service transaction permission.
Specifications subject to change without notice.
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