Buck-Boost Transformers

Buck-Boost Transformers
BUCK-BOOST TRANSFORMERS
Selecting and Applying
Buck-Boost Transformers
United CoolAir
manufactures units that
can be applied with a
variety of voltages. Some
applications utilize an
input or supply voltage of
277-1-60. This power supply
comes from a 460-3-60
(4-wire) system (The Neutral
Leg and the Line side
opposite the neutral leg).
While some components
are available for direct
application of 277-1-60
power, most manufacturers
(including United CoolAir)
find that the use of a
buck-boost transformer
to lower the voltage is
more cost effective. The
units are fabricated using
components suitable
for 208/230-1-60 power
supply. The control voltage
transformer is wired on the
230-volt tap to provide the
24-volt control voltage.
Selecting a Buck-Boost
Transformer
The following information
should be confirmed for
the application:
•Line Voltage – Confirm
that the supply / input
voltage is 277.
•Frequency – Input power
supply frequency must
match the equipment –
either 50 or 60 Hertz (Hz).
This TechTip is based on
only applications of 60
Hz.
•Phase – The supply / input power
phasing must be the same as
the equipment requirements.
The TechTip is based on singlephase applications.
•Load KVA or Load Amps – You
only need to know one or the
other. This information usually
can be found on the unit
nameplate(s). On United CoolAir
equipment the Minimum Circuit
Ampacity (MCA) should be used
as the Load Amps.
The transformer is used to buck
(decrease) the incoming power
supply from 277 volts down to the
230 volts required for the unit. Table
1 lists the buck-boost transformers
available from United CoolAir.
Read down the column until you
see a KVA or Amp value that is just
higher than the equipment to be
operated.
Table 1 – Available Buck-Boost Transformers
Single-Phase
Line
Voltage277
UCA
Part Number
Model (Available)
Load Voltage
(Output)230
KVA
1.44
Amps
6.25
4CA1901 T-1-81064Load
Max. Size of
10
Fuse or Breaker
KVA
2.88
Amps
12.50
4CA1902 T-1-81065Load
Max. Size of
15
Fuse or Breaker
KVA
4.31
Amps
18.75
4CA1903
T-1-81066Load
Max. Size of
20
Fuse or Breaker
KVA
5.75
Amps
25.00
4CA1904 T-1-37920Load
Max. Size of
30
Fuse or Breaker
KVA
8.63
Amps
37.50
4CA1905 T-1-37921Load
Max. Size of
40
Fuse or Breaker
KVA
11.5
Amps
50.00
4CA1906 T-1-37922Load
Max. Size of
60
Fuse or Breaker
KVA
17.25
Amps
75.00
4CA1907(1) T-1-37923Load
Max. Size of
80
Fuse or Breaker
(1) Model contains lifting ears.
BUCK-BOOST TRANSFORMERS
Connect the transformer
according to the diagram to the
right. Only one (1) transformer is
required in the wiring diagram
for each power supply to the
equipment.
Figure 1 – Transformer Connection Diagram
CAUTION: Do not make
connections other than those
shown. The transformer must
be as large (KVA) as the load it
must operate. Never exceed the
nameplate rating as this could
result in overheating, reduced life
expectancy or worst cases, fire.
Notes:
General
1.The symbol “O” used in
this connection diagram
illustrates where to field
install an Overcurrent
protective device (typically
a fuse or circuit breaker)
when one input conductor
is grounded and the
other input conductor is
ungrounded.
The installation, operation
and maintenance of drytype transformers should be
performed by an electrician or
other qualified personnel who
are familiar with international,
national or local electrical
codes. Familiarity with the
potential shock hazards
associated with electrical
equipment is also necessary.
2.When both input conductors
are ungrounded an
Overcurrent protection
device is required to be
installed in series with each
input conductor.
Encapsulated units are NEMA
3R enclosures suitable for either
indoor use in harsh environments
or for outdoor use. CE marked
units have a protection index of
IP23.
3.For additional information
refer to the National
Electrical Code, Article 450-4.
The transformer must be
installed per the National
Electrical Code (NEC) and local
code requirements. CE marked
transformers must be installed
per EN 60742.
Inspection and Handling
The transformer should be
inspected carefully upon receipt
to check for any visible or
concealed damage that may
have occurred during shipment.
If damage is found, a claim
should be filed immediately with
the carrier.
Transformers fifty-five (55)
pounds or larger are provided
with lifting ears. Incorrect
handling can bend the
enclosure, cause other damage
or result in personal injury. (P/N
4CA1907 contains lifting ears).
Installation
When installing a buck-boost
transformer, always follow all
applicable national and local
codes. Outside installation of
the transformer should have the
wiring in a conduit or as required
by national and local codes.
Encapsulated transformers can
be installed indoors or outdoors.
When installed outdoors, these
units should be installed with
the wiring compartment down
to prevent the entrance of
moisture. Some encapsulated
units have a top-entry wiring
compartment and can be
installed vertically (wiring
compartment up).
For indoor floor mounting of
an encapsulated unit that
has a bottom-entry wiring
compartment, the unit can be
installed horizontally (on its back
side) for ease of making wire
connections.
BUCK-BOOST TRANSFORMERS
Maintenance
Hazardous Voltage.
Will Cause Severe
Personal Injury or
Death.
Turn Power Off
Supplying Device
Before Installing
WARNING: Danger of electric
shock! Do not remove parts
or make connections while
transformer is energized.
Electrical Connections
Refer to the transformer
nameplate label or enclosed
wiring diagram for primary
and secondary voltage
combinations, frequency
and number of phases. Tap
connections and voltage
combinations are also listed on
the diagram or nameplate.
Proper assembly of the field
wiring to the transformer leads
is extremely important. Make
certain that the connector or
terminal is sized for the cable.
Space and insulate connections
or terminals per the NEC.
Non-ventilated encapsulated
styles only require periodic
wiping of dust and dirt from
the outside of the case
under normal conditions
and environments. Adverse
conditions may require more
frequent inspections.
CAUTION: Never perform internal
maintenance while the unit is
energized!
If a dry-type transformer
accidentally gets wet, it must
be cleaned and thoroughly
dried before energizing.
Otherwise, complete failure
could result.
Storage
Encapsulated transformers
should be stored in a clean,
dry area. Care shoud be
taken to prevent moisture or
condensation from entering
the transformer. If stored
outside, the transformer must
be covered and protected
from water, dust and other
airborne contaminants.
Grounding
All dry-type transformers have
a ground stud in the enclosure.
The transformer enclosure
should be solidly grounded
to protect personnel. The
customer-supplied grounding
conductor should have a
current-carrying capacity to
meet international, national and
/ or local requirements.
NOTICE: These instructions are
general in nature and may not
cover all variations in transformer
design or conditions of installation,
operation and maintenance in
enough detail to meet customer
needs. Additional instructions may
be included with the transformer.
If you need further information or
should a problem arise, please
contact the manufacturer.
BUCK-BOOST TRANSFORMERS
Notes
491 East Princess Street, York, PA 17403
Toll Free 1-877-905-1111
Phone (717) 843-4311
e-mail: uca@unitedcoolair.com
www.unitedcoolair.com
© 2008 United CoolAir Corporation
Manufacturer reserves the right to make changes without notice.
Fax (717) 854-4462
Form TT002 (0513)
BEA 1K (0513)
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