SECTION 2
HPS Universal
Why Use Buck-Boost Transformers?
The advantages of using a buck-boost transformer over an equivalent standard isolation transformer are:
Advantages
1. Used in a variety of applications
2. Inexpensive and stocked voltage correction
3. Smaller and lighter than an isolation transformer
Disadvantages
1. No circuit isolation
2. Cannot create a neutral
3. KVA and voltages do not match what’s on the nameplate kVA
and voltages.
Buck-Boost Application
™
SECTION 2
Buck-boost transformers offer an economical solution to the adjustment of line voltages that are slightly above or below
normal. When a buck-boost transformer is connected as an autotransformer, only a portion of the load kVA is actually
transformed. The majority of the load kVA is passed directly through to the source. For this reason a buck-boost transformer
may be used to supply a much larger kVA load than is indicated on the nameplate.
Buck-boost transformers can be used to adjust stable voltages only.
BUCK-BOOST STANDARD SPECIFICATIONS
UL Listed
CSA Certified
Frequency
Insulation System
Standard Design
50 to 1000 VA 1500 to 5000 VA
File: E50394 File: E50394
File: LR3902 File: LR3902
50/60 Hz 50/60 Hz
130°C (80°C rise) 180°C (115°C rise)
Single phase, welded core construction made
with high quality, high permeability silicon
steel laminations. Computer designed coils,
accurately wound from high quality copper
magnetic wire.
Single phase, welded core construction made
with high quality, high permeability silicon
steel laminations. Computer designed coils,
accurately wound from high quality copper
magnetic wire.
Encapsulation
Enclosure Type
Enclosure Finish
Termination
Conduit Knock-Outs
Mounting
All units from 50VA to 5kVA are encapsulated
with electrical grade silica sand and resin
compounds.
Heavy Duty Type 3R
(optional Type 4, 4X and 12 available)
ANSI 61 Grey, UL50 ANSI 61 Grey, UL50
Front accessible separate high and low voltage
lead wires or copper tabs.
Side and rear standard on all units (no knockouts on Stainless Steel enclosures).
Standard Wall Mounting. Standard Wall Mounting.
© Hammond Power Solutions Inc.
All units from 50VA to 5kVA are encapsulated
with electrical grade silica sand and resin
compounds.
Heavy Duty Type 3R
(optional Type 4, 4X and 12 available)
Front accessible separate high and low voltage
lead wires or copper tabs.
Side and rear standard on all units (no knockouts on Stainless Steel enclosures).
80
Data subject to change without notice.
SECTION 2
BUCK-BOOST TRANSFORMERS
Voltage Is the Key
Buck-boost transformers represent an economical way to both raise supply voltage caused by line drop or equipment
demand on the distribution system, or lower voltage caused by increased system voltages due to supply line adjustments.
Some loads including lighting and resistive loads require a stable supply to maintain performance. The detrimental effects of
incorrect supply line voltage can cause equipment failure. Buck-boost transformers can correct line voltage within 5 to 25%
of nominal.
Steps for Selecting Buck-Boost Transformers
The following information is required before selecting a buck-boost transformer:
1. Line Voltage - The voltage that you want to buck (decrease) or boost (increase). This can be determined by
measuring the supply line voltage with a voltmeter.
2. Load Voltage - The voltage at which your equipment is designed to operate. This is listed on the nameplate of
the load equipment.
3. Load kVA or Load Amps - You do not need to know both - one or the other is sufficient. This information
usually can be found on the nameplate of the equipment that you want to operate. It is the sum of all the
equipment that represents the load.
4. Frequency - The supply line frequency must be the same as the equipment to be operated - either 50 or 60
Hertz.
5. Phase - The supply line should be the same as the load - either single or three phase.
SECTION 2
Four Steps to Select the Correct Buck-Boost Transformer
1. From the top row of each “Selection Chart”, select a ‘high voltage’ and ‘low voltage’ combination that is the
closest to matching the high voltage and low voltage correction that is required for your application.
2. Move down that column to the kVA or current rating equal to, or greater than, the rating required by the total
load. It is not likely that the exact value of the load will be found, so go to the next higher rating.
3. From the far left column, select the corresponding catalog number of the exact buck-boost transformer
required. Refer to specification tables for dimensional information.
4. Connect the transformer in accordance with the connection diagram referenced at the bottom of the same
column where you selected your high voltage and low voltage combination. Connection diagrams are on
pages 90 to 92 in this catalog section. They are also packaged with each transformer.
© Hammond Power Solutions Inc.
81
Data subject to change without notice.
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