Buck–Boost Transformers
Buck-Boost
transformers
are small, single phase, dry type distribution transformers designed and shipped
as insulating/isolating transformers. They have a dual voltage primary and a dual voltage secondary. These transformers
can be connected for a wide range
of voltage combinations.
The most common use is to buck (lower) or boost (raise)
the supply
voltage a small amount,
usually
5 to
27%. Buck-boost transformers are in compliance with NEC Article 210.9, Exception 1 when field connected as
an autotransformer.
The major advantages of Buck-boost transformers are their low cost, compact size and light weight.
They are also more
efficient and cost less
than equivalent isolation transformers. When connected as an autotransformer, they can handle
loads up to 20 times the nameplate rating. A
buck-boost transformer is the ideal solution
for changing line voltage
by small amounts.
When a buck-boost has the primary and secondary windings connected, per recommended instructions, it
becomes an autotransformer. Now,
only the secondary windings are transforming voltage
and current. The majority
of the kVA
load passes directly from the supply
to the load. This is the
reason buck-boost transformers can supply
a load with a much larger kVA rating than the nameplate indicates.
Low voltage lighting
control applications
SolaHD buck-boost transformers are designed to
supply power to low voltage lighting circuits,
control panels or other systems requiring 12, 16, 24, 32, or 48 Volts. When connected as an insulating transformer (by following the wiring diagram
located after
the specification tables on the inside
of the transformer case), the transformer’s capacity matches the nameplate kVA
rating.
SolaHD buck-boost transformers are also suited for low
voltage landscape lighting. They are UL Listed
for outdoor service and their compact size makes them
the perfect solution for providing power to accent lighting applications. Electrical Connection diagrams
are shown at the end of
this section.
Use dimmers on
the output of the transformer that are
designed and rated for use with magnetic loads. We strongly
recommend contacting the
dimmer manufacturer for advice on your specific lighting
application.
Certifications and Compliances
• Listed
- UL 506
- CSA C22.2
No. 66
Accessories
• Surge Protective Devices
• Active Tracking® Filters
Three phase, buck-boost applications require two or three transformers. Check the “Quantity Required” column of the
Three Phase Selection Tables for the exact quantity.
Fusing Buck-Boost
Transformers
For determining the correct
size of breaker or fuse for a given
range of input or output
ampere ratings,
refer to Section
450.4, of the National Electric
Code (NEC).
Where an overcurrent
protection device
is required, the electrical connections
and selection tables will
reference appropriately.
Using the Selection
Tables
1. Determine if you are trying to Boost (raise) or Buck (lower) your voltage. Select an input/output voltage
combination that comes closest to matching your application from the appropriate single
or three phase
charts on the following pages.
2. Move across your selected input/output voltage row to the amperage or kVA rating closest
to, but greater than the rating
required by
your load.
3. Reading the top of the column will give you the catalog number of the exact buck-boost transformer you need. See
the Specification Tables on the
next page.
4. Connect the transformers according to the diagram
indicated. See the Electrical Connections section at the end
of this section.
Connection diagrams are packed
with each transformer.
Selection Steps
1. Input Line Voltage
Measure the supply voltage
with a voltmeter.
2. Voltage Required for the Load
Check the load equipment to
determine the voltage
requirement.
3. kVA or Ampere Rating
of the Load
Find either the load kVA or the load amperage requirements. This information is listed on the
nameplate of the load equipment.
4. Frequency
Either 50 or 60 Hz.
The frequency of
the transformer must match the frequency
of the load.
5. Number of Phases
Single or three phase line and load must match.
(A transformer
cannot
convert single to three phase.)
A common application is
to make a single phase
connection from a three phase
supply by using one
phase of the three phase supply
circuit. Be careful not to overload that phase of
the three phase supply. For buck-boost
applications the supply must provide load kVA – not just the nameplate rating of the buck-boost.
Refer
to the Selection Tables on
the following pages.