Buck-Boost transformers are single
phase, four winding transformers designed for two purposes. The
first purpose is as a low voltage isolation transformer for use on
12, 16, 24, 32, or 48 volt circuits. Their second, and more
important use, is as a "Buck-Boost" transformer. Buck-Boost means
that these transformers are used to buck (lower) or boost (increase)
line voltage to match required load voltage.
transformers are used to
correct consistently low or high voltage conditions, where the
voltage difference ranges from approximately 5% to 27%. Variation of
the input voltage is passed through to the output side of the
transformer in the same percentage. This concept is important
because the question is frequently asked if Buck-Boost transformers
will stabilize variable voltages. They will not!
The most common
applications for these transformers are boosting 208 volt lines to
230 or 240 volts, and vice-versa. These applications include
both single and
three phase lines and are particularly common in HVAC applications
for air conditioning appliances. Additionally, Buck-Boost
transformers are very well suited to motor loads, boosting 240 to
277 for lighting loads and many applications where nominal voltage
is above or below 120 volts.
Their use should be considered where
supply line voltage is found to be consistently above or below
desired nominal values of load voltage.
Buck-Boost transformers are also
commonly used on the input line side of phase converters. Most
three-phase utility service is 208 volts and single-phase service is
240 volts. Phase converters produce three-phase power equal in
voltage to the single-phase input voltage of 240 volts. While most
three-phase equipment can operate on 208 or 240 volts, other
equipment is designed to operate only on 208 volts and 240 volts
will be outside its operating range. Reducing the input voltage to
a safer level with a Buck-Boost transformer is a convenient,
affordable solution to this problem.