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 trans formers are in compliance with NEC Article 210-9, Exception 1 when field connected as
However, Buck-Boost transformers will not compensate for fluctuating line voltages. They should only be used when line voltage is relatively constant. Fluctuating line voltages should be regulated with a Line Voltage Conditioner.
The advantages of using a buck boost transformer over an equivalent standard isolation transformer are as follows:
1) Used in a variety of applications
3) Smaller and lighter
4) More efficient nameplate
5) 5-10 times increase in KVA
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 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 transformers may be used to supply a much larger load kVA than is indicated on the nameplate.