Buck / Boost Transformers

Buck-Boost Transformers are small single phase isolation transformers that will reduce (Buck) or raise (Boost) line voltage when connected as an Autotransformer. The most common application is Boosting 208 to 230V. Two or three may be banked for three phase application where the neutral is available from the input. Much smaller transformers may be used in Buck-Boost applications, since the size of the transformer is roughly proportional to the change in voltage.
i.e. A 10kVA load at 240V can be increased to 264V, a 10% change can be achieved with a 1kVA transformer.

Voltage Change Table

Multiply Input voltage by the appropriate number in Voltage Change Table for output voltage.

Transformer Multiplier Table

Multiply Load by the appropriate number in Transformer Multiplier Table for approximate transformer size.

Transformer Boosting Circuit Diagram

Diagram A1: Boosting	Diagram B1: Boosting	Diagram C1: Boosting	Diagram D1: Boosting

Transformer Bucking Circuit Diagram

Diagram A2: Bucking	Diagram B2: Bucking	Diagram C2: Bucking	Diagram D2: Bucking