3-Phase Transformer Connections

Practically all of the electric power in commercial power systems is generated as three phase, although a large part of the total is consumed as single phase and in the form of direct current. However, there are a number of 3-phase voltage transformations between the generator terminals and buses in the distribution centers.

It is possible to convert 3-phase power from one voltage to another by a suitable connection of two or three single-phase transformers or by making use of one 3-phase transformer. When a 3-phase transformer or three single-phase transformers are available, several 3-phase arrangements are possible; among them are the delta-delta, the wye-wye, and the wye-delta or delta-wye connections.