A three-phase transformer consists of six windings, three for the primary and three for the secondary. The windings on each side (primary and secondary side) can be connected in either delta or star configurations. These windings can be viewed as separate single-phase windings.

A distribution transformer or service transformer is a transformer that provides the final voltage transformation in the electric power distribution system, stepping down the voltage used in the distribution lines to the level used by the customer.

Smaller pole-mounted transformers, such as those used for residential power distribution, may contain anywhere from a few pounds to several dozen pounds of copper.Distribution transformers consist of a magnetic core made from laminations of sheet silicon steel (transformer steel) stacked and either glued together with resin or banded together with steel straps, with the primary and secondary wire windings wrapped around them.