Power Transformers convert power-level voltages from one level or phase configuration to another. They can include features for electrical isolation, power distribution and control and instrumentation applications. Power Transformers can be configured as either a single-phase primary configuration or a three-phase configuration.The size and cost of a transformer increases when you move down the listing of primary windings.

Single-phase primary configurations include single, dual, quad (2+2), 5-lead, and ladder. A 5-Lead primary requires more copper than a Quad (2+2) primary. A Ladder is the least economical primary configuration. Three-phase transformers are connected in delta or wye configurations. A wye-delta transformer has its primary winding connected in a wye and its secondary winding connected in a delta. A delta-wye transformer has its primary winding connected in delta and its secondary winding connected in a wye. Three phase configuration choices include delta - delta, delta - wye (Y), wye (Y) – wye (Y), wye (Y) – delta, wye (Y) – single-phase, delta – single phase, and international. Primary frequencies of incoming voltage signal to primaries available for power transformers include 50 Hz, 60 Hz, and 400 Hz. 50 Hz is common for European power. 60 Hz is common in North American power. 400 Hz is most widely used in aerospace applications. The maximum primary voltage rating is another important parameter to consider. A transformer should be provided with more than one primary winding if it is to be used for several nominal voltages.