Delta-wye transformer
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A delta-wye transformer is a type of three-phase
electric power Electric power is the rate at which electrical energy is transferred by an electric circuit. The SI unit of power is the watt, one joule per second. Standard prefixes apply to watts as with other SI units: thousands, millions and billions ...
transformer A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer' ...
design that employs delta-connected windings on its primary and wye/star connected windings on its secondary. A neutral wire can be provided on wye output side. It can be a single three-phase transformer, or built from three independent single-phase units. An equivalent term is delta-star transformer.


Transformers

Delta-wye transformers are common in commercial, industrial, and high-density residential locations, to supply three-phase distribution systems. An example would be a distribution transformer with a delta primary, running on three 11 kV phases with no neutral or earth required, and a star (or wye) secondary providing a 3-phase supply at 415 V, with the domestic voltage of 240 available between each phase and the earthed (grounded) neutral point. The delta winding allows third-harmonic currents to circulate within the transformer, and prevents third-harmonic currents from flowing in the supply line. ''Electrical Transmission and Distribution Reference Book'', Westinghouse Electric Corporation, 1964, Chapter 5, table 15. Delta-wye transformers introduce a 30, 150, 210, or 330 degree phase shift. Thus they cannot be paralleled with wye-wye (or delta-delta) transformers. However, they can be paralleled with identical configurations and some different configurations of other delta-wye (or wye-delta with some attention) transformers.


See also

* Electric power distribution * High-leg delta * Mains power systems *
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Three-phase transformer circuits
{{Electric transformers Electric transformers Three-phase AC power