Delta-wye transformer

A delta-wye transformer is a type of three-phase electric power transformer design that employs delta-connected windings on its primary and wye/star connected windings on its secondary.

It can be a single three-phase transformer, or built from three independent single-phase units.

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.

[2] Delta-wye transformers introduce a 30, 150, 210, or 330 degree phase shift.

An example delta-wye transformer schematic.
One possible delta-wye transformer configuration. [ 1 ]