Easy understanding of 3-phase transformer connections (Delta–Delta - The dashed strains suggest the transformer outlines. The 3 single-phase transformer implementation may be visible with the aid of dismissing the outer dashed outline and the bushing labels shown at that outline, and concentrating on the 3 smaller (unmarried-section transformer) outlines. The 2 maximum normally used three-phase winding configurations are delta and wye, named after the greek and english letter that every resembles. In a delta configuration, the three windings are connected stop-to-end to shape a closed direction. A phase is connected to every nook of the delta.
At the same time as 3-segment devices are typically the more value-powerful option, the single-phase alternative offers greater versatility and can be appealing from a reliability and maintenance viewpoint. If several equal transformers are wanted at one vicinity, the single-section option can include the acquisition of a spare unit to reduce outage time within the occasion of a failure. The three-segment load is generally motor load even as the single-segment aspect is often lighting and occasional voltage energy. The single-phase load can be fed with the aid of grounding a center tap on one of the legs of the delta secondary, then connecting the unmarried-phase load among one of the stages at the grounded leg and this grounded impartial.
Subsequent a part of this text will talk three-section transformers using the open-delta and open-wye connections, where one of the single-section transformers making up the 3-section bank is not noted. The leg of the transformer with the missing transformer is referred to as the phantom leg. Even though delta windings are often operated ungrounded, a leg of the delta may be center tapped and down to earth, or a nook of the delta can be grounded. In a wye configuration, one cease of every of the three windings is hooked up to form a impartial. A segment is connected to the opposite end of the three windings. The impartial is normally grounded.
As the loading on a delta–delta transformer turns into unbalanced, high currents can flow into within the delta windings main to a voltage imbalance. Balanced loading requires the choice of three transformers with equal voltage ratios and identical impedances.