Electrical Engineering ⇒ Topic : Delta-Star Connection

Delta-Star Connection

Figure (a) shows three-phase transformer having delta and star connections on primary and secondary windings, respectively.

Figure (b) shows the phasor diagram of both the primary and secondary sides. From ,Figure  (b), it can be seen that there is 300 phase difference between the primary and secondary line voltages. The neutral is available on secondary side and single-phase and three-phase loads can be supplied with this type of transformers. The main use of this transformer is to step up the voltages and hence it is used at the beginning of transmission, i.e., at the sending-end

                    Figure (a) Delta-star connection.           Figure (b) Phasor diagram of delta-star connection.

Let V_L1 and V_ph1 be the line and phase voltages respectively on the primary side, and V_L2 and V_ph2 be the line and phase voltages respectively on secondary side, and a be the turns ratio.