Delta / Delta Connection of a Transformer

•    In delta-delta connection the primary side and secondary side are connected in delta.

•    The ratio of line voltages of primary and secondary sides is same as the transformation ratio of each transformer.

•    For the connections, the line voltage on primary side will be in phase with the corresponding line voltage on secondary side.

•    Similarly the phase voltage on primary side will be in phase with the corresponding phase voltage on secondary side.

•    If the connections on secondary side are changed as a1c2, c1b2 and b1a2 then corresponding line and phase voltages on primary and secondary side will be in phase opposition.

•    In the connection line voltage is equal to phase voltage on both sides.

•    Line current is 3 times phase current on both sides.

•    In delta-delta connected transformers number of turns required in each phase winding will be high.

•    Cross sectional area of the conductor will be less.

•    Therefore it is economical to use this type of connection for high capacity low voltage transformers.
   
This connection has the following advantages.

1. The voltage waveform is more sinusoidal, we can reduce the effect of harmonics in the output voltage using this type of connections.

2. We can easily handle unbalanced load with this type of connection.

3. If any one set of windings become disabled the system can continue to operate in open delta with reduced available capacity.