The phase-shift between the primary and secondary voltages in a Y/Delta connection is (choose one)

Thread Starter

Ibnul Jaif Farabi

Joined Nov 27, 2016
1) Always 30 degrees (Y side leading)
2) The Delta side can lead or lag the Y side by 30 degrees depending on the method of connection.
3) The Delta side can lag by 30 degrees or lead by 210 degrees depending on the method of connection.


Joined Nov 13, 2010
So the problem describes the connection of three single-phase transformers in a Y/Delta configuration where each of the Y voltages (with respect to ground) are shifted from each other by 120 degrees. Since there is only one way to make a Y/Delta connection, it is not clear just what the problem statement might mean by "...depending on the method of connection." Consider: is there any voltage phase shift from the primary to the secondary of any of the transformers? If not, then any Delta voltage must be either the vector sum or difference of two Y voltages (multiplied by the turns ratio). How would you determine which it should be? The only other variable is what should be the reference for the phase measurement? It seems that it should be one of the Y voltages, but which one?

There is a good phasor diagram for this problem here: