What is transformer groupings?

Question

what does YD11, yd11, yyo, YyoD1 etc actually mean

Answer 1

Y and D stand for "Y" and delta. They are the 2 methods for connecting 3-phase power to a 3 single-phase transformers.

In the "Y" method each phase is represented by one of the 3 lines in the letter Y, with a common ground point in the middle. In the delta configuration (from the Greek letter capital Delta) each phase is represented by one of the lines in that letter, with no common point connection.

YD11 would represent a 3 transformers where the primaries are connected in a Y and the secondaries are connected in a Delta, and the turns ratio is 1:1.

Y0 or D0 are methods of using 2 single-phase transformers to connect 3-phase power to loads for lighting and motor power while keeping 3-phases fairly balanced. This saves money because you only need 2 transformers, instead of 3.

I have a reference book with a few of these Y0, D0 type connections if you are interested.

.