Open Wye Open Delta Connection

[jtester]

Re: Open Wye Open Delta Connection

paul32
The discussion I had with Charlie was related to high voltage, 15kv and up. Wye primary connections are fine, if you have a high voltage neutral, and and you ground the transformer high side neutral also. If you don't ground the high side neutral, during a single phase condition, the secondary line to neutral voltages can go crazy.

Your second question was relating to delta primary connections in wye systems. Delta-wye transformers are most common in low voltage applications, 480 to 120/208 volts for example, because the delta will tend to balance an imbalance in the wye, and present more of a balanced load to the 480 side. It also is effective in limiting the transfer of harmonics between the 208 side and the 480 side.
I don't think they are the most common in high voltage applications by a long shot.

Jim T

 

[rattus]

Re: Open Wye Open Delta Connection

John, thanks for the clarification on xfmr polarities. Putting the little dots on the schematic really pins it down.

 

[rattus]

Re: Open Wye Open Delta Connection

Finally found the book with an explanation of the open delta. They make the point that even with a resistive load, the open delta xfrmrs will operate at a PF less than unity. Of course you power guys already knew that.