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Wrong voltage on 167 KVA bank.
2

Wrong voltage on 167 KVA bank.

Wrong voltage on 167 KVA bank.

(OP)
  3- 167 KVA transformers, they are hooked up wye-wye. 14.4 Ø to grd. This goes to a reda pump. They want 2500 volts Ø to Ø on the secondary. We have 2500 volts c to b, 1445 a to b,1445 a to c. 1445 Ø to grd. on a,b,and c. The 3 phases were all hot, polarity was the same. H2 was grounded. Anyone with any ideas on what I can look at next. Thank you, Bob.

RE: Wrong voltage on 167 KVA bank.

The wrong end of "A" phase is connected to the wye point.
Your phase angles are probably 60 deg, 60 deg, and 240 deg.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Wrong voltage on 167 KVA bank.

(OP)
  Would you explain in more detail? Thank you, Bob

RE: Wrong voltage on 167 KVA bank.

Phase A transfomrer is connected reverse polarity from the other two.

Draw the wye vector diagram and then flip the A phase voltage 180 degrees and you will see what happens.

Assume the high side voltage vectors are:
A-G 8.3 kV @ 0 degrees
B-G 8.3 kV @ -120 degrees
C-G 8.3 kV @ -240 degrees
A-B = 14.4 kv @ +30 degrees
B-C = 14.4 kv @ -90 degrees
C-A = 14.4 kv @ +210 degrees

Low voltage on a wye- wye has no phase shift, voltages should be (asuming 14.4-2500V ratio):

A-G 1445 V @ 0 degrees
B-G 1445 V @ -120 degrees
C-G 1445 V @ -240 degrees
A-B = 2500 V @ +30 degrees
B-C = 2500 V @ -90 degrees
C-A = 2500 V @ +210 degrees


But if A transformer is connected backwards, it will be 180 degrees out and low side voltages become:

A-G 1445 V @ -180 degrees
B-G 1445 V @ -120 degrees
C-G 1445 V @ -240 degrees
A-B = 1445 V @ +60 degrees
B-C = 2500 V @ -90 degrees
C-A = 1445 V @ +120 degrees

 

RE: Wrong voltage on 167 KVA bank.

(OP)
Thanks for the help, I had to stay in today. Tomorrow I will go out and see what we can do. I will let you know. Bob

RE: Wrong voltage on 167 KVA bank.

(OP)
When I went back they had the transformers changed out. The transformers they took down, I could not find. On the dock, with other transformers. Thank you for all the help. Bob

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