Transformer Polarity
Transformer Polarity
(OP)
OK guys, I'm trying to put a subtractive polarity transformer into a substation that previously had an additive transformer. The new and old transformers were both delta-wye grounded.
Does any one have a link to information on how I will have to change the phases coming into and out of the station to allow this new transformer to phase in properly with the existing system.
Thanks
Does any one have a link to information on how I will have to change the phases coming into and out of the station to allow this new transformer to phase in properly with the existing system.
Thanks






RE: Transformer Polarity
You DO need to verify that the phase shifts are the same if this is a delta-wye transformer. This should be indicated on the nameplate.
RE: Transformer Polarity
It would help if you could link to a photos of the nameplates or winding diagrams.
RE: Transformer Polarity
I disagree. Subtractive versus additive tells you where the bushings are physically located. X1 marks the polarity end of the winding wherever it happens to exit the can.
Nameplates are not always correct. Always take voltage readings prior to closing the switch.
RE: Transformer Polarity
For single-phase ANSI standard distribution transformers, The X1 bushing coincides with with the H1 bushing on positive polarity transformers, but with the H2 bushing on negative polarity transformers. See p. 15.14 of ww
RE: Transformer Polarity
When we put the new subtractive transformer in where there was once an additive transformer, there was a 30 degree phase shift between the phases on the secondary of the transformer and the rest of the system. Obviously this is an for our customer as they want the ability to parallel stations.
Basically as best i can tell, by changing from additive to subtractive there is a 180 degree phase shift in the secondary vector diagram. I'm looking for information on what phases i could switch to correct the 30 degree difference.
RE: Transformer Polarity
I stand by my statement. The difference in the two in your link is the physical location of the X1 and X2 bushings. In both cases Vx1x3 is in phase with Vh1h2. In order to parallel these two transformers, connect H1 to H1, H2 to H2, X1 to X1, X2 to X2 (if used), and X3 to X3.
RE: Transformer Polarity
A 30 degree shift means one of your delta wye transformers is not. It is either wye wye or auto. There is no way to fix this by swapping phases.
RE: Transformer Polarity
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RE: Transformer Polarity