If the primary feeds are in phase and rotation, why isn't secondary?
If the primary feeds are in phase and rotation, why isn't secondary?
(OP)
I have three 15 KV X 480 Volt transformers fed by three 15 KV feeders from the same 15 KV switch line up. Here's the problem: The primary feeders of the three transformers are in phase and rotation and the secondary sides are not. All three are straight from the factory with no field mods. What I found is that the voltages measured between phases from Transformer One and Transformer two are roughly 277V. Interestingly enough, the measured voltages between phases "A" and "C" from Transformer One to Transformer Two measures about 554V. The voltages measured between Transfomer Two and Transformer Three are right at "zero," with voltages from phase "A" to "C" being right about 480V. I am trying to pinpoint the problem and fully understand the possibilities so I can go back to manufacturer for a fix.






RE: If the primary feeds are in phase and rotation, why isn't secondary?
Were they made twins? And born at same time?
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: If the primary feeds are in phase and rotation, why isn't secondary?
RE: If the primary feeds are in phase and rotation, why isn't secondary?
If the transformers are core form, please disregard this post.
respectfully
RE: If the primary feeds are in phase and rotation, why isn't secondary?
H1 H2
X1 X2
OR
H1 H2
X2 X1
Additionally, you can test the 'polarity' of the phases. The Megger TTR20 will identify normal (in phase) and reverse polarity of the single-phase transformers.
RE: If the primary feeds are in phase and rotation, why isn't secondary?
RE: If the primary feeds are in phase and rotation, why isn't secondary?
k is the number of times that values on low voltage side are late for high voltage side. If you take that first transformer has k=k1 second transformer has k=k2=k1+6 that would make the difference between phases 180 degrees and voltage difference between same phases 2times nominal voltage.