3 phase transformer question

[phil b]

I've read patty3's postings about how to calculate and wind a single phase transformer. Excellent post patty3! http://www.fieldlines.com/story/2004/12/13/14635/709

Unfortunately, I need a 3 phase xformer. Can anyone explain the differences, other than they have 3 phases vs. 1?  How are they wound? Are 3 phase xformers simply 3 single phase ones put together? Do they have seperate E's and I's? How is the induction controlled between phases that are out of phase? Any advice is appreciated!

[Flux]

You can use 3 single phase transformers and unless you have a scrap 3 phase transformer to obtain the core from that is likely to be your best bet.

Three phase transformers have 3 equal sized limbs and one phase is wound on each leg.

This works because the instantaneous sum of the 3 magnetic fields is zero.

You can use any combination of star and delta, but star/star is usually used with a neutral. If there is no neutral it is usual to have a delta winding to keep voltage balance.

Flux

[phil b]

Thanks Flux, I hoped you'd chime in.

Phil