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· Registered
1,887 Posts
Discussion Starter · #1 ·
We are doing a job that involves the installation of two 30kva UPS units. There is a 600 volt feeder coming from an ATS feeding an MDP which feeds two 75 KVA 600-120/208 volt transformers.

Both transformers have a panel on their secondary sides. Each panel has two breakers, UPS 1 and UPS 2 so the UPS units are double fed. That all makes sense but one of the transformers is 30 degrees out of phase while the other is 0...I am curious as to why they would use a phase shifting transformer in this setup? Can't say I have come across this before...

· Bilge Rat
motors and controls.........
10,061 Posts
It's likely that one of the transformers id ∆-Y while the other is Y-Y.

As noted, all ∆-Y transformers will have a 30º phase shift, while Y-Y would be 0º.

The only way to get 0º from a ∆-Y is to have a Y-Y with the center of the Y on the high side spliced but not connected to anything.
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