[cdnelectrician]

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...

 

[don_resqcapt19]

All delta/wye transformers have a 30° phase shift primary to secondary. That being said I am not sure how you can get a 30° phase shift between the secondaries of the two transformers, I could understand a 60° shift, but not a 30.

 

[cdnelectrician]

All delta/wye transformers have a 30° phase shift primary to secondary. That being said I am not sure how you can get a 30° phase shift between the secondaries of the two transformers, I could understand a 60° shift, but not a 30.

I was thinking the same....will look into more tomorrow.

 

[micromind]

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.

 

[don_resqcapt19]

Wye/wye transformers are very rare in other than utility systems.

 

[micromind]

Wye/wye transformers are very rare in other than utility systems.

Yes they are. The only time I've seen them is when 0º phase shift is specified.

 

[cdnelectrician]

Had a look in the specs today...the transformer is indeed 0 degrees...I will take a pic of the nameplate tomorrow. From what I can tell it appears to be delta to wye.

Edit: Got my answer, good article.

https://www.google.com/url?q=http:/...IQFjAI&usg=AFQjCNFsdEPBi23RzLav7aZrlgBD2FaJhQ