Delta to wye with 1P transformers

[VernB]

Thanks to everyone for the education on delta 3 phase from my last post!

So, here I am still dealing with 240V ungrounded delta. I've come across a lovely stash of 240 to 120 1 phase transformers so I think I'm going to try my hand at setting a set up as a delta to wye transformer bank (yes, I'm thoroughly familiar with the two configurations!).

So, two questions here:

1. Are the 120V secondary windings the proper deal to produce 208/120Y in a wye config?

2. This seems WAY too simple, any gotchas to watch out for doing this?

Vern

 

[LarryFine]

1. Yes.

2. Make sure you phase properly.

Yes, it is that simple. Do bond to ground that derived neutral.

 

[Smart $]

So, two questions here:

1. Are the 120V secondary windings the proper deal to produce 208/120Y in a wye config?

2. This seems WAY too simple, any gotchas to watch out for doing this?

Vern

#1... Yes, they can be configured for 208Y/120. I wouldn't, given a choice... but that's strictly personal preference.

#2... Yes there is a gotcha. If you reverse polarity on one of the transformers you'll end up with a shared-leg, double open delta output ("W"), instead of a wye ("Y"), where line-to-line voltages will be 120, 120, and 208 (in no particular order). The leg that is common to both 120V outputs is the one with reversed polarity.

 

[VernB]

1. Yes.

2. Make sure you phase properly.

Yes, it is that simple. Do bond to ground that derived neutral.

Thank you! Got everything up and running perfectly, it's the snazziest transformer configuration in the whole place .

Vern

 

[VernB]

#1... Yes, they can be configured for 208Y/120. I wouldn't, given a choice... but that's strictly personal preference.

#2... Yes there is a gotcha. If you reverse polarity on one of the transformers you'll end up with a shared-leg, double open delta output ("W"), instead of a wye ("Y"), where line-to-line voltages will be 120, 120, and 208 (in no particular order). The leg that is common to both 120V outputs is the one with reversed polarity.

Thanks for the assist!

Vern