3 phase delta 480 to secondary 208Y/120

[Jpflex]

My coworker swears he’s right in wiring up a 3 phase 30 KVA 480delta/ 208Y120 transformer primary H1 to 480v supply line 1 and supply line 2 to Delta H2 and supply line 3 to H3

However, where I say is obviously wrong is trying to hook up the Y transformer secondary X1 to feed single phase panel bus A, X2 of transformer to neutral bus of single phase panel and x3 of transformer to bus B of single phase panel

He is simply trying to get the 240 volts from single phase panel A and B busses from the Y secondary shown. (Even when output would be 208)

The neutral having transformer x 2 potential will energize all metal cabinets to its potential and is not like deriving a neutral from a single phase transformer

I have only wired up single phase transformers in the past such as using 2 legs from a 3 phase system to feed a single phase panel and got proper 240 volts between buses A and B and 120 volts from A or B to derived neutral or mid point of secondary single phase winding and all was well

Under the condition attempted by coworker shouldn’t the transformer be hooked up only to a 3 phase panel or could you omit one phase lead from the Y portion of the transformer to feed only A and B of single phase panel to get 208 but not get 120 volt option?

Any thoughts?

 

[LarryFine]

You are correct. It should be two X lines and X-0.

That would give you 120v L-N and 208v L-L 1ph.

 

[Jpflex]

You are correct. It should be two X lines and X-0.

That would give you 120v L-N and 208v L-L 1ph.

I haven’t wired up a 3 phase transformer yet but if I did wouldn’t I use all 3 line a b and c phases connected to H1, H2 And H3 respectively?

And have 3 legs out on secondary X1, x2 and x3 for phases and ass a derived neutral at Xo if needed?

 

[LarryFine]

I haven’t wired up a 3 phase transformer yet but if I did wouldn’t I use all 3 line a b and c phases connected to H1, H2 And H3 respectively?

And have 3 legs out on secondary X1, x2 and x3 for phases and ass a derived neutral at Xo if needed?

Yes and yes, even if you don't have a load on one of the Xs. You should bond and earth X-0.