WYE Delta Transformer Question

pguerra75

Member
Location
US
We have a building with 480 Service (no neutral). We have called in an electrician to install a 45kVA transformer to test some machines we build that use 208.
My question is about the type and connections of the transformer, we have a 45kVA 480 WYE-208 DELTA transformer and the electrician seems convinced we can use that. I however am a little skeptical as we don't have a neutral. He told me it does not need to be connected or it can be connected to ground (the second part had me a bit more on edge).
Am I getting good advice?
 

hillbilly1

Senior Member
Location
Atlanta,Ga
Occupation
Field coordinator/ technical support
Kinda strange transformer configuration, you do know you will not get 120 volts out of the secondary? A much more common transformer would be a 480 volt Delta to 120/208 Wye. You will not need a neutral on the primary side with either transformer, so whether the service has a neutral or not, is irrelevant. You will need XO bonded on the 208 side if you use the delta/wye, whether you need a neutral or not, or if you use the wye/delta, one phase can be grounded.
 

pguerra75

Member
Location
US
Kinda strange transformer configuration, you do know you will not get 120 volts out of the secondary? A much more common transformer would be a 480 volt Delta to 120/208 Wye. You will not need a neutral on the primary side with either transformer, so whether the service has a neutral or not, is irrelevant.
Agreed, the reason we have the transformer we do now is because our old facility only had 208 power, so it was used to step up for a our 480 vac machines(some had neutrals hence the WYE).
 

hillbilly1

Senior Member
Location
Atlanta,Ga
Occupation
Field coordinator/ technical support
Agreed, the reason we have the transformer we do now is because our old facility only had 208 power, so it was used to step up for a our 480 vac machines(some had neutrals hence the WYE).
Now I’m confused? You said the service was ungrounded 480 in the original post…….Oh! This is a new facility, and you are using the transformer from the old facility. Gotcha! Then one phase of the 208 output would be bonded for the overcurrent protection to work if a fault to ground occurs. Be forewarned you will have 208 to ground on two of the three phases. A ground detector can be used if that voltage is objectionable, and not bond the one phase.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Will this equipment operate normally on a corner grounded 208 volt system? If I were testing something for use in the real world I would want to test it with a voltage system that will be used in the real world which would be a 208Y/120 system. IMO you should buy another transformer.
 

paulengr

Senior Member
Will this equipment operate normally on a corner grounded 208 volt system? If I were testing something for use in the real world I would want to test it with a voltage system that will be used in the real world which would be a 208Y/120 system. IMO you should buy another transformer.

It CAN work if it is delta anyway. A motor for instance does not need a neutral but if you have 120 V control wiring fed from a neutral you do. If you run corner grounded delta (recommended if you insist on the transformer) delta loads won’t know the difference but say a lighting circuit is going to be 0 or 208 V, neither of which is right.

As with others unless you know what you are doing, don’t make it delta delta.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
It CAN work if it is delta anyway. A motor for instance does not need a neutral but if you have 120 V control wiring fed from a neutral you do. If you run corner grounded delta (recommended if you insist on the transformer) delta loads won’t know the difference but say a lighting circuit is going to be 0 or 208 V, neither of which is right.

As with others unless you know what you are doing, don’t make it delta delta.
Yes it will work but my question is why would you test equipment on a system different than the one it will be used on in the real world?
 

pguerra75

Member
Location
US
Yes it will work but my question is why would you test equipment on a system different than the one it will be used on in the real world?
You pose some of the same questions we did to the electrician, in the end we decided to buy a Delta-Wye transformer. Its more important to test our machines in real world conditions then to save a couple bucks.
 
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