We have a Delta-Star Oil filled 300kVA, 480/480V transformer, which is providing an additional 30 Degree phase shift on the secondary side. If we convert the secondary star configuration to Delta configuration, will it help and what are the consequences of doing that(i.e. effect on impedance etc).
Transformer Phasing
- Thread starter LumenChan
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- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
Re: Transformer Phasing
Will it help what? What is the problem that you are trying to fix? I can't think of a reason that a 30 degree phase shift would cause any operational problems. That phase shift is inherent in the delta-star configuration.
If you don't need the neutral (i.e., no 277 volt loads), and if you want to eliminate the 30 degree phase shift, then wiring it as a delta-delta would accomplish that goal.
But I have to ask why the transformer exists in the first place. Why do you need a 480/480 transformer?
Will it help what? What is the problem that you are trying to fix? I can't think of a reason that a 30 degree phase shift would cause any operational problems. That phase shift is inherent in the delta-star configuration.
If you don't need the neutral (i.e., no 277 volt loads), and if you want to eliminate the 30 degree phase shift, then wiring it as a delta-delta would accomplish that goal.
But I have to ask why the transformer exists in the first place. Why do you need a 480/480 transformer?
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
Re: Transformer Phasing
I'd have a couple of questions first.
Why is the phase shift a problem? It's simply the natural consequence of a delta-star configuration.
Are you planning to replace or rewind the transformer or simply reconfigure the existing secondary winding?
Beyond the questionable action of reconfiguring it for warranty and possible listing violations it would result in a 277V delta.
The PU self-impedance would generally be unaffected assuming you used the same core.
You would loose a good safety feature of grounding the common star point.
In general, unless the phase shift is genuine problem, I wouldn't recommend doing anything.
I'd have a couple of questions first.
Why is the phase shift a problem? It's simply the natural consequence of a delta-star configuration.
Are you planning to replace or rewind the transformer or simply reconfigure the existing secondary winding?
Beyond the questionable action of reconfiguring it for warranty and possible listing violations it would result in a 277V delta.
The PU self-impedance would generally be unaffected assuming you used the same core.
You would loose a good safety feature of grounding the common star point.
In general, unless the phase shift is genuine problem, I wouldn't recommend doing anything.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: Transformer Phasing
No, you cannot rewire the transformer delta-delta.
If the original unit is a 480Y/277 unit then the secondary winding voltage is only 277V. If you reconnect it as a delta you will have a phase to phase voltage of 277V not 480V.
No, you cannot rewire the transformer delta-delta.
If the original unit is a 480Y/277 unit then the secondary winding voltage is only 277V. If you reconnect it as a delta you will have a phase to phase voltage of 277V not 480V.
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