240 volt to 480 volt
- Thread starter domnic
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- San Francisco Bay Area, CA, USA
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- Electrical Engineer
CAN you? Yes from a purely technical standpoint, because if you energize one set of windings on the 3 phase primary, one set of windings on the 3 phase secondary will give you what you want.
Should you? No. The transformer will be inherently unbalanced so will have a serious problem with negative sequence currents resulting in either it heating up disproportionately to the load it is technically rated for, or you will have to seriously de-rate it from what it's nameplate says it is good for, which would mean a single phase transformer would have cost you less. Also, the other terminals will have a voltage induced on them as well, both on the primary and secondary sides. Someone looking at that mess someday in the future may not understand that and be at risk for injury.
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- Location
- Illinois
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- retired electrician
Why would you want to use a 3 phase transformer?
petersonra
Senior Member
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- Northern illinois
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- Semi-retired engineer
you can use a 3 phase transformer if you only wire in one phase of it.
249/480
249/480
I did not say I want to. I asked if it work. and be code compliant .
249/480
I did not say I want to. I asked if it work. and be code compliant .
- Location
- San Francisco Bay Area, CA, USA
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- Electrical Engineer
Well, it might be interpreted as a violation of article 110...
kwired
Electron manager
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- NE Nebraska
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- EC
First to get 480/240 you would need a delta - delta transformer (at least if using something sort of common stock)
But if using delta-delta you could just hook up one phase and effectively only have a single phase transformer with about a third of the kVA capacity of the nameplate.
But if using delta-delta you could just hook up one phase and effectively only have a single phase transformer with about a third of the kVA capacity of the nameplate.
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- Placerville, CA, USA
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- Retired PV System Designer
Except that you would have the additional magnetizing current for the other two coils in series across the coil you connected.
If you happen to have a suitable three phase transformer on hand, and do not care at all about inefficiencies, it would work.
A wye-wye would not have that problem.
kwired
Electron manager
- Location
- NE Nebraska
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- EC
Ok, you would need to disconnect at least the tie between the other two phases - if you can get to a place where they are connected. When I posted that I was thinking more so about how the POCO's typically build delta banks out of single phase transformers, but since those often are configured wye on the primary side I wasn't really on the right path anyway.
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