overfused
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- eldersburg md. usa
if you had a 208 volt 3 wire delta to 277/480 volt wye connected transformer with no load on the secondary side would you get a voltage reading between any of the secondary phases and xo
transformers
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stevebea
Senior Member
- Location
- Southeastern PA
Yes... is there a reason for this question?
Good question. X0 should denote the low voltage side, and there shouldn't be any if the primary is delta configured. It should be H0 for the 480/277 secondary.
I'm confused as to what we are dealing with here due to my limited dealings with different transformer windings and associated wiring diagrams.
The OP states(I think) that the transformer is a delta-wye configuration and the primary is 3-phase 208v delta & the secondary is 3-phase 480/277v wye with the common neutral point labeled "XO". If that is the case then it is a boost transformer,right?
This is a transformer style I have never worked with but in answer to the question, the answer would be yes as stated by others. It would also breed a couple of additional questions from me, "Is this a standard configuration", and if so, "is it often used"?
dick
The OP states(I think) that the transformer is a delta-wye configuration and the primary is 3-phase 208v delta & the secondary is 3-phase 480/277v wye with the common neutral point labeled "XO". If that is the case then it is a boost transformer,right?
This is a transformer style I have never worked with but in answer to the question, the answer would be yes as stated by others. It would also breed a couple of additional questions from me, "Is this a standard configuration", and if so, "is it often used"?
dick
There may be exceptions, but in my experience "X" has always been the lower voltage on the transformer. If that is the case here, his "XO" would be on the 208 (input) side of his transformer and would and should not be connected. IMO, his high side neutral terminal would be "H1".
By virtue of common grounding, i would think he would read voltage when measuring to XO although it should not be connected to anything.
By virtue of common grounding, i would think he would read voltage when measuring to XO although it should not be connected to anything.
BPoindexter
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- Location
- MT Vernon, WA
If the OP called it X0 but he meant a Neutral point (should have been H0) on the 480 side then any of the phase terminals on will measure 277V between it and the neutral.
Provided proper voltage and tap settings are used that is.
Provided proper voltage and tap settings are used that is.
No load voltages are generally unspecified and perhaps uncontrolled by the factory.
For small transformers I've seen them up to 1.3x the full-load voltage.
mike_kilroy
Senior Member
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- United States
g_s, how true for wallwart little guys. but I don't think you could find a single large (say >.5kva) that does not have Vnl as well as Vfull load specified or at least within a few small percent of each other. No decent one will have 1.3x Vnl
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Electric-Light
Senior Member
Those tiny ones have to do it to make up for the massive (comparatively) secondary copper resistance.
12v wall warts do put up upwards of 18v fairly commonly.
The ones I measured were bought to some guv spec' and were orange-sized and smaller, 6.3vac & so on.
If the voltage regulation of the transformer is poor, say , a welding transformer, it may be so.
brian john
Senior Member
- Location
- Leesburg, VA
As noted on the step up transformer we have in stock (utilized for temporary applications) the Primary (208VAC) is, X1, X2, X3 and the secondary (480/277 VAC) is H1, H2, H3 and H0.
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