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Discussion Starter · #1 ·
I just finished troubleshooting a Sorgel 3 phase general purpose transformer from square D. Primary 480v secondary 208y/120v. Transformer x2 has 0 volts to ground. X1, x3 roughly 200v to ground(too high). H1,h2,h3 277 on the money to ground. 480v phase to phase. I shut down power checked terminations, bonding etc. Onsite maintenance says it's about 12 year old unit. It's indoors, temp controlled room. Does this sound normal? Any suggestions? Thanks.
 

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Winding resistance? Insulation resistance? DAR? Turns ratio?

You do any of these tests?
 

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Discussion Starter · #3 ·
Winding resistance? Insulation resistance? DAR? Turns ratio?

You do any of these tests?
No, but would that change the fact that there's no voltage from B phase? Just trying to get some seasoned input here, if such tests would benefit me, let me know. The party without power is losing money daily.
 

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I just finished troubleshooting a Sorgel 3 phase general purpose transformer from square D. Primary 480v secondary 208y/120v. Transformer x2 has 0 volts to ground. X1, x3 roughly 200v to ground(too high). H1,h2,h3 277 on the money to ground. 480v phase to phase. I shut down power checked terminations, bonding etc. Onsite maintenance says it's about 12 year old unit. It's indoors, temp controlled room. Does this sound normal? Any suggestions? Thanks.
Meter X1 to X3 and you should be around 208 volts.. With X2 to ground reading 0 volts you have a fault on that phase somewhere in the system...Isolate each load until your voltage returns to normal (120 to ground on all 3 and 208 phase to phase).
 

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It appears that XO is not bonded to a GEC and there is a ground fault on X2. If XO was properly bonded and there was a ground fault on any phase, a fuse/breaker would trip. If XO is not bonded on a wye system, any phase to ground readings will be meaningless.
 

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...Could you explain this to me?
He already knows his L-G voltages, so if he measures his L-L voltages and they are dead-nuts then that means he doesn't have a winding failure, so it just confirms the grounding issue.

If he gets some screwball L-L voltages, then there's something else going on. But he should also do his N-G voltage.
 

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Discussion Starter · #10 ·
He already knows his L-G voltages, so if he measures his L-L voltages and they are dead-nuts then that means he doesn't have a winding failure, so it just confirms the grounding issue.

If he gets some screwball L-L voltages, then there's something else going on. But he should also do his N-G voltage.

X1 to x3 was coming in around 220v and N to G was 120v.
 

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X1 to x3 was coming in around 220v and N to G was 120v.
The terminology is messed up here. I read that his neutral conductor is bonded in his panel. We're calling it X0, but it's not. I don't think we know what the actual X0 to ground reading is.
The top quote is his post previous to the one I quoted. Does this help?
 
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