2 phase problem
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High leg delta ?
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Ungrounded delta.
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did you read post 1?
This is an 240 volt 3∆ 3 wire ungrounded system.
The odd phase to ground voltages were the result of capacitive coupling. If you were to read them with a solenoid type tester (or anything else that loads the circuit) the reading would be 0.
There is no 120 with this system, 240 only.
The odd phase to ground voltages were the result of capacitive coupling. If you were to read them with a solenoid type tester (or anything else that loads the circuit) the reading would be 0.
There is no 120 with this system, 240 only.
Not very long; they'll have to dissipate more watts than they're designed for.
Yeah, I read that after I wrote my post......
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Winner winner chicken dinner with a good bottle of wine.
So help the apprentice out with some theory . . .
Are the different voltages to ground because of the loads between each leg aren't perfectly balanced? And because the system is not grounded (and has a reference point), it causes the phase to ground voltages to fluctuate?
I was taught that systems are grounded to maintain a common reference point so that the voltages don't fluctuate depending on the load. Well that's one of the reasons. Also to dissapate surges and lightning strikes. I'm just trying to get this all in perspective. Am I right/wrong in my assumptions?
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That is correct. In an unearthed system you do not have any physical connection to the mass of earth, however you are still earthed mainly through distributed capacitance of the system. This means if your three phase system is balance(the load on each phase is the same), the capacitive coupled current flowing between each phase and earth would sum to zero, effectively holding your neutral point of the system at earth potential. So if I measured the line to earth voltages in a balanced system they would be equal to your line to neutral voltage.
But as the load on each phase changes this current no longer sums to zero at the earth point. This shifts the neutral point of the system, so your line to earth voltages will also reflect this.
In a solidly earthed system your line to earth voltages do not change as the system becomes more unbalanced.
Line to earth overvoltages brought on by earth faults, distributed capacitance and lightning is the main draw back to unearthed systems.
Ummmm....I got a really good article on unearthed systems on my computer, but can't seem to upload it due to the file being to large.
Most are dual 208/240 rated. Most.
Pm or Email It if you can. Ive been looking for a good doc on ungrounded systems.That is correct. In an unearthed system you do not have any physical connection to the mass of earth, however you are still earthed mainly through distributed capacitance of the system. This means if your three phase system is balance(the load on each phase is the same), the capacitive coupled current flowing between each phase and earth would sum to zero, effectively holding your neutral point of the system at earth potential. So if I measured the line to earth voltages in a balanced system they would be equal to your line to neutral voltage.
But as the load on each phase changes this current no longer sums to zero at the earth point. This shifts the neutral point of the system, so your line to earth voltages will also reflect this.
In a solidly earthed system your line to earth voltages do not change as the system becomes more unbalanced.
Line to earth overvoltages brought on by earth faults, distributed capacitance and lightning is the main draw back to unearthed systems.
Ummmm....I got a really good article on unearthed systems on my computer, but can't seem to upload it due to the file being to large.
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