Ground to phase measurement on Wye 3 phase motor curcuit
Ground to phase measurement on Wye 3 phase motor curcuit
(OP)
Hello,
I was tasked with measuring a 3 phase motor for imbalance. The imbalance is less than 1% for current and phase to phase voltage. The phase to ground imbalance is 8% at the max deviation. Is there a standard as far as the phase to ground imbalance? It is a Wye 3 phase 120 phase to phase circuit.
Thanks,
Rachel
I was tasked with measuring a 3 phase motor for imbalance. The imbalance is less than 1% for current and phase to phase voltage. The phase to ground imbalance is 8% at the max deviation. Is there a standard as far as the phase to ground imbalance? It is a Wye 3 phase 120 phase to phase circuit.
Thanks,
Rachel





RE: Ground to phase measurement on Wye 3 phase motor curcuit
RE: Ground to phase measurement on Wye 3 phase motor curcuit
respectfully
RE: Ground to phase measurement on Wye 3 phase motor curcuit
How are you calculating imbalance?
What are the phase-to-phase and phase-to-ground voltages you've measured?
What type of meter was used (i.e. - Fluke 87, etc.)?
So far as I know 'phase-to-ground phase imbalance' is as waross stated, and should not affect motor operation, but it seems an odd variance if you indeed have a solidly grounded wye power system (but not too uncommon if power is derived from a delta transformer).
I've seen cheap throw-away digital multimeters give all sorts of odd readings in the presence of harmonics (which is why I asked about the meter).
RE: Ground to phase measurement on Wye 3 phase motor curcuit
Hi,
The Phase to Phase looks to be balanced. I just thought the differences in voltage on the phase to ground would have been closer. But I have learned from this thread that this is not the case.
Phase to phase:
L1-L2 =122.1V, L2-L3 = 121.9V, L3-L1 = 121.8V
Phase to Ground
L1 64.3 V, L2 75.4, V L3 69.4
Thanks to all.