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unbalance voltage

unbalance voltage

unbalance voltage

(OP)
hi
when generator run, measured voltages : Vab= 417, Vbc=420, Vca= 392.
Vca is much lower than the others. what's the problem ? how can i fix it? thanks

RE: unbalance voltage

Need more info...

What are your loads comprised of?

Single phase and 3 phase?

What kind are they?

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: unbalance voltage

It sounds like unbalanced loads.
yours

RE: unbalance voltage

(OP)
3 phases. run unload

RE: unbalance voltage

If the stator is delta connected, maybe an interturn fault could be considered.
Is it possible to measure the winding resistance between terminals?

RE: unbalance voltage

Hi wuqn;
What size is the generator?
Is it delta or wye?
If it is wye, is the center point grounded?
Have you tried putting a load on it?
yours

RE: unbalance voltage

(OP)
the stator is wye. the center point is grounded.
it's ok when i put load on it. but the voltage is still unbalance. the generator is paralled with other generators.
may be the ground resistance is high ?

RE: unbalance voltage

(OP)
the generator is 550kVA.

RE: unbalance voltage

Sounds like a winding fault or connection problem.  Should check internal resistances and possibly do a insulation resistance test and a polarization index test.  

RE: unbalance voltage

What's OK when you put a load on it? Are the voltages normal or not when the generator is loaded? If so, you don't have a problem.

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