unbalance voltage

[wuqn]

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

 

[itsmoked]

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

 

[waross]

It sounds like unbalanced loads.
yours

 

[wuqn]

3 phases. run unload

 

[Alex68]

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

 

[waross]

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

 

[wuqn]

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 ?

 

[wuqn]

the generator is 550kVA.

 

[TheBlacksmith]

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

 

[DanDel]

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.