I have a duplex 20HP submersible sewage pump station with permanent standby generation connected through an ATS. Utility secondary is 480/3 wye. When I measure current on load side of motor starters under normal utility power, I get greater than 10% current imbalance. When I run system with standby generator the current imbalance goes away. Comments?
Motor current imbalance
- Thread starter matwater
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bphgravity
Senior Member
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- Florida
Re: Motor current imbalance
Is this a new installation? If so, is it possible that under normal power the rotation is wrong and making the pump motor operate improperly, but when the transfer is engaged, the rotation is corrected from generator power?
If this is existing, does the pumping capacity increase or diminish on either system? Meaning, is the electrical effect also contributing to a mechanical effect.
One more question. Is the actual tested voltage the same from both utility and the generator? I just wonder if the utility is supplying under or over voltage on one or more of the legs.
Is this a new installation? If so, is it possible that under normal power the rotation is wrong and making the pump motor operate improperly, but when the transfer is engaged, the rotation is corrected from generator power?
If this is existing, does the pumping capacity increase or diminish on either system? Meaning, is the electrical effect also contributing to a mechanical effect.
One more question. Is the actual tested voltage the same from both utility and the generator? I just wonder if the utility is supplying under or over voltage on one or more of the legs.
wanderer20001us
Senior Member
Re: Motor current imbalance
Check the voltage imbalance on the utility compared to the generator. A 2% voltage imbalance can produce a 10% current imbalance on a loaded motor.
Check the voltage imbalance on the utility compared to the generator. A 2% voltage imbalance can produce a 10% current imbalance on a loaded motor.
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