current and balance

Merry Christmas
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newt

Senior Member
customers complaining of a current imbalance on his motor. Voltage is fine. Open delta transformer bank. The motor has been rebuilt. Currently the motor is tripping out on over-current. When the leads are changed on the motor, the high current leg always stays with incoming power, indicating that the problem is not load related. Service appears to be fine, voltage only drops 2 volts when load is applied. Are open delta banks notorious for load imbalance on motors? Any help would be appreciated
 

charlie

Senior Member
Location
Indianapolis
Re: current and balance

It depends on the size of the bank in relation to the size of the 3? motor. The 240 volts across the transformers will be solid but the phantom phase will tend to collapse under load. Too much load and the voltage imbalance with smoke a motor. We install a lot of open deltas and don't have any problems unless the customer adds too much 3? load without telling us about it. :D
 
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