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No Load Current


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I have a 500 kW 400 V slip ring motor driving a load. The current drawn by the motor without load but still couple to the drive is very high, 750 Amps. This is too high for an unloaded motor. This should be the current drawn under loading conditions. What basically could be cause of the high current ?





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  • 2 weeks later...

Hi Bob


Yes, that sounds very high. Assuming that the motor is running with the rotor shorted and is at full speed, that current suggests a lot of energy going somewhere, either out the shaft as a mechanical load, or as losses in the motor.

If the motor losses are that high, the motor will not last long so you need to determine the cause pretty quickly.


I would strongly recommend decoupling the motor from any load and retrying.

Is there a possibility of a star designed stator connected in delta?


Best regards,


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