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3-phase Synchronous Motor


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Hello Everyone. I have a 3 phase synchronous motor from the 1930's that is drawing too much current. The motor is rated at 220V/28amps or 440/14amps. We currently have it wired for 220V. When the motor is not mechanically loaded, and is started, it runs and draws roughly 23-24amps. This is fine and it does not trip the 30 amp breaker (even though I think this may be too high for an unloaded motor). When I place a slight load on the motor, the amps jump to 50-55 and it trips the breaker. I had the motor tested and the shop said the motor windings were fine and there was not a short within the motor. They said that this was a brushless motor and were not sure where the problem may be. Is there any relay I should be looking for within the motor? Could the recitifiers not be working? Is it drawing so much current because the DC part of the motor is not working? Should it be drawing so much current unloaded? Any help on fixing this motor would be much appreciated. Thanks



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Hello Bifkali


Welcome to the forum.


Assuming that it is a true synchronous motor, there may be a problem with the DC excitation system. I would get this checked out.


Best regards,

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