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Low Voltage Effect On Motors


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Please post student related questions in the student section or they will not be answered!!

Hello all,

in a discussion I heard from a person that at low voltage or very low voltage, motors get damaged..? Is it so? I replied him about frequency effect but he was insisting that the problem is so...!


Pls reply.

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Hello asif


Welcome to the forum.


As you reduce the fvoltagte applied to a motor, you reduce the flux in the iron.

The result of the reducing flux, is that the torque capacity of the motor is reduced, and therefore the maximum power capacity of the motor is reduced.


If the motor is operating at a fixed shaft torque, then as you reduce the voltage, the slip will increase in order to develop the same torque. This will increase the slip losses in the rotor and rotor heating. If you reduce the voltage too much, the motor will not be able to produce the torque and the motor will stall.

A stalled motor has a very high stator current and a very high slip loss. The slop loss is disipated in the rotor causeing the rotor to overheat and could cause a rotor failure.


If there is no load on the shaft, then you can operate at a very low voltage without problem. The issue is related to operating the motor under stalled or semistalled conditions.


Best regards,


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