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For large motors what is the ratio of compensating winding is required for increasing the speed of the motor?

For large motors what is the ratio of compensating winding is required for increasing the speed of the motor? Correct Answer 2:1

For motors requiring a wide range of speed control, the field ampere-turns are much smaller than the armature ampere-turns at high speeds causing extreme distortion of the flux density in the air-gap. This leads to poor commutation. Compensating winding can be used to increase the speed range which can be 2 to 1 for large motors.

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