SSC JE Electrical Engineering 2014 Set 1 Paper

Question : 151 of 200

Marks: +1, -0

In a 3-phase induction motor crawling happens at

any speed
no-load speed
odd multiples of fundamental
even multiples of fundamental

Solution:

Pin induction motor is a single excited machine.
The crawling word it self-suggest crawl means moving with low speed. This characteristic is Result of improper functioning of the motor that mean either motor is Running at very slow speed or it not taking the load.
The Resultant speed is nearly

{1/7} ^{\th}

of itssynchronous speed. This action is due to the hormonics fluxes produced in the gap of the stator winding of odd harmonics like 3

^{\rd}

, 5

^{\th}

, 7

^{\th}

etc

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