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Question 9.1: A four-pole, three-phase induction when supplied with 400 V,...

A four-pole, three-phase induction when supplied with 400 V, 50 Hz supply rotates at a slip of 4 per cent. What is the speed of the motor?

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N_{s} =\frac{120 f}{p}=\frac{120 \times 50}{4}=1500 rpm

S =\frac{N_{s}-N_{r}}{N_{s}}  Substituting values, 0.04=\frac{1500-N_{r}}{1500}

or,     N_{r} =1500-60=1440 rpm

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