3. A4-pole, 50-Hz induction motor has a full-load slip of 5%. Each rotor phase has a resistance of 0.3 Qand a standstill reactance of 1.2 . Find the ratio of maximum torque to full-load torque and the speedat which maximum torque occurs.[2.6 %; 1125 г.р.m.]4. A3-phase, 4-pole, 50-Hz induction motor has a star-connected rotor. The voltage of each rotor phaseat standstill and on open-circuit is 121 V. The rotor resistance per phase is 0.3 Q and the reactance atstandstill is 0.8 Q. If the rotor current is 15 A, calculate the speed at which the motor is running.Also, calculate the speed at which the torque is a maximum and the corresponding value of the inputpower to the motor, assuming the flux to remain constant.[1444 г.p.m.; 937.5 г.р.m.]

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ratio of maximum torque to full-load torque and the speed

Delmar's Standard Textbook Of Electricity

7th Edition

ISBN:9781337900348

Author:Stephen L. Herman

Publisher:Stephen L. Herman

Chapter32: Three-phase Motors

Section: Chapter Questions

Problem 6RQ: Name three factors that determine the torque produced by an induction motor.

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Concept explainers

Speed control of motor

Speed control by DC motor-speed controller is required to realize variable speed drive. Whenever a motor drives a particular load, it is called drive, and variable speed drive refers to a load requiring variable speed. All this is obtained by a DC motor speed controller.

Question

3. A4-pole, 50-Hz induction motor has a full-load slip of 5%. Each rotor phase has a resistance of 0.3 Q
and a standstill reactance of 1.2 . Find the ratio of maximum torque to full-load torque and the speed
at which maximum torque occurs.
[2.6 %; 1125 г.р.m.]
4. A3-phase, 4-pole, 50-Hz induction motor has a star-connected rotor. The voltage of each rotor phase
at standstill and on open-circuit is 121 V. The rotor resistance per phase is 0.3 Q and the reactance at
standstill is 0.8 Q. If the rotor current is 15 A, calculate the speed at which the motor is running.
Also, calculate the speed at which the torque is a maximum and the corresponding value of the input
power to the motor, assuming the flux to remain constant.
[1444 г.p.m.; 937.5 г.р.m.]

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