A 3-phase, 50-Hz induction motor with its rotor star-connected gives 500 V (r.m.s.) at standstill between the slip-rings on open-circuit. Calculate the current and power factor at standstill when the rotor winding is joined to a star-connected external circuit, each phase of which has a resistance of 10 2 and an inductance of 0.04 H. The resistance per phase of the rotor winding is 0.2 2 and its inductance is 0.04 H. Also, calculate the current and power factor when the slip-rings are short-circuited and the motor is running with a slip of 5 per cent. Assume the flux to remain constant. [10.67 A; 0.376; 21.95 A; 0.303]

A 3-phase, 50-Hz induction motor with its rotor star-connected gives 500 V (r.m.s.) at standstill between the slip-rings on open-circuit. Calculate the current and power factor at standstill when the rotor winding is joined to a star-connected external circuit, each phase of which has a resistance of 10 2 and an inductance of 0.04 H. The resistance per phase of the rotor winding is 0.2 2 and its inductance is 0.04 H. Also, calculate the current and power factor when the slip-rings are short-circuited and the motor is running with a slip of 5 per cent. Assume the flux to remain constant. [10.67 A; 0.376; 21.95 A; 0.303]

Electrical Transformers and Rotating Machines

4th Edition

ISBN:9781305494817

Author:Stephen L. Herman

Publisher:Stephen L. Herman

Chapter13: Harmonics

Section: Chapter Questions

Problem 3RQ

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Question

4. A 3-phase, 50-Hz induction motor with its rotor star-connected gives 500 V (r.m.s.) at standstill
between the slip-rings on open-circuit. Calculate the current and power factor at standstill when the
rotor winding is joined to a star-connected external circuit, each phase of which has a resistance of
10 2 and an inductance of 0.04 H. The resistance per phase of the rotor winding is 0.2 2 and its
inductance is 0.04 H.
Also, calculate the current and power factor when the slip-rings are short-circuited and the motor is
running with a slip of 5 per cent. Assume the flux to remain constant.
[10.67 A; 0.376; 21.95 A; 0.303]

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