15. A three phase induction motor designed for a rated voltage of Vi at 50 Hz isaccidentally switched on directly to a voltage of V2at 60 Hz. Stator impedanceof the motor is negligible. Calculate the ratios of currents and torques atstarting and maximum torques when V2= V1. Also find the ratio of V2to Vi toobtain the same values of starting current and torque at 60 Hz. (Ans: 0.834,0.695, 0.695, ; 1.2) 14. An 8 pole 50 Hz, three phase induction motor runs at a speed of 720 rpmwhen delivering full load torque. Its stand still rotor resistance and reactanceare 0.1 ohm and 0.6 ohm per phase respectively. An additional resistance of0.5 ohm per phase is inserted in the rotor circuit to control the speed.Calculate the speed at which the motor runs now with full load torqueremaining the same. (Ans: 570 rpm)

according to guidelines we need to solve only the first question. According to the question we have…

A three phase induction motor designed for a rated voltage of Vi at 50 Hz is accidentally switched on directly to a voltage of V2at 60 Hz. Stator impedance of the motor is negligible. Calculate the ratios of currents and torques at starting and maximum torques when V2= V1. Also find the ratio of V2to Vi to obtain the same values of starting current and torque at 60 Hz. (Ans: 0.834, 0.695, 0.695, ; 1.2)

A three phase induction motor designed for a rated voltage of Vi at 50 Hz is accidentally switched on directly to a voltage of V2at 60 Hz. Stator impedance of the motor is negligible. Calculate the ratios of currents and torques at starting and maximum torques when V2= V1. Also find the ratio of V2to Vi to obtain the same values of starting current and torque at 60 Hz. (Ans: 0.834, 0.695, 0.695, ; 1.2)

Delmar's Standard Textbook Of Electricity

7th Edition

ISBN:9781337900348

Author:Stephen L. Herman

Publisher:Stephen L. Herman

Chapter35: Harmonics 916

Section: Chapter Questions

Problem 3RQ: Would a positive-rotating harmonic or a negative-rotating harmonic be more harmful to an induction...

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