A 4-pole squirrel-cage rotor asynchronous motor operating in a 60 hz network operates continuously in the following options. Which statement or statements are true? (rpm = number of revolutions per minute. Clockwise rotation is given as +, reverse is given as -.) i) Generator runs at 1900 rpm ii) Generator runs at 1850 rpm iii) Works as a motor at 1750 rpm iv) -1750 rpm works as a brake A) ii-iv B) i C) ii D) i-iii-iv E) i-ii-iii

A 4-pole squirrel-cage rotor asynchronous motor operating in a 60 hz network operates continuously in the following options. Which statement or statements are true? (rpm = number of revolutions per minute. Clockwise rotation is given as +, reverse is given as -.) i) Generator runs at 1900 rpm ii) Generator runs at 1850 rpm iii) Works as a motor at 1750 rpm iv) -1750 rpm works as a brake A) ii-iv B) i C) ii D) i-iii-iv E) i-ii-iii

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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Concept explainers

Synchronous Motor

The synchronous motor is an AC electric type motor where at a steady-state the shaft rotation is synchronized with the supply current variable-frequency. To an integral number of AC cycles, the rotation period is exactly equal. The stator of the motor in the synchronous motor contains multi-phase AC electromagnets due to which a magnetic field is created that rotates in time with the oscillation of the line current. The rotor contains a permanent magnet and the rotor rotates in synchronization with the stator field at the same rate and provides the second synchronized magnetic field which is rotating in nature as a result. When the synchronous motor is supplied with independently excited multi-phase AC electromagnets on both the rotor and the stator, it is termed as a doubly-fed machine. The most widely used AC-type motors are the synchronous AC motor and the induction AC motors.

Question

i) Generator runs at 1900 rpm

ii) Generator runs at 1850 rpm

iii) Works as a motor at 1750 rpm

iv) -1750 rpm works as a brake

A) ii-iv

B) i

C) ii

D) i-iii-iv

E) i-ii-iii

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