multiple choice questions on induction machines # 12

Hi friends, this post is about induction motor objectives. These are some of the questions asked in previous question papers of Gate, IES and other competitive exams. check out and comment if you have any doubts.....

1) The synchronous watt is
A) the torque which under synchronous speed would develop a power of 1watt or power input to rotor in watts
B) shaft output in watts
C) input power to stator
D) the unit of ratings of synchronous machines

Ans:A

2) The power factor of a lightly loaded induction motor is quite low because
A) the current drawn is largely a magnetising current due to air gap
B) of the current due to air gap
C) the current drawn is largely a magnetising component due to laminated core
D) the current drawn is largely an energy component due to laminated core

Ans:A

3) The output power of a 3-phase induction motor will be maximum when the equivalent load resistance is equal to the standstill leakage.............. of the motor
A) impedence Z1'
B) reactance X1'
C) resistance
D) capacitance

Ans:A

4) An induction motor is said to be crawling when
A) it runs at one-seventh of rated speed
B) it accelerates too fast
C) it is subjected to fluctuating loads
D) it is started on full load

Ans:A

5) Zero sequence impedance of a 3-phase cage induction motor is due to
A) stator circuit 3rd time harmonic
B) stator circuit 3rd space harmonic
C) rotor circuit 3rd time harmonic
D) rotor circuit 3rd space harmonic

Ans:B

6) The synchronous speed for the seventh space harmonic mmf wave of a 3-phase, 8-pole, 50 Hz induction machine is
A) 107.14 rpm in forward direction
B) 107.14 rpm in reverse direction
C) 5250 rpm in forward direction
D) 5250 rpm in reverse direction

Ans:A

7) A 3-phase induction motor when started picks up speed but runs stably at about half the normal speed. This is because of
A) unbalance in the supply voltage
B) non sinusoidal nature of the supply voltage
C) stator circuit asymmetry
D) rotor circuit asymmetry

Ans:B

8) In the circle diagram of an induction motor the diameter of the circle represents the
A) rotor current
B) line voltage
C) operating torque
D) maximum torque

Ans:A

9) Circle diagram is employed to determine the performance of a/an
A) synchronous motor
B) induction motor
C) dc motor
D) transformer

Ans:B

10) Circle diagram of an induction motor can be used to determine its
A) power factor
B) efficiency
C) output
D) slip
E) all of the above

Ans:E

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