# 3 Phase Induction Motors MCQ Questions & Answers

3 Phase Induction Motors MCQs : This section focuses on the "3 Phase Induction Motors". These Multiple Choice Questions (MCQs) should be practiced to improve the 3 Phase Induction Motors skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.

Question 1

A 3-phase induction motor runs at almost 1000 rpm at no load and 950 rpm at full load when supplied with power from a 50 Hz, 3-phase supply. What is the corresponding speed of the rotor field with respect to the rotor?

A. 30 revolution per minute
B. 40 revolution per minute
C. 60 revolution per minute
D. 50 revolution per minute

Question 2

A 50 Hz, 4poles, a single phase induction motor is rotating in the clockwise direction at a speed of 1425 rpm. The slip of motor in the direction of rotation & opposite direction of the motor will be respectively.

A. 0.05, 0.95
B. 0.04, 1.96
C. 0.05, 1.95
D. 0.05, 0.02

Question 3

A three-phase slip ring induction motor is fed from the rotor side with the stator winding short-circuited. The frequency of the current flowing in the short-circuited stator is ____________

A. Slip frequency
B. Supply frequency
C. The frequency corresponding to rotor speed
D. Zero

Question 4

An 8-pole, 3-phase, 50 Hz induction motor is operating at a speed of 720 rpm. The frequency of the rotor current of the motor in Hz is __________

A. 2
B. 4
C. 3
D. 1

Question 5

Calculate the active power in a 487 H inductor.

A. 2482 W
B. 1545 W
C. 4565 W
D. 0 W

Question 6

Calculate the active power in a 788 ? resistor with 178 A current flowing through it.

A. 24.96 MW
B. 24.44 MW
C. 24.12 MW
D. 26.18 MW

Question 7

Calculate the moment of inertia of the disc having a mass of 54 kg and diameter of 91 cm.

A. 5.512 kgm2
B. 5.589 kgm2
C. 5.487 kgm2
D. 5.018 kgm2

Question 8

Calculate the moment of inertia of the thin spherical shell having a mass of 73 kg and diameter of 36 cm.

A. 1.56 kgm2
B. 1.47 kgm2
C. 1.38 kgm2
D. 1.48 kgm2

Question 9

Calculate the phase angle of the sinusoidal waveform z(t)=78sin(456?t+2?÷78).

A. ?÷39
B. 2?÷5
C. ?÷74
D. 2?÷4

Question 10

In an induction motor, when the number of stator slots is equal to an integral number of rotor slots _________

A. There may be a discontinuity in torque slip characteristics
B. A high starting torque will be available
C. The maximum torque will be high
D. The machine may fail to start

Question 11

The frame of an induction motor is made of _________

A. Aluminum
B. Silicon steel
C. Cast iron
D. Stainless steel

Question 12

The slope of the V-I curve is 5°. Calculate the value of resistance. Assume the relationship between voltage and current is a straight line.

A. .3254 ?
B. .3608 ?
C. .3543 ?
D. .3443 ?

Question 13

Calculate the active power in a 788 ω resistor with 178 A current flowing through it.

A. 24.96 MW
B. 24.44 MW
C. 24.12 MW
D. 26.18 MW

Question 14

Calculate the phase angle of the sinusoidal waveform z(t)=78sin(456πt+2π÷78).

A. π÷39
B. 2π÷5
C. π÷74
D. 2π÷4