# 3-phase IM Braking MCQ Questions & Answers

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

Question 1

A 3  phase, 4 pole IM is supplied from a 40 Hz source. Calculate rotor frequency when the rotor runs 100 rpm.

A. 35 Hz
B. 36.6 Hz
C. 9 Hz
D. 8 Hz

Question 2

Calculate the three-phase power using the following data: Vp=23 V, Ip=23 A, ?=60.

A. 793.5 W
B. 790 W
C. 792 W
D. 791 W

Question 3

For motoring mode, the phase angle between the stator phase voltage and stator phase current should be _______

A. < 90°
B. > 90°
C. < 40°
D. 180°

Question 4

Magnetizing current in the induction motor is ______

A. more than the transformer
B. equal as a transformer
C. less than the transformer
D. 0

Question 5

Power input to an induction motor is given by _________

A. 3VpIpcos?
B. 2VpIpcos?
C. VpIpcos?
D. 5VpIpcos?

Question 6

Single phase induction motor is self-starting.

A. True
B. False

Question 7

The ratio of the rotor copper loss and air gap power is _______

A. s
B. 1-s
C. 1+s
D. 0

Question 8

The relative speed between the rotor and stator in the induction motor is ______

A. Nr
B. Ns-Nr
C. Ns+Nr
D. 0

Question 9

The relative speed between the stator magnetic field and rotor in the induction motor is ______

A. Ns
B. Ns-Nr
C. Ns+Nr
D. 0

Question 10

The relative speed between the stator magnetic field and stator in the induction motor is ______

A. Ns
B. Ns-Nr
C. Ns+Nr
D. 0

Question 11

What is the speed of the 11th order harmonics in the induction motor?

A. Ns
B. Ns/11
C. 2×Ns
D. Nr

Question 12

What is the speed of the 6th order time harmonics in the induction motor?

A. Ns
B. Ns/6
C. 6×Ns
D. 0

Question 13

What will happen if we increase the air gap in the induction motor?

A. Power factor will reduce
B. Power factor will increase
C. Reduction in harmonics
D. Speed will increase

Question 14

A 3 – phase, 4 pole IM is supplied from a 40 Hz source. Calculate rotor frequency when the rotor runs 100 rpm.

A. 35 Hz
B. 36.6 Hz
C. 9 Hz
D. 8 Hz

Question 15

Calculate the three-phase power using the following data: Vp=23 V, Ip=23 A, ∅=60.

A. 793.5 W
B. 790 W
C. 792 W
D. 791 W