Explore topic-wise MCQs in Electrical Machines.

This section includes 17 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Machines knowledge and support exam preparation. Choose a topic below to get started.

1.

The rotor winding for 3-phase slip ring induction motor having delta connected stator must be connected in _________

A. star
B. delta
C. tertiary
D. any of the mentioned
Answer» B. delta
Discussion
2.

In a three phase slip ring induction motor, brushes are connected to _________

A. external star connected resistors
B. dc supply
C. 3-phase ac supply
D. any of the mentioned
Answer» B. dc supply
Discussion
3.

The rotor of th 3-phase induction motor rotates in the same direction as that of stator field. This can be explained by _________

A. Newton s laws of motion
B. Farady s laws of electromagnetic induction
C. Lenz s law
D. Fleming s right hand rule
Answer» B. Farady s laws of electromagnetic induction
Discussion
4.

The 3-phase induction motor with rotor circuit open will _________

A. not run
B. run normally
C. get over heated
D. make noise
Answer» B. run normally
Discussion
5.

Stator flux induces emf in the rotor conductors _________

A. magnitude depending on the load
B. rotating at synchronous speed around stator
C. constant in magnitude
D. none of the mentioned
Answer» B. rotating at synchronous speed around stator
Discussion
6.

For a 4-pole, 3-phase induction motor the rotor speed found is 2100 rpm at 50 Hz. Then the phase sequence of the emf generated will be?

A. acb
B. abc
C. no emf will be induced
D. cba
Answer» B. abc
Discussion
7.

A 4-pole, 3-phase slip ring induction motor is used as a frequency changer. Its stator is excited from 3-phase, 50 Hz supply. A load requiring 3-phase, 20 Hz supply is connected to the star-connected rotor through three slip-rings of SRIM. At what two speeds the prime mover should drive the rotor of this SRIM?

A. 900 rpm
B. 600 rpm
C. 1500 rpm
D. 0
Answer» B. 600 rpm
Discussion
8.

A properly shunted center zero galvanometer is connected in the rotor circuit of a 6-pole, 50 hz wound rotor induction motor. If the makes 90 complete oscillations in one minute, the rotor speed is?

A. 1000 rpm
B. 970 rpm
C. 950 rpm
D. 930 rpm
Answer» C. 950 rpm
Discussion
9.

A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. Speed of the rotor field w.r.t. stator field is?

A. zero
B. 150 rad/s
C. 6.28 rad/s
D. 145 rad/s
Answer» B. 150 rad/s
Discussion
10.

A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. Speed of the rotor field w.r.t. rotor structure is?

A. 157 rad/s
B. 150 rad/s
C. 6.28 rad/s
D. 145 rad/s
Answer» D. 145 rad/s
Discussion
11.

A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. Speed of the stator field revolving rotor structure is?

A. 157 rad/s
B. 150 rad/s
C. 6.28 rad/s
D. 145 rad/s
Answer» D. 145 rad/s
Discussion
12.

A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. Speed of the stator filed with respect to stator structure is?

A. 157 rad/s
B. 150 rad/s
C. 6.28 rad/s
D. 145 rad/s
Answer» B. 150 rad/s
Discussion
13.

A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. Rotor frequency is?

A. 2 Hz
B. 50 Hz
C. 52 Hz
D. 58 Hz
Answer» B. 50 Hz
Discussion
14.

A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. The full load slip will be?

A. 4%
B. 5%
C. 2.4%
D. 3%
Answer» B. 5%
Discussion
15.

A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. The number of poles of this motor is?

A. 4
B. 6
C. 5
D. 2
Answer» B. 6
Discussion
16.

For a 4 pole three phase induction motor having synchronous speed of 1500 rpm is operating at 1450rpm. The frequency of the induced emf in rotor is?

A. 100 Hz
B. 50 Hz
C. 150 Hz
D. 0 Hz
Answer» B. 50 Hz
Discussion
17.

Slip is defined as _________ (Ns as the synchronous speed and Nr is the rotor speed)

A. Ns-Nr/Ns
B. Ns-Nr/Nr
C. Nr-Ns/Ns
D. Ns-Nr
Answer» B. Ns-Nr/Nr
Discussion