Multiply Choice Questions on 3-Phase Induction Motor

 

1. Slip rings are usually made of

A) Copper
B) Carbon
C) phosphor bronze
D) Aluminium

ANSWER= (C) phosphor bronze.

 

2. Which of the following data is required to draw the circle diagram for an induction motor?

A) Block rotor test, no-load test and stator resistance test
B) Block rotor test, no-load test
C) No-load test only
D) Block rotor test only

ANSWER= (A) Block rotor test, no-load test and stator resistance test.  

 

3. The frame of an induction motor is usually made of

A) Silicon steel
B) Cast iron
C) Aluminium
D) Bronze

ANSWER= (B) Cast iron

 

4. The shaft of an induction motor is made of

A) Carbon steel
B) Cast iron
C) Aluminium
D) Stainless steel

ANSWER= (A) Carbon steel

 

5. The shaft of an induction motor must be of

A) Solid
B) Hollow
C) Flexible
D) Any of the above

ANSWER= (B) Hollow
Explain:- The hollow shaft can resist more torsion load with the same resisting area (same weight) as compared to the solid shaft.

 

6. In three-phase squirrel-cage induction motors

A) Rotor conductors are kept open
B) Rotor conductor ends are short-circuited through slip rings
C) Rotor conductors are short-circuited through end rings
D) Rotor conductors are connected to the insulation

ANSWER= (C) Rotor conductors are short-circuited through end rings

 

7. Which of the following motor has high starting torque?

A) Slip ring Induction motor
B) Squirrel cage induction motor
C) Both 1 & 2
D) None of the above

ANSWER= (A) Slip ring Induction motor

 

8. At standstill condition the value of slip is

A) 0
B) 1
C) Infinity
D) None of the above

ANSWER= (B) 1

 

9. An induction motor is analogous to

A) Auto-transformer
B) Two windings transformer with secondary open circuited
C) Two windings transformer with secondary short circuited
D) Synchronous motor

ANSWER= (C) Two windings transformer with secondary short circuited

 

10. Induction motors have the advantage of

A) Less Maintenace
B) Simple in construction
C) Less cost
D) All of the above

ANSWER= (D) All of the above