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) Whenever any polyphase induction motor is loaded
A) motor speed decrease
B) stator flux cuts the rotor bars more rapidly
C) emf induced in the rotor as well as its frequency increases
D) current in rotor bars increases
E) all of the above
Ans:E
2) With increase in load on a squirrel cage induction motor
A) stator current increases
B) power factor improves
C) slip increases
D) the torque developed by the motor increases till its becomes equal to the load torque
E) all of the above
Ans:E
3) An induction motor has a rotor resistance of 0.002 ohm/phase. If the resistance is increased to 0.004 ohm/phase then the maximum torque will
A) reduce to half
B) increase by 100%
C) increase by 200%
D) remain unaltered
Ans:D
4) In a 3-phase induction motor, the torque developed is maximum when the rotor circuit resistance per phase is equal to
A) rotor leakage reactance per phase at standstill
B) slip times the rotor leakage reactance per phase at standstill
C) stator resistance per phase
D) stator leakage reactance per phase
Ans:B
5) A 4-pole, 50 Hz, 3-phase induction motor has blocked rotor reactance per phase which is four times the rotor resistance per phase. The speed at which maximum torque develops is
A) 1125 rpm
B) 1500 rpm
C) 1050 rpm
D) 1210 rpm
Ans:A
6) In an induction motor, what is the ratio of rotor copper loss and rotor input?
A) 1/s
B) s
C) (1-s)
D) s/(1-s)
Ans:B
7) The rotor power output of a 3-phase induction motor is 15 kw. The rotor copper losses at a slip of 4% will be
A) 600 W
B) 625 W
C) 650 W
D) 700 W
Ans:B
8) In induction motor, air gap power is 10 KW and mechanically developed power is 8 KW. What are the rotor ohmic losses?
A) 1 KW
B) 3 KW
C) 2 KW
D) 0.5 KW
Ans:C
9) The no load current in an induction motor is ................ in comparison to that of a power transformer
A) much lower
B) much higher
C) slightly less
D) slightly more
Ans:B
10) The power factor of an induction motor at no load is around
A) 0.2 lead
B) 0.2 lag
C) 0.5 lag
D) 0.8 lag
Ans:B
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1) Whenever any polyphase induction motor is loaded
A) motor speed decrease
B) stator flux cuts the rotor bars more rapidly
C) emf induced in the rotor as well as its frequency increases
D) current in rotor bars increases
E) all of the above
Ans:E
2) With increase in load on a squirrel cage induction motor
A) stator current increases
B) power factor improves
C) slip increases
D) the torque developed by the motor increases till its becomes equal to the load torque
E) all of the above
Ans:E
3) An induction motor has a rotor resistance of 0.002 ohm/phase. If the resistance is increased to 0.004 ohm/phase then the maximum torque will
A) reduce to half
B) increase by 100%
C) increase by 200%
D) remain unaltered
Ans:D
4) In a 3-phase induction motor, the torque developed is maximum when the rotor circuit resistance per phase is equal to
A) rotor leakage reactance per phase at standstill
B) slip times the rotor leakage reactance per phase at standstill
C) stator resistance per phase
D) stator leakage reactance per phase
Ans:B
5) A 4-pole, 50 Hz, 3-phase induction motor has blocked rotor reactance per phase which is four times the rotor resistance per phase. The speed at which maximum torque develops is
A) 1125 rpm
B) 1500 rpm
C) 1050 rpm
D) 1210 rpm
Ans:A
6) In an induction motor, what is the ratio of rotor copper loss and rotor input?
A) 1/s
B) s
C) (1-s)
D) s/(1-s)
Ans:B
7) The rotor power output of a 3-phase induction motor is 15 kw. The rotor copper losses at a slip of 4% will be
A) 600 W
B) 625 W
C) 650 W
D) 700 W
Ans:B
8) In induction motor, air gap power is 10 KW and mechanically developed power is 8 KW. What are the rotor ohmic losses?
A) 1 KW
B) 3 KW
C) 2 KW
D) 0.5 KW
Ans:C
9) The no load current in an induction motor is ................ in comparison to that of a power transformer
A) much lower
B) much higher
C) slightly less
D) slightly more
Ans:B
10) The power factor of an induction motor at no load is around
A) 0.2 lead
B) 0.2 lag
C) 0.5 lag
D) 0.8 lag
Ans:B
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