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) An induction motor always operates on lagging power factor. This is due to
A) stator reactance
B) rotor leakage reactance
C) the large reactive lagging magnetizing current essential to produce the magnetic field
D) all of the above
Ans:D
2) In a 3-phase induction motor when the load is increased from light load
A) rotor pf increases but stator pf decreases
B) stator pf increases but the rotor pf decreases
C) both stator and rotor pf increase
D) both stator and rotor pf decrease
Ans:B
3) The power factor of a 3-phase induction motor is likely to be maximum when it will operate at
A) full load
B) no load
C) maximum slip
D) maximum torque
Ans:A
4) The power factor of an induction motor at full load is likely to be
A) unity
B) 0.85 lead
C) 0.85 lag
D) 0.5 lag
Ans:C
5) If the load on an induction motor is increased from no-load to full load, its slip and the power factor will, respectively.
A) decrease, decrease
B) decrease, increase
C) increase, decrease
D) increase, increase
Ans:D
6) In a 3-phase induction motor, the variable mechanical load is represented electrically by a variable ........................ only
A) inductance
B) capacitance
C) resistance
D) any of these
Ans:C
7) Rotor input of a three phase induction motor is equal to
A) input to motor-stator copper and iron losses
B) mechanical power developed-windage and friction losses
C) input to motor-windage and friction losses
D) input to motor-stator iron losses-windage and friction losses
Ans:A
8) For an induction motor, operating at slip s, the ratio of gross power output to air gap power is equal to
A) (1-s)^2
B) (1-s)
C) √(1-s)
D) (1-√s)
Ans:B
9) The power input to a 415 V, 50 Hz, 6-pole, 3-phase induction motor running at 975 rpm is 40 KW. The stator losses are 1 KW and friction and windage losses total 2 KW. The efficiency of the motor is
A) 92.5%
B) 92%
C) 90%
D) 88%
Ans:C
10) A 400 V, 15 KW , 4-pole, 50 Hz y-connected induction motor has full load slip of 4%. The output torque of the machine at full load is
A) 1.66 Nm
B) 95.5 Nm
C) 99.47 Nm
D) 624.73 Nm
Ans:C
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1) An induction motor always operates on lagging power factor. This is due to
A) stator reactance
B) rotor leakage reactance
C) the large reactive lagging magnetizing current essential to produce the magnetic field
D) all of the above
Ans:D
2) In a 3-phase induction motor when the load is increased from light load
A) rotor pf increases but stator pf decreases
B) stator pf increases but the rotor pf decreases
C) both stator and rotor pf increase
D) both stator and rotor pf decrease
Ans:B
3) The power factor of a 3-phase induction motor is likely to be maximum when it will operate at
A) full load
B) no load
C) maximum slip
D) maximum torque
Ans:A
4) The power factor of an induction motor at full load is likely to be
A) unity
B) 0.85 lead
C) 0.85 lag
D) 0.5 lag
Ans:C
5) If the load on an induction motor is increased from no-load to full load, its slip and the power factor will, respectively.
A) decrease, decrease
B) decrease, increase
C) increase, decrease
D) increase, increase
Ans:D
6) In a 3-phase induction motor, the variable mechanical load is represented electrically by a variable ........................ only
A) inductance
B) capacitance
C) resistance
D) any of these
Ans:C
7) Rotor input of a three phase induction motor is equal to
A) input to motor-stator copper and iron losses
B) mechanical power developed-windage and friction losses
C) input to motor-windage and friction losses
D) input to motor-stator iron losses-windage and friction losses
Ans:A
8) For an induction motor, operating at slip s, the ratio of gross power output to air gap power is equal to
A) (1-s)^2
B) (1-s)
C) √(1-s)
D) (1-√s)
Ans:B
9) The power input to a 415 V, 50 Hz, 6-pole, 3-phase induction motor running at 975 rpm is 40 KW. The stator losses are 1 KW and friction and windage losses total 2 KW. The efficiency of the motor is
A) 92.5%
B) 92%
C) 90%
D) 88%
Ans:C
10) A 400 V, 15 KW , 4-pole, 50 Hz y-connected induction motor has full load slip of 4%. The output torque of the machine at full load is
A) 1.66 Nm
B) 95.5 Nm
C) 99.47 Nm
D) 624.73 Nm
Ans:C
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1 comments:
Write commentsA 2 kVA, 250/500 V single-phase transformer is reconnected as an auto-transformer such that its kVA rating is maximum. The new rating, in kVA, is
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