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1) What is the operating slip of a 400 V, 50 HZ, 6-pole 3-phase induction motor, while speed is 936 rpm with a 400 V, 48 HZ, 3-phase supply?
A) 0.036
B) 0.064
C) 0.025
D) 0.075
Ans:C
2) Which of the following is the correct statement:
In a 3-phase induction motor, the resultant flux is of a constant nature and is
A) equal to Ï•m, where Ï•m is maximum flux due to any phase
B) 1.5 times maximum value of flux due to any phase
C) √3/2 times maximum value flux due to any phase
D) 3 Ï•m
Ans:B
3) The rotor of an induction motor rotates in the direction of the rotation of stator field in order to
A) reduce the relative speed between the rotating stator field and the stationary rotor conductors
B) oppose the rotor current
C) increase the relative speed between the rotating stator field and stationary rotor conductors
D) none of the above
Ans:A
4) The voltage actually used for setting up of the useful flux in the air gap of 3-phase induction motor is
A) = applied voltage
B) > applied voltage
C) < applied voltage
D) = rotor induced emf
Ans:A
5) The maximum possible speed of a 3-phase squirrel cage induction motor running at a slip of 4% is
A) 2880 rpm
B) 3000 rpm
C) 1440 rpm
D) 960 rpm
Ans:A
6) A balanced 3-phase induction motor runs at slip s. If ws is its synchronous speed, what is the relative speed between the stator mmf and rotor mmf?
A) sws
B) (1-s)ws
C) ws
D) zero
Ans:D
7) An 8-pole alternator runs at 750 rpm. It suppies power to a 6-pole induction motor which has a full load slip of 3%. The full load speed of the motor is
A) 1050 rpm
B) 970 rpm
C) 960 rpm
D) 1250 rpm
Ans:B
8) If the full load speed of a 6-phase, 50 HZ induction motor is 950 rpm, what is its half-load speed nearly equal to
A) 1000 rpm
B) 450 rpm
C) 1900 rpm
D) 975 rpm
Ans:D
9) The mmf produced by the current of a 3-phase induction motor
A) rotates at the speed of rotor in the air gap
B) is standstill with respect to stator mmf
C) rotates at slip speed with respect to stator mmf
D) rotates at synchronous speed with respect to rotor
Ans:B
10) What is the frequency of rotor current of a 50 HZ induction motor operating at 2% slip
A) 1 Hz
B) 100 Hz
C) 2 Hz
D) 50 Hz
Ans:A
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1) What is the operating slip of a 400 V, 50 HZ, 6-pole 3-phase induction motor, while speed is 936 rpm with a 400 V, 48 HZ, 3-phase supply?
A) 0.036
B) 0.064
C) 0.025
D) 0.075
Ans:C
2) Which of the following is the correct statement:
In a 3-phase induction motor, the resultant flux is of a constant nature and is
A) equal to Ï•m, where Ï•m is maximum flux due to any phase
B) 1.5 times maximum value of flux due to any phase
C) √3/2 times maximum value flux due to any phase
D) 3 Ï•m
Ans:B
3) The rotor of an induction motor rotates in the direction of the rotation of stator field in order to
A) reduce the relative speed between the rotating stator field and the stationary rotor conductors
B) oppose the rotor current
C) increase the relative speed between the rotating stator field and stationary rotor conductors
D) none of the above
Ans:A
4) The voltage actually used for setting up of the useful flux in the air gap of 3-phase induction motor is
A) = applied voltage
B) > applied voltage
C) < applied voltage
D) = rotor induced emf
Ans:A
5) The maximum possible speed of a 3-phase squirrel cage induction motor running at a slip of 4% is
A) 2880 rpm
B) 3000 rpm
C) 1440 rpm
D) 960 rpm
Ans:A
6) A balanced 3-phase induction motor runs at slip s. If ws is its synchronous speed, what is the relative speed between the stator mmf and rotor mmf?
A) sws
B) (1-s)ws
C) ws
D) zero
Ans:D
7) An 8-pole alternator runs at 750 rpm. It suppies power to a 6-pole induction motor which has a full load slip of 3%. The full load speed of the motor is
A) 1050 rpm
B) 970 rpm
C) 960 rpm
D) 1250 rpm
Ans:B
8) If the full load speed of a 6-phase, 50 HZ induction motor is 950 rpm, what is its half-load speed nearly equal to
A) 1000 rpm
B) 450 rpm
C) 1900 rpm
D) 975 rpm
Ans:D
9) The mmf produced by the current of a 3-phase induction motor
A) rotates at the speed of rotor in the air gap
B) is standstill with respect to stator mmf
C) rotates at slip speed with respect to stator mmf
D) rotates at synchronous speed with respect to rotor
Ans:B
10) What is the frequency of rotor current of a 50 HZ induction motor operating at 2% slip
A) 1 Hz
B) 100 Hz
C) 2 Hz
D) 50 Hz
Ans:A
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