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) Crawling in an induction motor is due to
A) time harmonics in supply
B) slip ring motor
C) space harmonics produced by winding currents
D) insufficient starting torque
Ans:C
2) The crawling in the induction motor is caused by
A) improper design of stator laminations
B) low voltage supply
C) high loads
D) harmonics developed in motor
Ans:D
3) An induction motor when started on load does not accelerate upto full speed but runs at 1/7th of the rated speed. The motor is said to be
A) locking
B) plugging
C) crawling
D) cogging
Ans:C
4) The presence of a dominant 7th harmonic in the winding distribution of a 3-phase, 6-pole, 50Hz induction motor may cause the motor to crawl at a speed of about
A) 750 rpm
B) 500 rpm
C) 242 rpm
D) 143 rpm
Ans:D
5) The phenomenon of crawling in a 3-phase induction motor may be due to
A) unbalanced supply voltage
B) 7th space harmonics of air-gap voltage
C) 7th time harmonics of voltage wave
D) 5th space harmonics
Ans:B
6) In an induction motor, when the number of stator slots is equal to an integral multiple of rotor slots
A) there may be a discontinuity in torque slip characteristics
B) a high starting torque will be available
C) the maximum torque will be high
D) the machine will fail to start
Ans:D
7) Presence of 5th harmonics in induction motor causes
A) cogging
B) crawling
C) small reverse braking torque
D) hunting
Ans:C
8) Cogging of induction motor occurs at
A) high voltage and when the number of stator teeth and rotor teeth are equal
B) high voltage and when the number of stator teeth and rotor teeth are not equal
C) low voltage and when the number of stator teeth and rotor teeth are equal
D) low voltage and when the number of stator teeth and rotor teeth are not equal
Ans:C
9) Cogging and crawling are phenomenon associated with
A) cage induction machines and they are essentially the same
B) squirrel cage induction machines, the former during starting and the latter at a fraction of its rated speed
C) squirrel cage induction machines, the former at a fraction of its rated speed and the latter during starting
D) wound rotor induction machines and they are reduced by skewing,chording and distribution of windings
Ans:B
10) In an induction motor, if the air-gap is increased
A) speed will reduce
B) efficiency will improved
C) power factor will be lowered
D) breakdown torque will reduce
Ans:C
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1) Crawling in an induction motor is due to
A) time harmonics in supply
B) slip ring motor
C) space harmonics produced by winding currents
D) insufficient starting torque
Ans:C
2) The crawling in the induction motor is caused by
A) improper design of stator laminations
B) low voltage supply
C) high loads
D) harmonics developed in motor
Ans:D
3) An induction motor when started on load does not accelerate upto full speed but runs at 1/7th of the rated speed. The motor is said to be
A) locking
B) plugging
C) crawling
D) cogging
Ans:C
4) The presence of a dominant 7th harmonic in the winding distribution of a 3-phase, 6-pole, 50Hz induction motor may cause the motor to crawl at a speed of about
A) 750 rpm
B) 500 rpm
C) 242 rpm
D) 143 rpm
Ans:D
5) The phenomenon of crawling in a 3-phase induction motor may be due to
A) unbalanced supply voltage
B) 7th space harmonics of air-gap voltage
C) 7th time harmonics of voltage wave
D) 5th space harmonics
Ans:B
6) In an induction motor, when the number of stator slots is equal to an integral multiple of rotor slots
A) there may be a discontinuity in torque slip characteristics
B) a high starting torque will be available
C) the maximum torque will be high
D) the machine will fail to start
Ans:D
7) Presence of 5th harmonics in induction motor causes
A) cogging
B) crawling
C) small reverse braking torque
D) hunting
Ans:C
8) Cogging of induction motor occurs at
A) high voltage and when the number of stator teeth and rotor teeth are equal
B) high voltage and when the number of stator teeth and rotor teeth are not equal
C) low voltage and when the number of stator teeth and rotor teeth are equal
D) low voltage and when the number of stator teeth and rotor teeth are not equal
Ans:C
9) Cogging and crawling are phenomenon associated with
A) cage induction machines and they are essentially the same
B) squirrel cage induction machines, the former during starting and the latter at a fraction of its rated speed
C) squirrel cage induction machines, the former at a fraction of its rated speed and the latter during starting
D) wound rotor induction machines and they are reduced by skewing,chording and distribution of windings
Ans:B
10) In an induction motor, if the air-gap is increased
A) speed will reduce
B) efficiency will improved
C) power factor will be lowered
D) breakdown torque will reduce
Ans:C
If you like my post share it with your friends and subscribe for latest updates..
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