Polyphase Induction Motors(Electrical Engineering Questions ) Questions and Answers

Question 1. The starting torque of a three phase induction motor can be increased by__________?
  1.    increasing slip
  2.    increasing current
  3.    both A. and (b)
  4.    none of the above
Explanation:-
Answer: Option C. -> both A. and (b)
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!
Question 2. Insertion of resistance in the stator of an induction motor___________?
  1.    increases the load torque
  2.    decreases the starting torque
  3.    increases the starting torque
  4.    none of the above
Explanation:-
Answer: Option B. -> decreases the starting torque
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!
Question 3. Slip ring motor is preferred over squirrel cage induction motor where___________?
  1.    high starting torque is required
  2.    load torque is heavy
  3.    heavy pull out torque is required
  4.    all of the above
Explanation:-
Answer: Option A. -> high starting torque is required
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!
Question 4. The rotor of an induction motor runs at__________?
  1.    synchronous speed
  2.    below synchronous speed
  3.    above synchronous speed
  4.    any of the above
Explanation:-
Answer: Option B. -> below synchronous speed
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!
Question 5. In a star-delta starter of an induction motor___________?
  1.    resistance is inserted in the stator
  2.    reduced voltage is applied to the stator
  3.    resistance is inserted in the rotor
  4.    applied voltage perl stator phase is 57.7% of the line voltage
Explanation:-
Answer: Option D. -> applied voltage perl stator phase is 57.7% of the line voltage
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!
Question 6. A squirrel cage induction motor is not selected when___________?
  1.    initial cost is the main consideration
  2.    maintenance cost is to be kept low
  3.    higher starting torque is the main consideration
  4.    all above considerations are involved
Explanation:-
Answer: Option C. -> higher starting torque is the main consideration
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!
Question 7. Less maintenance troubles are experienced in case of___________?
  1.    slip ring induction motor
  2.    squirrel cage induction motor
  3.    both A. and (b)
  4.    none of the above
Explanation:-
Answer: Option B. -> squirrel cage induction motor
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!
Question 8. Reduced voltage starter can be used with_____________?
  1.    slip ring motor only but not with squirrel cage induction motor
  2.    squirrel cage induction motor only but not with slip ring motor
  3.    squirrel cage as well as slip ring induction motor
  4.    none of the above
Explanation:-
Answer: Option C. -> squirrel cage as well as slip ring induction motor
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!
Question 9. In a squirrel cage motor the induced e.m.f. is___________?
  1.    dependent on the shaft loading
  2.    dependent on the number of slots
  3.    slip times the stand still e.m.f. induced in the rotor
  4.    none of the above
Explanation:-
Answer: Option C. -> slip times the stand still e.m.f. induced in the rotor
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!
Question 10. The purpose of using short-circuit gear is___________?
  1.    to short circuit the rotor at slip rings
  2.    to short circuit the starting resistances in the starter
  3.    to short circuit the stator phase of motor to form star
  4.    none of the above
Explanation:-
Answer: Option A. -> to short circuit the rotor at slip rings
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!
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