Induction Motor Multiple Choice Questions and Answers - Set 06 - ObjectiveBooks

Induction Motor Multiple Choice Questions and Answers - Set 06

Practice Test: Question Set - 06

1. In case of the induction motors the torque is
    (A) Inversely proportional to (V-slip)
    (B) Directly proportional to (slip)2
    (C) Inversely proportional to slip
    (D) Directly proportional to slip

2. In the circle diagram for induction motor, the diameter of the circle represents
    (A) Slip
    (B) Rotor current
    (C) Running torque
    (D) Line voltage

3. If an induction motor with certain ratio of rotor to stator slots, runs at 1/7 of the normal speed, the phenomenon will be termed as
    (A) Humming
    (B) Hunting
    (C) Crawling
    (D) Cogging

4. Short-circuit test on an induction motor cannot be used to determine
    (A) Windage losses
    (B) Copper losses
    (C) Transformation ratio
    (D) Power scale of circle diagram

5. In the squirrel-cage induction motor the rotor slots are usually given slight skew
    (A) To reduce the magnetic hum and locking tendency of the rotor
    (B) To increase the tensile strength of the rotor bars
    (C) To ensure easy fabrication
    (D) None of the above

6. The low power factor of induction motor is due to
    (A) Rotor leakage reactance
    (B) Stator reactance
    (C) The reactive lagging magnetizing current necessary to generate the magnetic flux
    (D) All of the above

7. The rotor of an induction motor runs at
    (A) Synchronous speed
    (B) Below synchronous speed
    (C) Above synchronous speed
    (D) Any of the above

8. In induction motor, percentage slip depends on
    (A) Supply frequency
    (B) Supply voltage
    (C) Copper losses in motor
    (D) None of the above

9. In three-phase induction motors sometimes copper bars are placed deep in the rotor to
    (A) Improve starting torque
    (B) Reduce copper losses
    (C) Improve efficiency
    (D) Improve power factor

10. If a 3-phase supply is given to the stator and rotor is short circuited rotor will move
    (A) In the opposite direction as the direction of the rotating field
    (B) In the same direction as the direction of the field
    (C) In any direction depending upon phase sequence of supply
    (D) None of these

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