Objective Questions on Induction Motors Polyphase - Set 08 - ObjectiveBooks

Objective Questions on Induction Motors Polyphase - Set 08

Practice Test: Question Set - 08


1. If any two phases for an induction motor are interchanged
    (A) The motor will run in reverse direction
    (B) The motor will run at reduced speed
    (C) The motor will not run
    (D) The motor will burn

2. Slip ring motor is recommended where
    (A) Speed control is required
    (B) Frequent starting, stopping and reversing is required
    (C) High starting torque is needed
    (D) All above features are required

3. The torque of a rotor in an induction motor under running condition is maximum
    (A) At the unit value of slip
    (B) At the zero value of slip
    (C) At the value of the slip which makes rotor reactance per phase equal to the resistance per phase
    (D) At the value of the slip which makes the rotor reactance half of the rotor

4. Less maintenance troubles are experienced in case of
    (A) Slip ring induction motor
    (B) Squirrel cage induction motor
    (C) Both (A) and (B)
    (D) None of the above

5. In case the air gap in an induction motor is increased
    (A) The magnetizing current of the rotor will decrease
    (B) The power factor will decrease
    (C) Speed of motor will increase
    (D) The windage losses will increase

6. The maximum torque in an induction motor depends on
    (A) Frequency
    (B) Rotor inductive reactance
    (C) Square of supply voltage
    (D) All of the above

7. In a three-phase induction motor
    (A) Iron losses in stator will be negligible as compared to that in rotor
    (B) Iron losses in motor will be negligible as compared to that in rotor
    (C) Iron losses in stator will be less than that in rotor
    (D) Iron losses in stator will be more than that in rotor

8. Lubricant used for ball bearing is usually
    (A) Graphite
    (B) Grease
    (C) Mineral oil
    (D) Molasses

9. A squirrel cage induction motor is not selected when
    (A) Initial cost is the main consideration
    (B) Maintenance cost is to be kept low
    (C) Higher starting torque is the main consideration
    (D) All above considerations are involved

10. The power scale of circle diagram of an induction motor can be found from
    (A) Stator resistance test
    (B) No-load test only
    (C) Short-circuit test only
    (D) None of the above

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