Oct 31, 2019


Induction Motor important questions-Electrical Engineering, Three-phase induction motor important questions for Electrical Engineering students.

List of 25 important questions about Induction motor

1) In an induction motor, rotor slots are usually not quite parallel to the salt nut arc given a slight skew for the reason: to reduce the magnetic hum and the locking tendency of the rotor

2) In an induction motor, rotor runs as a speed: lower than the speed of stator field

3) When an induction motor runs at rated load and speed, the iron losses are: negligible

4) The starting torque of an induction motor is maximum when: rotor resistance equals rotor reactance

5) Wattmeter reading in no-load test induction motor gives: total losses in the rotor on no load

6) At zero slip is an induction motor: motor does not run

7) Increase in the air gap flux density in an induction motor result in: increased iron loss and decreased efficiency 

8) The rotor of a 3-phase induction motor receives energy from: inverted do supply

9) When the rotor of a 3-phase induction motor runs at synchronous speed, the rotor: current, torque and emf are zero

10) Torque developed by a three-phase induction motor equals: power input to rotor minus rotor losses

11) The direction of rotation of a three-phase: interchanging the connection of a two phases

12) A 3-phase induction motor running at 1400rpm on rated supply will run at the following rpm when a fuse of one phase gets burnt: 1380 rpm

13) A three-phase 6 pole 50Hz induction motor works with 5% slip. The actual speed of the motor is: 950 rpm

14) The field winding of a three-phase synchronous machine is excited: dc supply

15) If in a 3-phase induction motor, Two phases open accidentally, the motor will: continue to run depending on load

16) A 4-pole 50Hz induction motor normally runs at a speed of: 1440 rpm

17) Squirrel cage induction motor has: very small starting torque

18) The advantage of double squirrel cage rotor as compared to the round bar cage rotor: lower starting torque

19) On open circuiting, the rotor of a squirrel cage induction motor, rotor: does not run

20) External resistance can be added to start the motor: slip ring induction motor

21) An induction motor has a rated speed of 715 rpm. The number of poles in its rotating magnetic field equals: 4 poles 

22) For 4% drop in supply voltage, the torque of an induction motor increased by: 16%

23) Improvement of the power factor in an induction motor results in: increased torque and decreased current due to increased impedance

24) The function is served by the resistance placed in parallel with one phase of three-phase induction motor: smooth starting

25) The rotor output of an induction motor is 15kW and the slip is 4%. Then the rotor copper loss is: 600 watts

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