Page 726 - Basic Electrical Engineering

b.

c.

d.

9. A four-pole, 50 Hz, 400 V, three-phase induction motor is running at 1440 rpm. The
frequency of rotor-induced EMF is

a. 2 Hz
b. 4 Hz
c. 1 Hz
d. 50 Hz.

10. A four-pole, three-phase induction motor when fed from a 400 V, 50 Hz supply, runs at 1440
rpm. The frequency of EMF induced in the rotor is

a. 2 Hz
b. 45 Hz
c. 50 Hz
d. 3 Hz.

11. If an induction motor by some means is rotated at synchronous speed, then

a. the EMF induced in the rotor will be maximum
b. the EMF induced in the rotor will be zero
c. the torque developed by the rotor will be maximum
d. the frequency of induced EMF will be slip times the supply frequency.

12. Increase in the rotor-circuit resistance of an induction motor will

a. increase the starting torque
b. decrease the starting torque
c. increase the maximum torque developed
d. decrease the maximum torque developed.

13. Torque developed by a three-phase induction motor depends on

a. the supply voltage
b. the rotor-circuit resistance
c. the slip of the rotor
d. all the above.