Related Mcqs:

1. A 500 kW, 3-phase, 440 volts, 50 Hz, A.C. induction motor has a speed of 960 r.p.m. on full load. The machine has 6 poles. The slip of the machine will be__________?

   A. 0.01
   B. 0.02
   C. 0.03
   D. 0.04

2. When /?2 is the rotor resistance, .X2 the rotor reactance at supply frequency and s the slip, then the condition for maximum torque under running conditions will be_____________?

   A. sR2X2 = 1
   B. sR2 = X2
   C. R2 = sX2
   D. R2 = s2X2

3. 5 H.P., 50-Hz, 3-phase, 440 V, induction motors are available for the following r.p.m. Which motor will be the costliest ?

   A. 730 r.p.m.
   B. 960 r.p.m.
   C. 1440 r.p.m.
   D. 2880 r.p.m.

4. Slip ring motor is preferred over squirrel cage induction motor where___________?

   A. high starting torque is required
   B. load torque is heavy
   C. heavy pull out torque is required
   D. all of the above

5. In a three-phase induction motor, the number of poles in the rotor winding is always__________?

   A. zero
   B. more than the number of poles in stator
   C. less than number of poles in stator
   D. equal to number of poles in stator

6. 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 squence of supply

7. The number of slip rings on a squirrel cage induction motor is usually____________?

   A. two
   B. three
   C. four
   D. none

8. In Ns is the synchronous speed and s the slip, then actual running speed of an induction motor will be___________?

   A. Ns
   B. s.N,
   C. (l-s)Ns
   D. (Ns-l)s

9. Slip of an induction motor is negative when_____________?

   A. magnetic field and rotor rotate in opposite direction
   B. rotor speed is less than the synchronous speed of the field and are in the same direction
   C. rotor speed is more than the synchronous speed of the field and are in the same direction
   D. none of the above

10. In induction motor, percentage slip depends on__________?

    A. supply frequency
    B. supply voltage
    C. copper losses in motor
    D. none of the above