The term ‘cogging’ is associated with___________?

Related Mcqs:

1. The ‘cogging’ of an induction motor can be avoided by____________?

   A. proper ventilation
   B. using DOL starter
   C. auto-transformer starter
   D. having number of rotor slots more or less than the number of stator slots (not equal)

2. The efficiency of an induction motor can be expected to be nearly____________?

   A. 60 to 90%
   B. 80 to 90%
   C. 95 to 98%
   D. 99%

3. 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

4. The crawling in the induction motor is caused by____________?

   A. low voltage supply
   B. high loads
   C. harmonics develped in the motor
   D. improper design of the machine
   E. none 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 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

7. A pump induction motor is switched on to a supply 30% lower than its rated voltage. The pump runs. What will eventually happen ? It will____________?

   A. stall after sometime
   B. stall immediately
   C. continue to run at lower speed without damage
   D. get heated and subsequently get damaged

8. 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

9. What will happen if the relative speed between the rotating flux of stator and rotor of the induction motor is zero ?

   A. The slip of the motor will be 5%
   B. The rotor will not run
   C. The rotor will run at very high speed
   D. The torque produced will be very large

10. The starting torque of a three phase induction motor can be increased by__________?

    A. increasing slip
    B. increasing current
    C. both A. and (b)
    D. none of the above