For which motor the speed can be controlled from rotor side ?

Related Mcqs:

1. Size of a high speed motor as compared to low speed motor for the same H.P. will be__________?

   A. bigger
   B. smaller
   C. same
   D. any of the above

2. 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

3. 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

4. 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

5. 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

6. The speed of a squirrel-cage induction motor can be controlled by all of the following except_____________?

   A. changing supply frequency
   B. changing number of poles
   C. changing winding resistance
   D. reducing supply voltage

7. 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

8. The injected e.m.f. in the rotor of induction motor must have__________?

   A. zero frequency
   B. the same frequency as the slip frequency
   C. the same phase as the rotor e.m.f.
   D. high value for the satisfactory speed control

9. 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

10. Insertion of resistance in the rotor of an induction motor to develop a given torque?

    A. decreases the rotor current
    B. increases the rotor current
    C. rotor current becomes zero
    D. rotor current rernains same