To limit the operating temperature an electrical machine should have proper____________?

Related Mcqs:

1. If load (or torque) angle of a 4-pole synchronous motor is 6° electrical, its value in mechanical degrees is__________?

   A. 2
   B. 3
   C. 4
   D. 6

2. Armature of a synchronous machine is____________?

   A. of reducing number of slip rings on the rotor
   B. armature is associated with large power as compared to the field circuits
   C. of difficulty of providing high voltage insulation on rotor
   D. all of the above reasons

3. When the rotor speed, in a synchronous machine, becomes more than the synchronous speed during hunting, the damper bars develop_________________?

   A. inductor motor torque
   B. induction generator torque
   C. synchronous motor torque
   D. d.c. motor toque
   E. none of the above

4. Synchronsizing power of a synchronous machine is_____________?

   A. direcly proportional to the synchronous reactance
   B. inversely proportional to the synchronous reactance
   A. equal to the synchronous reactance
   D. none of the above

5. A synchronous machine with large air gap has______________?

   A. a higher value of stability limit
   B. a small value of inherent regulation
   C. a higher synchronizing power which makes the machine less sensitive to load variations
   D. all of the above

6. Stability of a synchronous machine:

   A. decreases with increase in its excitation
   B. increases with increase in its excitation
   C. remains unaffected with increase in excitation
   D. any of the above

7. A synchronous machine with low value of short-circuit ratio has___________?

   A. lower stability limit
   B. high stability limit
   C. good speed regulation
   D. good voltage regulation
   E. none of the above

8. The operating speed of a synchronous motor can be changed to new fixed value by___________?

   A. changing the load
   B. changing the supply voltage
   C. changing frequency
   D. using brakes

9. The rotor copper losses, in a synchronous motor, are met by____________?

   A. d.c. source
   B. armature input
   C. motor input
   D. supply lines

10. Riunting in a synchronous motor takes place___________?

    A. when supply voltage fluctuates
    B. when load varies
    C. when power factor is unity
    D. motor is under loaded