. In a synchronous motor which loss varies with load ?

Related Mcqs:

1. A synchronous motor installed at the receiving end substation operates with such an excitation that it takes power at lagging power factor. Now if the applied voltage of the synchronous motor goes down, the power factor of the synchronous motor will___________?

   A. remain same
   B. go down
   C. improve
   D. none of the above

2. A synchronous motor is running on a load with normal excitation. Now if the load on the motor is increased

   A. power factor as well as armature current will decrease
   B. power factor as well as armature current will increase
   C. power factor will increase but armature current will decrease
   D. power factor will decrease and armature current will increase

3. If the synchronous motor, properly synchronised to the supply is running on no load and is having negligible loss then_____________?

   A. the stator current will be zero
   B. the stator current will be very small
   C. the stator current will be very high
   D. the back e.m.f. will be more than the supply voltage
   E. none of the above

4. As the load is applied to a synchronous motor, the motor takes more armature current because

   A. the increased load has to take more current
   B. the rotor by shifting its phase backward causes motor to take more current
   C. the back e.m.f. decreases causing an increase in motor current
   D. the rotor strengthens the rotating field casuing more motor current

5. In a 3-phase, 4-pole, 50 Hz synchronous motor, the frequency, pole number and load torque all are halved. The motor speed will be____________?

   A. 3000 r.p.m.
   B. 1500 r.p.m.
   C. 750 r.p.m.
   D. none of the above

6. When V is the applied voltage, then the breakdown torque of a synchronous motor varies as_________?

   A. V
   B. V312
   C. V2
   D. 1/V

7. A synchronous motor can be used as a synchronous capacitor when it is____________?

   A. under-loaded
   B. over-loaded
   C. under-excited
   D. over-excited

8. A synchronous motor can develop synchronous torque:

   A. when under loaded
   B. while over-excited
   C. only at synchronous speed
   D. below or above synchronous speed

9. A synchronous motor develops maximum power when load angle is____________?

   A. 45°
   B. 60°
   C. 90°
   D. 120°

10. In a synchronous motor running with fixed excitation, when the load is increased three times, its torque angle becomes approximately

    A. one-third
    B. twice
    C. thrice
    D. six times
    E. nine times