A. zero
B. one
C. two
D. infinity
Related Mcqs:
- While starting a salient pole synchronous motor by induction motor action and connecting field discharge resistance across field, starting and accelerating torque is produced by_____________?
A. induction motor torque in field winding
B. induction motor torque in damper winding
C. eddy current and hysteresis torque in pole faces
D. reHetance motor torque due to saliency of the rotor
E. all of the above methods - 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 - 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 - 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 - 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 - 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 - 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 - While starting a synchronous motor by induction motor action, field winding is usually_____________?
A. connected to D.C. supply
B. short-circuited by low resistance
C. kept open-circuited
D. none of the above - 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 - The maximum torque which a synchronous motor will develop at rest for any angular position of the rotor, at rated stator supply voltage and frequency, is known as__________?
A. locked-rotor torque
B. synchronous torque
C. pull up torque
D. reluctance torque
