Top 150+ Solved Synchronous Motors MCQ Questions Answer
Q. Slip rings are usually made of
a. carbon or graphite
b. brass or steel
c. silver or gold
d. copper or aluminium
Q. An over excited synchronous motor is used for
a. fluctuating loads
b. variable speed loads
c. low torque loads
d. power factor corrections
Q. When the voltage applied to a synchronous motor is increased, which of the followingwill reduce ?
a. Stator flux
b. Pull in torque
c. Both (a) and (b)
d. None of the above
Q. The efficiency of a properly designed synchronous motor will usually fall in range
a. 60 to 70%
b. 75 to 80%
c. 85 to 95%
d. 99 to 99.5%
Q. To limit the operating temperature an electrical machine should have proper
a. voltage rating
b. current rating
c. power factor
d. speed
Q. Slip-rings in a synchronous motor carry
a. direct current
b. alternating current
c. no current
d. all of the above
Q. 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
Q. The armature current of the synchronous motor has higher values for
a. high excitation only
b. low excitation only
c. both (a) and (b)
d. none of the above
Q. In a synchronous motor running with fixed excitation, when the load is increasedthree times, its torque angle becomes approximately
a. one-third
b. twice
c. thrice
d. six times
Q. The angle between the rotating stator flux and rotor poles is called _____ angle.
a. torque
b. obtuse
c. synchronizing
d. power factor
Q. Which of the following methods is used to start a synchronous motor ?
a. Damper winding
b. Star-delta starter
c. Damper winding in conjunction with star-delta starter
d. Resistance starter in the armature circuit
Q. 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. c. motor toque
Q. An important advantage of a synchronous motor over wound round induction motoris that
a. its power factor may be varied at will
b. its speed is independent of supply frequency
c. its speed may be controlled more easily
d. none of the above
Q. The mechanical displacement of the rotor with respect to the stator, in polyphasemultipolar synchronous motors running at full load, is of the order of
a. zero degree
b. two degrees
c. five degrees
d. ten degrees
Q. Power factor of a synchronous motor is unity when
a. the armature current is maximum
b. the armature current is minimum
c. the armature current is zero
d. none of the above