Top 150+ Solved Synchronous Motors MCQ Questions Answer
Q. In which of the following motors the stator and rotor fields rotate simultaneously ?
a. D.C. motor
b. Reluctance motor
c. Universal motor
d. Synchronous motor
Q. The speed of a synchronous motor
a. increases as the load increases
b. decreases as the load decreases
c. always remains constant
d. none of the above
Q. A rotory converter can also be run as a
a. d.c. shunt motor
b. d.c. series motor
c. d. compound motor
d. synchronous motor
Q. The maximum speed variation in a 3-phase synchronous motor is
a. 10 per cent
b. 6 per cent
c. 4 per cent
d. zero
Q. Which of the following resistances can be measured by conducting insulation resistance test on a synchronous motor ?
a. Phase to phase winding resistance
b. Stator winding to earthed frame
c. Rotor winding to earthed shaft
d. All of the above
Q. Due to which of the following reasons a synchronous motor fails to pull into synchronism after applying D.C. field current ?
a. High field current
b. Low short circuit ratio
c. High core losses
d. Low field current
Q. In a synchronous motor, the maximum power developed depends on all of the following except
a. rotor excitation
b. maximum value of coupling angle
c. direction of rotation
d. supply voltage
Q. In a 3-phase synchronous motor, the negative phase sequence exists when the motor is
a. supplied with unbalanced voltage
b. under-loaded
c. over-loaded
d. none of the above
Q. In a synchronous motor, damper windings are provided on
a. stator frame
b. rotor shaft
c. pole faces
d. none of the above
Q. The induced e.m.f. in a synchronous motor working on leading power factor will be
a. more than the supply voltage
b. less than the supply voltage
c. equal to the supply voltage
d. none
Q. The effect of increasing the load on a synchronous motor running with normalexcitation is to
a. decrease both armature current and power factor
b. decrease armature current but increase power factor
c. increase armature current but decrease power factor
d. increase both its armature current and power factor
Q. The net armature voltage of a synchronous motor is equal to the
a. vector sum of Eb and V
b. arithmetic sum of Eb and V
c. arithmetic difference of Eb and V
d. vector difference of Eh and V
Q. The ratio of starting torque to running torque in a synchronous motor is
a. zero
b. one
c. two
d. infinity
Q. In a synchronous motor, the magnitude of stator back e.m.f. Eb depends on
a. load on the motor
b. d.c. excitation only
c. both the speed and rotor flux
d. none of the above
Q. A 3-phase synchronous motor is running clockwise. If the direction of its field currentis reversed
a. the motor will stop
b. the motor continue to run in the same direction
c. the winding of the motor will burn
d. the motor will run in the reverse direction