Top 80+ Solved 3 Phase Induction Motors MCQ Questions Answer
Q. In the circle diagram for induction motor, the diameter of the circle represents
a. slip
b. rotor current
c. running torque
d. line voltage
Q. For which motor the speed can be controlled from rotor side ?
a. Squirrel-cage induction motor
b. Slip-ring induction motor
c. Both (a) and (b)
d. None of the above
Q. If any two phases for an induction motor are interchanged
a. the motor will run in reverse direction
b. the motor will run at reduced speed
c. the motor will not run
d. the motor will burn
Q. An induction motor is
a. self-starting with zero torque
b. self-starting with high torque
c. self-starting with low torque
d. non-self starting
Q. The maximum torque in an induction motor depends on
a. frequency
b. rotor inductive reactance
c. square of supply voltage
d. all of the above
Q. In three-phase squirrel-cage induction motors
a. rotor conductor ends are short-circuited through slip rings
b. rotor conductors are short-circuited through end rings
c. rotor conductors are kept open
d. rotor conductors are connected to insulation
Q. In a three-phase induction motor, the number of poles in the rotor winding is always
a. zero
b. more than the number of poles in stator
c. less than number of poles in stator
d. equal to number of poles in stator
Q. DOL starting of induction motors is usually restricted to
a. low horsepower motors
b. variable speed motors
c. high horsepower motors
d. high speed motors
Q. The speed of a squirrel-cage induction motor can be controlled by all of the followingexcept
a. changing supply frequency
b. changing number of poles
c. changing winding resistance
d. reducing supply voltage
Q. The 'crawling" in an induction motor is caused by
a. high loads
b. low voltage supply
c. improper design of machine
d. harmonics developed in the motor
Q. The power factor of an induction motor under no-load conditions will be closer to
a. 0.2 lagging
b. 0.2 leading
c. 0.5 leading
d. unity
Q. The 'cogging' of an induction motor can be avoided by
a. proper ventilation
b. using DOL starter
c. auto-transformer starter
d. having number of rotor slots more or less than the number of stator slots (not equal)
Q. If an induction motor with certain ratio of rotor to stator slots, runs at 1/7 of thenormal speed, the phenomenon will be termed as
a. humming
b. hunting
c. crawling
d. cogging
Q. Slip of an induction motor is negative when
a. magnetic field and rotor rotate in opposite direction
b. rotor speed is less than the syn-chronous speed of the field and are in the same direction
c. rotor speed is more than the syn-chronous speed of the field and are in the same direction
d. none of the above
Q. Size of a high speed motor as compared to low speed motorfor the same H.P. will be
a. bigger
b. smaller
c. same
d. any of the above