Top 80+ Solved 3 Phase Induction Motors MCQ Questions Answer
Q. Star-delta starting of motors is not possible in case of
a. single phase motors
b. variable speed motors
c. low horse power motors
d. high speed motors
Q. The term 'cogging' is associated with
a. three phase transformers
b. compound generators
c. D.C. series motors
d. induction motors
Q. In case of the induction motors the torque is
a. inversely proportional to (Vslip)
b. directly proportional to (slip)2
c. inversely proportional to slip
d. directly proportional to slip
Q. The good power factor of an induction motor can be achieved if the average fluxdensity in the air gap is
a. absent
b. small
c. large
d. infinity
Q. An induction motor is identical to
a. D.C. compound motor
b. D.C. series motor
c. synchronous motor
d. asynchronous motor
Q. The injected e.m.f. in the rotor of induction motor must have
a. zero frequency
b. the same frequency as the slip fre-quency
c. the same phase as the rotor e.m.f.
d. high value for the satisfactory speed control
Q. Which of the following methods is easily applicable to control the speed of thesquirrel-cage induction motor ?
a. By changing the number of stator poles
b. Rotor rheostat control
c. By operating two motors in cascade
d. By injecting e.m.f. in the rotor circuit
Q. The crawling in the induction motor is caused by
a. low voltage supply
b. high loads
c. harmonics develped in the motor
d. improper design of the machine
Q. The auto-starters (using three auto transformers) can be used to start cage inductionmotor of the following type
a. star connected only
b. delta connected only
c. (a) and (b) both
d. none of the above
Q. The torque developed in the cage induction motor with autostarter is
a. k/torque with direct switching
b. K x torque with direct switching
c. K2 x torque with direct switching
d. k2/torque with direct switching
Q. When the equivalent circuit diagram of doouble squirrel-cage induction motor isconstructed the two cages can be considered
a. in series
b. in parallel
c. in series-parallel
d. in parallel with stator
Q. It is advisable to avoid line-starting of induction motor and use starter because
a. motor takes five to seven times its full load current
b. it will pick-up very high speed and may go out of step
c. it will run in reverse direction
d. starting torque is very high
Q. Stepless speed control of induction motor is possible by which of the followingmethods ?
a. e.m.f. injection in rotor eueuit
b. Changing the number of poles
c. Cascade operation
d. None of the above
Q. Rotor rheostat control method of speed control is used for
a. squirrel-cage induction motors only
b. slip ring induction motors only
c. both (a) and (b)
d. none of the above