Top 80+ Solved 3 Phase Induction Motors MCQ Questions Answer
Q. A 3-phase induction motor stator delta connected, is carrying full load and one of itsfuses blows out. Then the motor
a. will continue running burning its one phase
b. will continue running burning its two phases
c. will stop and carry heavy current causing permanent damage to its winding
d. will continue running without any harm to the winding
Q. A 3-phase induction motor delta connected is carrying too heavy load and one of its fuses blows out. Then the motor
a. will continue running burning its one phase
b. will continue running burning its two phase
c. will stop and carry heavy current causing permanent damage to its winding
d. will continue running without any harm to the winding
Q. Low voltage at motor terminals is due to
a. inadequate motor wiring
b. poorely regulated power supply
c. any one of the above
d. none of the above
Q. In an induction motor the relationship between stator slots and rotor slots is that
a. stator slots are equal to rotor slots
b. stator slots are exact multiple of rotor slots
c. stator slots are not exact multiple of rotor slots
d. none of the above
Q. Slip ring motor is recommended where
a. speed control is required
b. frequent starting, stopping and reversing is required
c. high starting torque is needed
d. all above features are required
Q. As load on an induction motor goes on increasing
a. its power factor goes on decreasing
b. its power factor remains constant
c. its power factor goes on increasing even after full load
d. its power factor goes on increasing upto full load and then it falls again
Q. If a 3-phase supply is given to the stator and rotor is short circuited rotor will move
a. in the opposite direction as the direction of the rotating field
b. in the same direction as the direction of the field
c. in any direction depending upon phase squence of supply
d. none
Q. It is advisable to avoid line starting of induction motor and use starter because
a. it will run in reverse direction
b. it will pick up very high speed and may go out of step
c. motor takes five to seven times its fullload current
d. starting torque is very high
Q. The speed characteristics of an induction motor closely resemble the speedloadcharacteristics of which of the following machines
a. D.C. series motor
b. D.C. shunt motor
c. universal motor
d. none of the above
Q. Which type of bearing is provided in small induction motors to support the rotor shaft?
a. Ball bearings
b. Cast iron bearings
c. Bush bearings
d. None of the above
Q. A pump induction motor is switched on to a supply 30% lower than its rated voltage.The pump runs. What will eventually happen ? It will
a. stall after sometime
b. stall immediately
c. continue to run at lower speed without damage
d. get heated and subsequently get damaged
Q. 5 H.P., 50-Hz, 3-phase, 440 V, induction motors are available for the following r.p.m.Which motor will be the costliest ?
a. 730 r.p.m.
b. 960 r.p.m.
c. 1440 r.p.m.
d. 2880 r.p.m.
Q. A 3-phase slip ring motor has
a. double cage rotor
b. wound rotor
c. short-circuited rotor
d. any of the above
Q. The circle diagram for an induction motor cannot be used to determine
a. efficiency
b. power factor
c. frequency
d. output
Q. Blocked rotor test on induction motors is used to find out
a. leakage reactance
b. power factor on short circuit
c. short-circuit current under rated voltage
d. all of the above