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Electrical Engineering Objective Questions { Induction Motors }



50. In three-phase induction motors sometimes copper bars are placed deep in the rotor to
A. improve starting torque
B. reduce copper losses
C. improve efficiency
D. improve power factor

51.  In a three-phase induction motor
A. power factor at starting is high as compared to that while running
B. power factor at starting is low as compared to that while running
C. power factor at starting in the same as that while running
D. power factor remains through out constant

52.  The value of transformation ratio of an induction motor can be found by
A. open-circuit test only
B. short-circuit test only
C. stator resistance test
D. none of the above

53.  The power scale of circle diagram of an induction motor can be found from
A. stator resistance test
B. no-load test only
C. short-circuit test only
D. none of the above

54. The shape of the torque/slip curve of induction motor is
A. parabola
B. hyperabola
C. rectangular parabola
D. straight line

55. A change of 4% of supply voltage to an induction motor will produce a change of approximately
A. 4% in the rotor torque
B. 8% in the rotor torque
C. 12% in the rotor torque
D. 16% in the rotor torque

56. The stating torque of the slip ring induction motor can be increased by adding
A. external inductance to the rotor
B. external resistance to the rotor
C. external capacitance to the rotor
D. both resistance and inductance to rotor

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