Most recently Polyphase Induction Motors Multiple choice Questions and Answers pdf

51.    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
Ans: d

52.    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
Ans: b

53.    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
Ans: c

54.    The speed characteristics of an induction motor closely resemble the speedload characteristics of which of the following machines
(a)    D.C. series motor
(b)    D.C. shunt motor
(c)    universal motor
(d)    none of the above
Ans: b

55.    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
 Ans: a

56.    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
Ans: d

57.    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.
Ans: a

58.    A 3-phase slip ring motor has
(a)     double cage rotor
(6)     wound rotor
(c)    short-circuited rotor
(d)    any of the above
Ans: b

59.    The starting torque of a 3-phase squirrel cage induction motor is
(a) twice the full load torque
(b) 1.5 times the full load torque
(c) equal to full load torque
Ans: b


60.    Short-circuit test on an induction motor cannot be used to determine
(a)     windage losses
(b)     copper losses
(c)    transformation ratio
(d)    power scale of circle diagram
Ans: a

Read More Questions:
Polyphase Induction Motors MCQs Part1
Polyphase Induction Motors MCQs Part2
Polyphase Induction Motors MCQs Part3
Polyphase Induction Motors MCQs Part4
Polyphase Induction Motors MCQs Part5
Polyphase Induction Motors MCQs Part6
Polyphase Induction Motors MCQs Part7
Polyphase Induction Motors MCQs Part8
Polyphase Induction Motors MCQs Part9
Polyphase Induction Motors MCQs Part10