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Tricky Single Phase Induction Motors Multiple choice Questions and Answers pdf

81.    Starting winding of a single phase motor of a refrigerator is disconnected from the circuit by means of a
(a) magnetic relay
(b) thermal relay
(c) centrifugal switch
(d) none of the above
Ans: a

82.    If a single phase induction motor runs slower than normal, the most likely defect is
(a)     worn bearings
(b)     short-circuit in the winding
(c)    open-circuit in the winding
(d)    none of the above
Ans: a

83.    Which of the following motors is used in tape-recorders ?
(a)    Hysteresis motor
(b)    Reluctance motor
(c)    Capacitor-run motor
(d)     Universal motor
Ans: a

84.    Which of the following statements regarding two value capacitor motor is incorrect ?
(a) It is a reversing motor
(b) It is preferred to permanent-split single-value capacitor motor where frequent reversals are required
(c) It has low starting as well as rush¬ing currents
(d) It has high starting torque
Ans: b

85.    Two-value capacitor motor finds increased application as compressor motor in small home air-conditioners because
(a)     it is comparatively cheaper
(b)     it has almost non-destructible capacitor
(c)    it has low starting as well as running currents at relatively high power factor
(d)    it is quiet in operation
Ans: c

86.    If the centrifugal switch of a two-value capacitor motor using two capacitors fails to open then
(a)    motor will not come upto speed
(b)    motor will not carry the load
(c)    current drawn by the motor will be excessively high
(d)     electrolytic capacitor will, in all probability, suffer break down
Ans: d

87.    In a universal motor, the most common cause of brush sparking is
(a)    open armature winding
(b)    shorted armature winding
(c)    shorted field winding"
(d)    high commutator mica
(e)    all of the above
Ans: e

88.    If starting winding of a single-phase induction motor is left in the circuit, it will
(a)    run faster
(b)    spark at light loads
(c)    draw excessive current and overheat
(d)    run slower
Ans: c

89.    Most of the fractional horsepower motors have either
(a)    hard and annealed bearings
(b)    ball or roller bearings
(c)    soft and porous bearings
(d)    plain or sleeve bearings
Ans: d

90.    Which of the following statements regarding reluctance-start motor is incorrect ?
(a)     It is similar to reluctance motor
(b)     It is basically an induction motor and not a synchronous one
(c)    So far as its basic working principle is concerned, it is similar to shaded pole motor
(d)    the air-gap between rotor and salient poles is non- uniform
Ans: a
Posted by at 07:45:00
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