Tricky Polyphase Induction Motors Multiple choice Questions and Answers pdf

91.    The purpose of using short-circuit gear is
(a)     to short circuit the rotor at slip rings
(b)     to short circuit the starting resis¬tances in the starter
(c)    to short circuit the stator phase of motor to form star
(d)    none of the above
Ans: a

92.    In a squirrel cage motor the induced e.m.f. is
(a)    dependent on the shaft loading
(b)    dependent on the number of slots
(c)    slip times the stand still e.m.f. induced in the rotor
(d)    none of the above
Ans: c

93.    Less  maintenance  troubles  are  experienced in case of
(a) slip ring induction motor
(6) squirrel cage induction motor
(c) both (a) and (b)
(d) none of the above
Ans: b

94.    A squirrel cage induction motor is not selected when
(a)    initial cost is the main consideration
(b)    maintenance cost is to be kept low
(c)    higher starting torque is the main consideration
(d)    all above considerations are involved
Ans: c

95.    Reduced voltage starter can be used with
(a) slip ring motor only but not with squirrel cage induction motor
(b) squirrel cage induction motor only but not with slip ring motor
(c) squirrel cage as well as slip ring induction motor
(d) none of the above
Ans: c

96.    Slip ring motor is preferred over squirrel cage induction motor where
(a)     high starting torque is required
(b)     load torque is heavy
(c)    heavy pull out torque is required
(d)    all of the above
Ans: a

97.    In a star-delta starter of an induction motor
(a)    resistance is inserted in the stator
(b)    reduced voltage is applied to the stator
(c)    resistance is inserted in the rotor
(d)    applied voltage per1 stator phase is 57.7% of the line voltage
Ans: d

98.    The torque of an induction motor is
(a) directly proportional to slip
(b) inversely proportional to slip
(c) proportional to the square of the slip
(d) none of the above
Ans: a

99.    The rotor of an induction motor runs at
(a)    synchronous speed
(b)    below synchronous speed
(c)    above synchronous speed
(d)     any of the above
Ans: b

100.    The starting torque of a three phase induction motor can be increased by
(a)    increasing slip
(b)    increasing current
(c)    both (a) and (b)
(d)    none of the above
Ans: c

101.    Insertion of resistance in the stator of an induction motor
(a)    increases the load torque
(b)    decreases the starting torque
(c)    increases the starting torque
(d)    none of the above
Ans: b

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