Latest Polyphase Induction Motors Multiple choice Questions and Answers pdf

31.    In the circle diagram for induction motor, the diameter of the circle represents
(a) slip
(b) rotor current
(c) running torque
(d) line voltage
Ans: b

32.    For which motor the speed can be controlled from rotor side ?
(a)    Squirrel-cage induction motor
(b)    Slip-ring induction motor
(c)    Both (a) and (b)
(d)    None of the above
Ans: b

33.    If any two phases for an induction motor are interchanged
(a)     the motor will run in reverse direction
(b)     the motor will run at reduced speed
(c)    the motor will not run
(d)    the motor will burn
Ans: a

34.    An induction motor is
(a) self-starting with zero torque
(b) self-starting with high torque
(c) self-starting with low torque
(d) non-self starting
Ans: c

35.    The maximum torque in an induction motor depends on
(a)     frequency
(b)     rotor inductive reactance
(c)    square of supply voltage
(d)    all of the above
Ans: d

36.    In three-phase squirrel-cage induction motors
(a)    rotor conductor ends are short-circuited through slip rings
(b)    rotor conductors are short-circuited through end rings
(c)    rotor conductors are kept open
(d)    rotor conductors are connected to insulation
Ans: b

37.    In a three-phase induction motor, the number of poles in the rotor winding is always
(a)    zero
(b)    more than the number of poles in stator
(c)    less than number of poles in stator
(d)    equal to number of poles in stator
Ans: d

38.    DOL starting of induction motors is usually restricted to
(a)     low horsepower motors
(b)     variable speed motors
(c)    high horsepower motors
(d)    high speed motors
Ans: a

39.    The speed of a squirrel-cage induction motor can be controlled by all of the following except
(a)    changing supply frequency
(b)    changing number of poles
(c)    changing winding resistance
(d)    reducing supply voltage
Ans: c

40.    The 'crawling" in an induction motor is caused by
(a)     high loads
(6)     low voltage supply
(c)    improper design of machine
(d)    harmonics developed in the motor
Ans: d

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