120 TOP Synchronous Motors Multiple choice Questions and Answers pdf

71.    When a 3-phase synchronous generator is supplying a zero power factor lagging load, the armature field affects the main field in the following way
(a)    augments it directly
(b)    directly opposes it
(c)    cross-magnetises it
(d)    none of the above
Ans: b

72.    Stability of a synchronous machine
(a)    decreases with increase in its excitation
(b)    increases with increase in its excitation
(c)    remains unaffected with increase in excitation
(d)    any of the above
Ans: b

73.    The power factor of a synchronous motor is better than that of induction motor because
(a)    stator supply is relieved of responsibility of producing magnetic field
(b)    mechanical load on the motor can be adjusted
(c)    synchronous motor runs at synchronous speed
(d)    synchronous motor has large air gap
Ans: a

74.    If in a synchronous motor, driving a given mechanical load and drawing current at a leading power factor from constant voltage supply its field excitation is increased, its power factor
(a)     will become more
(b)     will become less
(c)    will remain unchanged
(d)    none of the above.
Ans: b

75.    A synchronous motor is running with normal excitation. When the load is increased, the armature current drawn by it increases because
(a)    speed of the motor is reduced
(b)    power factor is decreased
(c)    Eb (back e.m.f.) becomes less than V (applied voltage)
(d)    Er (net resultant voltage) in armature is increased
(e)    none of the above
Ans: d

76.    If one-phase of a 3-phase synchronous motor is short-circuited, motor
(a)    will refuse to start
(b)    will overheat in spots
(c)    will not come upto speed
(d)     will fail to pull into step
Ans: a

77.    If the field circuit of an unloaded salientpole synchronous motor gets suddenly open-circuited, then
(a)    it runs at a slower speed
(b)    the motor stops
(c)    it continues to run at the same speed
(d)    it runs at a very high speed
Ans: b

78.    In which of the following motors the stator and rotor fields rotate simultaneously ?
(a)    D.C. motor
(b)    Reluctance motor
(c)    Universal motor
(d)    Synchronous motor
(e)    Induction motor
Ans: d

79.    The speed of a synchronous motor
(a)    increases as the load increases
(b)    decreases as the load decreases
(c)    always remains constant
(d)    none of the above
 Ans: c

80.    A rotory converter can also be run as a
(a)     d.c. shunt motor
(b)     d.c. series motor
(c)    d.c. compound motor
(d)    induction motor
(e)    synchronous motor
Ans: e

Read More Questions:
Synchronous Motors MCQs Part1
Synchronous Motors MCQs Part2
Synchronous Motors MCQs Part3
Synchronous Motors MCQs Part4
Synchronous Motors MCQs Part5
Synchronous Motors MCQs Part6
Synchronous Motors MCQs Part7
Synchronous Motors MCQs Part8
Synchronous Motors MCQs Part9
Synchronous Motors MCQs Part10
Synchronous Motors MCQs Part11
Synchronous Motors MCQs Part12