Synchronous Motor Questions and Answers
MCQ type Questions And answers of synchronous motor is provided in this post which is more helpful in preparation of gate examination and also for competitive examination.
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| Synchronous Motor Questions and Answers |
Question And Answer (Synchronous Motor)
Q.1
Hunting in a synchronous motor takes
place
place
(a)when supply voltage fluctuates
(b)when load varies
(c)when power factor is unity
(d)motor is under loaded
Ans.
(b)when load varies
Q.2
When load on an over-excited or under-
excited synchronous motor is increased,
rate of change of its armature current
as compared with that of power factor
is
excited synchronous motor is increased,
rate of change of its armature current
as compared with that of power factor
is
(a)more
(b)less
(c)equal
(d)twice
Ans.
(b)less
Q.3
The rotor copper losses, in a synchronous motor are met by
The rotor copper losses, in a synchronous motor are met by
(a) D.C. source
(b)armature input
(c)motor input
(d)supply lines
Ans.
(a) D.C. source
Q.4
The maximum power developed in a
synchronous motor occurs at a coupling
angle of
synchronous motor occurs at a coupling
angle of
(a)30°
(b)60°
(c)90°
(d)180°
Ans.
(c)90°
Q.5
When the stator windings are connected in such a fashion that the number of poles are made half, the speed of the rotor of a synchronous motor
(a)remains same as the original value
(b)decreases to half the original value
(c)tends to becomes zero
(d)increases to two times the original
value
Ans.
(d)increases to two times the original
value
value
Q.6
In which of the following motors the
stator and rotor magnetic field rotate
at the same speed?
stator and rotor magnetic field rotate
at the same speed?
(a)Universal motor
(b)Synchronous motor
(c)Induction motor
(d)Reluctance motor
Ans.
(b)Synchronous motor
Q.7
Synchronizing power of a synchronous
machine is
machine is
(a)directly proportional to the synchronous reactance
(b)inversely proportional to the synchronous reactance
(c)equal to the synchronous reactance
(d)none of the above
Ans.
(b)inversely proportional to the synchronous reactance
Q.8
Synchronous motors are
(a)not-self starting
(b)self-starting
(c)essentially self-starting
(d)none of the above
Ans.
(a)not-self starting
Q.9
The standard full-load power factor ratings for synchronous motors are
(a)zero or 0.8 leading
(b)unity or 0.8 lagging
(c)unity or 0.8 leading
(d)unity or zero
Ans.
(c)unity or 0.8 leading
Q.10
A synchronous motor running with normal excitation adjusts to load increases essentially by increase in
(a)back e.m.f.
(b)armature current
(c)power factor
(d)torque angle
Ans.
(b)armature current
Q.11
A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because
(a)synchronous motor has no slip
(b) stator supply is not required to produce magnetic field
(c)mechanical load on the rotor remains constant
(d)synchronous motor has large air gap
Ans.
(b) stator supply is not required to produce magnetic field
Q.12
A synchronous motor working at leading
power factor can be used as
power factor can be used as
(a)voltage booster
(b)phase advancer
(c)noise generator
(d)mechanical synchronizer
Ans.
(b)phase advancer
Q.13
Slip rings are usually made of
(a)carbon or graphite
(b) brass or steel
(c)silver or gold
(d)copper or aluminum
Ans.
(b) brass or steel
Q.14
An over-excited synchronous motor is used for
(a)fluctuating loads
(b)variable speed loads
(c)low torque loads
(d)power factor corrections
Ans.
(d)power factor corrections
Q.15
When the voltage applied to a synchronous motor is increased, which of the following will reduce?
(a)Stator flux
(b)Pull in torque
(c)Both(a)and(b)
(d)None of the above
Ans.
