Question is ⇒ VVhen the voltage applied to a synchronous motor is increased, which of the following will reduce ?, Options are ⇒ (A) Stator flux, (B) Pull in torque, (C) Both (a) and (b), (D) None of the above, (E) , Leave your comments or Download question paper.

Question is ⇒ VVhen the voltage applied to a synchronous motor is increased, which of the following will reduce ?, Options are ⇒ (A) Stator flux, (B) Pull in torque, (C) Both (a) and (b), (D) None of the above, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	VVhen the voltage applied to a synchronous motor is increased, which of the following will reduce ?
A.	Stator flux [Wrong Answer]
B.	Pull in torque [Wrong Answer]
C.	Both (a) and (b) [Wrong Answer]
D.	None of the above [Correct Answer]
View Answer 7 -4 Explanation:- Answer : D Discuss it below : !! OOPS Login [Click here] is required to post your answer/result Help other students, write article, leave your comments

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⇒ The net armature voltage of a synchronous motor is equal to the
vector sum of Eb and V
arithmetic sum of Eb and V
arithmetic difference of Eb and V
vector difference of Eb and V

⇒ The power developed by a synchronous motor will be maximum when the load angle is
zero
45°
90°
120°

⇒ Stability of a synchronous machine
decreases with increase in its excitation
increases with increase in its excitation
remains unaffected with increase in excitation
any of the above

⇒ The shaft of synchronous motor is made of
mild steel
chrome steel
alnico
stainless steel

⇒ In a synchronous motor, the damping winding is generally used to
prevent hunting and provide the starting torque
reduce the eddy currents
provide starting torque only
reduce noise level

⇒ The angle between the rotating stator flux and rotor poles is called____ angle
torque
obtuse
synchronizing
power factor

⇒ The maximum power developed in a synchronous motor will depend on
the rotor excitation only
the supply voltage only
the rotor excitation and supply voltage both
the rotor excitation, supply voltage and maximum value of coupling angle (90°)

⇒ An important advantage of a synchronous motor over wound round induction motor is that
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its speed is independent of supply frequency
its speed may be controlled more easily
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⇒ The mechanical displacement of the rotor with respect to the stator, in polyphase multipolar synchronous motor running at full load, is of the order of
zero degree
two degrees
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⇒ In a synchronous motor it the back e.m.f. generated in the armature at noload is approximately equal to the applied voltage, then
the motor is said to be fully loaded
the torque generated is maximum
the excitation is said to be zero per cent
the excitation is said to be hundred per cent

⇒ Which of the following losses, in a synchronous motor, does not vary with load ?
Windage loss
Copper losses
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None of the above

⇒ A synchronous machine with large air gap has
a higher value of stability limit
a small value of inherent regulation
a higher synchronizing power which makes the Machine less sensitive to load variations
all of the above

⇒ At no-load, the armature current in a synchronous motor
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lags the applied voltage by 900
leads the applied voltage by 90°
is in phase with the applied voltage

⇒ A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because
synchronous motor has no slip
stator supply is not required to produce magnetic field
mechanical load on the rotor remains constant
synchronous motor has large airgap

⇒ An over-excited synchronous motor takes
leading current
lagging current
both (a) and (b)
none of the above

⇒ A synchronous motor develops maximum power when load angle is
45°
60°
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⇒ While starting a salient pole synchronous motor by induction motor action and connecting field discharge resistance across field, starting and accelerting torque is produced by
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induction motor torque in damper winding
eddy current and hysteresis' torque in pole faces
reluctance motor torque due to saliency of the rotor

⇒ The speed regulation of a synchronous motor is always
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0.005
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⇒ A synchronous motor which works on a leading power factor and does not drive a mechanical load is called as
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synchronous condenser
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⇒ For power factor correction, synchronous motors operate at
no-load and greatly over-excited fields
no-load and under-excited fields
normal load with minimum excitation
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⇒ When V is the supply voltage and R is the rotor resistance per phase, the mechanical power developed by the synchronous motor will be proportional to

V²

R²

⇒ A synchronous motor running with normal excitation adjusts to load increases essentially by increase in
back e.m.f.
armature current
power factor
torque angle

⇒ The efficiency of a properly designed synchronous motor will usually fall in range
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75 to 80%
85 to 95%
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⇒ VVhen the voltage applied to a synchronous motor is increased, which of the following will reduce ?
Stator flux
Pull in torque
Both (a) and (b)
None of the above

⇒ Which of the following methods is used to start a synchronous motor ?
Damper winding
Star-delta starter
Damper winding in conjunction with star-delta starter
Resistance starter in the armature circuit

⇒ Slip rings are usually made of
carbon or graphite
brass or steel
silver or gold
copper or aluminium

⇒ The armature current of the synchronous motor
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has large values for high excitation only
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⇒ Higher the applied ____voltage will be the stator flux and____ will be the pullin torque
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⇒ The minimum armature current of the synchronous motor corresponds to operation at
zero power factor leading
unity power factor
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⇒ Exciters of synchronous machines are
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d.c. series machines
d.c. compound machines
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