Question is ⇒ An important advantage of a synchronous motor over wound round induction motor is that, Options are ⇒ (A) its power factor may be varied at will, (B) its speed is independent of supply frequency, (C) its speed may be controlled more easily, (D) none of the above, (E) , Leave your comments or Download question paper.

Question is ⇒ An important advantage of a synchronous motor over wound round induction motor is that, Options are ⇒ (A) its power factor may be varied at will, (B) its speed is independent of supply frequency, (C) its speed may be controlled more easily, (D) none of the above, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	An important advantage of a synchronous motor over wound round induction motor is that
A.	its power factor may be varied at will [Correct Answer]
B.	its speed is independent of supply frequency [Wrong Answer]
C.	its speed may be controlled more easily [Wrong Answer]
D.	none of the above [Wrong Answer]
View Answer 4 -4 Explanation:- Answer : A 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 efficiency of a properly designed synchronous motor will usually fall in range
60 to 70%
75 to 80%
85 to 95%
99 to 99.5%

⇒ The speed of a synchronous motor
increases as the load increases
decreases as the load decreases
always remains constant
none of the above

⇒ Slip-rings in a synchronous motor carry
direct current
alternating current
no current
all of the above

⇒ Synchronsizing power of a synchronous machine is
direcly proportional to the synchronous reactance
inversely proportional to the synchronous reactance
equal to the synchronous reactance
none of the above

⇒ The size of a synchronous motor decreases with the increase in
flux density
horse power rating
speed
all of the above

⇒ A synchronous motor is running with normal excitation. When the load is increased, the armature current drawn by it increases because
speed of the motor is reduced
power factor is decreased
Eb (back e.m.f.) becomes less than V (applied voltage)
Er (net resultant voltage) in armature is increased

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

⇒ The speed regulation of a synchronous motor is always
0.01
0.005
positive
zero

⇒ Higher the applied ____voltage will be the stator flux and____ will be the pullin torque
lower, lower
lower, greater
greater, lower
greater, greater

⇒ 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

⇒ Which of the following motors is nonself starting ?
D.C. series motor
synchronous motor
Squirrel cage induction motor
Wound round induction motor

⇒ In a synchronous motor, V-curves represent relation between
armature current and field current
power factor and speed
field current and speed
field current and 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°)

⇒ The rotor copper losses, in a synchronous motor, are met by
d.c. source
armature input
motor input
supply lines

⇒ The maximum value of torque that a synchronous motor can develop without losing its synchronism is known as
slip torque
pull-out torque
breaking torque
synchronising torque

⇒ VVhen the rotor speed, in a synchronous machine, becomes more than the synchronous speed during hunting, the damper bars develop
inductor motor torque
induction generator torque
synchronous motor torque
d.c. motor toque

⇒ A synchronous motor develops maximum power when load angle is
45°
60°
90°
120°

⇒ Hunting in a synchronous motor cannot be due to
windage friction
variable load
variable frequency
variable supply voltage

⇒ A synchronous motor can be used as a synchronous capacitor when it is
under-loaded
over-loaded
under-excited
over-excited

⇒ A synchronous motor installed at the receiving end substation operates with such an excitation that it takes power at lagging power factor. Now if the applied voltage of the synchronous motor goes down, the power factor of the synchronous motor will
remain same
go down
improve
none of the above

⇒ In which of the following motors the stator and rotor magnetic field rotate at the same speed ?
Universal motor
Synchronous motor
Induction motor
Reluctance motor

⇒ The effect of increasing the load on a synchronous motor running with normal excitation is to
decrease both arrnature current and power factor
decrease armature current but increase power factor
increase armature current but decrease power factor
increase both its armature current and power factor

⇒ A synchronous motor which works on a leading power factor and does not drive a mechanical load is called as
static condenser
condenser
synchronous condenser
none of the above

⇒ 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

⇒ 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

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

⇒ When V is the applied voltage, then the breakdown torque of a synchronous motor varies as
V
V^3/2
V²
1/V

⇒ While starting a synchronous motor by induction motor action, field winding is usually
connected to D.C. supply
short-circuited by low resistance
kept open-circuited
none of the above

⇒ The working of a synchronous motor is similar to
gear train arrangement
transmission of mechancial power by shaft
distribution transformer
turbine

⇒ If excitation of a synchronous motor running with a constant load is decreased from its normal value, ignoring effects of armature reaction, it leads to
increase in both armature current and power factor angle
increase in back e.m.f. but decrease in armature current
increase in both armature current and power factor which is lagging
increase in torque angle but decrease in back e.m.f.