Question is ⇒ A synchronous motor can develop synchronous torque, Options are ⇒ (A) when under loaded, (B) while over-excited, (C) only at synchronous speed, (D) below or above synchronous speed, (E) , Leave your comments or Download question paper.

Question is ⇒ A synchronous motor can develop synchronous torque, Options are ⇒ (A) when under loaded, (B) while over-excited, (C) only at synchronous speed, (D) below or above synchronous speed, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	A synchronous motor can develop synchronous torque
A.	when under loaded [Wrong Answer]
B.	while over-excited [Wrong Answer]
C.	only at synchronous speed [Correct Answer]
D.	below or above synchronous speed [Wrong Answer]
View Answer 9 -2 Explanation:- Answer : C Discuss it below : !! OOPS Login [Click here] is required to post your answer/result Help other students, write article, leave your comments

Previous question Next question

Also Read Similar Questions Below :

⇒ 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

⇒ In a synchronous motor, the breakdown torque is
directly proportional to applied voltage
directly proportional to the square of the applied voltage
inversely proportional to applied voltage
none of the above

⇒ 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 minimum armature current of the synchronous motor corresponds to operation at
zero power factor leading
unity power factor
0.707 power factor lagging
0.707 power factor leading

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

⇒ Synchronous motor always runs at
the synchronous speed
less than synchronous speed
more than synchronous speed
none of the above

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

⇒ 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 pony motor is basically a
small induction motor
D.C. series motor
D.C. shunt motor
double winding A.C./D.C. motor

⇒ Under which of the following conditions hunting of synchronous motor is likely to occur ?
Periodic variation of load
Over-excitation
Over-loading for long periods
Small and constant load

⇒ 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.

⇒ 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

⇒ Synchronous motors are generally not self-starting because
the direction of rotation is not fixed
the direction of instantaneous torque reverses after half cycle
startes cannot be used on these machines
starting winding is not provided on the machines

⇒ The maximum torque which a synchronous motor will develop at rest for any angular position of the rotor, at rated stator supply voltage and frequency, is known as
locked-rotor torque
synchronous torque
pull up torque
reluctance torque

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

⇒ 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

⇒ In a synchronous motor, the armature current has large values for
high excitation only
low excitation only
both high and low excitation
none of the above

⇒ 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

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

⇒ When the field of a synchronous motor is under-excited, the power factor will be
leading
lagging
unity
zero

⇒ Armature of a synchronous machine is kept fixed because
of reducing number of slip rings on the rotor
armature is associated with large power as compared to the field circuits
of difficulty of providing high voltage insulation on rotor
all of the above reasons

⇒ 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 a synchronous motor running with fixed excitation, when the load is increased three times, its torque angle becomes approximately
one-third
twice
thrice
six times

⇒ In a synchronous motor, the maximum power developed depends on all of the following except
rotor excitation
maximum value of coupling angle
direction of rotation
supply voltage

⇒ Change of D.C. excitation of a synchronous motor changes
applied voltage of the motor
motor speed
power factor of power drawn by the motor
any of the above

⇒ A synchronous motor can develop synchronous torque
when under loaded
while over-excited
only at synchronous speed
below or above synchronous speed

⇒ 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
five degrees
ten degrees

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

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