Question is ⇒ A synchronous motor can operate at, Options are ⇒ (A) lagging power factor only, (B) leading power factor only, (C) unity power factor only, (D) lagging, leading and unity power factors, (E) , Leave your comments or Download question paper.

Question is ⇒ A synchronous motor can operate at, Options are ⇒ (A) lagging power factor only, (B) leading power factor only, (C) unity power factor only, (D) lagging, leading and unity power factors, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	A synchronous motor can operate at
A.	lagging power factor only [Wrong Answer]
B.	leading power factor only [Wrong Answer]
C.	unity power factor only [Wrong Answer]
D.	lagging, leading and unity power factors [Correct Answer]
View Answer 6 -6 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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Also Read Similar Questions Below :

⇒ Due to which of the following reasons a synchronous motor fails to pull into synchronism after applying D.C. field current ?
High field current
Low short circuit ratio
High core losses
Low field current

⇒ The oscillations in a synchronous motor can be damped out by
maintaining constant excitation
running the motor on leading power factors
providing damper bars in the rotor pole faces
oscillations cannot be damped

⇒ The magnitude of field flux in a 3-phase synchronous motor
remains constant at all loads
varies with speed
varies with the load
varies with power factor

⇒ The armature current of the synchronous motor
has large values for low excitation only
has large values for high excitation only
has large values for low and high excitation
any of the above

⇒ The power factor of a synchronous motor is better than that of induction motor because
stator supply is relieved of responsibility of producing magnetic field
mechanical load on the motor can be adjusted
synchronous motor runs at synchronous speed
synchronous motor has large air gap

⇒ 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

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

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

⇒ When load on an over-excited or underexcited synchronous motor is increased, rate of change of its armature current as compared with that of power factor is
more
less
equal
twice

⇒ 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

⇒ 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

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

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

⇒ 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
induction motor torque in field winding
induction motor torque in damper winding
eddy current and hysteresis' torque in pole faces
reluctance motor torque due to saliency of the rotor

⇒ Which of the following resistances can be measured by conducting insulation resistance test on a synchronous motor?
Phase to phase winding resistance
Stator winding to earthed frame
Rotor winding to earthed shaft
All of the above

⇒ If one-phase of a 3-phase synchronous motor is short-circuited, motor
will refuse to start
will overheat in spots
will not come upto speed
will fail to pull into step

⇒ Power factor of a synchronous motor is unity when
the armature current is maximum
the armature current is minimum
the armature current is zero
none of the above

⇒ 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

⇒ The maximum speed variation in a 3- phase synchronous motor is
10 per cent
6 per cent
4 per cent
2 per cent

⇒ When a 3-phase synchionous generator is supplying a zero power factor lagging load, the armature field affects the main field in the following way
augments it directly
directly opposes it
cross-magnetises it
none of the above

⇒ The construction of a synchronous motor resembles
a series motor
an induction motor
an alternator
a rotary converter

⇒ 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 3-phase synchronous motor is running clockwise. If the direction of its field current is reversed
the motor will stop
the motor continue to run in the same direction
the winding of the motor will burn
the motor will run in the reverse direction

⇒ The angle between the rotor poles and stator poles, in a synchronous motor, is known as
power factor angle
torque angle
synchronizing angle
angle of retardation

⇒ 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

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