Question is ⇒ 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, Options are ⇒ (A) induction motor torque in field winding, (B) induction motor torque in damper winding, (C) eddy current and hysteresis' torque in pole faces, (D) reluctance motor torque due to saliency of the rotor, (E) all of the above methods, Leave your comments or Download question paper.

Question is ⇒ 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, Options are ⇒ (A) induction motor torque in field winding, (B) induction motor torque in damper winding, (C) eddy current and hysteresis' torque in pole faces, (D) reluctance motor torque due to saliency of the rotor, (E) all of the above methods, Leave your comments or Download question paper. Previous question Next question


Q1.	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
A.	induction motor torque in field winding [Wrong Answer]
B.	induction motor torque in damper winding [Wrong Answer]
C.	eddy current and hysteresis' torque in pole faces [Wrong Answer]
D.	reluctance motor torque due to saliency of the rotor [Wrong Answer]
E.	all of the above methods [Correct Answer]
View Answer 6 -1 Explanation:- Answer : E 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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⇒ A synchronous motor is running on a load with normal excitation. Now if the load on the motor is increased
power factor as well as armature current will decrease
power factor as well as armature current will increase
power factor will increase but armature current will decrease
power factor will decrease and armature current will increase

⇒ 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

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

⇒ The synchronous motor is not inherently self-starting because
the force required to accelerate the rotor to the synchronous speed in an instant is absent
the starting device to accelerate the rotor to near synchronous speed is absent
a rotating magnetic field does not have enough poles
the rotating magnetic field is produced by only 50 Hz frequency currents

⇒ If the field circuit of an unloaded salientpole synchronous motor gets suddenly open-circuited, then
it runs at a slower speed
the motor stops
it continues to run at the same speed
it runs at a very high speed

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

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

⇒ 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

⇒ 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

⇒ A three-phase synchronous motor will have
no slip-rings
one slip-ring
two slip-rings
three slip-rings

⇒ In a 3-phase, 4-pole, 50 Hz synchronous motor, the frequency, pole number and load torque all are halved. The motor speed will be
3000 r.p.m.
1500 r.p.m.
750 r.p.m.
none of the above

⇒ If the synchronous motor, properly synchronised to the supply is running on no load and is having negligible loss then
the stator current will be zero
the stator current will be very small
the stator current will be very high
the back e.m.f. will be more than the supply voltage

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

⇒ A synchronous motor connected to infinite bus-bars has at constant full load, 100% excitation and unity power factor. On changing the excitation only, the armature current will have
no change of power factor
lagging power factor with over-excitation
leading power factor with underexcitiltion
leading power factor vvith over-excitation

⇒ The back e.m.f. in the stator of a synchronous motor depends on
number of poles
flux density
rotor speed
rotor excitation

⇒ In which of the following motors the stator and rotor fields rotate simultaneously ?
D.C. motor
Reluctance motor
Universal motor
Synchronous motor

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

⇒ 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

⇒ A synchronous motor can be started by
pony motor
D.C. compound motor
providing damper winding
any of the above

⇒ Which of the following losses is not dissipated by tile stator core surface in a synchronous motor ?
Eddy current losses in the conductors
Iron losses in the stator
Copper losses in the slot portion of the conductors
Windage losses

⇒ 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.

⇒ When the excitation of an unloaded salient pole synchronous motor suddenly gets disconnected
the motor stops
it runs as a reluctance motor at the same speed
it runs as a reluctance motor at a lower speed
none of the above

⇒ Which of the following motors will be used in electric clocks ?
D.C. shunt motor
D.C. series motor
A.C. induction motor
A.C. synchronous motor

⇒ The torque angle, in a synchronous motor, is the angle between
the supply voltage and the back e.m.f.
magnetising current and back e.m.f.
the rotating stator flux and rotor poles
none of the above

⇒ As the load is applied to a synchronous motor, the motor takes more armature current because
the increased load has to take more current
the rotor by shifting its phase backward causes motor to take more current
the back e.m.f. decreases causing ah increase in motor current
the rotor strengthens the rotating field casuing more motor current

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

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

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

⇒ The coupling angle or load angle of synchronous motor is defined as the angle between the
rotor and stator teeth
rotor and the stator poles of opposite polarity
rotor and the stator poles of the same polarity
none of the above