Question is ⇒ Which of the following resistances can be measured by conducting insulation resistance test on a synchronous motor?, Options are ⇒ (A) Phase to phase winding resistance, (B) Stator winding to earthed frame, (C) Rotor winding to earthed shaft, (D) All of the above, (E) , Leave your comments or Download question paper.

Question is ⇒ Which of the following resistances can be measured by conducting insulation resistance test on a synchronous motor?, Options are ⇒ (A) Phase to phase winding resistance, (B) Stator winding to earthed frame, (C) Rotor winding to earthed shaft, (D) All of the above, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	Which of the following resistances can be measured by conducting insulation resistance test on a synchronous motor?
A.	Phase to phase winding resistance [Wrong Answer]
B.	Stator winding to earthed frame [Wrong Answer]
C.	Rotor winding to earthed shaft [Wrong Answer]
D.	All of the above [Correct Answer]
View Answer 6 -3 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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⇒ 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

⇒ In a synchronous motor, the magnitude of stator back e.m.f. Eb depends on
load on the motor
d.c. excitation only
both the speed and rotor flux
none of the above

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

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

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

⇒ 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

⇒ Exciters of synchronous machines are
d.c. shunt machines
d.c. series machines
d.c. compound machines
any of the above

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

⇒ 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

⇒ 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
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⇒ Slip-rings in a synchronous motor carry
direct current
alternating current
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all of the above

⇒ 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

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

⇒ 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

⇒ To limit the operating temperature an electrical machine should have proper
voltage rating
current rating
power factor
speed

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

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

⇒ If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will
stop
run as induction motor
function as static condenser
burn with dense smoke

⇒ 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 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

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

⇒ 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

⇒ 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

⇒ 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
normal load with zero excitation

⇒ A synchronous motor can be made selfstarting by providing
damper winding on rotor poles
damper winding on stator
damper winding on stator as well as rotor poles
none 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
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⇒ The angle between the rotor poles and stator poles, in a synchronous motor, is known as
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torque angle
synchronizing angle
angle of retardation

⇒ 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 operating speed of a synchtunous motor can be changed to new fixed value by
changing the load
changing the supply voltage
changing frequency
using brakes

⇒ 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
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1500 r.p.m.
750 r.p.m.
none of the above