Question is ⇒ In which of the following motors the stator and rotor magnetic field rotate at the same speed ?, Options are ⇒ (A) Universal motor, (B) Synchronous motor, (C) Induction motor, (D) Reluctance motor, (E) , Leave your comments or Download question paper.

Question is ⇒ In which of the following motors the stator and rotor magnetic field rotate at the same speed ?, Options are ⇒ (A) Universal motor, (B) Synchronous motor, (C) Induction motor, (D) Reluctance motor, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	In which of the following motors the stator and rotor magnetic field rotate at the same speed ?
A.	Universal motor [Wrong Answer]
B.	Synchronous motor [Correct Answer]
C.	Induction motor [Wrong Answer]
D.	Reluctance motor [Wrong Answer]
View Answer 5 -3 Explanation:- Answer : B 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 :

⇒ 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

⇒ If load (or torque) angle of a 4-pole synchronous motor is 6° electrical, its value in mechanical degrees is
2
3
4
6

⇒ If in a synchronous motor, driving mechanical load and drawing current at lagging power factor from constant voltage supply, its field excita.6.on is increased, then its power factor
become more
become less
remain constant
none of the above

⇒ In a synchronous motor, damper windings are provided on
stator frame
rotor shaft
pole faces
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

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

⇒ 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

⇒ Which of the following methods is used to start a synchronous motor ?
Damper winding
Star-delta starter
Damper winding in conjunction with star-delta starter
Resistance starter in the armature circuit

⇒ An over-excited synchronous motor is used for
fluctuating loads
variable speed loads
low torque loads
power factor corrections

⇒ 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

⇒ 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

⇒ The ratio of starting torque to running torque in a synchronous motor is
zero
one
two
infinity

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

⇒ The standard full-load power factor ratings for synchronous motors are
zero or 0.8 leading
unity or 0.8 lagging
unity or 0.8 leading
unity or zero

⇒ Slip-rings in a synchronous motor carry
direct current
alternating current
no current
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

⇒ 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 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

⇒ 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

⇒ 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

⇒ 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

⇒ 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

⇒ 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 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

⇒ 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

⇒ 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

⇒ In a synchronous machine in case the axis of field flux is in line with the armature flux, then
the machine is working as synchronous generator
the machine is working as synchronous motor
the machine will vibrate violently
none of the above

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

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

⇒ 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