Question is ⇒ The back e.m.f. of a synchronous motor depends on, Options are ⇒ (A) speed, (B) load, (C) load angle, (D) all of the above, (E) , Leave your comments or Download question paper.

Question is ⇒ The back e.m.f. of a synchronous motor depends on, Options are ⇒ (A) speed, (B) load, (C) load angle, (D) all of the above, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	The back e.m.f. of a synchronous motor depends on
A.	speed [Wrong Answer]
B.	load [Wrong Answer]
C.	load angle [Correct Answer]
D.	all of the above [Wrong Answer]
View Answer 11 -17 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

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Also Read Similar Questions Below :

⇒ 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

⇒ The back e.m.f. of a synchronous motor depends on
speed
load
load angle
all of the above

⇒ The net armature voltage of a synchronous motor is equal to the
vector sum of Eb and V
arithmetic sum of Eb and V
arithmetic difference of Eb and V
vector difference of Eb and V

⇒ 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

⇒ Stability of a synchronous machine
decreases with increase in its excitation
increases with increase in its excitation
remains unaffected with increase in excitation
any of the above

⇒ 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 synchronous motor, the magnitude of stator back e.m.f. Eb depends on
d.c. excitation only
speed of the motor
load on the motor
both the speed and rotor flux

⇒ 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

⇒ 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

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

⇒ 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°)

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

⇒ 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

⇒ 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

⇒ When the stator windings are connected in such a fashion that the number of poles are made half, the speed of the rotor of a synchronous motor
remains same as the original value
decreases to half the original value
tends to becomes zero
increases to two times the original value

⇒ 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

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

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

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

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

⇒ Which of the following losses, in a synchronous motor, does not vary with load ?
Windage loss
Copper losses
Any of the above
None of the above

⇒ 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

⇒ 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
power factor
torque angle

⇒ 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

⇒ The maximum constant load torque under which a synchronous motor will pull into synchronism at rated rotor supply voltage and frequency is known as
pull-up torque
pull-in torque
pull-out torque
none of the above

⇒ 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

⇒ 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