Question is ⇒ If one-phase of a 3-phase synchronous motor is short-circuited, motor, Options are ⇒ (A) will refuse to start, (B) will overheat in spots, (C) will not come upto speed, (D) will fail to pull into step, (E) , Leave your comments or Download question paper.

Question is ⇒ If one-phase of a 3-phase synchronous motor is short-circuited, motor, Options are ⇒ (A) will refuse to start, (B) will overheat in spots, (C) will not come upto speed, (D) will fail to pull into step, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	If one-phase of a 3-phase synchronous motor is short-circuited, motor
A.	will refuse to start [Correct Answer]
B.	will overheat in spots [Wrong Answer]
C.	will not come upto speed [Wrong Answer]
D.	will fail to pull into step [Wrong Answer]
View Answer 16 -6 Explanation:- Answer : A Discuss it below : Movies Trailer Said on 2020-09-02 03:54:15 Ssc je me ans...B Movies Trailer Said on 2020-09-02 03:53:33 Ssc je made easy me ans .....A Movies Trailer Said on 2020-06-11 04:16:24 Jbg me ans ...D hai...(que..291) LiFE CHAnGer Said on 2020-04-23 19:07:12 Jbg !! 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 :

⇒ The speed of the synchronous motor
increases with increase in load
decreases as load increases
varies with power factor
always remains constant

⇒ 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

⇒ 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

⇒ 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

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

⇒ 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

⇒ 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

⇒ 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

⇒ Higher the applied ____voltage will be the stator flux and____ will be the pullin torque
lower, lower
lower, greater
greater, lower
greater, greater

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

⇒ A synchronous motor installed at the receiving end substation operates with such an excitation that it takes power at lagging power factor. Now if the applied voltage of the synchronous motor goes down, the power factor of the synchronous motor will
remain same
go down
improve
none of the above

⇒ The speed of a synchronous motor
increases as the load increases
decreases as the load decreases
always remains constant
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

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

⇒ Mostly, synchronous motors are of
alternator type machines
induction type machines
salient pole type machines
smooth cylindrical type machines

⇒ A synchronous machine with low value of short-circuit ratio has
lower stability limit
high stability limit
good speed regulation
good voltage regulation

⇒ By which of the following methods the constant speed of a synchronous motor can be changed to new fixed value ?
By changing the supply frequency
By interchanging any two phases
By changing the applied voltage
By changing the load.

⇒ VVhen the voltage applied to a synchronous motor is increased, which of the following will reduce ?
Stator flux
Pull in torque
Both (a) and (b)
None of the above

⇒ The induced e.m.f. in a synchronous motor working on leading power factor will be
more than the supply voltage
less than the supply voltage
equal to the supply voltage

⇒ 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

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

⇒ In case one phase of a three-phase synchronous motor is short-circuited the motor will
not start
run at 2/3 of synchronous speed
run with excessive vibrations
take less than the rated load

⇒ 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

⇒ 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

⇒ 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

⇒ 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

⇒ 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%

⇒ 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

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

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