Which of the following methods is used to start a synchronous motor ?
Resistance starter in the armature circuit
Star-delta starter
Damper winding
Damper winding in conjunction with star-delta starter
Damper winding in conjunction with star-delta starter
The angle between the rotating stator flux and rotor poles is called _____ angle.
obtuse
synchronizing
torque
power factor
torque
Slip-rings in a synchronous motor carry
direct current
all of the above
no current
alternating current
direct current
The armature current of the synchronous motor has higher values for
both and
low excitation only
high excitation only
none of the above
both and
In which of the following motors the stator and rotor magnetic field rotate at the same speed ?
Reluctance motor
Synchronous motor
Universal motor
Induction motor
Synchronous motor
Synchronous motors are
not-self starting
self-starting
essentially self-starting
none of the above
not-self starting
The efficiency of a properly designed synchronous motor will usually fall in range
99 to 99.5%
75 to 80%
60 to 70%
85 to 95%
85 to 95%
The mechanical displacement of the rotor with respect to the stator in polyphase multipolar synchronous motors running at full load is of the order of
zero degree
two degrees
five degrees
ten degrees
five degrees
While starting a synchronous motor by induction motor action field winding is usually
short-circuited by low resistance
none of the above
kept open-circuited
connected to D.C. supply
short-circuited by low resistance
Power factor of a synchronous motor is unity when
the armature current is minimum
the armature current is zero
the armature current is maximum
none of the above
the armature current is minimum
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