The back e.m.f. of a synchronous motor depends on
load angle
load
speed
all of the above
load angle
A synchronous motor can operate at
unity power factor only
lagging leading and unity power factors
lagging power factor only
leading power factor only
lagging leading and unity power factors
A synchronous motor can be used as a synchronous capacitor when it is
over-excited
under-loaded
over-loaded
under-excited
over-excited
A synchronous motor is running on a load with normal excitation. Now if the load on the motor is increased
power factor will increase but armature current will decrease
power factor as well as armature current will increase
power factor as well as armature current will decrease
power factor will decrease and armature current will increase
power factor will decrease and armature current will increase
A pony motor is basically a
D.C. series motor
D.C. shunt motor
small induction motor
double winding A.C./D.C. motor
small induction motor
A synchronous motor can develop synchronous torque
only at synchronous speed
below or above synchronous speed
while over-excited
when under loaded
only at synchronous speed
A synchronous motor can be started by
any of the above
D.C. compound motor
pony motor
providing damper winding
any of the above
Synchronous motors are generally not self-starting because
starting winding is not provided on the machines
the direction of instantaneous torque reverses after half cycle
the direction of rotation is not fixed
starter cannot be used on these machines
the direction of instantaneous torque reverses after half cycle
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
not start
A three-phase synchronous motor will have
three slip-rings
one slip-ring
no slip-rings
two slip-rings
two slip-rings
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