If the field winding of an unloaded salient pole synchronous motor is open circuited the motor will
burn with dense smoke
function as static condenser
run as induction motor
stop
stop
The induced e.m.f. in a synchronous motor working on leading power factor will be
less than the supply voltage
equal to the supply voltage
more than the supply voltage
None
more than the supply voltage
A 3-phase synchronous motor is running clockwise. If the direction of its field current is reversed
the motor continue to run in the same direction
the motor will run in the reverse direction
the winding of the motor will burn
the motor will stop
the motor continue to run in the same direction
The net armature voltage of a synchronous motor is equal to the
vector difference of Eh and V
arithmetic sum of Eb and V
vector sum of Eb and V
arithmetic difference of Eb and V
vector difference of Eh and V
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
none of the above
1500 r.p.m.
3000 r.p.m.
750 r.p.m.
1500 r.p.m.
In a synchronous motor the magnitude of stator back e.m.f. Eb depends on
d.c. excitation only
load on the motor
both the speed and rotor flux
none of the above
d.c. excitation only
The magnitude of field flux in a 3-phase synchronous motor
varies with power factor
varies with the load
varies with speed
remains constant at all loads
remains constant at all loads
The effect of increasing the load on a synchronous motor running with normal excitation is to
decrease both armature 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
increase armature current but decrease power factor
The torque angle in a synchronous motor is the angle between
the rotating stator flux and rotor poles
none of the above
magnetising current and back e.m.f.
the supply voltage and the back e.m.f.
the rotating stator flux and rotor poles
The ratio of starting torque to running torque in a synchronous motor is
zero
two
one
infinity
zero
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