Which of the following methods is used to start a synchronous motor?
(A) Damper winding
(B) Star-delta starter
(C) Damper winding in conjunction with star-delta starter
(D) Resistance starter in the armature circuit
In a synchronous motor running with fixed excitation, when the load is increased three times, its torque angle becomes approximately
(A) one-third
(B) twice
(C) thrice
(D) six times
(D) nine times
A synchronous machine with large air gap has______________?
(A) a higher value of stability limit
(B) a small value of inherent regulation
(C) a higher synchronizing power which makes the machine less sensitive to load variations
(D) all of the above
To limit the operating temperature an electrical machine should have proper____________?
(A) voltage rating
(B) current rating
(C) power factor
(D) speed
An over excited synchronous motor is used for____________?
(A) fluctuating loads
(B) variable speed loads
(C) low torque loads
(D) power factor corrections
Slip rings are usually made of__________?
(A) carbon or graphite
(B) brass or steel
(C) silver or gold
(D) copper or aluminium
A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because?
(A) synchronous motor has no slip
(B) stator supply is not required to produce magnetic field
(C) mechanical load on the rotor remains constant
(D) synchronous motor has large airgap
Synchronous motors are_____________?
(A) not-self starting
(B) self-starting
(C) essentially self-starting
(D) none of the above
In which of the following motors the stator and rotor fields rotate simultaneously?
(A) D.C. motor
(B) Reluctance motor
(C) Universal motor
(D) Synchronous motor
(D) Induction motor
If the field circuit of an unloaded salientpole synchronous motor gets suddenly open-circuited, then
(A) it runs at a slower speed
(B) the motor stops
(C) it continues to run at the same speed
(D) it runs at a very high speed