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_____________?
(A) zero degree
(B) two degrees
(C) five degrees
(D) ten degrees
An important advantage of a synchronous motor over wound round induction motor is that
(A) its power factor may be varied at will
(B) its speed is independent of supply frequency
(C) its speed may be controlled more easily
(D) none of the above
The angle between the rotating stator flux and rotor poles is called _________ angle.
(A) synchronizing
(B) obtuse
(C) torque
(D) power factor
Slip-rings in a synchronous motor carry____________?
(A) direct current
(B) alternating current
(C) no current
(D) all of the above
A synchronous motor working at leading power factor can be used as____________?
(A) voltage booster
(B) phase advancer
(C) noise generator
(D) mechanical synchronizer
A synchronous motor connected to infinite bus-bars has at constant full load, 100% excitation and unity power factor. On changing the excitation only, the armature current will have_____________?
(A) no change of power factor
(B) lagging power factor with over-excitation
(C) leading power factor with under-excitation
(D) leading power factor with over-excitation
A synchronous motor develops maximum power when load angle is____________?
(A) 45°
(B) 60°
(C) 90°
(D) 120°
The armature current of the synchronous motor
(A) has large values for low excitation i niy
(B) has large values for high excitation only
(C) has large values for low and high excitation
(D) any of the above
The duration of sudden snort-circuit test on a synchronous motor is usually about_____________?
(A) one hour
(B) one minute
(C) one second
(D) none of the above
The maximum value of torque that a synchronous motor can develop without losing its synchronism, is known as_____________?
(A) slip torque
(B) pull-out torque
(C) breaking torque
(D) synchronising torque