A. the motor is said to be fully loaded
B. the torque generated is maximum
C. the excitation is said to be zero per cent
D. the excitation is said to be hundred per cent
Related Mcqs:
- A synchronous motor installed at the receiving end substation operates with such an excitation that it takes power at lagging power factor. Now if the applied voltage of the synchronous motor goes down, the power factor of the synchronous motor will___________?
A. remain same
B. go down
C. improve
D. none of the above - As the load is applied to a synchronous motor, the motor takes more armature current because
A. the increased load has to take more current
B. the rotor by shifting its phase backward causes motor to take more current
C. the back e.m.f. decreases causing an increase in motor current
D. the rotor strengthens the rotating field casuing more motor current - The net armature voltage of a synchronous motor is equal to the_______________?
A. vector sum of Eb and V
B. arithmetic sum of Eb and V
C. arithmetic difference of Eb and V
D. vector difference of Eh and V - When V is the applied voltage, then the breakdown torque of a synchronous motor varies as_________?
A. V
B. V312
C. V2
D. 1/V - When the voltage applied to a synchronous motor is increased, which of the following will reduce?
A. Stator flux
B. Pull in torque
C. Both A. and (b)
D. None of the above - 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 - 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 - The minimum armature current of the synchronous motor corresponds to operation at______________?
A. zero power factor leading
B. unity power factor
C. 0.707 power factor lagging
D. 0.707 power factor leading - If excitation of a synchronous motor running with a constant load is decreased from its normal value, ignoring effects of armature reaction, it leads to____________?
A. increase in both armature current and power factor angle
B. increase in back e.m.f. but decrease in armature current
C. increase in both armature current and power factor which is lagging
D. increase in torque angle but decrease in back e.m.f. - A synchronous motor is running with normal excitation. When the load is increased, the armature current drawn by it increases because
A. speed of the motor is reduced
B. power factor is decreased
C. Eb (back e.m.f.) becomes less than V (applied voltage)
D. Er (net resultant voltage) in armature is increased
E. none of the above
