Related Questions

If in a synchronous motor, driving mechanical load and drawing current at lagging power factor from constant voltage supply, its field excitation is increased, then its power factor
A become more
B become less
C remain constant
D none of the above
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
A synchronous motor is running on a load with normal excitation. Now if the load on the motor is increased
A power factor as well as armature current will decrease
B power factor as well as armature current will increase
C power factor will increase but armature current will decrease
D power factor will decrease and armature current will increase
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
A synchronous motor which works on a leading power factor and does not drive a mechanical load is called as
A static condenser
B condenser
C synchronous condenser
D none of the above
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
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.
The maximum constant load torque under which a synchronous motor will pull into synchronism at rated rotor supply voltage and frequency is known as
A pull-up torque
B pull-in torque
C pull-out torque
D none of the above
When load on an over-excited or under excited synchronous motor is increased, rate of change of its armature current as compared with that of power factor is
A more
B less
C equal
D twice
A synchronous motor running with normal excitation adjusts to load increases essentially by increase in
A back e.m.f.
B armature current
C power factor
D torque angle

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