Related Questions

In a synchronous motor it the back e.m.f. generated in the armature at noload is approximately equal to the applied voltage, then
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
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
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
In an actual transformer the iron loss remains practically constant from noload to fullload because
A value of transformation ratio remains constant
B permeability of transformer core remains constant
C core flux remains practically constant
D primary voltage remains constant
An over-excited synchronous motor takes
A leading current
B lagging current
C both (A) and (B)
D none of the above
One D.C. motor drives another D.C. motor. The second D.C. motor when excited and driven
A Runs as a generator
B Does not run as a generator
C Also runs as a motor comes to stop after sometime
D None of these
When the field of a synchronous motor is under-excited, the power factor will be
A leading
B lagging
C unity
D zero
A separately excited generator as compared to a self-excited generator
A Is amenable to better voltage control
B Is more stable
C Has exciting current independent of load current
D Has all above features
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
A synchronous motor can be used as a synchronous capacitor when it is
A under-loaded
B over-loaded
C under-excited
D over-excited

Next steps