300 Important Alternator MCQ Question and Answer | PDF Free Download
1.Synchronizing current in alternator means
- AThe total current supplied to the load by the alternators operating in parallel
- BThe current supplied by the synchronous generator
- CThe current circulation in the local circuit of two alternators operating in parallel which brings the alternator in synchronism once they are out of it
- DNone of the above
2.If the voltage of one of the two machines operating in parallel suddenly falls
- ABoth the machines will stop
- BThe machine whose voltage has suddenly decreased will stop
- CThe synchronous torque will come into operation to restore synchronism
- DNone of the above
3.Synchronizing torque will come into operating whenever
- AThere is a difference in the magnitude of voltages
- BThere is a phase difference in the voltages
- CThere is a frequency difference between the two voltages and Excitation of one of the alternator is changed
- DIn all of the above cases
4.The electrical stiffness of a synchronous generator connected to a very large grid can be increased by
- AIncreasing the excitation or power angle of the machine
- BReducing the excitation or the synchronous reactance of the machine
- CIncreasing the synchronous reactance of the machine
- DOperating the generator at a much lower MW level compared to the steady state limit.
5.Two alternators A and B are sharing an inductive load equally. If the excitation of alternator A is increased
- AAlternator B will deliver more current and alternator A will deliver less current
- BAlternator B will deliver less current and alternator A will deliver more current
- CBoth will continue to share load equally
- DBoth will deliver more current
6.Two similar synchronous generators are working in parallel to supply a common load demand with identical excitations and steam supply to their prime movers. Now, if the steam supply to the prime mover of one of the generators is increased compared to the other, with field excitation kept unchanged, then
- AIts active power component will remain same but the reactive power contribution will increase.
- BIts active power will decrease while the reactive power will increase
- CBoth active and reactive components of power will increase
- DIts active power contribution will increase but reactive power contributions of both will remain unchanged.
7.When two alternators are operating in parallel, if the power input to one of the alternators is cut off, the alternator will
- AContinue to run as a synchronous motor rotating in the same direction
- BContinue to run as a synchronous motor rotating in opposite direction
- CStop running
- DGet damaged due to burning of stator and rotor windings
8.An infinite bus bar has
- AConstant voltage
- BConstant frequency
- CInfinite voltage
- DBoth (a) and (b)
9.If the excitation of an alternator connected to an infinite bus bar is changed, keeping the power input to kits prime mover unchanged its ____will change.
- APower factor
- BKVA output
- CKVAR output
- DAll the above
10.A stationary alternator should not be connected to the live bus bar because
- AIt is likely to operate as a synchronous motor
- BIt will get short circuited
- CIt will reduce bus bar voltage
- DAll of the above
11.A 3-phase synchronous generator with constant power input is supplying electrical power to an infinite bus at a lagging power factor. If its excitation is reduced
- ABoth power factor and power angle will increase
- BBoth power factor and power angle will decrease
- CPower factor will improve but power angle will decrease
- DPower angle will increase but power factor will decrease
12.If the prime mover of an alternator supplying load to an infinite bus is suddenly shutdown, then it will
- AStop
- BContinue to run as an alternator
- CContinue to run as a synchronous motor in the reverse direction
- DContinue to run as a synchronous motor in the same direction