Synchronous Generator ( Alternator) MCQ Part -02

Synchronous generator ( alternator) MCQ Part -02

Results

HD Quiz powered by harmonic design

#1. If the excitation to an alternator connected to an infinite busbar is changed, keeping the power input to its prime-mover unchanged, then-

(a) PF will be change

(b) KVA output will be change

(d) all of the above

#2. An infinite busbar has –

(a) Constant voltage

(b) Constant frequency

(d) none of the above

#3. In a synchronous generator, the armature winding is generally placed on the:

a) Stator

b) Rotor

c) Poles

d) Shaft

#4. The rotor of a synchronous generator is supplied with:

a) AC supply

b) DC supply

c) Both AC and DC supply

d) Pulsating DC

#5. In an alternator, reactance e.m.f –

leads the current by 90°

lags behind current by 90°

is in phase with current

None of the above

#6. A salient pole rotor is best suited for:

a) High-speed applications (turbo-alternators)

b) Low-speed applications (hydro-alternators)

c) Both high and low-speed applications

d) Medium-speed applications

#7. The frequency of the generated voltage in an alternator is given by the formula:

a) f = PN / 120

b) f = 120 / PN

c) f = P / 120N

d) f = N / 120P

#8. Damper windings are used in synchronous generators to:

a) Increase the generated voltage

b) Reduce hunting

c) Excite the field

d) Reduce armature reaction

#9. A cylindrical rotor (non-salient pole) is used in:

a) Low-speed alternators

b) High-speed turbo-alternators

c) Hydro-alternators

d) Small-capacity alternators

#10. In an alternator, the armature reaction influences

a) the operating speed

b) the windage losses

c) generated voltage / phase

d) none of the above

#11. The frame of a synchronous generator is made of:

a) Cast iron or welded steel

b) Copper

c) Aluminum

d) Laminated steel

#12. The main function of the exciter in a synchronous generator is to:

a) Provide AC to the armature

b) Provide DC to the field winding

c) Cool the machine

d) Step up the output voltage

#13. The rotating part of a synchronous generator is the:

a) Stator

b) Armature

c) Field winding (on the rotor)

d) Frame

#14. Distributing the armature winding in several slots results in:

a) A smoother voltage waveform

b) Increased harmonics

c) Higher induced EMF per coil

d) Increased machine size

#15. The number of electrical degrees per slot in a 36-slot, 4-pole alternator is

a) 10

b) 20

c) 30

d) 40

#16. For a full pitched winding, induced e.m.f in both coil sides are-

a) subtractive

b) additive

c) in quadrature

d) none of these

#17. The effect of armature reaction at a lagging power factor is:

a) Purely magnetizing

b) Purely demagnetizing

c) Purely cross-magnetizing

d) Partially demagnetizing and partially cross-magnetizing

#18. At a leading power factor, the armature reaction in an alternator is:

a) Magnetizing

b) Demagnetizing

c) Cross-magnetizing

d) None of the above

#19. Which of the following methods for voltage regulation calculation is the most accurate?

a) Synchronous Impedance Method (EMF Method)

b) Ampere-Turn Method (MMF Method)

c) Zero Power Factor Method (Potier Method)

d) American Standards Association (ASA) Method

#20. Negative voltage regulation occurs in an alternator when the load power factor is:

a) Lagging

b) Unity

c) Leading

d) Zero

#21. The relative speed between the magnetic fields of stator and rotor under steady state operation is zero for

a) a dc machine

b) a synchronous machine

c) an induction machine

d) all the above machine

#22. which of the following prime moverhas normally high rotating speed

a) Hydraulic Turbine

b) Diesel engine

c) Steam Turbine

d) Steam engine

#23. The synchronous impedance of an alternator is the ratio of:

a) Open circuit voltage to short circuit current at the same field current

b) Short circuit voltage to open circuit current at the same field current

c) Open circuit voltage to open circuit current

d) Short circuit voltage to short circuit current

#24. The Potier triangle method is used to determine:

a) Armature leakage reactance and armature reaction MMF

b) Synchronous reactance only

c) Armature resistance only

d) Efficiency of the alternator

#25. The Synchronous Impedance Method is also known as the:

a) Pessimistic method

b) Optimistic method

c) Accurate method

d) Direct method

#26. At unity power factor, the armature reaction is:

a) Magnetizing

b) Demagnetizing

c) Cross-magnetizing

d) Zero

#27. The frequency of emf generated per revolution in an alternator is equal to

a) number of poles

b) twice the number of poles

c) number of pair of poles

d) no of armature conductors/pole

#28. A higher value of synchronous reactance indicates

a) A more stable machine

b) A less stable machine

c) Higher efficiency

d) Lower copper losses

#29. For the parallel operation of two alternators, which of the following conditions is not essential?

a) Same voltage rating

b) Same frequency

c) Same phase sequence

d) Same kVA rating

#30. The load sharing between two alternators operating in parallel is primarily determined by their:

a) Excitation

b) Prime mover speed characteristics

c) kVA ratings

d) Winding resistance

Finish