Multiple Choice Question (MCQ) of Alternator and Synchronous Motors page-6

51. The armature reaction of an alternator will be cross-magnetizing if the power factor of the load is

a) Zero leading
b) less than unity
c) Unity
d) More than unity

Ans: (c)

52. The effect of cross-magnetizing field in an alternator may be reduced by

a) Shifting the brush positions
b) Using interpoles
c) Using a magnetizing pole
d) None of these

Ans: (a)

53. The following method is best suited for finding the voltage regulation of an alternator

a) Synchronous impedance method
b) Politer triangle method
c) MMF method
d) None of these

Ans: (b)

54. Power factor of an alternator driven by constant prime mover input can be changed by changing its

a) Speed
b) Load
c) Field excitation
d) Phase sequence

Ans: (c)

55. Salient pole machines have

a) Large number of poles
b) Small number of poles
c) Small diameters
d) Long cores

Ans: (a)

56. The stator of modern alternators are wound for

a) 60° phase groups
b) 120° phase groups
c) 180° phase groups
d) 240° phase groups

Ans: (a)

57. The armature reaction of an alternator influences

a) Windage losses
b) Operating speed
c) Generated voltage per phase
d) Waveform of generated voltage

Ans: (c)

58. When an alternator is supplying unity power factor load, the armature reaction will produce

a) Magnetization of the main field
b) Demagnetization of the main field
c) Distortion of the main field
d) None of these

Ans: (c)

59. Two alternators are running in parallel. The excitation of one of the alternators is increased. The result will be that

a) Machine with excess excitation will burn
b) Both machines will start vibrating
c) Power output will decrease
d) Wattles component will change

Ans: (d)

60. Alternators are generally designed to generate

a) Fixed frequencies
b) Variable frequencies
c) Fixed currents
d) Fixed power factors

Ans: (a)

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Multiple Choice Question (MCQ) of Alternator and Synchronous Motors page-6

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