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Electrical Engineering Objective Questions { Alternators }

71. In an alternator short pitch coils are used
A. to reduce the stray losses
B. to reduce the size of the machine
C. to provide accurate phase difference of 1200 between each phase
D. to reduce the harmonics in generated e.m.f.

72. If the input to the prime mover of an alternator is kept constant but the excitation is increased, then
A. kVA will be lagging
B. kVA with the leading
C. kW will be changed
D. the power factor of the load remains constant

73. Generated e.m.f. for same field current and double speed will be
A. same
B. double
C. less than double
D. more than double

74. If the space flux distribution is nonsinusoidal, e.m.f. induced in the distributed winding
A. will be less sinusoidal than flux distribution
B. will be more sinusoidal than flux distribution
C. will be equally non-sinusoidal
D. none of the above

75. Voltage regulation obtained by synchronous impedance method is
A. equal to that given by actual tests
B. less than that given by actual tests
C. more than that given by actual tests
D. none of the above

76. In an alternator short-circuit current is limited by
A. the saturated synchronous impedance
B. the unsaturated synchronous impedance
C. either of the above
D. none of the above

77. In an alternator, armature reaction is considered equivalent to
A. fictitious impedance
B. fictitious conductance
C. fictutius reactance
D. fictitious resistance

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