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Electrical Engineering Objective Questions { Alternators }

113. In an alternator, the flux created by the armature m.m.f. subtracts directly from the main flux for the following conditions of the load
A. load power factor is unity
B. load power factor is 0.6 lagging
C. load power factor is zero lagging
D. load power factor is zero leading
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114. Synchronous impedance method of finding voltage regulation of an alternator is called pessimistic method because
A. it is simplest to perform and compute
B. it gives regulation value higher than is actually found by direct loading
C. armature reaction is wholly magnetizing
D. none of the above
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115. Two alternators are running in parallel. If the field of one of the alternators is adjusted it will
A. change its power factor
B. change its frequency
C. reduce its speed
D. change its load
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116. In a synchronous machine, if the field flux axis is ahead of the armature field axis, in the direction of rotation, the machine is working as
A. synchronous generator
B. asynchronous generator
C. synchronous motor
D. asynchronous motor
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117. The advantage of salient poles in an alternator is
A. reduced winding loss
B. reduced bearing loads and noise
C. reduced noise
D. adaptability of low and medium speed operation
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118. For parallel operation of the two alternators, desirable feature is that both should have
A. same reactance
B. same resistance
C. more of resitance as compared to synchronous reactance
D. less of resistance as compared to synchronous reactance
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119. It two alternators are running in parallel and the excitation of one of the alternators is increased, then
A. power output will decrease
B. wattless component will change
C. machine with excess excitation will burn
D. both machies will start vibrating
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