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Electrical Engineering Objective Questions { Alternators }



50. In an alternator, for a coil having a span of 2/3 of pole pitch, the coil span factor will be
A.0.866
B.0.707
C.0.6
D.0.2
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51. Regulation of an alternator supplying leading load is
A. always negative
B. always positive
C. sometimes positive and sometimes negative depending upon load and power factor
D. Always absolute value
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52. An infinite bus bar has
A. constant frequency and constant voltage
B. contant frequency and variable voltage
C. variable frequency and variable voltage
D. infinite frequency and infinite voltage
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53. If an alternator is operating at leading power factor, then it can be concluded that
A. the alternator is under-excited
B. the alternator is over-excited
C. the torque angle of the alternator has negative value
D. the residual magnetism of the poles is zero
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54. Damper winding on alternator results in all of the following except
A. increases instability of machine
B. elimination of harmonic effects
C. absorption of energy of oscillations when operating in parallel with other alternators
D. suppression of spontaneous hunting when supplying power to transmission line with high resistance to reactance ratio
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55. In a cylindrical rotor how much portion of the rotor is wound?
A. One third
B. Half
C. Two third
D. Full
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56. The speed of an alternator is changed from 3000 r.p.m. to 1500 r.p.m. The generated e.m.f./phase will become
A. one fourth
B. half
C. double
D. unchanged
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