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Electrical Engineering Objective Questions { Alternators }

43. For eliminating 7th harmonics from the e.m.f. wave of an alternator, the fractional-pitch must be
A. 2/3
B. 5/6
C. 7/8
D. 6/7

44. A synchronous machine has higher capacity for
A. leading p.f.
B. lagging p.f.
C. it does not depend upon the pl. of the machine
D. it depend upon the pl. of the load

45. Turbo-alternators are generally used to run at
A. 1500 r.p.m.
B. 3000 r.p.m.
C. 5000 r.p.m.
D. 15000 r.p.m.

46. The frequency of voltage generated in large alternators is
A. 50 Hz
B. 60 Hz
C. in kilo cycles
D. in mega cycles

47. The dark and bright lamp method is used for
A. transfer of load
B. synchronizing
C. balancing of load
D. phase sequence

48. In a synchronous machine, all of the following losses are fixed except
A. core loss
B. copper loss
C. bearing friction loss
D. windage loss

49. An alternator is capable of delivering power at a particular efficiency. The frequency can be increased by
A. reversing the armature rotation
B. reversing the field polarity
C. increasing the current supplied to the field electromagnets
D. increasing the armature speed

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