D.C Generator: [ ISRO,DRDO,DMRC,SAIL, ODNANCE, HAL, WBSEDCL, RAILWAY & Others competitive]
51. Compensating windings are used in D.C. generators
(a) mainly to reduce the eddy currents by providing local
short-circuits
(b) to provide path for the circulation of cooling air
(c) to neutralise the cross-magnetising effect of the armature
reaction
(d) none of the above
Ans: c
52.Which of the following components of a D.C, generator plays vital role for providing direct current of a D.C. generator?
(a) Dummy coils
(b) Commutator
(c) Eye bolt
(d) Equalizer rings
Ans: b
53. In a D.C. generator the ripples in the direct e.m.f. generated are reduced by
(a) using conductor of annealed copper
(b) using commutator with large number of segments
(c) using carbon brushes of superior quality
(d) using equaliser rings
Ans: c
54. In D.C. generators, lap winding is used for
(a) high voltage, high current
(b) low voltage, high current
(c) high voltage, low current
(d) low voltage, low current
Ans: b
55. Two generators A and B have 6-poles each. Generator A has wave wound armature while generator B has lap wound armature. The ratio of the induced e.m.f. is generator A and B will be
(a) 2 : 3
(b) 3 : 1
(c) 3 : 2
(d) 1 : 3
Ans: b
56. Permeance is the reciprocal of
(a) flux density
(b) reluctance
(c) ampere-turns
(d) resistance
Ans: b
57. In D.C. generators the polarity of the interpoles
(a) is the same as that of the main pole ahead
(b) is the same as that of the immediately preceding pole
(c) is opposite to that of the main pole ahead
(d) is neutral as these poles do not play part in generating
e.m.f.
Ans: a
58. The e.m.f. generated in a D.C. generator is directly proportional to
(a) flux/pole
(b) speed of armature
(c) number of poles
(d) all of the above
Ans: b
59. In a D.C. generator the magnetic neutral axis coincides with the geometrical neutral axis, when
(a) there is no load on the generator
(b) the generator runs on full load
(c) the generator runs on overload
(d) the generator runs on designed speed
Ans: a
60. In a D.C. generator in order to reduce sparking at brushes, the self-induced e.m.f.
in the coil is neutralised by all of the following except..
(a) interpoles
(b) dummy coils
(c) compensating winding
(d) shifting of axis of brushes
Ans: b
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