D.C. Generators

101. To avoid formation of grooves in the commutator of a D.C. machine

1. the brushes of opposite polarity should track each other
2. the brushes of same polarity should track each other
3. brush position has no effect on the commutator grooving
4. none

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102. Two D.C. shunt generators, each with armature resistance of 0.02 ohm and field resistance of 50 ohm run in parallel and supply a total current of 1000 amperes to the load circuit. If their e.m.fs. are 270 V and 265 V, their bus bar voltage will be

1. 270 V
2. 267.5 V
3. 265 V
4. 257.4 V

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103. 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

1. 2 : 3
2. 3 : 1
3. 3 : 2
4. 1 : 3

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104. Two generators are running in parallel. One of the generators may run as motor for which of the following reasons ?

1. The direction of that generator is reversed
2. The speed of that generator is increased
3. The field of that generator is weakened
4. That generator takes large share of loads

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105. Wave winding is composed of

1. any even number of conductors
2. any odd number of conductors
3. that even number which is exact multiple of poles + 2
4. that even number which is exact multiple of poles

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106. Welding generator will have

1. lap winding
2. wave winding
3. delta winding
4. duplex wave winding

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107. When two D.C. generators are running in parallel an equilizer bar is used

1. to increase the series flux
2. to increase the generated e.m.f.
3. to reduce the combined effect of ar-mature reaction of both the machines
4. so that the two identical machines will pass approximately equal cur¬rents to the load

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108. When two D.C. series generators are running in parallel, an equilizer bar is used

1. to increase the speed and hence generated e.m.f.
2. to increase the series flux
3. so that two similar machines will pass approximately equal currents to the load
4. to reduce the combined effect of ar-mature reaction of both machines

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109. Which generator would you prefer for feeding long D.C. transmission lines ?

1. Series generator
2. Shunt generator
3. Over compound generator
4. Flat compound generator

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110. Which of the following components of a D.C, generator plays vital role for providing direct current of a D.C. generator ?

1. Dummy coils
2. Commutator
3. Eye bolt
4. Equilizer rings

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