DC Generator MCQ Quiz - Multiple Choice Questions & Answers Page 9

81. Which of the following generators will be preferred if they are required to be run inparallel ?

1. Shunt generators
2. Series generators
3. Compound generators
4. None of the above

82. In D.C. generators on no-load, the air gap flux distribution in space is

1. sinusoidal
2. triangular
3. pulsating
4. flat topped

83. For both lap and wave windings, there are as many commutator bars as the number of

1. slots
2. armature conductors
3. winding elements
4. poles

84. Iron losses in a D.C. machine are independent of variations in

1. speed
2. load
3. voltage
4. speed and voltage

85. Two D.C. shunt generators, each with armature resistance of 0.02 ohm and fieldresistance of 50 ohm run in parallel and supply a total current of 1000 amperes to the loadcircuit. 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

86. The number of brushes in a commutator depends on

1. speed of armature
2. type of winding
3. voltage
4. amount of current to be collected

87. Two generators are running in parallel. One of the generators may run as motor forwhich 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

88. The main factor which leads to unstable parallel operation of flat and over compounded generators is

1. their rising voltage characteristics
2. unequal number of turns in their series field windings
3. unequal speed regulation of their primemovers
4. unequal series field resistances

89. In a D.C. generator the magnetic neutral axis coincides with the geometrical neutralaxis, when

1. there is no load on|he generator
2. the generator runs on full load
3. the generator runs on overload
4. the generator runs on designed speed

90. D.C. generators are connected to the busbars or disconnected from them only under thefloating condition

1. to avoid sudden loading of the primemover
2. to avoid mechanicaljerk to the shaft
3. to avoid burning of switch contacts
4. all above