DC Generator Questions and Answers in Quiz Form 7 for Practice

91. 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 currents to the load

92. 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

93. The purpose of providing dummy coils in a generator is

1. to reduce eddy current losses
2. to enhance flux density
3. to amplify voltage
4. to provide mechanical balance for the rotor

94. The function of pole shoes in the case of D.C. machine is

1. to reduce the reluctance of the magnetic path
2. to spread out the flux to achieve uniform flux density
3. to support the field coil
4. to discharge all the above functions

95. D.C. series generator is used

1. to supply traction load
2. to supply industrial load at constant voltage
3. voltage at the toad end of the feeder
4. for none of the above purpose

96. In a D.C. machine stray loss is the sum of

1. total copper loss and mechanical loss
2. armature copper loss and iron loss
3. shunt field copper loss and mechanical loss
4. iron loss and mechanical loss

97. As a result of armature reaction, the reduction in the total mutual air gap flux in a D.C.generator is approximately

1. 40 percent
2. 25 percent
3. 10 percent
4. 5 percent

98. In a D.C. generator the ripples in the direct e.m.f. generated are reduced by

1. using conductor of annealed copper
2. using commutator with large number of segments
3. using carbon brushes of superior quality
4. using equiliser rings

99. In case of a flat compounded generator

1. voltage generated is less than the rated voltage
2. generated voltage is proportional to the load on the generator
3. voltage remains constant irrespec¬tive of the load
4. speed varies in proportion to the load on the generator

100. For the parallel operation of two or more D.C. compound generators, we should ensurethat

1. voltage of the incoming generator should be same as that of bus bar
2. polarity of incoming generator should be same as that of bus bar
3. all the series fields should be run in parallel by means of equilizer connection
4. series fields of all generators should be either on positive side or negative side of thearmature(e) all conditions mentioned above should be satisfied

101. Equilizer rings are required in case armature is

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

102. Copper brushes in D.C. machine are used

1. where low voltage and high currents are involved
2. where high voltage and small cur-rents are involved
3. in both of the above cases
4. in none of the above cases

103. The open circuit voltage of a compound generator is 250 V. At full load the terminalvoltage

1. will be less than 250 V
2. will always be 250 V
3. may be greater or less than 250 V
4. none of the above

104. A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armaturevoltage wave

1. will be zero
2. will be of 5 Hz
3. willbeof5xiVHz
4. will be of v Hz 5

105. A 220 V D.C. generator is run at full speed without any excitation. The open circuitvoltage will be

1. zero
2. about 2 V
3. about 50 V
4. 220 V