Electrical Engineering MCQs

Page No. 275

With a D.C. generator which of the following regulation is preferred ?


a100% regulation

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binfinite regulation

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c50% regulation

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d1% regulation

✓


View Answer 1% regulation

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_____________________?


a270 V

✖


b267.5 V

✓


c265 V

✖


d257.4 V

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View Answer 267.5 V

The essential condition for parallel operation of two D.C. generators is that they have ________________?


asame kW rating

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bthe same operation r.p.m.

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cthe same drooping voltage characteristics

✓


dsame percentage regulation

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When two D.C. generators are running in parallel an equilizer bar is used______________?


ato increase the series flux

✖


bto increase the generated e.m.f.

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cto reduce the combined effect of ar-mature reaction of both the machines

✖


d so that the two identical machines will pass approximately equal cur¬rents to the load

✓



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


aThe direction of that generator is reversed

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bThe speed of that generator is increased

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cThe field of that generator is weakened

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dThat generator takes large share of loads

✓



Which of the following generators will be preferred if they are required to be run in parallel?


aShunt generators

✓


bSeries generators

✖


c Compound generators

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dNone of the above

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View Answer Shunt generators

Which of the following generating machine will offer constant voltage on all loads?


aSelf-excited generator

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b Separately excited generator

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cLevel compounded generator

✓


dAll of the above

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If a self excited D.C. generator after being installed, fails to build up on its first trial run, the first thing to do is to______________?


areverse the field connections

✓


b increase the field resistance

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c increase the speed of primemover

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dcheck armature insulation resistance

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The main factor which leads to unstable parallel operation of flat and over compounded generators is_____________?


atheir rising voltage characteristics

✓


b unequal number of turns in their series field windings

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c unequal speed regulation of their primemovers

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d unequal series field resistances

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


ato increase the speed and hence generated e.m.f.

✖


bto increase the series flux

✖


cso that two similar machines will pass approximately equal currents to the load

✓


d to reduce the combined effect of ar-mature reaction of both machines

✖



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