Electrical Engineering MCQs

Page No. 275

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


a100% regulation


binfinite regulation


c50% regulation


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


View Answer 267.5 V

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


asame kW rating


bthe same operation r.p.m.


cthe same drooping voltage characteristics


dsame percentage regulation



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.


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


bThe speed of that generator is increased


cThe field of that generator is weakened


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


dNone of the above


View Answer Shunt generators

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


aSelf-excited generator


b Separately excited generator


cLevel compounded generator


dAll of the above



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


c increase the speed of primemover


dcheck armature insulation resistance



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


c unequal speed regulation of their primemovers


d unequal series field resistances



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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