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.Management Sciences
Category: D.C. Generators
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_____________________?
A. 270 V
B. 267.5 V
C. 265 V
D. 257.4 V
When two D.C. series generators are running in parallel, an equilizer bar is used________________?
A. to increase the speed and hence generated e.m.f.
B. to increase the series flux
C. so 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
With a D.C. generator which of the following regulation is preferred ?
A. 100% regulation
B. infinite regulation
C. 50% regulation
D. 1% regulation
According to Fleming’s right-hand rule for finding the direction of induced e.m.f., when middle finger points in the direction of induced e.m.f., forefinger will point in the direction of____________?
A. motion of conductor
B. lines of force
C. either of the above
D. none of the above
Shunt generators are most suited for stable parallel operation because of their______________?
A. rising voltage characteristics
B. identical voltage characteristics
C. drooping voltage characteristics
D. linear voltage characteristics
A series generator can self-excite:______________?
A. only if the load current is zero
B. only if the load current is not zero
C. irrespective of the value of load current
D. none of the above
In the case of lap winding resultant pitch is____________?
A. multiplication of front and back pitches
B. division of front pitch by back pitch
C. sum of front and back pitches
D. difference of front and back pitches
The following constitute short-circuit in the armature winding.
A. Insulation failure between two commutator bars
B. Insulation failure between two turns of a coil
C. Two of more turns of the same coil getting grounded
D. All of the above
In D.C. generators the polarity of the interpoles_____________?
A. is the same as that of the main pole ahead
B. is the same as that of the immediately preceding pole
C. is opposite to that of the main pole ahead
D. is neutral as these poles do not play part in generating e.m.f.
For both lap and wave windings, there are as many commutator bars as the number of_____________?
A. slots
B. armature conductors
C. winding elements
D. poles
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