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.Management Sciences
Category: D.C. Generators
A separately excited generator as compared to a self-excited generator_____________?
A. is amenable to better voltage control
B. is more stable
C. has exciting current independent of load current
D. has all above features
In case of D.C. machines, mechanical losses are primary function of____________?
A. current
B. voltage
C. speed
D. none of above
In a four-pole D.C. machine____________?
A. all the four poles are north poles
B. alternate poles are north and south
C. all the four poles are south poles
D. two north poles follow two south poles
Copper brushes in D.C. machine are used_____________?
A. where low voltage and high currents are involved
B. where high voltage and small cur-rents are involved
C. in both of the above cases
D. in none of the above cases
In a D.C. generator the magnetic neutral axis coincides with the geometrical neutral axis, when_______________?
A. there is no load on|he generator
B. the generator runs on full load
C. the generator runs on overload
D. the generator runs on designed speed
For the parallel operation of two or more D.C. compound generators, we should ensure that_______________?
A. voltage of the incoming generator should be same as that of bus bar
B. polarity of incoming generator should be same as that of bus bar
C. all the series fields should be run in parallel by means of equilizer connection
D. series fields of all generators should be either on positive side or negative side of the armature
E. all conditions mentioned above should be satisfied
The armature core of a D.C. generator is usually made of__________________?
A. silicon steel
B. copper
C. non-ferrous material
D. cast-iron
If residual magnetism is present in a D.C. generator, the induced e.m.f. at zero speed will be____________?
A. zero
B. small
C. the same as rated voltage
D. high
In a separately excited generator supplying rated load the armature reaction.
A. is always present
B. is always absent
C. may be sometimes present
D. none of the above
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