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.Management Sciences
Category: D.C. Generators
If brushes of a D.C. generator are moved in order to bring these brushes in magnetic neutral axis, there will be________________?
A. demagnetisation only
B. cross magnetisation as well as mag¬netisation
C. crossmagnetisation as well as demagnetising
D. cross magnetisation only
The commutator segments are connected to the armature conductors by means of___________?
A. copper lugs
B. resistance wires
C. insulation pads
D. brazing
The demagnetising component of armature reaction in a D.C. generator___________?
A. reduces generator e.m.f.
B. increases armature speed
C. reduces interpoles flux density
D. results in sparking trouble
Flashing the field of D.C. generator means:______________?
A. neutralising residual magnetism
B. creating residual magnetism by a D.C. source
C. making the magnetic losses of forces parallel
D. increasing flux density by adding extra turns of windings on poles
If a D.C. generator fails to build up the probable cause could not be_____________?
A. imperfect brush contact
B. field resistance less than the critical resistance
C. no residual magnetism in the generator
D. faulty shunt connections tending to reduce the residual magnetism
In case of a flat compounded generator:
A. voltage generated is less than the rated voltage
B. generated voltage is proportional to the load on the generator
C. voltage remains constant irrespective of the load
D. speed varies in proportion to the load on the generator
Following energized winding of a D.C. machine should not be opened as it would produce high inductive voltage which may be dangerous to personnel and may cause its own insulation failure.
A. Series field
B. Compensating field
C. Inter pole field
D. Shunt field
The voltage drop for which of the following types of brush can be expected to be least ?
A. Graphite brushes
B. Carbon brushes
C. Metal graphite brushes
D. None of the above
To avoid formation of grooves in the commutator of a D.C. machine?
A. the brushes of opposite polarity should track each other
B. the brushes of same polarity should track each other
C. brush position has no effect on the commutator grooving
D. None
In D.C. generators on no-load, the air gap flux distribution in space is______________?
A. sinusoidal
B. triangular
C. pulsating
D. flat topped
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