41.
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
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Shunt generators are most suited for stable parallel operation because of their
rising voltage characteristics
identical voltage characteristics
drooping voltage characteristics
linear voltage characteristics
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
reverse the field connections
increase the field resistance
increase the speed of primemover
check armature insulation resis¬tance
The demagnetising component of armature reaction in a D.C. generator
reduces generator e.m.f.
increases armature speed
reduces interpoles flux density
results in sparking trouble
The armature of D.C. generator is laminated to
reduce the bulk
provide the bulk
insulate the core
reduce eddy current loss
A D.C. generator can be considered as
rectifier
primemover
rotating amplifier
power pump
In a D.C. generator the number of mechanical degrees and electrical degrees will be the same when
r.p.m. is more than 300
r.p.m. is less than 300
number of poles is 4
number of poles is 2
Eddy currents are induced in the pole shoes of a D.C. machine due to
oscillating magnetic field
pulsating magnetic flux
relative rotation between field and armature
all above
A series generator can self-excite
only if the load current is zero
only if the load current is not zero
irrespective of the value of load current
none of the above
Number of tappings for each equilizer ring is equal to
number of pole pairs
number of poles
number of parallel paths
number of commutator segments
In case of D.C. machine winding, number of commutator segments is equal to
number of armature coils
number of armature coil sides
number of armature conductors
number of armature turns
Flashing the field of D.C. generator means
neutralising residual magnetism
creating residual magnetism by a D.C. source
making the magnetic losses of forces parallel
increasing flux density by adding extra turns of windings on poles
Interpole flux should be sufficient to
neutralise the commutating self induced e.m.f.
neutralise the armature reaction flux
neutralise both the armature reaction flux as well as commutating e.m.f. induced in thecoil
perform none of the above functions
In a level compounded D.C. generator, full load terminal voltage is
negligibly low
equal to no-load terminal voltage
more than no-load terminal voltage
less than no-load terminal voltage
In the case of lap winding resultant pitch is
multiplication of front and back pitches
division of front pitch by back pitch
sum of front and back pitches
difference of front and back pitches
According to Flemings 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
motion of conductor
lines of force
either of the above
none of the above
The terminal voltage of a series generator is 150 V when the load current is 5 A. If theload current is increased to 10 A, the terminal voltage will be
150 V
less than 150 V
greater than 150 V
none of the above
The material for commutator brushes is generally
mica
copper
cast iron
carbon
The field coils of D.C. generator are usually made of
mica
copper
cast iron
carbon
Compensating windings are used in D.C. generators
mainly to reduce the eddy currents by providing local short-circuits
to provide path for the circulation of cooling air
to neutralise the cross-magnetising effect of the armature reaction
none of the above
Flemings right-hand rule regarding direction of induced e.m.f., correlates
magnetic flux, direction of current flow and resultant force
magnetic flux, direction of motion and the direction of e.m.f. induced
magnetic field strength, induced voltage and current
magnetic flux, direction of force and direction of motion of conductor