1301.
A separately excited generator as compared to a self-excited generator
A
is amenable to better voltage con-trol
B
is more stable
C
has exciting current independent of load current
D
has all above features
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A separately excited generator as compared to a self-excited generator
is amenable to better voltage con-trol
is more stable
has exciting current independent of load current
has all above features
In a separately excited generator supplying rated load the armature reaction ,
is always present
is always absent
may be sometimes present
none of the above
In a D.C. generator in order to reduce sparking at brushes, the self-induced e.m.f. in thecoil is neutralised by all of the following except
interpoles
dummy coils
compensating winding
shifting of axis of brushes
In a D.C. generator the critical resistance can be increased by
increasing its field resistance
decreasing its field resistance
increasing its speed
decreasing its speed
In a D.C. generator in case the resistance of the field winding is increased, then outputvoltage will
increase
decrease
remain unaffected
fluctuate heavily
If a D.C. generator fails to build up the probable cause could not be
imperfect brush contact
field resistance less than the critical resistance
no residual magnetism in the generator
faulty shunt connections tending to reduce the residual magnetism
In D.C. generators, lap winding is used for
high voltage, high current
low voltage, high current
high voltage, low current
low voltage, low current
The voltage drop for which of the following types of brush can be expected to be least ?
Graphite brushes
Carbon brushes
Metal graphite brushes
None of the above
The insulating material used between the commutator segments is normally
graphite
paper
mica
insulating varnish
The e.m.f. generated in a D.C. generator is directly proportional to
flux/pole
speed of armature
number of poles
all of the above
A shunt generator running at 1000 r.p.m. has generated e.m.f. as 200 V. If the speedincreases to 1200 r.p.m., the generated e.m.f. will be nearly
150 V
175 V
240 V
290 V
Permeance is the reciprocal of
flux density
reluctance
ampere-turns
resistance
The critical resistance of the D.C. generator is the resistance of
field
brushes
armature
load
In a D.C. generator
external resistance = internal char-acteristic - armature reaction
internal characteristic = magnetisation characteristic - ohmic drop
external characteristic = magnetisation characteristic - ohmic drop - armature reaction
magnetisation characteristic = external characteristic
The series field of a short-shunt D.C. generator is excited by
external current
armature current
shunt current
load current
The e.m.f. generated by a shunt wound D.C. generator is E. Now while pole flux remainsconstant, if the speed of the generator is doubled, the e.m.f. generated will be
E/2
2E
slightly less than E
E
Which of the following components of a D.C, generator plays vital role for providingdirect current of a D.C. generator ?
Dummy coils
Commutator
Eye bolt
Equilizer rings
In lap winding, the number of brushes is always
double the number of poles
same as the number of poles
half the number of poles
two
While applying Flemings right-hand rule to And the direction of induced e.m.f., the thumb points towards
direction of induced e.m.f.
direction of flux
direction of motion of the conductor if forefinger points in the direction of generatede.m.f.
direction of motion of conductor, if forefinger points along the lines of flux
If brushes of a D.C. generator are moved in order to bring these brushes in magneticneutral axis, there will be
demagnetisation only
cross magnetisation as well as magnetisation
crossmagnetisation as well as demagnetising
cross magnetisation only