107 practice sets · Page 2 of 6
Two generators are running in parallel. One of the generators may run as motor forwhich of the following reasons ?
The direction of that generator is reversed
The speed of that generator is increased
The field of that generator is weakened
That generator takes large share of loads
The number of brushes in a commutator depends on
speed of armature
type of winding
voltage
amount of current to be collected
Two D.C. shunt generators, each with armature resistance of 0.02 ohm and fieldresistance of 50 ohm run in parallel and supply a total current of 1000 amperes to the loadcircuit. If their e.m.fs. are 270 V and 265 V, their bus bar voltage will be
270 V
267.5 V
265 V
257.4 V
Iron losses in a D.C. machine are independent of variations in
speed
load
voltage
speed and voltage
For both lap and wave windings, there are as many commutator bars as the number of
slots
armature conductors
winding elements
poles
In D.C. generators on no-load, the air gap flux distribution in space is
sinusoidal
triangular
pulsating
flat topped
Which of the following generators will be preferred if they are required to be run inparallel ?
Shunt generators
Series generators
Compound generators
None of the above
In D.C. generators, the cause of rapid brush wear may be
severe sparking
rough commutator surface
imperfect contact
any of the above
Which generator would you prefer for feeding long D.C. transmission lines ?
Series generator
Shunt generator
Over compound generator
Flat compound generator
Which of the following D.C. generators will be in a position to build up without anyresidual magnetism in the poles ?
Series generator
Shunt generator
Compound generator
None of the above
Which of the following generator will have negligible terminal voltage while running onno-load ?
Series generator
Shunt generator
Compound generator
Separately excited generator
D.C. generator generally preferred for charging automobile batteries is
series generator
shunt generator
long shunt compound generator
any ofthe above
Following D.C. generator will be in a position to build up without any residualmagnetism in the poles
series generator
shunt generator
compound generator
self-excited generator
Following energized winding of a D.C. machine should not be opened as it wouldproduce high inductive voltage which may be dangerous to personnel and may cause itsown insulation failure.
Series field
Compensating field
Inter pole field
Shunt field
An exciter for a turbo generator is a
separately excited generator
shunt generator
series generator
compound generator
Which of the following generating machine will offer constant voltage on all loads ?
Self-excited generator
Separately excited generator
Level compounded generator .
All of the above
The essential condition for parallel operation of two D.C. generators is that they have
same kW rating
the same operation r.p.m.
the same drooping voltage charac-teristics
same percentage regulation
In case of a 4-pole D.C. generator provided with a two layer lap winding with sixteen coils, the pole pitch will be
4
8
16
32
In any rotating machine that part which houses the conductors and in which e.m.f.induced is to be utilised is called
rotor
stator
field
armature
In D.C. generators the pole shoes are fastened to the pole core by
rivets
counter sunk screws
brazing
welding
