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Armature reaction in a generator results in
demagnetisation of leading pole tip and magnetisation of trailing pole tip
demagnetisation of trailing pole tip and magnetisation of leading pole tip
damagnetising the centre of all poles
magnetising the centre of all poles
With a D.C. generator which of the following regulation is preferred ?
100% regulation
infinite regulation
50% regulation
1% regulation
In case of D.C. machines, mechanical losses are primary function of
current
voltage
speed
none of above
A cumulatively compounded long shunt generator when operating as a motor would be
cumulatively compounded long shunt
differentially compounded long shunt
cumulatively compounded short shunt
differentially compounded short shunt
Armature reaction of an unsaturated D.C. machine is
crossmagnetising
demagnetising
magnetising
none of above
The commutator segments are connected to the armature conductors by means of
copper lugs
resistance wires
insulation pads
brazing
In a commutator
copper is harder than mica
mica and copper are equally hard
mica is harder than copper
none of the above
Which of the following statement about D.C. generators is false ?
Compensating winding in a D.C. machine helps in commutation
In a D. C. generator interpoles winding is connected in series with the armaturewinding
Back pitch and front pitch are both odd and approximately equal to the pole pitch
Equilizing bus bars are used with parallel running of D.C. shunt generators
Which of the following could be lamina-proximately the thickness of laminations of a D.C. machine ?
0.005 mm
0.05 mm
0.5 m
5 m
In D.C. generators, current to the external circuit from armature is given through
commutator
solid connection
slip rings
none of above
Laminations of core are generally made of
case iron
carbon
silicon steel
stainless steel
Brushes of D.C. machines are made of
carbon
soft copper
hard copper
all of above
In a D.C. generator the critical resistance refers to the resistance of
brushes
field
armature
load
The bearings used to support the rotor shafts are generally
ball bearings
bush bearings
magnetic bearmgs
needle bearings
The terminal voltage of a D.C. shunt generator drops on load because of all of thefollowing reasons except
armature reaction
armature resistance drop
field weakening due to armature reaction and armature
commutation
Wave winding is composed of
any even number of conductors
any odd number of conductors
that even number which is exact multiple of poles + 2
that even number which is exact multiple of poles
Lap winding is composed of
any even number of conductors
any odd number of conductors
that even number which is exact multiple of poles + 2
that even number which is exact multiple of poles
Armature coil is short circuited by brushes when it lies
along neutral axis
along field axis
in any of the above positions
in none of the above positions
In over compounded generator, full load terminal voltage is
almost zero
less than noload terminal voltage
more than noload terminal voltage
equal to no-load terminal voltage
In a four-pole D.C. machine
all the four poles are north poles
alternate poles are north and south
all the four poles are south poles
two north poles follow two south poles
