DC MACHINES MCQS 3
31) Width of a carbon brush should be equal to
a) less than the width of one commutator segment
b) the width of 1to 2 commutator segment
c) the width of 2 to 3 commutator segment
d) the width of more than 3 commutator segments
ANS:C
32) Wave winding is composed of
a) any odd number of conductors
b) any even number of conductors
c) that even number which is exact multiple of poles
+or- 2
d) that even number which is exactly multiple of
poles
ANS:C
33) For a 4-pole machine wave winding is impossible
with --- armature conductors
a) 30 b)
32 c) 34 d) 38
ANS:B
34) A homopolar generator usually has
a) high voltage and high current b) low voltage and high current
c) low voltage and low current d) high voltage and low current
ANS:D
35) In a dc generator,the ripples in the direct emf
generated are reduced by employing
a) cpmmutator with large number of segments
b) equalizer rings c)
carbon brushes d) graphite brushes
ANS:A
36) The coil span
a) must be exactly equal to pole pitch
b) can never be equal to pole pitch
c) may or may not be exactly equal to pole pitch
d) none of the above
ANS:C
37) The commutator pitch for simplex wave winding is
equal to
a) +1 or -1 b)
twice average pitch c)
average pitch d) half average pitch
ANS:C
38) The commutator pitch for simplex lap winding is
a) +1 b) -1 c) +1 or -1 d)
average pitch
ANS:C
39) In a dc machine armature windind,the number of commutator
segments is equal to the number of armature
a) coils b)
coils sides c) conductors d) turns
ANS:A
40) How many segments will be there for the
commutator of a 6-pole dc machine having a simple wave-wound armature with 72
slots?
a) 73 b)72 c) 71 d)
70
ANS:B
41) For both lap and wave windings, there are as
many commutator bar as the number of
a) armature
conductors b) winding elements
c) poles d)
slots
ANS:B
42) In a drum type dc armature winding the back
pitch and front pitch in terms of the coil-sides must be
a) even and odd respectively b) odd and even respectively
c) both even d)
both odd
ANS:D
43) In a dc machine, fractional pitch winding is
employed to
a) increase generated voltage b) reduce sparking
c) save copper d)
both b and c
ANS:D
44) Aluminum is not used as winding wire in dc
machine armature as it
a) is costlier b)
is of low resistivity
c) is of lower thermal conductivity d) requires large winding space
ANS:D
45) In a lap wound dc generator having P poles and Z
conductors the maximum number of equalizes rings will be
a) Z/P b)
2Z/P c) Z/2P d) Z/4P
ANS:B
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