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.Management Sciences
Category: D.C. Generators
The insulating material used between the commutator segments is normally_____________?
A. graphite
B. paper
C. mica
D. insulating varnish
Which of the following D.C. generators will be in a position to build up without any residual magnetism in the poles?
A. Series generator
B. Shunt generator
C. Compound generator
D. None of the above
Brushes of D.C. machines are made of_________?
A. carbon
B. soft copper
C. hard copper
D. all of above
The purpose of providing dummy coils in a generator is__________________?
A. to reduce eddy current losses
B. to enhance flux density
C. to amplify voltage
D. to provide mechanical balance for the rotor
Iron losses in a D.C. machine are independent of variations in_____________?
A. speed
B. load
C. voltage
D. speed and voltage
Which of the following statement about D.C. generators is false ?
A. Compensating winding in a D.C. machine helps in commutation
B. In a D. C. generator interpoles winding is connected in series with the armature winding
C. Back pitch and front pitch are both odd and approximately equal to the pole pitch
D. Equilizing bus bars are used with parallel running of D.C. shunt gen¬erators
In D.C. generators, the cause of rapid brush wear may be___________?
A. severe sparking
B. rough commutator surface
C. imperfect contact
D. any of the above
The resistance of armature winding depends on
A. length of conductor
B. cross-sectional area of the conductor
C. number of conductors
D. all of the above
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