Direct Current Machine Or DC Machine Objective Questions and Answers
16. The Interpole air gap is ........that under the field poles, in DC machine
A. Smaller than
B. Larger than
C. Equal to
D. None of the above
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B. Larger then
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17. The Inter polls in DC machines have a tempering shape in order to
A. Reduce the overall weight
B. Reduce the saturation in the Interpole
C. Economics on the material required for Interpoles and their windings
D. Increase the acceleration of commutation
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18. The sparking at the brushes, in a DC machine is due to
A. Armature reaction
B. Reactance voltage
C. Presence of commutator
D. High resistance of carbon brushes
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19. In a DC machine, the sparking between brushes and commutator surface may be due to
A. Under commutation
B. Over commutation
C. Too rapid reversal of current
D. Any of the above
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20. Commutation in a DC machine may be explained as a process
A. In which magnetic field is set up
B. By virtue of which EMF is induced in the armature conductors
C. By which currently in a coil is reversed during the period it is short-circuited by the brush
D. How armature flux affects the main field flux
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