In DC generators, armature reaction is produced actually by (A) Its field current. (B) Armature conductors. (C) Field pole winding. (D) Load current in armature.

In DC generators, armature reaction is produced actually by
 (A) Its field current. (B) Armature conductors.
 (C) Field pole winding. (D) Load current in armature.
by

1 Answer

Answer :

Ans: D
Because load current in armature gives rise to armature mmf which react with
main field mmf.
by

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The function of the commutator in a DC motor is to ________. A. reverse the flow of current through the armature B. reverse the flow of current in the field poles C. reduce the reluctance of the magnetic path through the motor D. shift the neutral running plane of the brushes to prevent sparking

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The purpose of the commutator and brushes on a DC generator is to _____________. A. transfer generated direct current voltage from the armature to the line B. convert the alternating voltage generated within the armature to a direct voltage C. provide a sliding contact method to excite the field D. reduce sparking between the armature and the carbon brushes

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A loss of field excitation to an AC generator while operating in parallel will cause it to ____________. A. absorb more and more load due to decreased armature reaction B. lose its load due to the inherent speed droop built into the governor C. smoke and overload due to field flashover as residual field flux changes polarity D. lose its load, begin to motorize, trip out on reverse power relay, and possibly overspeed

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The insulation of electric generators during short idle periods should be _____________. A. allowed to cool slowly to ambient temperatures B. flashed with direct current to remove any residual magnetism C. kept warm by using strip or space heaters D. relieved of all capacitive charge by grounding the conductors

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Last Answer : Answer: D

The amount of mechanical force or torque produced by an electric motor depends on the ________________. A. strength of its magnetic field B. amount of armature current flow C. length of conductor in the field D. all of the above

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In a dc generator why does total flux per pole decrase if the load on the machine increases even thought the field current is constsn?

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Last Answer : Answer: C

Aluminium is not used as winding wire for the armature of a dc machine because

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