316. Armature reaction of an unsaturated D.C. machine is
A. crossmagnetising
B. demagnetizing
C. magnetizing
D. none of above

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317. D.C. generators are connected to the busbars or disconnected from them only under the floating condition
A. to avoid sudden loading of the primemover
B. to avoid mechanical jark to the shaft
C. to avoid burning of swith contacts
D. all above

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318. Eddy current are induced in the pole shoes of a D.C. machine due to
A. oscillating magnetic field
B. pulsating magnetic flux
C. relative rotation between field and armature
D. all above

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319. In a D.C. machine, short-circuited field coil will result in
A. odour of burning insulation
B. unbalanced magnetic pull producing vibrations
C. reduction of generated voltage for which excitation has to be increased to maintain the voltage
D. all above

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320. Equilizer rings are required in case armature is
A. wave wound
B. lap wound
C. delta wound
D. duplex wound

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321. Welding generator will have
A. lap winding
B. wave winding
C. delta winding
D. duplex wave winding

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322. In case of D.C. machine winding, number of commutator segments is equal to
A. number of armature coils
B. number of armature coil sides
C. number of armature conductors
D. number of armature turns

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