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
The rapid wear of brushes takes place due to____________?
(A) abrasion from dust
(B) excessive spring pressure
(C) rough commutator bars
(D) high mica insulation between com-mutation bars
(D) all of the above factors
Which of the following components of a D.C, generator plays vital role for providing direct current of a D.C. generator ?
(A) Dummy coils
(B) Commutator
(C) Eye bolt
(D) Equilizer rings
Compensating windings are used in D.C. generators______________?
(A) mainly to reduce the eddy currents by providing local short-circuits
(B) to provide path for the circulation of cooling air
(C) to neutralise the cross-magnetising effect of the armature reaction
(D) none of the above
The following constitute short-circuit in the armature winding.
(A) Insulation failure between two commutator bars
(B) Insulation failure between two turns of a coil
(C) Two of more turns of the same coil getting grounded
(D) All of the above
The number of brushes in a commutator depends on______________?
(A) speed of armature
(B) type of winding
(C) voltage
(D) amount of current to be collected
To avoid formation of grooves in the commutator of a D.C. machine?
(A) the brushes of opposite polarity should track each other
(B) the brushes of same polarity should track each other
(C) brush position has no effect on the commutator grooving
(D) None
The demagnetising component of armature reaction in a D.C. generator___________?
(A) reduces generator e.m.f.
(B) increases armature speed
(C) reduces interpoles flux density
(D) results in sparking trouble
A cumulatively compounded long shunt generator when operating as a motor would be____________?
(A) cumulatively compounded long shunt
(B) deferentially compounded long shunt
(C) cumulatively compounded short shunt
(D) differentially compounded short shunt
Armature coil is short circuited by brushes when it lies_____________?
(A) along neutral axis
(B) along field axis
(C) in any of the above positions
(D) in none of the above positions