Practice Dc Machines Interview Multiple Choice Questions with Answers Quiz-1

Q.1.

In a DC generator the ripples in the direct emf generated can be reduced by________

a) Using conductor of annealed copper
b) Using commutator with large number of segments
c) Using carbon brushes of superior quality
d) Using equalizer rings

Explanation

Q.2.

The drop in the voltage for which of the following types of brush can be expected to be least?

a) Graphite brushes
b) Carbon brushes
c) Metal graphite brushes
d) Cannot be determined

Explanation

Q.3.

What is the requirement of the good commutation?

a) Brushes should be of proper grade, size and material
b) Brushes should smoothly run in the holders
c) Smooth, concentric commutator properly undercut
d) Brushes should be of proper grade, size, material, run smoothly in the holders and concentric commutator properly undercut

Explanation

Q.4.

How to avoid grooves in the commutation of DC machine with the help of brush?

a) Brushes of opposite polarity should track each other
b) Brushes of same polarity should track each other
c) Brush position has no effect on the commutator grooving
d) Brushes should not track each other

Explanation

Q.5.

Reason behind the rapid wear of brushes is __________

a) Abrasion from dust
b) Excessive spring pressure
c) Rough commutator bars
d) Abrasion from dust, excessive spring pressure and rough commutator bars

Explanation

Q.6.

For both lap and wave windings, what is the number of commutator bars equal to?

a) Slots
b) Armature conductors
c) Winding elements
d) Poles

Explanation

Q.7.

Spacing between the brushes for a 4-pole machine in terms of commutator segments forconductor segments is _____

a) 48
b) 3
c) 2
d) 6

Explanation

Q.8.

Spacing between the brushes for a 4-pole machine in terms of commutator segments is equal toWhat will be the number of armature slots?

a) 48
b) 3
c) 24
d) 6

Explanation

Q.9.

What is the range of the brush friction coefficients for medium category?

a) 0.40 and above
b) 0.22 to 0.40
c) 0.11 to 0.22
d) 0.08 to 0.11

Explanation

Q.10.

Specific resistance for a brush is given by _________

a) R = (E * W * T) / (I * L)
b) R = (E * W * I) / (T * L)
c) R = (E * W * I) * (T * L)
d) Doesn’t depend on E, W, T, I, L.

Explanation

Q.11.

How many poles to be used in DC machine if brushes are placed 4 commutator segments apart forcommutator segments?

a) 8
b) 12
c) 2
d) 4

Explanation

Q.12.

DC generators are disconnected/connected from/to the busbars only under the floating condition because ____________

a) To avoid sudden loading of the prime mover
b) To avoid burning of all switch contacts
c) To avoid mechanical jerk to the shaft
d) To avoid sudden loading of the prime mover, burning of all switch contacts and avoid mechanical jerking to the shaft

Explanation

Support mcqgeeks.com by disabling your adblocker.