(a) commutator with large number of segments.
(b) equalizer rings.
(c) carbon brushes.
(d) graphite brushes.
Answer: (a) commutator with large number of segments.
Explanation:
CONCEPT: Ripple in DC Generator EMF
- The
EMF generated in the armature conductors of a DC
generator is alternating in nature.
- The commutator converts
this internally generated AC into unidirectional (DC) output.
- However,
the DC obtained is pulsating, containing ripples.
- Ripple
magnitude depends on how smoothly the AC is mechanically rectified.
Role of Commutator Segments
- A commutator
with a large number of segments:
- Divides
the armature winding into many small sections
- Causes more
frequent current reversal
- This
makes the rectified output:
- Closer
to pure DC
- Smoother
with reduced ripple content
EXPLANATION
- Increasing
the number of commutator segments:
- Increases
the number of overlapping EMF waves
- Reduces
the amplitude of voltage fluctuations
- Hence,
ripple reduction is directly related to the number of commutator
segments.
Why Other Options Are Incorrect
(b) Equalizer rings ❌
- Equalizer
rings are used in lap windings to:
- Prevent
circulating currents
- They
do not reduce voltage ripples.
(c) Carbon brushes ❌
- Carbon
brushes:
- Improve
commutation
- Reduce
sparking
- They
do not directly smooth the DC output voltage.
(d) Graphite brushes ❌
- Graphite
brushes are also used for:
- Better
commutation
- Lower
contact resistance
- They do
not affect ripple magnitude.
FINAL ANSWER
✅ Correct option: (a)
Commutator with large number of segments
✔️ Key One-Line Exam Statement
Increasing the number of commutator segments reduces
ripples in the DC generator output voltage.