(a) armature conductors.
(b) winding elements.
(c) poles.
(d) slots.
Answer: (d) slots.
Explanation:
CONCEPT: Commutator Bars / Segments
- A commutator is
a mechanical rectifier used in DC machines.
- It
converts the alternating EMF induced in the armature into unidirectional
(DC) output.
- The
commutator is made of:
- Copper
bars (segments)
- Insulated
from each other and from the shaft by mica
- Carbon
or graphite brushes collect current from the commutator and
deliver it to the external circuit.
Relationship Between Slots, Coils, and Commutator Bars
- The armature
core is provided with slots.
- Each
slot normally contains:
- One
coil side (in single-layer winding), or
- Two
coil sides (in double-layer winding)
- Every armature
coil has its ends connected to commutator segments.
- Hence:
- In
standard DC machines:
Applicability to Lap and Wave Windings
- This
relationship holds true:
- For lap
winding
- For wave
winding
- The type
of winding affects:
- Number
of parallel paths
- Current
and voltage rating
but does not affect the number of commutator segments.
Why This Is Important
- Using more
coils and commutator segments:
- Produces
smoother DC output
- Reduces
ripple in generated voltage
- Improves
commutation
FINAL CONCLUSION
- For
both lap and wave windings:
- Therefore,
the correct answer is:
Correct Answer
✅ Option (d): Slots
✔️ Key One-Line Exam Statement
In a DC machine, irrespective of lap or wave winding, the
number of commutator bars is equal to the number of armature slots (or coils).