(a) +1
(b) −1
(c) +1 or −1
(d) average pitch.
Answer: (c) +1 or −1
Explanation:
CONCEPT: Commutator Pitch in DC Armature Windings
- Commutator
pitch (
) is
defined as:
The distance between the two commutator segments to which
the two ends of a single armature coil are connected.
- It
is measured in terms of commutator segments, not conductors or
slots.
- Commutator
pitch indicates the direction and type of winding.
Commutator Pitch in Lap Winding
- In
a simplex lap winding:
(where 
is the multiplicity)
- For
simplex lap winding, the magnitude of commutator pitch
is:
- The sign of
commutator pitch depends on the winding direction:
- Progressive
(right-handed) winding:
- Retrogressive
(left-handed) winding:
- Hence,
for simplex lap winding:
General Rule (Multiplex Lap Winding)
- For
a multiplex lap winding:
- Therefore:
- Simplex
→
- Duplex
→
- Triplex
→
Related Pitches (Important Definitions)
Front Pitch ( 
)
- Front
pitch is defined as:
- The
distance between the second conductor of one coil and
the first conductor of the next coil
- Both
conductors are connected to the same commutator segment at the
front end.
Back Pitch ( 
)
- Back
pitch is defined as:
- The
distance by which a coil advances on the back of the armature
- It
can also be described as:
- The
distance between the first and last conductors of a coil.
Comparison with Wave Winding
- In simplex
wave winding:
- The
commutator pitch is not equal to 1
- It
is approximately equal to:
- This
large commutator pitch enables the wave winding to progress through all
poles before returning to the starting point.
FINAL CONCLUSION
- Commutator
pitch is the distance between commutator segments connected to a
coil.
- For simplex
lap winding:
- The
sign indicates progressive or retrogressive winding.
- This
is a key identifying feature of lap windings.
✔️ Key One-Line Exam Statement
For a simplex lap winding, the commutator pitch is always
±1; the sign depends on whether the winding is progressive or retrogressive.