- Lap Winding Definition: A lap winding is defined as a winding where successive coils overlap and connect to the same commutator segment under the same magnetic pole.
- Simplex Lap Winding: In Simplex Lap Winding, the number of parallel paths between the brushes equals the number of poles.
- Duplex Lap Winding: In Duplex Lap Winding, the number of parallel paths between the brushes is twice the number of poles.
- Lap Winding Formula: Important formulae include Back pitch (YB), Front pitch (YF), Resultant pitch (YR), and Commutator pitch (YC).
- Lap Winding Diagrams: Diagrams illustrate the coil connections in both Simplex and Duplex Lap Windings.
Armature windings on a DC machine come in two families: lap windings and wave windings. This page is about lap windings, including simplex and duplex lap.
Simplex lap has one set of paths (m = 1). Duplex lap has two (m = 2).
What is a Lap Winding?
Successive coils in a lap winding overlap. The name comes from each coil doubling back onto the next. The diagram below shows that fold.
The finish of one coil and the start of the next coil under the same pole land on the same commutator bar.
In the picture, coil 1 finishes and coil 2 starts on commutator segment 2. Both coils sit under the same N pole.
Two lap multiplexes are used:
- Simplex Lap Winding
- Duplex Lap Winding
Simplex Lap Winding
When the number of parallel paths equals the number of poles, the winding is a Simplex Lap Winding.
Duplex Lap Winding
When the number of parallel paths is twice the number of poles, the winding is a Duplex Lap Winding.
Design symbols used below:
If,
- Z = the number of conductors
- P = number of poles
- YB = Back pitch
- YF = Front pitch
- YC = Commutator pitch
- YA = Average pole pitch
- YP = Pole pitch
- YR = Resultant pitch
Back and front pitches then have opposite sign and unequal size.
YB = YF ± 2m
- m = multiplicity of the winding.
- m = 1 for Simplex Lap winding
- m = 2 for Duplex Lap winding
When
YB > YF, the winding is progressive.
YB < YF, the winding is retrogressive.
Back pitch and front pitch must both be odd.
Resultant pitch (YR) = YB – YF = 2m (take the signed 2m of the multiplex).
YR comes out even, as the difference of two odd numbers.
Commutator pitch (YC) = ±m
Number of parallel paths in the lap winding = mP
Start from the 1st conductor,
| Back connections | Front connections |
| 1 to (1+YB) = (1+5) = 6 | 6 to (6-YF) = (6 – 3) = 3 |
| 3 to (3+5) = 8 | 8 to (8-3) = 5 |
| 5 to (5+5) = 10 | 10 to (10-3) = 7 |
| 7 to (7+5) = 12 | 12 to (12-3) = 9 |
| 9 to (9+5) = 14 | 14 to (14-3) = 11 |
| 11 to (11+5) = 16 | 16 to (16-3) =13 |
| 13 to (13+5) = 18 = (18-16) = 2 | 2 to (18-3) = 15 |
| 15 to (15+5) = 20 = (20-16) = 4 | 4 to (20-3) = 17 = (17-16) = 1 |
Advantages of Lap Winding
Lap windings are used because:
Disadvantages of Lap Winding
Trade-offs versus wave winding:
- Generated emf per path is lower than in a wave winding, so more conductors are needed for the same voltage, which raises copper cost.
- Slot space is used less economically than in a wave winding.
thank you sir ….easy to understand
No problem at all Hamza – happy to hear it helped!