Wave winding
We know that, Yc is commutator pitch
- Here Yc ≠ 1 but Yc ≈ 2S/P
- Assume S=16 and P=4. Coil span = S/P =16/4 =4, Yc = 8
- The first coil is (1-5') and terminated on commutator 1 and 9. The second coil (9-13') to be connected in series with the first and to be terminated on commutator segment (9 + 8 = 17). Since there are only 16 commutator segments so 17 is identical to 1. Hence, we terminate where we started and cannot connect any more coils in series.
- Our inability to complete the winding, will persist till 2S is a multiple of P. So, we modify the expression for Yc = 2(S ± 1)/P
- No. of poles, P = 4
- No. of slots, S = 17
- Winding pitch, Yc = 2(S+1)/P choosing +1 for progressive winding
- Yc = 2(17+1)/4 = 9
- Coil span = S/P = 4
- First segment (1-5') starts from 1 and ends at 20, where second coil starts and ends on commutator segment-2
- Between any two consecutive commutator segments (P/2) coils will be present winding progresses like a wave. Hence the name wave winding.
- Number of commutator segment between positive and negative brushes = S/P
- Number of coils between positive and negative brushes = (S/P)*(P/2) = S/2
- So, only 2 brushes core required and each brush divides coil into 2 parallel paths.
Back pitch:- The distance between top and bottom coil sides of one coil measured at back of armature is called back pitch, Yb . We give odd numbers to top coil sides and even numbering to bottom coil sides. So, 5' can be numbered as 10.
As for example, for lap winding: Yb = 10 - 1 = 9
For wave winding: Yb =10 - 1 = 9
Front pitch:- The distance between two coil sides connected to same commutator segment is called front pitch, Yf .
For lap: Yf = 10 - 3 = 7 (using commutator segment 2)
For wave: Yf = 19 - 10 = 9 (using commutator segment 10)
Winding pitch:- The distance between two consecutive similar top or bottom coil sides as winding progresses is called winding pitch, Yw .
For lap, Yw = 3-1 = 2 = Yb - Yf
For wave, Yw = 19-10 = 18 = Yb + Yf
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