Question 4.3: Design and draw a 2 layer progressive duplex lap winding for...

Here, Number of poles, P=6

Number of slots =24

Number of coil sides, Z=24 \times 2=48  (2 layer winding)

For duplex winding, m=2

For progressive winding, Y_{B}=Y_{p}+1=8+1=9

The connections are to be made as per the following table.

Steps to draw developed winding diagram

1. Draw 24 \times 2=48 coil-sides and number them.
2. Since it is a two-layer winding draw all the upper (odd numbered) coil-sides by firm continuous lines and all the lower (even numbered) coil sides by dotted lines.
3. Draw six poles N, S, N, S, N and S alternately, each pole covers the space of 48 / 6=8 coil sides. Consider that the poles are below the coil sides.
4. Mark the direction of motion (or rotation) of the conductors, say it is from left to right as marked.
5. It is a duplex winding having two entrants, start the connections of one winding from conductor (or coil side) number 1. Connect 1 to 10 at the back and 10 to 5 at the front and so on as per the table.

For second winding start from coil side No. 3. Connect 3 to 12 at the back and 12 to 7 at the front and so on as per the table.

6. Mark the direction of flow of current in the coil-sides i.e., downwards in the coil sides which are under the influence of North-pole and upward for South Pole.
7. Connect each front end of the coil to each commutator segment as marked in Fig. 4.28.
8. Place six brushes at six places, each brush is to cover two commutator segments, as shown in Fig. 4.28. Brushes are placed where either current is meeting (segment No.1-2 ; 9-10 and 17-18 ) or separating (segment No. 5-6 ; 13-14 ; 21-22 )
9. The three brushes where current is meeting are joined together and a positive terminal is obtained. The other three brushes where current is separating are joined together and a negative terminal is obtained.
10. The series, spiral winding connections of the two windings with separate entrant are shown in Fig. 4.29, the brushes are placed as explained above.
11. The parallel paths formed by each winding are drawn in Figs. 4.30 and 4.31. Here, each winding is having six parallel paths. In all there are 12 (i.e., A=m P when m=2 and P=6 in this case) parallel paths.