The document describes two types of AC lap windings for electrical machines: 1) A single-phase, single-layer lap winding is developed for a 4-pole, 24-slot AC machine. The winding table is provided. 2) A double-layer lap winding is developed for a 3-phase, 4-pole, 24-slot AC machine. The slot distribution and winding table for the RYB phases are provided. A diagram of the complete main winding is included.

1. Name :- Smit Shah -140410109096
T.Y Electrical 2 Sem 5
Subject:-ELEMENTS OF ELECTRICAL
DESIGN
Topic :- 1

2. AC Lap windings….
• There are mainly two types of AC lap winding
is available…
1. AC SINGLE PHASE WINDINGS…
2. Double layer windings Lap winding…
2

3.  AC SINGLE PHASE WINDINGS…
AC Lap Winding : Develop a single phase, single layer AC lap winding for a 4 pole AC machine
having 24 slots.
Solution : In single layer winding, the number of coil is equal to half the number of slots on the
stator, so that each slots contains only one coil side. Therefore, number of coils, C = 12
the pole pitch = Number of slots/Number of Poles
=24/6
=4
slots per pole per phase, m = 24/4x1 = 6
Slots 1 to 6 and 13 to 18 lie under North pole regions N1 and N2 respectively. Similarly slots 7 to
12 and 19 to 24 lie under South pole regions S1 and S2 respectively. In other words, the first
pole pair covers slots 1 to 12 and the second pole pair covers slots from 13 to 24.
For full pitch winding, angle between the two sides of the same coil is 1800
ed. 1800
ed corresponds
to 6 slots.
3

4. Number of coils(or slots) per pole= 6.
The coil in slot no. 1 is to be connected to coil in slot no. (1 + slots per pole = 1 + 6 = ) 7 or back
pitch, Yb = 7, ie., if slot no. 1 is at the beginning of the first North Pole, N1, the slot no. 7 will
be at the beginning of the first South Pole, S1.
The winding pitch, Y = +2 (progressive winding)
Therefore, the front pitch, Yf = Yb – Y = 5.
Table 4.1 gives the complete winding table for 4 pole, 24 slot ac machine.
When the winding for one pole pair is completed then last coil side of this pair is connected to
the first coil side of the next pole pair, ie., coil in slot no. 12 is connected in series with the
coil in slot no. 13. Similarly, the winding for the second pole pair is completed.
4

5. S.No -Yf + Yb
1 1 7
2 2 8
3 3 9
4 4 10
5 5 11
6 6 12
7 13 19
8 14 20
9 15 21
10 16 22
11 17 23
12 18 24
5

6. To draw the main winding diagram, solid lines of equal length and equal distance
equal to number of slots is drawn. Connect the coils as per the Winding Table.
Arbitrarily assume a particular current direction to the coil sides under the pole pairs.
For the coil sides under North Pole regions, assume downward current direction
and vice versa for the South Pole regions, as shown in Fig..
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
N1 S1 N2 S2
6

7.  Double layer windings Lap winding…
Problem 1 : Develop the layout of a lap winding for a 3 phase ac machine having 4
pole and 24 slots. There are 2 coil sides per slot.
Solution : Coil groups per phase = 3 x 4 = 12
Slots per pole per phase, m =24/12
=2
Angle between adjacent slots, â =180/24
=30
For full pitch coils, the coil span, á = 0, ie., angle between the two sides of the same
coil is 1800e.
7

8. There are 3 phase groups per pole, each comprising of 2 slots. The distribution of
slots, of
phase sequence RYB or ABC, is shown in Table
Table Polar Groups
Poles N1 S1 N2 S2
Phase
R 1,2 7,8 13,14 19,20
B 3,4 9,10 15,16 21,22
Y 5,6 11,12 17,18 23,24
8

9. The start of the phases must be displaced by 1200 and so must be finishes.
The top coil side in slot no. 1 is to be connected to bottom coil side in slot no. (1 + 6 =)
7 or back pitch, Yb = 13, in terms of coil sides, ie., if slot no. 1 is at the beginning of
the first North Pole, N1, the slot no. 7 will be at the beginning of the first South
Pole, S1.
The winding pitch, Y = +2 (progressive winding).
The front pitch, Yf = Yb – Y = 13 – 2 = 11.
Now, coil sides 1 and 14 form a coil. Coil side 14 is connected to coil side (14 – Yf = ) 3,
and coil side 3 is connected to coil side (3 + Yb = ) 16. So coil sides 3 and 16 form
the second and the last coils of this pole phase groups.
9

10. Winding Table for RYB Phases
S.No. Top coil side (-Yf) Bottom coil side
(+Yb)
R or A phase per pole per phase
1 1 14
2 3 16
3 13 26
4 15 28
5 25 38
6 27 40
7 37 2
8 39 4
10

11. Y or B phase per pole per phase
9 9 22
10 11 24
11 21 34
12 23 36
13 33 46
14 35 48
15 45 10
16 47 12
11

12. B or C phase per pole per phase
17 5 18
18 7 20
19 17 30
20 19 32
21 29 42
22 31 44
23 41 6
24 43 8
12

13. Fig. gives the complete main winding diagram for 3 phase 4 pole 24 slots double layer
lap winding.
13