Name :- Smit Shah -140410109096

T.Y Electrical 2 Sem 5

Subject:-ELEMENTS OF ELECTRICAL DESIGN

Topic :-Lap winding for AC machine… 1

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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…

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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 =4slots 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 1800ed. 1800

ed corresponds to 6 slots.

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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.

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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

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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

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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.

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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 19,20B 3,4 9,10 15,16 21,22Y 5,6 11,12 17,18 23,24

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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.

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Winding Table for RYB Phases

S.No. Top coil side (-Yf) Bottom coil side (+Yb)

R or A phase per pole per phase

1 1 142 3 163 13 264 15 285 25 386 27 407 37 28 39 4

11

Y or B phase per pole per phase

9 9 2210 11 2411 21 3412 23 3613 33 4614 35 4815 45 1016 47 12

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B or C phase per pole per phase

17 5 1818 7 2019 17 3020 19 3221 29 4222 31 4423 41 624 43 8

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