Specifications

4. DEVELOPMENT OF WINDING - AC MACHINE

4.1 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

From equation 3.5, the pole pitch = = 6; and 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 180

. 180

corresponds to 6 slots.

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, Y

= 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, Y

= Y

– 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.

Table 4.1 Single Phase AC Lap Winding Table

S.No. -Y

+ Y

117

228

339

4410

5511

6612

71319

81420

91521

10 16 22

11 17 23

12 18 24

Number of slots

Number of Poles