Specifications

Fig. 4.11 gives the coil group connections for half coil winding for each phases.

They form a coil group. The rule for connecting together the coils in a coils group is that the

end wire of one coil must be connected to the beginning of next coil in the group and so on. This

is done in order that the emfs of the coils in a coil group, add.

Fig. 4.12 gives the complete main winding diagram for a 4 pole 24 slots ac machine using

single layer half coil winding. In Fig. 4.12, R

, R

, B

, Y

, and Y

indicate the starting and

finishing ends of RBY phases respectively.

Whole Coil Winding

Total number of coils =

= 6; Coils per phase =

= 4; Number of coils of groups per

phase = 3 x 2 = 6

If the first phase, say R or A phase starts at slot no.1, the Y or B phase should start at 120

/30

= 4 slots away ie., in slot (1 + 4 = ) 5, and the B or C phase should start at (5 + 4 =) 9.

Starting with coil in slot no. 2, the start of R phase lies in slot no. 2, that of Y phase in slot no.

(2 + 4 = ) 6 and that of B phase in slot no. (6 + 4 = ) 10.

Fig. 4.13 - Coil group connections for whole coil winding

Fig. 4.13 gives the coil group connections for whole coil winding for each phases.

To draw the main winding diagram, draw 24 solid lines of equal length and distance equal to

the number of slots, as shown in Fig. 4.14. For series connection, the finish of first coil of a

phase is connected to the finish of the second coil group of the same phase. The start of the

second coil group is connected to the start of the third coil group and so on. In Fig. 4.14, R

, R

, B

, Y

, and Y

indicate the starting and finishing ends of RBY phases respectively.