Specifications

Fig. 4.16 - Slots per pole per phase

Half coil winding

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

/15

= 8 slots away ie., in slot (1 + 8 = ) 9, and the B or C phase should start at (9 + 8 =) 17.

The winding should be connected between alternate North and South poles. First, R or A

phase winding is started. If one side of the coil is placed in slot no. 1, the other side of the coil

should be placed in slot no. 16, ie., the last coil side of phase R or A phase under the next pole.

The coil side in slot no. 2 should be connected to the last but one coil side of the same phase

under the next pole, ie., slot no. 15, in this case. Now, the coils formed by coil sides placed in the

slots 1 and 16, 2 and 15, 3 and 14, and 4 and 13 belong to the same phase, and are concentric

with each other. 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 add in a coil group.

Fig. 4.17 - Coil group connections for half coil wnding

Fig.4.17 gives the coil group connections for half coil winding for each phase.

Fig. 4.18 gives the complete main winding diagram for a 2 pole 24 slots ac machine using

single layer half coil winding. In Fig. 4.20, R

, R

, B

, Y

, and Y

indicate the starting and

finishing ends of RBY phases respectively.

910

R B

Pole pitch