Tom Bishop, P.E.
EASA Senior Technical Support Specialist

When the number of coils per group is the same throughout a three-phase lap winding, the grouping sequence is simply that number of coils repeated three (since it is three-phase) times the number of poles. For example, a 48-slot 4-pole winding has 12 groups of 4 coils.

The formula used to determine the average number of coils per group is:
Coils per group = slots divided by groups.

We don’t advocate using full slot coils with a lap winding; thus, the total number of coils is equal to the number of slots. The number of groups in an alternating pole winding is equal to the number of phases times the number of poles. In many cases, there are windings that have unequal coils per group, such as a 36-slot 8-pole winding, which has 24 groups with an average of 1.5 (36/24) coils per group.

LOGIN TO VIEW AND DOWNLOAD THE ARTICLE