Basic rewind terminology, formulas,
and definitions (continued)

COILS PER POLE-PHASE GROUP (C/PPG): As the name implies, this term refers to the number of coils that comprise an individual PPG. The number of coils in the PPGs may or may not be equal. C/PPG can be determined by dividing the total active coils by the number of pole-phase groups, or:

C/PPG =
total active coils ÷ pole-phase groups

C/PPG=TAC÷PPG

Example: How many C/PPGs will a four-pole, three-phase motor with 36 active coils have?

PPGs = 4 x 3 = 12
C/PPG = 36 ÷ 12 = 3

In this example, the result is a whole number meaning that each PPG will contain the same number of coils, in this case, 3.

When the result is a mixed number, the C/PPG will not be equal and the exact combinations of C/PPG must be determined.

Example: How many C/PPG will a six-pole, three-phase motor with 48 active coils have?

PPGs = 6 x 3 = 18
C/PPG = 48 ÷ 18 = 2-12/18

The mixed number 2-12/18 indicates that some groups will have two C/PPG and some will have three C/PPG. In this example, the numerator of the fraction indicates the number of PPGs that will contain the larger number of C/PPG. In other words, 12 of the 18 PPGs will contain 3 coils each and the remaining 6 groups will contain 2 coils each.

We can check this configuration by multiplying as follows:

12 PPG x 3 coils= 36 coils
6 PPG x 2 coils = 12 coils
36 + 12 = 48 coils

For electrical balance, coil grouping must be arranged so that each phase will contain the same number of active coils evenly distributed around the stator.

In our example, we had 12 groups of 3 coils each and 6 groups of 2 coils each. By dividing the groups by 3 (the number of phases), it can be seen that each phase will contain 4 groups of 3 coils and 2 groups of 2 coils or 16 coils per phase.

The most common method of determining how the grouping will be laid out is to draw a matrix and enter the smaller number of coils first, as shown below.

Then, enter the larger number of coils in the blank spaces and check both the number of active coils per phase as well as the total number of active coils, as in the example below.

Remember, this example was for a six-pole motor, and that computing uneven grouping can be done in the same way regardless of the number of poles.