Distribution factor problem

An armature of a three phase alternators has 120 slots. The alternators has 8 poles. Calculate its distribution factor.

Solution :

        n = Slots/Pole = 120/8  = 15

        m = slots/pole/phase = n/3 = 15/3 = 5

        β = 180^o/n = 180^o/5 = 12^o

             Kd   = 0.957