winding factor is what makes the rms generated voltage in a three-phase AC electrical generator become lesser. This is because the armature winding of each phase is distributed in a number of slots. Since the emf induced in different slots are not in phase, their phasor sum is less than their numerical sum. This reduction factor is called distribution factor Kd. Another factor that can reduce the winding factor is when the slot pitch is smaller than the pole pitch, called pitch factor Kp. The winding factor can be calculated as Kw = Kd * Kp.