Spatial Harmonic Magnetomotive Forces in Irregular Windings and Special Connections of Polyphase Windings

A general procedure for calculating the magnitudes of all the spatial harmonic magnetomotive-force (mmf) waves is developed. This method is applicable to any polyphase winding with uniform coils and slot pitches, which is excited by a balanced polyphase supply and in which any or all of the coils are energized, no matter how they are connected. The procedure was programmed for a digital computer and numerous illustrative examples were computed; these include: comparison of a 24-slot 6-pole irregular winding with a 27-slot fractional-slot winding, effects of transposition of phase coils between groups, part-winding starting with adjacent poles excited and with alternate groups excited, three double-delta starting arrangements, and a 2-speed motor with pole-amplitude modulation. Previously published studies on these connections confirm the accuracy of the analysis presented here.