Method to Minimize Space Harmonics of Fractional Slot Concentrated Windings in AC Machines

A winding method for AC Machines is presented to eliminate both the sub and super space harmonics of fractional slot concentrated windings where the stator slot numbers are integer multiples of six. The proposed method is based on three single-layer concentrated windings where the number of turns in one layer is optimized whereas the other layers are shifted to cancel the sub-harmonics. The cancellation of super-harmonics is achieved through series connection of two space shifted layers which effectively doubles the number of slots. The proposed method has been successfully validated in widely used 12-slot/10-pole and 18-slot/14-pole machine configurations. Applying the proposed winding concept to a Permanent Magnet Synchronous Machine (PMSM) demonstrates the cancellation of dominant sub and super harmonics, THD reduction, torque ripple reduction, and core loss minimization.