A New Space Harmonics Minimization Strategy for Fractional Slot Concentrated Windings

A new winding concept for fractional slot concentrated winding (FSCW) is proposed that can simultaneously cancel both sub and higher order harmonics of stator MMF. The new winding concept proposes two sets of three-phase windings by doubling the number of stator slots connected in wye-delta configuration. These two winding sets are shifted in space with respect to each other and are connected in series. The wye-delta configuration eliminates sub-harmonics and enhances the torque-producing component whereas their relative shifting angle eliminates the dominant higher order harmonics to provide a cleaner and enhanced spectrum. This concept is effective when the stator slot number is multiple of twelve. The application of the proposed winding to a PM machine demonstrated dominant sub and higher order harmonics cancellation, THD reduction, torque ripple reduction, and magnetic loss reduction along with torque density and power factor improvements.