Field Modulation and Torque Production Mechanism in Dual-PM Reluctance Machines with Harmonic Winding

Field modulation and torque production effects in dual-PM reluctance machines (DPM-RMs) with fundamental and high-order harmonic winding design are investigated and compared in this paper. In comparison to the original fundamental harmonic winding design (FHWD) making use of fundamental PM field harmonics, high-order harmonic winding design (HHWD) utilizes high-order PM field harmonic, contributing more to torque production. A magneto-motive force (MMF)-permeance model is built to showcase the effective working harmonics. Then, the torque contributions of main working harmonics of two winding designs are identified and quantified by the Maxwell stress tensor (MST) method to offer a comprehensive understanding of the torque production mechanism. In which, it is shown that the dominant working harmonics of HHWD are more clustered than that of FHWD. Next, the electromagnetic performance of DPM-RMs with FHWD and HHWD are compared, demonstrating that the proposed HHWD can realize a 142% higher torque density, and a 51.40% lower torque ripple. Finally, the prototype of DPM-RM with HHWD is fabricated, coinciding with FEA result.