Equivalent Magnetic Network Modeling of Variable-Reluctance Fractional-Slot V-Shaped Vernier Permanent Magnet Machine Based on Numerical Conformal Mapping

Abstract

The V-shaped permanent magnet synchronous machine (PMSM) has been successfully commercialized in hybrid-and all-electric vehicles fabricated by several famous companies. The advantages of PMSMs are a wide constant torque-speed range, high torque development capability and high power factor, and low torque ripple. In addition, the Vernier-PM (VPM) machines supersede conventional PMSM’s torque density and cogging torque. This paper presents a variable-reluctance fractional-slot V-shaped VPM (VR-FS-VVPM) machine with special rotor core surface. Hence, varying the air gap length over the direct and quadrature axes decreases the torque ripple considerably. Moreover, design of the PM-housing differs from previously introduced V-shaped VPM structures. As a result, the leakage flux in the yoke-side end-portion of the PM pieces reduces, enhancing the flux-linkage and power factor. To facilitate the design process further, an innovative equivalent magnetic network (EMN) model is established to improve performance prediction analytically. Moreover, conformal mapping is applied to create the permeance network for complex geometry air gap region. Here, a pentagonal-shape mesh-cell is used in the air gap region for capturing flux behaviour more accurately. The introduced method predicts the performance of the proposed VR-FS-VVPM machine. Finally, a typical 500 W, 12-slot/16-pole motor is designed and prototyped to validate the EMN-modelling against finite element analysis and experimental results.