Design Optimization and Comparative Study of Skewed Halbach-Array Magnets TORUS Axial-Flux Permanent Magnet Motors for Electric Vehicles

Abstract

The double-sided axial flux (TORUS) permanent magnet (PM) machine has been shown to be an efficient structure for electric vehicles (EVs). This paper introduces the combined techniques of skewed PMs and Halbach-array arrangement to improve the TORUS-type axial flux PM motor performance. The suitable configuration for implementing this combination in the TORUS PM machine was investigated, considering two possible models. Each model of the skewed Halbach-array PM TORUS motor is optimized using response surface methodology to meet the performance requirements of an EV application. A comparative evaluation of machine performance via 3D finite element analysis is performed and detailed insight into the design and configuration of the skewed Halbach-array PM TORUS machine is presented. Under no-load conditions, the optimal skewed Halbach-array PM TORUS motor exhibits 4% higher back-EMF and 9.3% lower cogging torque compared to a benchmark TORUS motor. During on-load operation, the proposed motor shows an 8% increase in average torque compared to the benchmark, accompanied by a significant 7.8% reduction in torque ripple. The rationale behind this enhanced torque capability is explained in detail and is found to be due to enhanced flux-concentration and flux-cancellation effects within the motor. The efficiency of the proposed TORUS motor is enhanced. The results confirm the superiority of the combined skewed Halbach PM Array techniques to improve TORUS PM motor performance and suggest suitable configurations for this combined technique in EV motors.

Keywords

• Axial flux permanent magnet machines
• double-sided axial flux machines
• skewed permanent magnet
• Halbach permanent magnet arrangement
• electric vehicles