Analysis and design considerations of an axial-flux dual-rotor consequent-pole Vernier-PM machine for direct-drive energy conversion systems

摘要

The Vernier permanent-magnet (VPM) machine is known as high-torque and low-speed drive solution suitable for direct-drive applications such as electric-vehicles and wind-turbines. This study presents a high-efficiency axial-flux VPM machine with dual-rotor of consequent-pole topology and one yoke-less concentrated-winding stator. The consequent-pole VPM machine is a special VPM structure that introduces high torque-density as the conventional-VPM machine incorporating a significantly lower volume of PM material. The proposed machine represents desirable features of higher efficiency, improved reliability and lower weight and axial-length compared to the traditional motor-gearbox approach. These advantages are achieved due to: dual-PM rotors for appropriate forming the magnetic flux lines and increasing torque-to-weight ratio, yokeless-stator for reducing flux path, concentrated winding with no overhang for reducing copper-loss, using rectangular-shaped copper conductors for increasing winding fill factor and selecting the core material from high-performance grain-oriented magnetic steel for reducing core-loss. After presenting the structure, the operating principles are discussed based on the magnetic flux behaviour and a quasi-3D magnetic-equivalent-circuit model is extracted. The accuracy of the analytical model is validated by comparing the results with the FE results. Finally, the effects of the design parameters on electro-magnetic performance are analytically investigated by studying a 10 kW machine.