Development of a High Power Density In-Wheel Motor Using Halbach Array Magnets

Abstract

In this study, a direct drive in-wheel system is proposed as a high power density system for reducing the intermediate parts, such as a speed reducer by increasing the torque. We propose a design strategy to show that multipolarization and the improvement of the gap magnetic flux density can effectively increase the power density. A Halbach array magnet rotor that combines the main electrode magnets and spoke magnets with the core is adopted as a technique for improving the gap magnetic flux density. We compare the Halbach array type rotor to the conventional SPM type rotor by using both of magnetic circuit calculation and FEM analysis. Moreover, the actual sized in-wheel motor prototype with the developed Halbach array magnet rotor is fabricated and measures the no-load induced back EMF. The measured no-load induced back EMF agrees well with the analyzed waveform.