A Study on the Magnetization level of Concentrated Flux Type Synchronous Motor Considering the Post-Assembly Process

Abstract

The number of devices using motors is increasing worldwide, and interest in permanent magnets, an essential component of permanent magnet synchronous motors with wide operating areas and high-power density, is growing rapidly. In particular, rare-earth permanent magnets with high residual induction are widely employed in different applications, including automotive drive motors and electric power steering (EPS) motors. However, because rare earth elements are limited to specific regions, problems such as supply and demand imbalances and price spikes could occur. To address this issue, various types of motors that do not require rare earth elements are currently being developed. In particular, research is being conducted on IPMSM that do not use rare earth elements but instead use ferrite permanent magnets. However, in the case of ferrite permanent magnets, the residual induction is about 1/3 of that of rare earth permanent magnets, so the rotor shape tends to become intricated to obtain high air gap magnetic flux density. Therefore, when magnetization is performed after post assembly to increase productivity, there is a problem in that the magnetization is not completely changed in local areas. In this paper, we reviewed methods for magnetizing permanent magnets and uneven magnetization that can occur in rotors of various shapes.