Performance Improvement of Spoke-Type PM Motor by Changing Magnet Shape with the Same Amount of Magnet Usage

Abstract

This paper investigates the characteristics of spoke-type PM motor according to the three types of magnet shape i.e. rectangle, trapezoid, and inverted trapezoid in order to improve motor performances such as torque, iron loss, efficiency. The three types of magnet are resulted from the combination of three design factors i.e. upper thickness, lower thickness, and width of magnet. 2-D FEM coupled with design of experiment (DOE) and response surface methodology (RSM) is carried out to analyze and optimize magnet shape at the rated current and at the max current. From the analysis results of FEA, the spoke-type PM motor having the inverted trapezoidal magnet (ITM) shows the best performance in the aspect of average torque and motor efficiency with the same amount of magnet usage. The reason is studied and explained by analyzing the additional magnetic fields such as linear analysis, armature reaction field without magnetization and torque calculated by Maxwell stress tensor.