Optimization Methods of Torque Density for Developing the Neodymium Free SPOKE-Type BLDC Motor

In this paper, we propose a method for optimizing the torque density to develop a SPOKE-type brushless direct current (BLDC) motor that does not require the use of a neodymium permanent magnet. Recently, the price of neodymium magnets has increased significantly owing to the rising prices of rare-earth minerals. Therefore, here we developed a method to maximize the torque density by using ferrite magnets instead of neodymium magnets. The proposed model was inserted into the auxiliary magnets in the center of a rotor after changing the existing interior permanent magnet-type BLDC motor to a SPOKE-type motor, and the effective air-gap flux density (Bg) was maximized. We also developed an optimization tool to determine the volume of a magnet that would generate the maximum torque at a SPOKE-type motor structure including an auxiliary magnet. We manufactured a SPOKE-type motor designed using these optimization tools. Finally, we compared and analyzed finite element method simulation results and experimental results.