2層IPMSMのコギングトルクを低減するための溝を設けたロータ形状の設計手法

抄録

Interior permanent magnet synchronous motor (IPMSM) has the disadvantage of many space-harmonic waves in air-gap flux density, leading to a large cogging torque. This study proposed a design method of a rotor structure with the notch for reducing the cogging torque of a double-layered IPMSM. The proposed method focused on the pulsating component of the cogging torque, which depends on the squared air-gap flux density (B_g²) of the motor. First, we analyzed B_g² of the motor without the notch using finite-element analysis (FEA), and the waveform of B_g² was approximated by a step waveform. Then, ideal waveform of B_g² was obtained theoretically so that the major components of the cogging torque can be zero. Based on the ideal waveform of B_g², we determined the notch position and width. Finally, we determined the optimal notch depth by FEA. The proposed method was applied to two types of IPMSM whose sizes, structures, and PM materials were different. The cogging torques of both the motors with optimal notches reduced significantly. Moreover, it also revealed that the notch hardly affects the maximum torque on load.