Optimal Design of Asymmetrical Rotor with MAS Method for Improving Torque Density of PMa-SynRM in High-Speed Railway Applications

In this paper, a novel approach is introduced to enhance the torque density of a permanent magnet-assisted synchronous reluctance motor (PMa-SynRM). The PMa-SynRM reduces permanent magnet usage by leveraging both reluctance and magnetic torques along the q-axis and d-axis. In this study, our objective was to enhance torque density by minimizing the phase difference between the d-axis and q-axis, which in turn narrows the gap between the reluctance and magnetic torques. The Magnet Axis Shift (MAS) method was employed to effectively reduce the phase difference between the two axes. Additionally, motors used in high-speed railways actively employ regenerative braking during deceleration, leading to limitations posed by back electromotive force (BEMF). Using Finite Element Analysis (FEA), we compared the performance of both Conventional PMa-SynRM and MAS PMa-SynRM. As a result, it was confirmed that the MAS PMa-SynRM is suitable for high-speed railway applications due to the improvement in torque density and reduction in BEMF, as demonstrated through the analysis.