Multi-Material Topology Optimization with Continuous Magnetization Direction for Permanent Magnet Synchronous Reluctance Motors

TL;DR

This paper introduces a novel multi-material topology optimization method with continuous magnetization directions for designing high-torque permanent magnet synchronous reluctance motors, reducing computational costs and enabling innovative rotor designs.

Contribution

It presents a new density-based distribution scheme with continuous magnetization angles, an efficient Nitsche-type mortaring approach, and a magnetization angle filtering method for optimal motor design.

Findings

The proposed method achieves higher torque designs.

Continuous magnetization directions enable more design flexibility.

Filtering improves the feasibility of magnetization angles.

Abstract

Permanent magnet-assisted synchronous reluctance motors (PMSynRM) have a significantly higher average torque than synchronous reluctance motors. Thus, determining an optimal design results in a multi-material topology optimization problem, where one seeks to distribute ferromagnetic material, air and permanent magnets within the rotor in an optimal manner. This study proposed a novel density-based distribution scheme, which allows for continuous magnetization direction instead of a finite set of angles. Thus, an interpolation scheme is established between properties pertaining to magnets and non-linear materials. This allows for new designs to emerge without introducing complex geometric parameterization or relying on the user's biases and intuitions. Toward reducing computation time, Nitsche-type mortaring is applied, allowing for free rotation of the rotor mesh relative to the stator mesh. The average torque is approximated using only four-point static positions. This study investigates several interpolation schemes and presents a new one inspired by the topological derivative. We propose to filter the final design for the magnetization angle using K-mean clustering accounting for technical feasibility constraints of magnets. Finally, the design of the electrical motor is proposed to maximize torque value.