Session: 02-03-01: Optimization

Paper Number: 150320

150320 - Multi-Material Topology Optimization of Permanent Magnet Synchronous Motor 

Permanent Magnet Synchronous Motors (PMSMs) have garnered significant attention due to their brushless operation, high reliability, and efficiency. These motors boast a high power-to-size ratio, allowing for smaller overall design sizes without sacrificing torque. A synchronous electric motor is an AC motor in which the rotation of the shaft is synchronized with the frequency of the supply current in a steady state. Synchronous motors use electromagnets in the stator to create a magnetic field that rotates synchronously with the oscillations of the current. A PMSM specifically employs permanent magnets embedded in the rotor to generate a constant magnetic field, while the stator, connected to an AC electricity supply, produces a synchronized rotating magnetic field. PMSMs are typically used for high-performance and high-efficiency motor drives, characterized by smooth and accurate rotation over the entire speed range of the motor. The PMSM design problem is approached as a variational problem constrained by Maxwell’s equations, which describe the behavior of electric and magnetic fields in the motor.

The complexity of the electromagnetic system structure has traditionally made the design process reliant on the engineer’s experience and intuition. However, topology optimization, a numerical tool, can optimize the material layout within a given design domain. In this study, topology optimization of the PMSM was performed using the Solid Isotropic Material with Penalization (SIMP) method with an MMA solver. The design domain was the rotor core, with the objective function to maximize axial torque and minimize torque ripple. The optimization constraints included the volume ratio of the permanent magnet and a target torque.

Performance measures in electric machines include magnetic field distribution, system energy, system power, force, and torque, etc. The interaction of rotor and stator magnetic fields generates net torque that is making the motor able to convert the windings current into mechanical power. In this design example, the performance of the PMSM was evaluated based on axial torque. After optimization, the axial torque in the optimized design showed a significant increase compared to the initial design. The average torque of the initial design was 107.12 Nm, whereas the optimized design achieved 1607.7 Nm. The volume ratio of the permanent magnet in the initial design was 22.454%, with the volume constraint of the permanent magnet in the optimized design set to an upper bound of 15% of the rotor core, resulting in a final optimized volume ratio of 15%.

The rotor structure of the eight-pole Permanent Magnet Synchronous Motor (PMSM) was designed using the Solid Isotropic Material with Penalization (SIMP) method, employing a Method of Moving Asymptotes (MMA) solver. Although the analysis of the PMSM is inherently time-dependent, this study conducts a magnetostatic field analysis at each rotor position. Multi-material topology optimization in PMSMs has numerous potential applications. Notably, it can significantly reduce the usage of rare-earth materials (permanent magnets) without compromising motor performance.

Presenting Author: Lingfeng Gao Stony Brook University

Presenting Author Biography: Lingfeng Gao is currently a Ph.D. Candidate in the Department of Mechanical Engineering at Stony Brook University, working under the supervision of Prof. Shikui Chen. Lingfeng Gao earned a Bachelor's degree in 2020 from Auburn University, followed by a Master's degree in 2021 from George Washington University. His research interests include computational modeling, structural design, and shape/topology optimization using level set-based and density-based methods, as well as the applications of additive manufacturing.

Authors:

Lingfeng Gao Stony Brook University
Shikui Chen Stony Brook University
Fang Luo Stony Brook University
Jon Longtin Stony Brook University
David Torrey GE Vernova