Multimaterial Magneto-Structural Topology Optimization of Wound Field Synchronous Machine Rotors

A combined magneto-structural topology optimization approach based on the solid isotropic with material penalization method is proposed for wound field synchronous machines (WFSMs) to optimally distribute multiple materials including electrical steel, copper, and air in a rotor design domain. Magnetic topology optimization is simultaneously combined with structural topology optimization to ensure rotors, which are mechanically feasible. A topology optimization approach does not require the use of a geometric template where dimensions are controlled by parameters. Example designs of salient pole WFSM rotors are used to demonstrate the proposed technique. The proposed topology optimization technique is compared with a multiobjective optimization with the rotor geometry defined by a geometric template. For the same torque level the topology optimized rotor has lower copper losses.

I. Introduction

The design of electric machines is difficult because of the necessity to meet multiple constraints and objectives including: output power, cost, average torque, speed, efficiency, size, inertia, torque ripple, drive voltage and current limits, temperature rise, inertia, acoustic noise and vibration, and other requirements. The sophistication of the electric machine analysis tools and techniques range from classical analytical approaches to template based magnetic equivalent circuit or finite element based software tools. In general, an iterative approach to design is used. The designer picks a machine topology, slot pole combination, materials and through experience or using an optimization algorithm varies the geometric parameters and current loadings. The electromagnetic performance is analyzed and the input geometric and current loading parameters are adjusted and perhaps a different topology or slot/pole combination is tried.