Topology optimization for structural mass reduction of direct drive electric machines

Topology optimization is well suited to computationally achieve highly optimized designs with respect to objective and constraint functions, and when coupled with additive manufacturing, enables the fabrication of complex structures that can offer improved generator performance and increased power density. Here, topology optimization was used for light-weighting high power direct drive generators. The rotor of a 5 MW wind turbine generator was analyzed to determine geometric avenues of mass reduction with varying safety factors. Three designs were created with safety factors between 1 and 2 which resulted in structural mass reductions ranging between 54%-67% compared to a baseline design leading to a 13%-25% increase in power density. These designs represent a similar to 50% structural mass reduction compared to a previous structural optimization design using triply periodic minimal surfaces. All deflections were less than their critical limits and the topology optimized rotor designs exhibited 64% lower radial deflection than baseline. Deflections of the topology optimized designs were verified with commercial code and supported through experimental validation using digital image correlation with additively manufactured rotors. Computational resource use was reduced as compared to past parameter optimization approaches, and manufacturability studies demonstrated that topology optimization holds potential for significant mass reduction of direct drive generators.