Reliability-Oriented Multiobjective Optimization of Electrical Machines Considering Insulation Thermal Lifetime Prediction

With the trend toward transportation electrification, the power density of electrical machines faces ever-increasing requirement owing to the stringent limit of weight, especially for aerospace applications. Conventionally, the reliability of electrical machines in such safety-critical application is guaranteed by considerable safety margins, i.e., the over-engineering approach, which prevents electrical machines from reaching higher power densities and leads to a design conflict. This paper proposes a reliability-oriented design approach for low-voltage electrical machines by integrating model-based lifetime prediction into a multi-objective optimization process. Accelerated thermal degradation tests are carried out on mainwall insulation and turn insulation, then the thermal degradation model is built to predict the lifetimes, accordingly. Thermal lifetime models are developed at several lifetime percentiles for both continuous duty and variable duty applications. Finally, a feasible reliability-oriented multi-objective optimization platform is established, based on which a study-case electrical machine for aerospace application is designed and optimized. The prototype is manufactured to verify the optimized performances.