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 overengineering approach, which prevents electrical machines from reaching higher power densities and leads to a design conflict. This article proposes a reliability-oriented design approach for low-voltage electrical machines by integrating model-based lifetime prediction into a multiobjective 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 multiobjective 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.