Extra Life Loss of Low Voltage Electrical Machine under Variable Temperature Aging

Low-voltage electric machines (EMs) with high power density and compact volume represent a key target in transportation electrification. In order to achieve optimal performance and simultaneously keep high reliability of EM, the lifetime prediction should be merged into the EM design. In literature, constant temperature accelerated lifetime tests (ALT) are frequently applied for EM lifetime prediction. However, most EMs experience variable temperature profiles (TPs) during their operations. Thus, the variable temperature ALTs considered by employing three periodic TPs experiments. The obtained results are post processed by Weibull distribution and related life models are constructed. Then, EM lifetimes under different TPs are analyzed by comparing the analytical and experimental results. Finally, the difference between the lifetime value of the model and experiment results is analyzed and the extra loss of life caused by thermal-mechanical stress is derived through experimental evidence.