A method for accelerated ageing of electric machine insulation

The most important stress factors for electric machines insulation in the automotive environment can be summarized by the mnemonic expression TEAM (thermal, electrical, ambient, and mechanical stress). Even already each individual of the above mentioned stresses can be fatal for the electric machine insulation they generally act simultaneously making even worse deterioration process and so faster ageing of insulation. In automotive applications, the electrical machines are designed to be smaller and lighter, with increased torque and power to volume ratio and in the same time these machines are often short-term overloaded during driving cycle. The aim of the paper is to estimate the impacts of these short-term over loadings (TEAM stresses) on insulation aging and on electrical machine life time period. After a brief review of the four most influential stresses in automotive environment we propose a method for an accelerated multi-factor stress insulation testing. In conclusion, there is an example how the proposed multi-factor stress ageing model can be integrated into optimization procedure and further into new e-machine lifetime estimator.