Prediction of the lifespan of enameled wires used in low voltage inverter-fed motors by using the Design of Experiments (DoE)

The electrical insulation of low voltage motors faces new hazards since the power electronic power supplies have been introduced. Due to the use of frequency inverters especially the primary insulation of the magnet wire is endangered. As an effect, partial discharges may be observed, causing fast degradation of the electrical insulation leading finally to a premature breakdown of the machine. In order to predict the lifespan of the insulation system the aging tests are conducted. Unfortunately, they are usually highly time consuming and far too accelerated to properly model the aging phenomena. The aim of this paper is to propose a method allowing to predict the long-term results basing only on the short-term experimental results. This study introduces a prediction based on the Design of Experiments method and the Weibull distribution. Thanks to the model obtained with short aging tests it is possible to predict the results of significantly longer ones. Moreover, the adapted methodology is proposed that allows to predict the scatter of the long tests basing on the short-time results dispersion. The predictions are compared with the experimental data in order to prove the model accuracy.