Ageing study in electromechanical chain: design of experiment definition using step stress tests

Energy transition leads to major challenges in reliability assessments of new systems of the electromechanical chain that attempt to reach higher energy densities in harsher environment. Thermal endurance over the mission profile of Electrical Insulation Systems (EIS), especially of winding components, is still under study to master the novel challenges regarding the guaranty of keeping Partial Discharge Inception Voltage (PDIV) above a certain level during the mission to keep the type I machine exempted from PD throughout its lifespan.This work consisted in the ageing of 20 motorettes by applying successive steps of different temperature to the very same specimens. Several electrical markers of the system such as PDIV, capacitance and leakage current, were monitored throughout the ageing campaign at a reference temperature. Changes observed as a function of time can then be treated like a first order chemical reaction. The computation of the activation energy from the piecewise Arrhenius fit can give an insight of the validity of such model on an assembly.Eventually, if the Arrhenian behavior is verified, it can be used to better design a proper ageing campaign on motorettes and thus to identify the acceleration factor.