Impact of Vibrations Exposure Cycles on Wire Insulation Lifetime during Thermal Qualification

This paper investigates the effect of the vibration exposure cycles on the lifetime during the thermal qualification tests of winding insulation. The study aims at evaluating the lifetime reduction and the consequent impact on the wire thermal class caused by mechanical stresses. Two groups of samples, i.e., motorettes, resembling the insulation system arrangement of an electrical machine for aerospace actuator application are built and tested. The first group is purely thermally aged, while the mechanical stress is also considered through extra vibrations cycles when the second group is aged (i.e., samples thermally aged and mechanically stressed). The recorded lifetime data are processed via the Weibull approach and the lifetime is determined for both sample groups. In addition, the dissipation factor is measured as a diagnostic marker after each aging cycle, and the results further demonstrate the dominant effect of thermal stress on the insulation lifetime.