AC voltage endurance of polyimide insulated magnet wire

This paper presents results from accelerated ageing of magnet wire insulated with a 43 ¿m thick layer of polyimide. Tests were performed using samples of twisted wires and single wires covered with a silver painted grounded electrode. Comparable endurance measurements were done at different voltage and temperatures from 23°C to 215°C. The result showed that the time to failure can be represented by the inverse power law and the Arrhenius equation with respect to test voltage and temperature respectively. Due to increasingly dominant partial discharge activity in the air gap between the twisted wires with increasing test voltage, extrapolation may lead to a too optimistic estimate of the expected time to breakdown at service conditions.