Electro-thermal aging tests on different kinds of enamelled wires

Considering the great importance of the degradation phenomena acting on the insulating materials of the inductor motor windings supplied by inverter drives based on IGBT the behaviour of different kinds of insulating organic enamels have been investigated. During the research activity, twisted pair specimens have been realized and subjected to severe voltage waveforms having peak to peak amplitudes higher than the partial discharge inception voltage level. Therefore all the tests, performed in presence of partial discharges activity, have been carried out hosting the specimens inside an oven, so to apply the synergic effect of the thermal stress to the enamel degradation. The insulating enamel breakdown condition has been selected as end-point criterion. Two kinds of enamel have been considered: a reference conventional non corona resistant enamel and a nano-filled enamel. Analyzing and comparing the obtained results it has been possible to highlight the different behaviours of the two enamelled wires.