Modeling of the Partial Discharge Process Between the Winding and the Stator of Low Voltage Machines for Traction Applications

The application of wide-band-gap-semiconductors in the power-electric circuit of future traction drives leads to an increased stress on the insulation system. This can cause partial discharge, which leads to a rapid breakdown of the insulation and must, therefore, be avoided. To enhance the durability of the insulation system and to fill up the air gaps between the enameled wires, impregnation material is applied. This leads to an increased partial discharge inception voltage between neighboring conductors as the discharge process only occurs in the remaining air enclosures. Due to the change of the electric field distribution, which is caused by the impregnation material, also the threshold voltage for partial discharge between the stator and the winding changes. While so-called twisted pairs are commonly applied to study the partial discharge behavior of the inter-turn insulation isolated from other effects, in this article a specimen that considers the phase-to-ground insulation is proposed.