Issues of Electrical Testing of Winding Wires

Reliable testing of winding wires is of utmost importance for electric vehicle manufacturers to maintain reliability across different suppliers. The IEC 60851-5 standard requires the wire to be bent and placed in a container filled with metallic shots. However, testing wires with high breakdown voltage, e.g. with double layer insulation, is problematic, as there will be very active surface discharge activity, making the results unreliable. Furthermore, using shots, especially the largest diameter allowed by the standard, creates an electric field that allows blind spots. The article details these issues and the mitigation attempts.