Effect of Winding Coil Diameter on AC Insulation Breakdown Voltage of Polyamideimide/Nanosilica Wire

The AC insulation breakdown voltage was investigated for seven types of winding coils made of polyamideimide (PAI), flexural PAI (nanosilica 5 wt%) and anti-corona PAI (nanosilica 15 wt%) wires with various winding coil diameters of phi 5, phi 15 and phi 25 mm. The winding coil was made of enameled wire with an enamel thickness of 30 similar to 50 mu m, and the rectangular copper wire had a thickness of 0.77 similar to to 0.83 mm and width of 1.17 similar to to 1.23 mm, respectively. The insulation breakdown voltages of the original PAI coils with diameters of phi 5, phi 15 and phi 25 mm were 7.30, 6.58, and 5.95 kV, respectively, and those values decreased as the winding coil diameter increased, regardless of the wire types.