Effect of Ambient Temperature on Insulation Lifetime of Winding Coil Prepared with Polyamideimide/Nanosilica Enamelled Wire

The effects of ambient temperature and diameter on the insulation lifetime of winding coils prepared with polyamideimide (PAI), flexural PAI (nanosilica 5 wt%) and anti-corona PAI (nanosilica 15 wt%) wires were investigated. The winding coils were made of enameled wire with enamel thickness of 30 similar to 50 mu m. The thickness and width of the rectangular copper wires were 0.77 similar to 0.83 mm and 1.17 similar to 1.23 mm, respectively. The insulation breakdown lifetime decreased with increasing ambient temperature regardless of wire type and winding coil diameter under an inverter surge of 1.5 kV/20 kHz. The insulation breakdown lifetimes of phi 5 mm winding coils at 150, 200, and 250 degrees C were 11.38, 5.19, and 4.22 min respectively, and those of phi 10 mm winding coils at 150, 200, and 250 degrees C were 11.32, 5.79, and 4.57min respectively. The winding coil diameter had little effect on the insulation lifetime.