Partial discharge endurence test on several kinds of nano-filled enameled wires under high-frequency AC voltage simulating inverter surge voltage

Partial discharge (PD) endurance test was performed on twisted pair specimens of enameled wires consisting of polyamide-imide resin with nanometer-size fillers. Specimens were prepared with containing nanometer-scale silica or titania fillers, as well as specimens without fillers. In the PD endurance test, so-called V-t characteristics of the twisted pair specimen were measured by applying a constant ac voltage 1-2 kV
_rms
at 10 kHz that simulated repetitive impulse voltage appearing in an inverter-fed motor. Temporal change of the thickness depletion of a tested specimen was also measured with a microscope. Moreover, the relation among PD charge estimated from measured PD current pulse, the thickness depletion and the life of the specimens were investigated. Experimental result revealed that the life of specimens with titania nano-fillers was longer than that of specimens with silica nano-fillers. It was also found that the thickness depletion caused by PD charge for the former was longer than that for the latter.