This paper describes the partial discharge characteristics of magnet wire under high frequency AC voltage. At first, high frequency harmonics of the inverter surges are analyzed by Fourier analysis in the pulse modulation width control system of the 5 levels and 11 levels. Analytical result shows that the higher harmonic spectra contain higher AC frequency up to several hundreds kHz. Next, partial discharge inception voltage and partial discharge characteristics of the magnet wires were studied under high frequency AC voltages from 20 kHz to 200 kHz. Lastly, humidity effect for partial discharge under high frequency voltage is also clarified in the paper.