The pulse voltage engendered by pulse width modulated（PWM） power may lead to premature failure of inverter-fed motors.Partial discharge under a sequence of high-frequency impulse is one of the key factors which lead to premature failure of inverter-fed motors.In this paper

aging experiment on magnetic wires for turn to turn insulation was conducted and partial discharge was measured.Phase distribution of partial discharge under pulse voltage was analyzed.The results show that with the increasing of aging time

the discharge phase become broader and appears scattering property;The appearance of the discharge between high phases is the symbol of some faults expanding rapidly

which means an early failure of insulation.