Partial discharge characteristics of insulation used in inverter-fed traction motor under high frequency impulse

Stator insulation in inverter-fed traction motors may prematurely lose its function due to continuous square impulses voltage of converters, whose insulation failure mechanism is different from that under power frequency AC voltage. Partial discharge (PD) is one of the key factors in insulation failure of inverter fed traction motor. To understand aging and failure mechanism of insulation material under high frequency impulse, and to provide a foundation for improvement of insulation material, we experimentally researched overvoltage at the end of motor and windings because of high frequency impulse, which would lead to partial discharge and accelerating aging on the insulation, and analyzed the life of the common polyimide and nanocomposite films. Moreover, the PDIV(partial discharge inception voltage), mean discharge quantity and discharge number were tested with different impulse frequencies, rise time, and temperature, respectively. Results show that PD activity are enhanced with increase of impulse frequency and temperature, as well as decrease of rise time. Furthermore, PD activity of common polyimide film is stronger than that of nanocomposite one. Because a lot of interface exists in the nanocomposite, conductance of nanocomposite film is larger than that of common one, transport speed is higher, and space charge effect of nanocomposite is reduced