Study On Influence Of Space Charge On Aging Of Inverter-Fed Motor Insulation Under High Voltage Pulse

Inverter-fed motor is an indispensable equipment for the development of high-speed railway in China. As a core component of AC drive electric locomotive, performance of inverter-fed motor directly influences the stability and reliability of locomotive running. However, Pulse Width Modulation (PWM) which was input from inverter is characterized by steep rising edge and high frequency, resulting in the too early failure of motor insulation. Presently, polyimide film characterized by high temperature resistance (400℃), low temperature tolerance (-269℃), radiation resistance and excellent dielectric properties widely applied in turn to turn insulation and turn to ground insulation of inverter-fed motors is a kind of basic insulating material. As traditional design method and theory for AC motor is not completely suitable for inverter-fed motor, consequently, research on the aging and failure mechanism of insulating material under high voltage pulse can provide theoretical foundation for the design of inverter-fed motor insulation structure and prolong service life.Space charge plays an important role in damaging insulation under high voltage pulse. Develop research work in accordance with influence of space charge on aging of inverter-fed motor insulation under high voltage pulse. Firstly, construct aging and space charge measurement system; measure space charge accumulation threshold field between corona-resistant (100CR) and common polyimide films (100HN) and analyze the influence of adding nano-particles on dielectric property of insulating material. Furthermore, space charge distribution in polyimide films under different temperature was measured, based on which space charge characteristics under high voltage pulse were researched. Secondly, by means of Scanning Electrical Microscope (SEM), effects of aging time and frequency on surface and section morphology were analyzed, based on which the cause for nano-particles improving corona-resistant property was researched. Finally, conduct experiment, including electrical breakdown, thermal breakdown and electrical tree breakdown, on magnet wires; meanwhile combining with SEM and energy spectrum analysis, the corresponding breakdown mechanisms were analyzed.All the done work lays a strong foundation for the further study of failure mechanism of inverter-fed motor insulation under high voltage pulse; meanwhile it also provides theoretical support for using inorganic nano-particles improving corona-resistant property.