Research On Effects Of Temperature And Gap On Insulation Characteristics Of Inverter-Fed Traction Motors And Material Modification

In recent years, our country has developed electrified railway rapidly. As one of the key equipment of electrification locomotive, the reliability of the inverter-fed traction motor directly affects the safety of the electric railway. Since the impedance mismatch among the traction inverter, traction motor and connecting cables, resulting in high frequency overvoltage between the motor winding turn insulation. The weak part of the winding insulation may cause partial discharge under overvoltage, which leads to the premature failure of motors. Developing corona resistance inter-turn insulation material is one of the important measures to prevent this situation. When the traction motor is operating, by motor copper loss, iron loss, mechanical loss, dielectric loss and the impact of space constraints, the motor winding temperature can exceed200℃. In addition, gap defects in the traction motor winding will result in severe partial discharge in the air gap, which will threat the reliability of the traction motor insulation. So it is of great importance to research temperature especially high temperature and air gap effects on the electrical insulation characteristics of traction motor winding insulation.In order to study the temperature effect on the electrical insulation characteristics of winding insulation used in inverter-fed traction motor, the dielectric temperature spectra of the polyimide nanocomposite films were investigated. The temperature effect on the partial discharge inception voltage (PDIV), the breakdown voltage (Ub) and the aging lifetime under square impulse voltage was tested. The space charge distribution property of the films during the aging was analyzed. Besides, the mechanism of temperature effect on the PDIV, Ub and aging lifetime was explained.In order to explore the effect of gap on the electrical insulation characteristics of winding insulation used in inverter-fed traction motor, the electric field distribution characteristics in the air gap were simulated. The gap influence on the partial discharge characteristics of the inverter-fed traction motor turn insulation under square impulse voltage was tested. The partial discharge spectrum of the gap model under square impulse voltage was obtained. Then the gap diameter effect on the aging lifetime of the films under square impulse was tested.Finally, the polyimide/Al2O3nanocomposite films were prepared based on in situ polymerization. The morphology of the films was observed. The infrared spectral features of the polyimide/AlO3nanocomposite films were analyzed. And the content of nano Al2O3influence on the dielectric property and corona resistance property was explained.