Studying On The Dielectric Properties And Thermal Properties Of Inverter Motor

Traction inverter motors are the power sources for High Speed EMU, and its excellent performance will affect the ability of the entire EMU unit. Polyimide(PI) is the basis of inturn insulation material in inverter moter. The quality of PI influence intverter motor’s life, while PI’s dielectric and thermal properties determines the disable time. Studying on the failure mechanism of dielectric and thermal are very important in PI breakdown process.Through making inverter motor turn insulation and twisted pair wire, we simulated and analyzed the dielectric properties and thermal properties of polyimide insulating materials. The simulation of the electric field distribution found the easily breakdown position. Meanwhile, the testing technologies of dielectric loss and Partial Discharge (PD) have been widely used as two effective diagnosis methods in insulation system. Dupont’s common polyimide films (100HN) and Dupont’s polyimide nano-composite films (100CR), as inter-turn insulating materials of inverter-fed traction motor, have been paid attention. In order to investigate the inter-turn insulation,100HN twisted pairs and100CR twisted pairs were aged respectively under square impulse voltage, and the dielectric loss and PD characteristics of different aging degree samples were tested. It is demonstrated that the dielectric loss, the mean PD quantity and PD numbers of both100HN and100CR increased with the aging time. The shallow traps are located at interfacial regions around nanoparticles in100CR, which raise the capacity of charge transport. It is beneficial to increase the loss and PD’s number, but the mean PD quantity is reduced. Meanwhile, the synergistic effects of nanoparticles can protect the polyimide matrix and extend life of100CR twisted pairs.Factors thermal conductivity of the polyimide film includes temperature, nanoparticles and humidity so on. The oscillations of original molecular weight smaller atoms, link, and perssad in the molecular chain will intensify while temperature rise, even trigger oscillations of a greater link relative molecular mass and perssad, then enhance the capacity of polyimide heat conduction; Add nanoparticles to increase the thermal conductivity of polyimide materials, if there is no effective thermal conductivity chains, the polyimide materials thermal conductivity changed little; Humidity increase the moisture content in material, improves the performance of thermal conductivity of polyimide film, but severely reduce the material dielectric properties.