Partial Discharge Inception Voltage under Positive Surge Voltage Application Influenced by Surface Charge on Polyimide Film

Inverter-fed motors is increasing from points of view of efficiency and controllability of power equipment. In the future, for improving a performance of power equipment such as high output or miniaturization, electrical insulation parts in motors are expected to become higher electric field. Motor windings have small gaps at which partial discharge may easily occur and it can lead to dielectric degradation and finally breakdown. Furthermore, inverter-fed motors have a problem that generated inverter surge voltage due to high speed switching with high voltage is affected its insulating system. In our previous study, under DC voltage application, it was found that partial discharge inception voltage (PDIV) increased or decreased according to surface potential on insulating film and PDIV without surface charge can be estimated by subtracting the surface potential from PDIV with surface charge. However, it has not been clarified the influence of surface charge on PDIV under surge voltage application in detail. In this study, it was investigated PDIV under surge voltage application influenced by surface charge on insulating sheet and relationship between surface charge and initial electron supply was estimated.