Challenges and Opportunities in RPDIV Testing of Automotive Electrical Machines After Assembly

The feasibility of detecting partial discharges in completely assembled electrical machines for transport electrification was investigated measuring the Repetitive Partial Discharge Inception Voltage (RPDIV) using different sensors placed outside a complete machine and on the stator of the same machine after a careful disassembly. Four sensors were investigated. When the angular position of the rotor gave rise to the maximum self inductance of the winding, the RPDIV values provided by these sensors were comparable to that measured on the stator after disassembly. Thus, these sensors can be used for quality control of complete machines, but also monitoring or while the vehicle is in the shop for periodic maintenance. The limit of the present investigation is that it could not be ascertained whether partial discharges were incepted in the end-winding or within the slots. It remains to be understood if the shielding of partial discharges happening in the slots due to the laminated core prevents partial discharge detection, limiting the effectiveness of the method. During the tests, it was observed a remarkable dependence of the RPDIV on the rotor angular position. This point is of concern as the RPDIV measured on the stator was not the minimum one.