This thesis explores the effectiveness of grounding devices and explores causes and mitigating of electrical discharge machining (EDM) in bearings used within oil-cooled electric motors powered by pulse-width modulation (PWM) inverters. While grounding rings are a common strategy to divert Common mode, capacitive, and high-frequency currents away from bearings, their effectiveness can be reduced in oil environments as different EDU cooling and lubrication systems have different impacts on grounding devices.

This research proposes a combined approach utilizing microfiber grounding rings and ceramic insulated bearings and use of conductive bearings. In this literature explanations of different bearing currents and bearing failure modes are discussed and also the test setup and installation of EDU are explained to measure the bearing currents and voltage. Different viable solutions are also proposed to mitigate the bearing failures. The high conductivity of the fibers in the grounding ring should effectively channel unwanted currents, while the inherent electrical resistance of ceramic bearings minimizes current flow within the bearing itself, offering a more robust defense against EDM in oil-cooled electric motors.