Characterization and lifetime prediction of roller and journal bearings in Si and SiC motor drive applications.

In the electrified propulsion system, a variable frequency drive (VFD) controls an electric motor. In many cases, this electric motor is an induction motor, which has been called the workhorse of industry. With semiconductor switching device advancements enabling higher power density inverter drives, mitigation techniques are being explored to remedy common issues that arise such as damaging bearing currents to ensure smooth implementation into motor drive systems. As higher power applications are enabled, the components within motors (including bearings) must have the capacity to handle the potential problems that arise from higher slew rates of advanced wide band gap (WBG) semiconductor switching devices in inverter drives. This thesis explores the behaviors of roller and journal bearings under electrical discharge conditions that are common in advanced motor drive applications, comparing the results with some known characteristics of ball bearings under similar conditions.