Assessment and Mitigation of Non-Circulating Bearing Currents in Bridgeless Rotor Synchronous Reluctance Machine

Abstract

Bearing currents in electric machines can lead to surface damage to bearings and eventual machine failure. Non-circulating bearing currents resulting from high-frequency common-mode voltages interacting with parasitic capacitances are particularly prevalent in modern variable-speed AC drive systems with PWM converter supply. This study analyzes parasitic currents in a bridgeless rotor synchronous reluctance machine (BLRSynRM) and evaluates the effectiveness of the Grounded Electrodes Approach (GEA) as a countermeasure. Utilizing finite element modeling, the study assesses parasitic capacitances and the Bearing Voltage Ratio (BVR) to determine the machine's susceptibility to non-circulating bearing currents. The application of GEA has demonstrated the potential to mitigate the risk of these currents by reducing capacitive coupling. This research provides insights into improving the longevity and reliability of synchronous reluctance machines, highlighting the need for continued studies to optimize electric machine performance and lifespan.