Optimization Design of Bearing Insulation for Traction Motors of High-Speed Trains under Overvoltage Impulses

The increasing speed and power of high-speed trains have intensified the occurrence and amplitude of overvoltage impulses caused by the operation of vacuum circuit breakers (VCBs) during the phase-changing process. These overvoltage impulses result in an abnormal rise in bearing voltage, far exceeding normal operational levels. With hundreds of overvoltage impulses occurring daily, the electrochemical corrosion of bearings is significantly deteriorated. Herein, the propagation paths of overvoltage within the traction system and the damage mechanisms affecting bearings are systematically investigated. Via launching a simulation model encompassing the traction power supply system, train body coupling paths, and bearing equivalent circuits, the propagation patterns of overvoltage through the train body, bogie, and motor coupling system is revealed. An experimental platform simulating transient overvoltage impulses under practical operational conditions is established, as the scanning electron microscopy of bearing cross-sections validates the correlation between insulation layer thickness and electrochemical damage. Based on the improved RIME optimization algorithm, an optimized method has been proposed to balance the electric field strength within the insulation layer and the voltage across the bearing. These findings offer solid theoretical support and experimental data for the optimization design of bearing insulation with the development of overvoltage suppression strategies in traction motors.