A major reliability concern is the mitigation strategies of traction motor bearings in high-speed trains, which are caused by bearing currents induced by train operations and electrical conditions. Bearing currents occur when voltage differences overcome the insulating effect of bearing lubrication, resulting in electric discharge machining (EDM) of the bearing surfaces and premature wear. In order to preserve bearings and increase motor longevity, mitigation techniques concentrate on lowering or rerouting these currents. Important strategies include installing shaft grounding brushes to safely channel currents away from sensitive components, employing insulated bearings to prevent current passage through the bearing race, and strengthening the bonding and grounding of motor frames and related systems to provide low-impedance pathways for fault currents. For larger power motors, common-mode filters can also be used to lower common-mode voltages that can cause bearing currents. Because high-speed trains have a variety of operating conditions and motor designs, a combination of these techniques is frequently needed for effective mitigation. In high-speed rail applications, the risk of bearing damage can be considerably decreased, and traction motor reliability can be increased by understanding the electrical and mechanical interaction mechanisms in conjunction with appropriate design and maintenance procedures.

Common-mode voltages, high-frequency switching inverters, and inadequate grounding are the main causes of bearing current, a crucial reliability problem in high-speed train traction motors. These currents shorten the lifespan and efficiency of motors by causing electrical discharge machining (EDM), lubricant deterioration, and significant mechanical damage to bearings. This study demonstrated that insulated bearings, common-mode filters or chokes, optimized grounding configurations, and shaft grounding techniques are all necessary for effective mitigation. Preventive maintenance and proper lubrication management are also important for reducing electrical damage and bearing wear. While improper middle grounding increases voltage stress, grounding end axles (1 and 4) effectively reduces overvoltage amplitude, according to an analysis of transient overvoltage and grounding configurations. Additionally, the design of vacuum circuit breakers (VCBs) has a major impact on the magnitude of surges, which in turn affects insulation life and bearing safety.

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