基于共模变压器原理的电机轴承电腐蚀非接触式主动抑制方法

Electrical corrosion of Motor bearings has become a serious, industry-wide issue that significantly threatens the reliability and lifetime of inverter-fed electric drive systems. The high-frequency pulse-width-modulated voltages generated by SiC-based inverters induce a common-mode voltage that causes the bearing voltage to exceed the breakdown threshold of the lubricating oil film, resulting in repetitive electric discharge machining (EDM) currents and progressive pitting on the bearing raceways. This paper proposes a novel non-contact active suppression method based on the common-mode transformer (CMT) principle. The motor shaft is treated as a single-turn secondary winding of the CMT, so that a compensating voltage can be injected into the bearing-voltage coupling path via a non-contact magnetic link. As a result, it cancels the bearing voltage and prevents electrical corrosion without the need for physical grounding brushes or conductive grease. First, a high-frequency bearing-voltage model (BVHM) is established to clarify the coupling relationship among the parasitic capacitances of the stator windings, rotor, and frame. The model parameters are extracted from experimental impedance curves measured by a Keysight E4990A impedance analyzer, including the common-mode, differential-mode, winding-to-rotor, and rotor-to-frame impedances. Then, the equivalent circuit, operating principle, and parameter calculation procedure of the proposed active bearing voltage canceller (ABVC) are analyzed. The ABVC consists of a compensation H-bridge circuit and two identical CMTs mounted on both sides of the motor shaft. By synchronizing the ABVC modulation strategy with the inverter's modulation, the injected compensation voltage maintains amplitude and phase alignment with the open-circuit bearing voltage. Second, to further improve the suppression performance, the effects of dead-time distortion and rise–fall time mismatch are investigated. A dead-time compensation strategy and an optimized driving resistor design are proposed to ensure dynamic phase synchronization between the injected voltage and the original bearing voltage during transient switching intervals. The theoretical expressions for the MOSFET gate-driving resistance are derived based on the turn-on and turn-off characteristics, enabling accurate control of the voltage rise and fall slopes. The compensation control scheme ensures that the proposed suppression method remains independent of bearing impedance and is robust to variations in speed, load, temperature, and lubrication state. Third, the CMT design procedure is described, including magnetic-core selection, determination of the turns ratio, and area-product (AP)– based size optimization. The CMTs are designed with nanocrystalline toroidal cores, achieving a working magnetic flux density of 0.38 T and a magnetizing current of 1.04 A under rated conditions. It ensures high magnetic coupling capability while maintaining a compact volume. The proposed design achieves a significantly smaller volume and lower copper loss than conventional passive and active common-mode filters, since the CMT does not carry large phase currents and operates only along the magnetic coupling path. Finally, the proposed suppression method is validated on a 60 kW automotive permanent-magnet synchronous motor (PMSM) test platform. The results show that the proposed method can eliminate the steady-state bearing voltage and reduce transient voltage spikes by approximately 85%. No bearing breakdown or discharge phenomena are observed during long-term operation, verifying the effectiveness and engineering feasibility of the proposed non-contact active suppression approach in preventing bearing electrical erosion.