Simulation and Influence Law Study on the Transient Breakdown Process of Bearing Oil Film Under Synergistic Effects of Voltage, Film Thickness, and Temperature

To address oil-film electrical breakdown in sliding bearings during operation, an electro-thermal coupled transient model that takes into account the electric field, oil film characteristics, heat conduction, and continuous damage was developed in this paper. The coupled effects of applied voltage U, initial oil-film temperature T0, and oil-film thickness h on the current density, heat generation rate, and temperature are investigated in the spatial film field and at the characteristic points. The transformation of the oil film from an insulating state to a highly conductive state is revealed. The influencing parameters and rules for the oil-film breakdown time tb and the characteristic point damage time tc are also obtained. The results show that increasing the applied voltage or decreasing the equivalent local oil-film thickness shortens the overall breakdown time tb, while increasing the current density and heat generation rate. In contrast, the initial oil-film temperature primarily affects the overall breakdown time tb. During oil-film breakdown, two distinct transition points, tc and tb, appear in the responses at the characteristic points. At these transition points, the current density and heat generation rate exhibit pronounced transient changes, whereas the oil-film temperature either remains stable or continues to increase.