Empirical formulae for the influence of real film thickness distribution on the capacitance of an EHL point contact and application to rolling bearings

Electrical bearing capacitance plays an important role in the prediction of harmful bearing currents, which could lead to premature failure of the bearing and the entire drive system. The effect of rolling speed, force, and material parameters on the electrical capacitance of an elliptical contact in elastohydrodynamic lubrication has been studied numerically. An empirical equation that describes the relationship between the areas of central film thickness and minimum film thickness of the HERTZ'ian contact area has been derived. Additional, another formula to calculate the total capacitance of a rolling bearing, based only on the HERTZ'ian contact capacitance with the central film thickness as single parameter, has been developed. Finally, a comparison was made between the calculated capacities and measured values.