  Various methods for calculating the capacitance of unloaded rolling elements
are compared to improve the electric characterization of rolling element
bearings. Semi-analytical approximations and finite element simulations are
applied and a closed-form analytical two-dimensional solution is derived for
comparison. The results show that the most common semi-analytical
approximation, which uses effective radii to express the contact geometry,
reproduces the trend from numerical and analytical calculations, but
overestimates the results derived from numerical simulations. Another
semi-analytical approach is presented that delivers better results for the
capacitance of unloaded point contacts.
