Influences of electrical stress and parasitic currents on rolling bearings within electrified environments
Marius Krewer
Value for the audience
The presentation gives insights in the damages electrical stress can induce on rolling bearings. It shows experimental results on how these damages influence service life and presents a new way to consider these damages for service live calculations. Capacitance measurements for a characterization of the processes in the rolling contact are shown.
Summary
Parasitic electric currents in the form of discharges through the lubricant film are significantly influenced by several key factors, including the lubricant film thickness, the microgeometry of the rolling surfaces, and the dielectric strength of the lubricant. Among these factors, the lubricant film thickness, primarily determined by the viscosity of the lubricant, plays an important role. The lubricant film thickness directly impacts the capacitance of elastohydrodynamic lubricated contacts in bearings and various other machine components. By measuring or calculating this capacitance, conclusions can be drawn about the current passages in the contact zone.
When discharges or breakdowns occur within bearings, they can lead to changes in the edge zone of the surfaces which are subjected to rolling stress. These discharges have a particularly significant impact on the microgeometry of these surfaces as they can lead to surface roughening. The resultant changes in microgeometry, in turn, influence the fatigue behavior of the bearings, similar to the effect of variations in the lubrication ratio (kappa) as in the calculation according to DIN ISO 281.
In this context, investigations were carried out to determine the conversion of electrically induced surface roughness into its corresponding kappa value. Such investigations aim to improve the understanding of the consequences of electrical discharges within rolling bearings and enable more accurate estimations of the service life of these crucial machine components in electrified environments. Additionally, capacitance measurements were conducted on different machine elements to gain a deeper insight into their electrical behavior.
