Influence of electric discharge activity on bearing lubricating grease degradation

The emergence of high-frequency converters has introduced additional stress on the bearings of the systems they are used in: the high-frequency components of the converter output voltage may lead to building up of voltage across the bearings. If it exceeds the voltage that the bearing can withstand these voltages may cause a discharge leading to so-called “discharge bearing currents”. This paper studies the influence of such discharges on the grease chemical composition, a parameter that is considered key for the further understanding of the bearing damage mechanism itself. The composition is analysed using Fourier Transform Infrared spectroscopy and X-Ray crystallography.