Project start: Electro-mechanically stressed lubricants

In key technologies such as wind turbines and electric cars, lubricants subject to mechanical stress are subjected to electrical loads. This additional, unavoidable electrical load leads to damage in components and thus to premature failure of components such as generator bearings (example wind turbine) or the bearings of the rotor of the driving electric motor (example electric car). Fans, mechanical seals, pumps, compressors and parts in the periphery of the drive train are also affected by the phenomenon of electric current passage and system failures are the result.

The assessment of electro-mechanical service life is a pressing issue for operators and designers of electric powertrains

Known current-induced damage includes cratering on the bearing raceway, corrugation across the raceway and burning of the lubricant in tribological contact (e.g. rolling element to bearing raceway or on the tooth flanks of a gear). A research gap exists, among other things, in the area of damage and property changes of lubricants under combined electrical and mechanical stress.

BMWK supports research project

For this reason, the BMWK is funding the project "Service life reduction of lubricants subjected to electro-mechanical stress" under the IGF, which will start on October 1, 2023.

The research work includes experiments on test rigs to investigate rolling bearing currents and lubricant analyses. For this purpose, test conditions are derived in which the lubricants (oils and greases) are electrically damaged in a targeted manner. Based on this, the damaged lubricants are examined using extensive analysis methods (IR spectrography, ICP analysis, rheological investigations, RULER methods, NMR spectroscopy) and aging and damage mechanisms are identified from these results. The findings can be used in an uncomplicated manner, as they are incorporated into a user guide that can be used to select suitable analytical methods for detecting an electro-mechanical change in the lubricant.

The project will make an essential contribution to assessing the suitability of lubricants in powertrains. The user is enabled to select lubricants specifically for the expected electrical load (bearing current and bearing voltage, switching frequency and lubrication condition) or to provide remedial measures. In this way, damage to components can be prevented and early failures and premature lubricant changes can be avoided by defining more efficient maintenance intervals - this point in particular allows sustainable use of resources.

Research Center

Rhineland-Palatinate Technical University
MEGT Chair of Machine Elements, Gears and Tribology

Cooperation

The project is being worked on in cooperation with experts from the FVA - Forschungsvereinigung Antriebstechnik e. V. (Drive Technology Research Association).