With regard to microgeometry, developers have improved the surfaces in order to reduce friction and thus the application of energy and wear. In addition, they have adjusted osculation to transmit rolling element normal forces across a large surface, reducing contact pressure. The rolling elements have also been specially profiled.
Adjustments in macrogeometry primarily comprise two aspects. First, the engineers have reduced the internal bearing clearance, which has improved the operating clearance. This has also reduced the rolling bearing forces and the axial sliding of the drive train. Second, they used a firm center rib for the locating bearing supports of the wind turbine rotor and increased axial rigidity, which reduced the axial displacement of the drive train. In addition, the firm center rib helps distribute the contact pressure along the roller. With these two measures, they have been able to increase the bearings’ robustness against wear, which is caused especially by axial displacement. As part of validation, the bearings were subjected to comprehensive testing to be granted Schaeffler’s “X-life” seal of approval. The necessary validation steps have been certified by Germanischer Lloyd (certificate GL-CER-002-2015).
The asymmetrical bearing design increases the axial load carrying capacity and thus the service life of the main bearings in wind turbines. It allows a greater contact angle on the row of bearings supporting the axial load and a flatter contact angle on the row of bearings that mainly support radial loads. This results in a better load distribution, reduced contact pressure and a significant reduction of the axial sliding distance.