The turbines in a new 33-gigawatt offshore project in the UK have extremely long rotor blades, up to 90 m, as well as a hub and blade weight of approximately 220 tonnes. The overhang from hub to tower centre is relatively large to provide adequate space for the bending blade tips. An objective is to develop drivetrains that are as light and as compact as possible in order to reduce the total cost of the machinery and the installation.
SKF offers a wide range of rotor bearings for differing drivetrain concepts in order to provide the best possible performance, in keeping with the turbine layout, and the lowest possible operating cost.
Spherical roller bearings in geared turbines
Two-point suspensions with a toroidal roller bearing (CARB) and a spherical roller bearing in separate rotor bearing housings have become established in the 5-MW category (fig. 1). The CARB bearing acts purely as a non-locating bearing; the axial movement function is realized by means of the flangeless bearing rings. The smaller spherical roller bearing, which is the locating bearing, is positioned at the generator side at a suitable distance from the CARB bearing. The inherent clearance in bearings of this size requires in future a more holistic, dynamic approach of the entire drivetrain and is, for example, relevant for the planetary carrier bearings of the gearbox as well as its gearbox mounts.