Most wind turbines use gearboxes to transform the relatively low rotational speed of the main shaft into higher speeds required for power generation. Because the forces a modern wind turbine gearbox has to transmit are forever increasing while the gearbox itself has to remain compact, single- or two stage planetary gearboxes are commonly used. The bearings of the planetary gears are among the highest-loaded in this specific application. In modern gearboxes an integrated planetary bearing arrangement is used, in which cylindrical roller bearings without anouter ring are fitted in the planetary gears, with the bore of the gear forming the outer raceway.
The modular concept is based on single-rowcylindrical roller bearings, without an outerring. They are equipped with a one-piece solid brass cage, which is guided by the innerring (MPB). This cage features inspection grooves for endoscopic inspection of the inner raceways as standard. Used consistentlythroughout the gearbox assembly, the modular concept has numerous advantages forthe user: the designs of planetary bearings can be simplified; the bearing design can be standardised for the first and second gear stage and across various gearbox sizes; the required number of bearing variants is reduced; the modular design simplifies the adaptation of bearing set characteristics to the requirements of each gear stage; the one-piece solid brass cage provides excellent rolling element guidance even during rapid acceleration; and the lubrication groovesprovided as standard improve the lubricationof the planetary gear bearings. The system is already in use in the 1.5MW, 2MW and 2.5MW wind turbine gearboxes of a well-known German gearbox manufacturer.