The input shaft of a wind turbine gearbox typically operates at a rotational speed of 10–20 revolutions per minute (rpm). Due to the relatively low speed, the formation of the oil film for the input shaft bearing, also known as the planet carrier support bearing, is often challenging. The role of the oil film is to separate the two metal contact surfaces during bearing operation, preventing direct metal-to-metal contact. To evaluate the lubrication performance of a bearing, we can introduce a parameter, λ, which is defined as the ratio of the oil film thickness to the combined roughness of the two contact surfaces.

If λ＞1, it indicates that the oil film is thick enough to fully separate the two metal surfaces, resulting in good lubrication performance. Conversely, if λ＜1, it means the oil film thickness is insufficient to completely separate the metal surfaces, leading to poor lubrication performance. Under such poor lubrication conditions, the bearing may suffer damage.

Since wind turbine gearboxes typically use ISO VG320 viscosity oil in their circulation lubrication systems, when λ＜1, the primary way to improve lubrication performance is to reduce the surface roughness of the bearing raceways and rollers. Lowering the roughness helps facilitate the formation of an effective oil film, even under low-speed conditions.

In addition, during gearbox design, it is important to avoid excessively small bearings on one end of the planet carrier support. Practical analysis has shown that, even if the service life requirements are met, such designs can result in extremely low linear speeds for these smaller bearings, further hindering the formation of a proper oil film.

Luoyang Bearing Research Institute Co., Ltd. can manufacture high-quality wind turbine bearings, providing reliable solutions to support the demands of the wind energy industry.