Development of highly reproducible test rig for pitch and yaw bearings of wind turbine

Pitch and yaw bearings are essential to the safe and efficient operation of wind turbines. They are classified as a large bearing, and they suffer from much more severe operational conditions compared to small bearings used for general industrial applications; in particular, they are subjected to greater external forces in each direction, very thin lubrication film thickness during operation, and so on. Furthermore, because they are installed on the wind turbine blade or a tower top of high altitude, it is costly and time consuming to repair or replace them in the field. Therefore, a laboratory-scale test is required for ensuring the performance of the pitch and the yaw bearings before application in the field. A test rig is developed to verify the performance of the pitch and the yaw bearings, including their fatigue life and static loading capacity. The test rig can reproduce actual operational conditions such as 6 degree of freedom (DOF) dynamic loadings and rotation of bearings for both directions. The mounting interfaces of the test rig are also the same as those used in the original environment, and various sizes of bearings can be applied by using a changeable adaptor. This high reproducibility of actual loading, driving, and mounting conditions simultaneously as well as applicability to wide size ranges are distinctively advantageous characteristics compared to previous test rigs. A structural analysis and preliminary friction torque test showed the suitability of the developed rig for use in pitch and yaw bearings of 2.0–3.0 MW class wind turbines.