Enhanced test strategy of pitch bearing based on detailed motion profile

Modern horizontal axis wind turbines exclusively use pitch regulation to effectively control rotational speed and power production. This is generally achieved by controlling the angle of blades during operation. Pitch bearings which allow the rotation between blades and hub are subjected to high bending moments whilst oscillating at low speeds and small oscillation amplitudes. The oscillating nature means that the bearing’s grease is likely to be squeezed out of the raceway/rolling element contacts leading to a breakdown of the lubricant film that separates the bearing components. Such harsh operating conditions may accelerate oscillation wear damage while still maintaining rolling contact fatigue damage as one of the basic failure modes. Pitch bearing test methodology during the turbine development stage is yet to be standardized. However, many past endurance test attempts have focused more on rolling contact fatigue failure under a single constant oscillation amplitude and test load condition. This study suggests an enhancing pitch bearing test strategy that brings the detailed pitch bearing motion profiles over various turbine operating scenarios into a controlled test environment for a more robust pitch bearing test. The suggested process can be utilized for any turbine, however as a demonstration, this article presents how the suggested methodology is applied to a 7 MW wind turbine acquired by ORE Catapult for research and demonstration purposes.