Results of wear endurance runs of wind turbine pitch bearings

Pitch bearings of wind turbines connect the rotor blade and the rotor hub. They have to cope with highly dynamic and stochastic loads and oscillating movements for lifetimes of 20 years and more. While several test rigs for pitch bearings are in operation, only very limited data is publicly accessible. Oscillating bearings typically suffer from wear, and this work covers the results of wear endurance tests of full-scale pitch bearings. Four bearings were tested approximately 120 days each under realistic conditions which included dynamic loads in five degrees of freedom. The bearings did not show any or very limited signs of raceway wear, in contrast to results of small-scale tests and short-term tests under worst-case conditions.