Failure prediction, monitoring and diagnosis methods for slewing bearings of large-scale wind turbine: A review

A study of grease lubricants under wind turbine pitch bearing conditions

Effect of the preload in the general static load‐carrying capacity of four‐contact‐point slewing bearings for wind turbine generators: theoretical model and finite element calculations

Friction torque in four contact point slewing bearings: Effect of manufacturing errors and ring stiffness

Several analytical models have been proposed to estimate the load distribution and the deformation of slewing bearing assemblies in wind turbine generators (WTGs). Even though they are a useful tool for designers as a first approach, most of them assume rigid rings and rigid supporting structures, leading to inaccurate results; even if compliance is considered in some models, only certain boundary conditions can be taken into account, and their complex and diverse nature make often these models inaccurate. For this reason, WTG manufacturers need costly FE analyses to obtain results adapted to the particular geometries and operational conditions of their yaw and pitch bearings assemblies. In this sense, this work presents a superelement-based FE model that significantly reduces the computational cost with a negligible accuracy loss.

A new finite element approach for the analysis of slewing bearings in wind turbine generators using superelement techniques

Four-contact-point slewing bearings are widely used in wind turbine generators (WTGs) to adjust the orientation of the blades and the nacelle to fully exploit wind resources. These bearings must withstand static and fatigue loads; however, at the first stages of the design process, the bearings are commonly selected by considering only static loads. This paper presents a further step of a previous theoretical work published by the authors in the field of the static load-carrying capacity of four-contact-point slewing bearings under axial, radial and tilting-moment loads. In that work, a generalization of the works by Sjovall and Rumbarger was presented, providing an acceptance surface of the bearing in the load space. The contact angle of the balls was assumed to be load independent. The present work improves that development by considering the influence of the variability of the contact angle with the applied load, and as a result, the acceptance surface has been redefined. By comparing the results with those of the finite element model published by the authors, it is proven that the new model presented in this work is more realistic than the previous one. Thus, it is believed that this methodology can be easily applied for the initial selection of blade and yaw bearings in WTGs. Copyright © 2012 John Wiley & Sons, Ltd.

General static load‐carrying capacity of four‐contact‐point slewing bearings for wind turbine generator actuation systems

Friction torque in four-point contact slewing bearings: Applicability and limitations of current analytical formulations

This work is a first step in FE modeling of friction moment in slewing bearings due to microslip. To this end, a multiparametric ball-raceway model has been built to map the friction moment due to one-ball sector of the bearing, in order to integrate it later in a load distribution model developed previously by the authors. Parameters as ball diameter, osculation ratio, mean diameter, and initial contact angle are considered, as well as radial and axial interferences to approximate the friction moment of a bearing sector.

Jon Plaza

Papers

Effect of the preload in the general static load‐carrying capacity of four‐contact‐point slewing bearings for wind turbine generators: theoretical model and finite element calculations

General static load‐carrying capacity of four‐contact‐point slewing bearings for wind turbine generator actuation systems

A new finite element approach for the analysis of slewing bearings in wind turbine generators using superelement techniques

Friction torque in four-point contact slewing bearings: Applicability and limitations of current analytical formulations

FEM Model for Friction Moment Calculations in Ball-Raceway Contacts for Applications in Four Contact Point Slewing Bearings