Experimental Investigation of Bearing Slip in a Wind Turbine Gearbox During a Transient Grid Loss Event

This work investigates the behaviour of the high-speed stage of a wind turbine gearbox during a transient grid loss event. Dynamometer testing on a full-scale wind turbine nacelle is used. A combination of external and internal gearbox measurements are analysed. Particular focus is on the characterization of the high-speed shaft tapered roller bearing slip behaviour. This slipping behaviour is linked to dynamic events by many researchers and described as a potential bearing failure initiator; however, only limited full-scale dynamic testing is documented. Strain gauge bridges in grooves along the circumference of the outer ring are used to characterize the bearing behaviour in detail. It is shown that during the transient event the high-speed shaft experiences a combined torsional and bending deformation. These unfavourable loading conditions induce roller slip in the bearings during the torque reversals, indicating the potential of the applied load case to go beyond the preload of the tapered roller bearing.