The dynamic loads on the rollers inside the bearings of large wind turbine gearboxes operating under transient conditions are presented with a focus on identifying conditions leading to slippage of rollers. The methodology was developed using a multi-body model of the drivetrain coupled with aeroelastic simulations of the wind turbine system. A 5 MW reference wind turbine is considered for which a three-stage planetary gearbox is designed on the basis of upscaling of an actual 750 kW gearbox unit. Multi-body dynamic simulations are run using the ADAMS software using a detailed model of the gearbox planetary bearings to investigate transient loads inside the planet bearing. It was found that assembly and pre-loading conditions have significant influence on the bearing’s operation. Also, the load distribution in the gearbox bearingsstrongly depends on wind turbine operation. Wind turbine start-up and shut-down under normal conditions are shown to induce roller slippage, as characterized by loss of contacts and impacts between rollers and raceways. The roller impacts occur under reduced initial pre-load on opposite sides of the load zone followed by stress variation, which can be one of the potential reasons leading to wear and premature bearing failures.
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