Wind energy generation systems - Part 4: Design requirements for wind turbine gearboxes

IEC 61400-4:2025 is applicable to enclosed speed increasing gearboxes for horizontal axis wind turbine drivetrains with a power rating in excess of 500 kW. This document applies to newly designed gearboxes for wind turbines installed onshore or offshore. The technical requirements given in this document are not intended for repaired or refurbished gearboxes, or for the extension of the service life beyond the design life. This document provides requirements and guidance on the analysis of the wind turbine loads in relation to the design of the gear and gearbox elements. The gearing elements covered by this document include such gears as spur, helical or double helical and their combinations in parallel and epicyclic arrangements in the main power path. This document does not apply to power take off (PTO) gears.

This document includes requirements, design recommendations, and rating of gearboxes with rolling bearings, plain bearings, or combinations of both bearing types. This document is supported by two Technical Reports: IEC TR 61400？4？2 provides additional information on lubrication of wind turbine drivetrains and IEC TR 61400？4？3 contains explanatory notes and supportive infor