Gear box loadings and wind turbine dynamics

The investigation has been divided in two parts: one dealing with a detailed modeling of the interaction of turbine dynamics and internal gearbox dynamics and one dealing with a validation of this model using full scale measurements on a turbine. For the latter project part, a fast scan measurement equipment has been developed and using this equipment accelerations and shaft torque has been analyzed up to a frequency of 2 kHz. The measurements have confirmed the results of the modeling work, which illustrated a very efficient load balancing effect in the gearbox planetary stage. For certain specific conditions, an interaction of the natural frequencies internally in the gearbox and the excitation frequencies from the global turbine dynamics can exist and for such cases an increase in the gearbox loadings can be seen. The developed model in the project can support an investigation of this in a specific design case. Results from the modeling work indicated during the project that the primary cause of gearbox failure was not the interaction of internal gearbox dynamics and excitation frequencies from the global turbine dynamics. This finding led to an additional activity along the project, which focused on the bearings in the planetary stage. The results from this activity indicate that for certain conditions special phenomena can occur in the bearings which can lead to significantly increased loadings in the gearbox