In the currently booming market of wind turbines, a clear focus is put on the design
of reliable and cost-effective subsystems, such as the gearbox. A requirement for reliable
gearbox design calculations is sufficient insight in the dynamics of the entire wind turbine
drive train. Since traditional wind turbine design codes reduce the drive train to just
a few degrees of freedom, considerable research effort is spent in advanced modelling
and simulation techniques to gain more insights in the dynamics at hand. This work
focusses on the gearbox modal behaviour assessment by means of three more complex
modelling techniques of varying complexity: the purely torsional-, rigid six degree of
freedom with discrete flexibility- and flexible multibody technique. Both simulation and
experimental results are discussed. Typical mode categories for traditional wind turbine
gearboxes are defined. Moreover the challenge of the definition of an accurate approach
to condense finite element models for representing the flexible components in the flexible
multibody models is overcome. Furthermore the interaction between the structural
modes of the planet carrier and planetary ring flexibility with the overall gearbox modes
is investigated, resulting in the definition of two new mode categories: the planet carrier
modes and planetary ring modes.status: publishe