The effect of the rotor adjustment on the vibration behaviour of the drive-train system for a 5 MW direct-drive wind turbine

Abstract

Direct-drive wind turbines, different from the standard geared wind turbines, widely use a direct-drive permanent-magnet generator to avoid the gearbox failures. In the absence of a gearbox in the drive-train system, the direct-drive generator operates at low rotating speeds. Thus direct-drive wind turbines require a larger sized generator (higher weight) to transfer the kinetic energy into electrical energy. The inherent unbalanced magnetic pull force of the generator can have impact on the vibration behaviour of the drive-train system. This paper studies the effect of rotor position and weight adjustment on the vibration behaviour of the drive-train system within a 5 MW direct-drive wind turbine by considering the unbalanced magnetic pull force. The adjustment of rotor position and weight changes the location of the centre of gravity of the drive-train system. The drive-train system which consists of the main shaft, rotor, hub and blades is modelled as a four degree-of-freedom nonlinear system. Both rotor displacement and bearing forces are obtained for a wide range of rotor position and weight under different rotating speeds. The obtained results would provide useful information on the optimized rotor position and mass ratio to improve the performance of the drive-train system.

Keywords

Wind turbine direct-drive generator unbalanced magnetic pull force drive-train system vibration

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