The aim of a transfer path analysis (TPA) is to view the transmission of vibrations in a mechanical system from the point of excitation over interface points to a reference point. For that matter, the Frequency Response Functions (FRF) of a system or the Transmissibility Matrix is determined and examined in conjunction with the interface forces at the transfer path. This paper will cover the application of an operational TPA for a wind turbine model. In doing so the path contribution of relevant transfer paths are made visible and can be optimized individually.

To reduce acoustic emissions of a wind turbine (WT), the source of the vibrations (e.g. blades, gearbox), the emitting surfaces (e.g. blades, tower, nacelle cover) and the transmission between the source and surface have to be studied. The focus of this paper lies on a method to identify relevant transfer paths between the WT drivetrain and the sound-emitting surfaces and their respective contribution. The identified transfer paths can be used to improve turbine acoustics, especially by identifying problematic transmission areas.This paper will cover the application of transfer path analysis methods for different wind turbine drivetrains. The method will be applied to an MBS model of a 3 MW turbine. Different Bearing arrangements of the drivetrain and their influence on the Transfer path are compared. With the result of the TPA, developers will be able to determine critical contributions to the tonal behavior of the turbine and optimize either the transfer characteristics or the excitation specifically responsible for tonal behavior. The methods described can be applied to field measurement as well as an MBS-Model of the turbine to be able to optimize transfer characteristics during development.

Due to recent advances in the field of broadband aerodynamic noise, tonalities of wind turbines (WT) are increasingly coming into focus in the wind industry. In this case, the structure is excited inside the drivetrain and the structure-borne sound propagates through the machinery and ultimately to the surfaces of the WT, where it is radiated into the ambient air. Since any tonalities are a system characteristic, they should be considered at an early stage of product development. On the one hand, great efforts are being made to develop ever lower-toned drivetrains. On the other hand, tonalities can efficiently be neutralised by systematically decoupling the excitations in the drivetrain from the sound-emitting surfaces of the wind turbine. In addition to the well-studied behaviour regarding the decoupling of non-torque rotor loads from the drivetrain, in this paper the influence of a low speed stage (LSS) coupling on the structure-borne sound propagation inside of an integrated drivetrain is investigated. In a previous study at the Center for Wind Power Drives, it could be shown that in an integrated drivetrain, the transfer paths through the main shaft and subsequently the main bearing becomes the dominant transfer path. This is in contrast to classic bearing configurations where the torque arms of the gearbox are the dominant transfer paths of excitations from the gearbox, revealing an increased potential of LSS Couplings especially for integrated drivetrains. Detailed numerical investigations are performed in order to understand and quantify the usage of a LSS coupling for lowering sound power levels of a WT.