ABSTRACT

Any changes in stiffness arising from the cyclic loading must also be well understood as there could be significant effects on the dynamic response of the turbine. Wind turbines are normally designed to have natural frequencies in the range between the frequency bands of the rotor rotation and the blade passing frequency, usually denoted by 1P and 3P. This avoids resonances, but changes in stiffness might result in interference between the first natural frequency and the excitation frequencies, 1P or 3P of the wind turbine.