Abstract
This paper presents experimental results of the torque ripple obtained from a three bladed 12 kW experimental H-rotor prototype. The measurements are performed by means of load cells installed on the base of the struts and by electrical measurements on the generator. The resulting torques are analysed in terms of frequency spectrum and order spectrum (synchronized with rotation). The measurements are compared to aerodynamic simulations of the turbine. The expected large torque ripple at three times the rotational speed (3 p) is only weakly represented at the hub and in the generator. This suggests that the system is filtering the ripple and/or that the simulations are overestimating the 3 p component. The torque ripple loads on the drive train are therefore lower than anticipated. Even if highly attenuated, most of the low frequencies correlating to aerodynamics are still represented in the generator electrical torque. Given a certain baseline, this opens for possible online monitoring of unbalances in the turbine by electrical measurements.
Highlights
The majority of the wind turbines operating today are horizontal axis turbines (HAWT)
Aerodynamic simulations predict the order spectrum to mainly depend on TSR
The experimental results analysed in order spectrum provided fairly consistent relative torque spectrum as a function of TSR for one blade
Summary
The majority of the wind turbines operating today are horizontal axis turbines (HAWT). There is a growing interest in vertical axis wind turbines (VAWT), since they have the potential to further reduce energy cost [1]. There are concerns associated with VAWTs. One of the main challenges is the varying aerodynamic forces on the blades that lead to a force oscillation on the structure and a torque ripple in the drive train [1]. One of the main challenges is the varying aerodynamic forces on the blades that lead to a force oscillation on the structure and a torque ripple in the drive train [1] To better understand these forces, simulations and verifying experiments have been performed. Sandia National Laboratories conducted studies on force measurements of large-scale VAWTs with troposkein shaped blades in the 1980s [2, 3, 4]
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