Vibration Characteristics of Blade Adjustment Gear Train for 8MW Class Offshore Wind Turbines

This paper reports on a study of the vibration characteristics of the blade adjustment gear train for 8MW class offshore wind turbines. A method for analyzing the vibrations of the blade adjustment gear train was proposed by combining the rotational vibration model of the planetary gear train with the finite element models of the housing and carrier using the substructuring method. Applying 10%, 20%, …, 100% of the largest LDD load showed that both bearing stiffness and the primary natural frequency increase with higher LDD loads. Furthermore, the primary natural frequency for the highest load in the LDD data was found to be 104.26 Hz, which exceeds the operating speed of 84.87 rpm (5.09 Hz), indicating that vibrations due to LDD load variations do not occur within the operating speed range. In addition, analysis of critical speeds for the blade adjustment gear train showed that critical speeds related to mass unbalance, gear mesh frequency, and bearing defects do not occur within the operating speed range (84.87 rpm). Also, by utilizing AGMA 6000-B96, an acceptable displacement for vibration was selected, and the displacement occurring under LDD load conditions was compared with the acceptable displacement to assess vibration safety. The response analysis results for the planetary gears and output shaft bearings at the 1st, 2nd, and 3rd stages all satisfied the acceptable levels.