Modal Analysis Of Wind Turbine Gearbox System

Gearbox is one of the most important parts of wind driven generator which has asignificant influence on the performance of wind power generation. It is necessary to analyzethe dynamic characteristics of the gearbox. Modal analysis is the important step and it canexplain the intrinsic attribute of the gearbox and conduct the practical operation. Thecomparison between finite element and experimental modal analysis is necessary.The primary content of this research involves the finite element modal analysis of the1.5MW wind turbine gearbox system using multi-body modeling technique. The box, annulargear, torque arm, bearings, gears, shafts and planet carrier are all taken into consideration toreflect the real situation. The small holes, filleted corners, chamfering and bolt holes areneglected when modeling the finite element model. In this study, two kinds of meshingmethod are discussed. Firstly, the bearings are simplified with springs in three directions toreduce the amount of calculation. Then the appropriate meshing and exact boundaryconditions are set in the simulation of modal analysis. The first ten modal frequencies andmode shapes are obtained and the animation shows how the gearbox may vibrate. Theinfluences of the bearing stiffness and gear contact stiffness on the gearbox system are alsodiscussed.The experimental method of single point excitation and multi-point response is appliedin the experimental modal analysis. The modal parameters are obtained through the rationalfraction polynomial method. In order to reflect the whole structure of the gearbox,107testingpoints are arranged in the gearbox to get the complete vibration information. Modalfrequencies and mode shapes are identified from the frequency response function curve. Theerror of the modal frequencies is less than6.9%and the biggest happens at the fourth modeshape for the combination of the box and gear drive system. This result shows an excellentagreement between the simulation and experimental results. This work can be applied in faultdiagnosis and structure optimization of the wind turbine gearbox.