Research On Modal Parameters Identification Based On Related Structures Of Large Turbo-generator Stator End Winding

There is electromagnetic force of 600 MW turbo-generators due to the action of current and magnetic in the running process,which will cause vibration of generator.If there are problems in the structural design,material properties and connection settings,it may result in large vibration.Furthermore,there will be resonance especially when the vibration approach twice the power frequency,which will destroy the winding structure and affect the operating life of generator.In servere case,the major safety accidents may occur.Therefore,the analyze for dynamic characteristics of the related structures of stator end windings,including the identification of modal parameters(modal mass,modal stiffness and natural frequency)and the establishment of its vibration model,has important guiding significance for engineering applications such as structural optimization design and fault detection.In this thesis,using ANSYS and MATLAB as research tools,the computational modal analysis method is used to identify the modal parameters of the finite element model and the analytical model of the related structure of the stator end winding of the large turbo-generator,respectively.The main work of this thesis can be divided into three parts:1.A three-dimensional simulation model of the 600 MW stator end winding is established by using ANSYS,and the modal analysis is used to obtain its elliptical and three-lobed modal shapes and corresponding natural frequencies,which proves that the three-dimensional model used in this thesis is reasonable in the construction of model and the setting of connection and constraint.It also proves the accuracy of modal parameters obtained through the simulation of finite element method.2.According to the characteristics of the stator end winding,the windings of singlelayer and double-layer can be equivalent to the anisotropic conical shell and the laminated anisotropic conical shell,respectively.By using Rayleigh-Ritz method with improved Fourier series,the modal stiffness and modal mass with complex elastic boundary can be obtained,and the natural vibration equations about the modal parameters can be established.By setting the elastic constants of the equivalent model and calculating the natural vibration equation,the natural frequencies and mode shapes of the related structures can be obtained.Finally,by calculating the inherent vibration equation,the analytical solutions of natural frequency and corresponding model shape of relevant structure are obtained,and the validity of modal parameters are proved.3.Using the winding of double-layer as shell and the supporting structures as ring stiffeners and stringer siffeners,the equivalent model of stiffened and ribbed conical shell for whole structure can be established.Caulculating the modal pamameters which is consistent with the finite element model.Then,based on the obtained modal parameters,the model sensitivity analysis of whole structure is carried out which provides a theoretical basis for the structural optimization of the stator end windings.