Generator End Winding Modal Test And Analysis

With the development of China economy,domestic electricity consumption get growth especially in 21 Century.People put more attention on better life,power generation equipment installed capacity increased year by year and the POWER GRID have been improved rapidly.Large thermal power generator still occupy a large proportion in china,the development of clean and efficient energy has ushered in a period of great opportunities with the improvement of the environmental awareness.In China SEC have manufactured 1200 MW thermal power generating units.With the increase of the generator capacity,the current and voltage are also synchronized growing.For large generator,the stator end winding is subjected to electromagnetic force and mechanical force.There is a huge exciting force in the direction of tangential direction,axial direction and radial direction.The stator end winding structure can be divided to banding structure,glue structure,plate structure.The fixation strength of stator winding determines the power of subject the electromagnetic force and mechanical force.The stator winding output current and voltage.In order to mass production and connecting the winding to the Power grid,the end winding has been designed to threedimensional structure on the involute cone.The involute structure is complicated,and the mould rely on the manufacture by hand for a long time in the history.With the development of multi-axis machining equipment and the application of computer technology,the generator manufacturing quality has been improved gradually.In recent years,,five axis machine tools and multi axis forming equipment have been applied in the preparation of the stator winding.The stator winding shape has been more uniform to the 3D model.The modal analysis and testing of large turbine generator stator end windings have gained more and more attention.Before 21 Century,the calculation of generator stator end winding mode is mainly rely on program and hand computation.In 1980 s,Shanghai Generator Plant and Harbin Generator Plant introduced 300 MW water hydrogen generator with end modal calculation theory,procedure.At that stage,mode test was concentrated in a single modal test and verify without theoretical studies on new design and structure.In 21 Century,with the increasing of generator capacity,the destruction caused by the vibration increased.All the major generator manufacturer put modal test and theoretical analysis on a higher level.Finite element analysis and three-dimensional model and other techniques are used in the modal analysis with the computer technology development and the progressing of numerical methods.The main test methods is excitation method.Take the vibration load on the end winding through the hammer,and arrange the accelerometer to collect the feedback signal.Compare the input and output signals and fit curves to obtain modal parameters of end winding.The stator end winding of large generator is subjected to the electromagnetic force of the core,rotor,and so on.The end winding fixed structure is rigid-flexible type.the end is integral and rigid,but the structure connected to stator core is flexible which can trace in the axial displacement.The modal is affected by temperature,manufacturing quality and so on.For the glue filling structure,its modal is closer to the resonance spectrum.The natural frequency of 1000 MW generator in the Shanghai generator factory is close to 100 Hz,but the structure is good enough because of the glue filling structure.This topic is mainly reserch the binding type structure and glue filling type structure.Calculate the end winding modal according to the experimental data and literature data using different modeling methods.And calculate the mode according to the winding step.Research the modal according to the change of elastic modulus of the material of the end of the generator.At present,the research on the mode of generator stator winding is mainly based on GB/T20140-2006 and JB/T8990-1999.According to the long-term operation and maintenance experience of the generator,this paper sorts out the measures of vibration protection under different conditions and analyzes the requirements of vibration and mode of the major manufacturers.