Research And Engineering Application Of End Region Electromagnetic Field And Core Interlamination Voltage Of Large Half Speed Nuclear Turbine Generator

In order to solve the long-existing problem of the failure mechanism of the end iron core over-flux burning and fusion and effective prevention of large-scale turbine generators at home and abroad,and to ensure the zero-failure safe and stable operation of our country's independent research and development of large half speed nuclear turbine generators,this dissertation relies on requirement of National Science and Technology Major Special Projects "Research on key common technologies of large half speed saturated steam turbines,large turbo-generators and other equipment"(No.2010ZX06004-13),"Development of CAP1400 half speed turbine generators"(No.2012ZX06002-17),then adopts the technical route of theoretical research-experimental verification-engineering application,and conducts in-depth research on the formation mechanism and prevention measures of such failures.The main research contents and related innovative results are as follows:Firstly,taking the magnetic flux leakage on the core back of end region and the interlamination voltage as the research focus,comprehensively considering key factors such as the end axial leakage magnetic field penetration depth,magnetic field saturation,and non-linearity,this dissertation established a full three-dimensional finite element model of the end region structure including the key bars of the generator base,coils,multi-segment end region iron cores and ventilation trenches,which fully includes the common areas of end core burning failures.Furthermore,according to the complex characteristics of the generator magnetic circuit and the difference in the magnetic permeability of the oriented silicon steel sheet in different directions,the magnetization parameters of the magnetic material of the oriented silicon steel sheet in different directions were tested,and the influence of the anisotropy of the iron core punching sheet on the magnetic field leakage was solved,which laid a theoretical method foundation for the accurate solution of the over flux and the end leakage electromagnetic field.On this basis,according to different stator and rotor length matching schemes and different operating conditions,the end region three-dimensional electromagnetic field calculation was carried out,and the three-dimensional spatial distribution law of end region leakage magnetic field was obtained.Combined with the actual test and verification of the real generator,this dissertation has revealed the mechanism of the over flux on the end region core yoke,proposed the core magnetic density limit values of different materials,and formed a new design specification.Secondly,based on the calculation results of the end region electromagnetic field,theoretical analysis and research on the formation mechanism and calculation method of the interlamination voltage of core are carried out.Considering the important factors that affect the voltage between the stator core lamination,such as the eddy current induced by the stator core lamination,the current of the lamination flowing to the key bars,the current in the frame,the contact resistance of the lamination and the key bars,this dissertation proposed a calculation method for the interlamination voltage of core of large turbine generator,and developed a calculation software package for industrial applications based on this.Furthermore,through a large number of comparative calculations,the influence of the size and balance of the contact resistance between the lamination and the key bars on the interlamination voltage was discovered,and the mechanism leading to the increase of the end interlamination voltage of core was revealed.The new structure of magnetic leakage hazard suppression and high electromagnetic load end is proposed,and a new electromagnetic matching technology of iron core and key bars system is formed.It provides theoretical basis and technical support for solving the problems of end structure safety design,preventing end cores from over-flux burning and fusion,and ensuring the safe operation of large turbine-generators.Thirdly,aiming at the problem of complex end region structure and three-dimensional time-varying moving electromagnetic field simulation,it overcomes the limitations of incomplete test verification on real generator,then produced an electromagnetic simulation device for the end region of a large generator,which realizes the 1:1 real simulation of the complex electromagnetic field at the end of the iron core under different structure types,different capacities,and different operating conditions,then filled the domestic gap.On this basis,this dissertation established a 1:1simulation of the domestic CAP1400 large half speed nuclear turbine generator,include the end region alternating electromagnetic field,the magnetic field in the iron core,the axial leakage magnetic field,the interlamination voltage,the current of the key bars,etc.Furthermore,a high-precision cross-checking technical system for the end region electromagnetic and structure of the large generator is constructed,which effectively realizes the cross-checking of the numerical calculation and experimental test of the end region electromagnetic physical state parameters of large generators.The research results of this dissertation have passed the acceptance of major national scientific and technological projects,and have been successfully applied in many major projects such as CAP1400 and Hualong No.1 developed by Dongfang Electric Group Dongfang Electric Co.,Ltd.,which have effectively improved the reliability and advancement of generator design.It has provided core technical support for our country's implementation of nuclear power's “going global” strategy and expansion of overseas markets,and has achieved good results.