Study On Electromagnetic Field And Loss In End Region Of Large Capacity Turbogenerator With Multi-layer Magnetic Screen Structure

In order to solve the problem of greenhouse gas emission and pollution,China has put forward the strategic goal of “Emission peak and Carbon neutrality”.As an efficient energy alternative to coal,accelerating the development of nuclear power has been put on the agenda.The capacity of the turbogenerator is large,which is the core equipment of the nuclear power plant.At present,the capacity of the turbogenerator for nuclear power has reached the level of one million k W.But the increase of capacity will lead to the increase flux density of component in the end region,and local overheating will inevitably occur,which will endanger the safe and stable operation of turbogenerator.As the basis of temperature field calculation,the electromagnetic field is very important to study it in detail.In this thesis,the end region electromagnetic field and the loss of each component of 1407 MVA turbogenerator for nuclear power are studied.Firstly,the electromagnetic field in the end region of turbogenerator is analyzed and calculated for nuclear power.According to the basic theory of electromagnetics,the stator end windings,rotor end windings,stator end core,finger plate,press plate,magnetic screen and screen plate are considered,the three-dimensional electromagnetic field mathematical model and physical model are established.The exciting current and power angle under rated-load are determined by dual convergent iteration method,and the electromagnetic field in the end region is calculated.On this basis,the distribution law of flux density of end structure is analyzed.Secondly,the influence factors of turbogenerator end electromagnetic field and loss are discussed for nuclear power.In view of the multi-layer magnetic screen structure,the thickness of magnetic screen is equal and unequal,and the thickness changes,whether there is circumferential ventilation ditch and the depth of ventilation ditch are studied in detail.The variation laws of electromagnetic and loss of end structure under different factors are compared.Finally,a field-circuit coupled finite element method is used to calculate the electromagnetic field in the end region of large-scale turbogenerator for nuclear power,which solves the complicated process of calculating the initial parameters by iteration.The results of the field-circuit coupled method and the traditional method are compared.The three-dimensional fluid and heat transfer coupling model of turbogenerator end region is established,and the loss value determined by field-circuit coupling method is used as the heat source to calculate the temperature rise of end structure.The results are compared with the measured values.It shows that the field-circuit coupled finite element method is feasible and the calculation results are accurate.