Analysis And Calculation Of Magnetic Field And Eddy Current Loss In The End Structure For Megawatt Synchronous Motor

Electromagnetic problem of end winding and structural parts of megawatt synchronous motor is one of the key problems in the design of large-scale motor.This dissertation studies the end magnetic field and eddy current loss of megawatt synchronous motor,puts forward the construction method of 3D physical model and mathematical model of motor end complex solution domain.And that establishs the transient time-stepping finite element numerical analysis model of 2D and 3D field-circuit coupling,calculates the end magnetic field,current density and eddy current loss distribution of the motor in steady and transient operation condition.Firstly,this dissertation establishs the end stator winding model of megawatt synchronous motor by using the end stator winding modeling method combining base circle and involute and constructs the involute model assembly of the end stator winding by the method of gradually linearization.Then,it forms an end 3D transient time-stepping finite element solution model,which includes stator and rotor core,end excitation winding,retaining ring,clamping ring and integrated grid-shaped clamping finger.And it analyzes the end magnetic field distribution of the motor at no-load and rated condition.Secondly,that calculates the eddy current density and eddy current loss of the end clamping ring and integral grid clamping finger of megawatt synchronous motor at two typical working conditions.Then this dissertation studies the influence of the material characteristics of the clamping ring on the eddy current density distribution and eddy current loss of the end structure and discusses the influence of the relative position between the clamping ring and the clamping finger,the copper shield and other factors on the eddy current density and eddy current loss of the end structure.And it puts forward a topological structure to reduce the eddy current loss of the clamping ring.Finally,it adopts the transient time-stepping finite element method with 2D and3 D field-circuit coupling,and couples the calculation results obtained by the 2D transient finite element method with the 3D analysis model.It calculates the magnetic field distribution,eddy current density and eddy current loss of the end structure of megawatt synchronous motor at different times under the three-phase short circuit fault and gives the concentrated area and amplitude of magnetic density and loss of structural parts in fault state,which provides theoretical basis for structural design.