Numerical Simulation Of Electromagnetic And Mechanical Behavior Of Superconducting Machines

Superconducting materials are widely favored in fields such as electric medicine,energy,and large scientific devices due to their unique electromagnetic properties.At present,superconductive materials have been applied in electric machine systems,which can achieve higher power density and output efficiency,and have important application potential in large wind turbines,marine propulsion systems,electric aircraft and other fields.Due to the influence of alternating magnetic field and current on the superconducting coil in a superconducting machine,the superconducting coil exhibits significant AC losses.In addition,the inner coil of the machine is in a complex mechanical environment.The high mechanical stress and strain not only affect the safety and reliability of the coil structure,but also lead to the degradation of the conductivity of superconducting materials,further restricting the design of superconducting machines.Therefore,the study of electromagnetic and mechanical behavior is the foundation for the development and stable operation of superconducting machines under real working conditions.This thesis focuses on the key problems in the load coil of the superconducting machines.By modifying the T-A formulation,the AC loss,temperature distribution and mechanical response of the coil under different conditions are given,and the quench propagation of superconducting coil under alternating load is discussed,which provides a basis for the quench protection design of superconducting coil in the machines.The main research content of the paper is as follows:Firstly,the application scope of the T-A formulation is extended.By combining the circuit model and modifying the T-A formulation,the calculation of electromagnetic field with unknown current in the layer is achieved.The results of H formulation and modified T-A formulation are compared for the charging process of stacked tapes,verifying the effectiveness and accuracy of the modified T-A formulation.Secondly,an electromagnetic numerical model of a synchronous superconducting machines is established,and the electromagnetic field,temperature,and mechanical behaviors under different operating conditions are analyzed.On the basis of the thermal and mechanical parameters of the anisotropy of the coil,the loss and temperature distribution of the coil under different working conditions are given based on the homogenization T-A formulation,and the thermal stress and electromagnetic stress in the coil are calculated quantitatively.Finally,a quench model is established for the coil under alternating load,and the effects of constant load and alternating load on the coil quench is compared.The variation law of the minimum quench energy of the coil under the action of alternating electromagnetic field is given.On this basis,the influence of magnetic field and component structure of strip on the thermal stability of coil with short circuit faults are analyzed.This model is helpful for the design and optimization of quench protection for the coils in superconducting motors.