Investigation Of Electromagnetic And Mechanical Behavior In Superconducting Rotating Machine And Composite Materials

The superconducting rotating machines are the machines which use superconducting tapes or wires instead of traditional conductors.The superconducting rotating machines have higher efficiency,lower weight and volume than traditional conductors.The high temperature superconductor composite materials which have excellent electromagnetic properties are widely used in the electric energy transport,thermonuclear reactor,superconducting generator/motor,magnetic,and superconducting storage.The non-linear superconductivity make it complex and difficult to simulation the superconducting rotating machines.The superconductor materials are usually work in the high external magnetic field and carrying high current.And the AC loss generated by superconductor will increase the load of cooling system.And the electromagnetic body force and mechanical load could lead to deformation and fracture in the application of superconductor.Thus,AC loss and mechanical stability are two key limitation in the application of superconductor material.So more effective numerical model is needed to calculate the AC loss and mechanical response in superconducting machine.In this paper,the critical current,AC loss and stress/strain distribution of superconductor tapes,wires and array under magnetic field/carrying transport current condition are investigated to study the key problems in the applications of high temperature superconductor materials and superconducting rotating machine.And a new numerical model has been built to simulate the superconductor rotating machines and calculated the AC loss and stress distribution.At first,the effect of mechanical load on the AC loss of Bi2223 composite tapes is investigated.A theoretical model is built to describe the relationship of fracture area and external bending strain,and the thermal residual strain is considered.The FEM is employed to calculate the current and magnetic field distribution of tape under different external magnetic field and transport current condition.The effect of bending strain on AC loss is discussed.Subsequently,the influence of geometry structure on the AC losses in different transport and external field conditions are investigated and discussed.Then,the influence of filament volume fraction of Bi2223 composite tape on the electromagnetic and mechanical behavior.The iteration method based on critical current density model and self-field effect is used to calculation the critical current density of Bi2223 composite superconductor tapes which have different volume fraction.The induced current and magnetic field are calculated by variational formulation.The two-scale expansion method is employed to calculate the effective mechanical module of tapes which have different volume fraction.The stress/strain distribution and magnetostriction of tapes under different external magnetic field based on finite element model(FEM).The most dangerous region witch suffer the largest stress/strain is investigated.Moreover,the electromagnetic and mechanical behaviors in structures of HTS materials are investigated.The tapes and wires in the superconducting rotating machines are usually wound as cables or coils,and the complex geometry structure make the calculations more difficult.The electro-magnetic behavior in superconducting structures such as multi-filament superconducting wire,cable,and the array structure of superconductor tapes are investigated.The distributions of the current and magnetic field are calculated by magnetic energy minimization(MEM)method based on critical state model.The distribution of stress and strain is determined by FEM and the electromagnetic body force.The most dangerous region witch suffer the largest stress/strain is investigated.And the influence of geometry structure on electro-mechanical behavior is discussed.At last,a new numerical model is built to simulate the superconducting rotating machine,and the electromagnetic/mechanical behavior of superconducting generator is investigated.The single calculation method is difficult to consider the rotate structure of rotating machine.The numerical is based on the T-A formulation and moving mesh method.The anisotropy critical current density and E-J power law are considered in our model.The virtual tape is introduced to simulate the stator current induced by the magnetic field.The results by our model and present numerical model is compared,and the results agree well.The AC loss and mechanical stress in rotating generator condition are calculated.And the effect of geometric structure on AC loss,electromagnetic body force and stress are also investigated.This model might benefit to the design of superconducting rotating machine.