Study On AC Loss Characteristics Of REBCO Cables And Coils With Different Geometric Structures

In recent years,as the application of high-temperature superconducting materials in power systems has become more and more widespread,especially in high-temperature superconducting coils and high-temperature superconducting cables.Its excellent electromagnetic performance can increase transmission efficiency in cable equipment,and can generate high-strength magnetic fields in the coil.However,the application environment of superconducting materials is relatively strict.High temperature superconductivity requires77 K liquid nitrogen.At the same time,due to the anisotropy of high temperature superconducting materials,power equipment is in a different or complex electromagnetic environment,and magnetic fields and transmission are applied.Current will increase the AC loss of superconducting power equipment.Excessive AC loss restricts the development of superconducting cables and the application of coils.Accurately assess and obtain the distribution of AC loss and loss of high-temperature superconducting cables with different geometries under different working conditions and during dynamic operation of magnets,which is helpful to improve equipment structure,reduce AC loss,and improve cooling system.Improve the stability and reliability of the device.In this paper,based on the finite element method that can handle complex electromagnetic problems,the traditional two-dimensional finite element simulation model is optimized,and two-dimensional models of high-temperature superconducting cables with the same duty cycle and different geometric structures are established and two superconducting coils based on two-dimensional symmetry axis models are established.Based on the research foundation of predecessors,a single-root simulation model was established,and the accuracy of the simulation was verified by experiments.The AC loss of high-temperature superconducting cables with the same duty cycle and different geometric structures under the transmission current,the external magnetic field,and the transmission current and the external magnetic field are compared and analyzed.First,the simulation is composed of 24 REBCO strips.The AC loss of the six cables with different geometrical structures of the company found that the newly proposed inner-eight outer-radiation cable structure and the double-layer regular dodecagonal cable structure have smaller AC loss when only considering the self-field loss;In the case of field and external field,the inner-eight outer-firing structure cable has smaller AC loss than other cable structures.Then three cable structures were selected for narrowing simulation analysis.The results show that the narrowed radioactive structure cable has the smallest AC loss in the self-field and external field;the narrowed radioactive structure cable is simulated and analyzed,and it is found that the strip is narrow After conversion,the AC loss of the cable is related to the width of the strip,the spacing of the strip arrangement,and the inner radius.If it is necessary to reduce the AC loss of the radioactive structure cable,appropriately increase the width of the strip,increase the inner radius,and reduce the strip arrangement.The spacing is very important to reduce the AC loss,but too large radius and strip width will increase the cross-sectional area of the cable and increase the cost;appropriately increasing the width of the outer arrangement strip can increase its critical current.Thereby reducing the overall AC loss,it is of great significance to prevent the quench of the external strip.A 40-turn high-temperature superconducting coil model was established.The magnetic field distribution and the AC loss of each turn of the coil were analyzed,and the accuracy of the simulation in the coil was verified by homogenization.Due to the complexity of the coil,the distribution of AC losses on each turn of the coil is not the same.From the perspective of the magnetic flux density mode,the value of the magnetic mode within the coil is very large.Considering the effect of the magnetic field on the high temperature superconducting coil,protecting the inner coil from quenching becomes the primary problem.The simulation of multi-turn coils adopts the homogenization model to simulate.It has the advantages of fast simulation time and easy convergence.