Structure Design And Electromagnetic Simulation Of Coils Based On REBaCuO Superconducting Tapes

REBaCuO?REBa₂Cu₃O_x,RE=Y,Gd,and other rare earth elements?high-temperature superconducting tape has developed rapidly in recent years,especially the improvement of artificial magnetic flux pinning technology,which makes its current carrying capacity under magnetic field better than most of other practical superconducting materials.It has good current-carrying performance in the liquid nitrogen temperature region.Especially in the low temperature,high field environment,REBaCuO superconducting tape has obvious advantages.Benefit from the alloy substrate,its axial mechanical properties are also good.It breaks through the limitation that the first-generation Bi2223/Bi2212 material is only suitable for low field or low temperature application,and has a wide application prospect in the field of eletrotechnics.It is not only suitable for DC high field magnets,but also for large superconducting AC devices that use liquid nitrogen for refrigeration.In the field of electrical engineering,REBaCuO high-temperature superconducting tape is mainly used in superconducting power technology and superconducting magnet technology.Based on REBaCuO high temperature superconducting tape and COMSOL Multiphysics simulation software,the simulation model of superconducting power device was built in this dissertation.Five kinds of practical superconducting magnet coils are designed and calculated,and their electromagnetic properties are optimized.The research goals include reducing the AC loss REBaCuO of superconductor coil,improving the magnetic field uniformity of joint-free REBaCuO superconducting magnet,designing a joint-free REBaCuO magnetic shielding coil which has stable shielding effectiveness in most of field frequency,designing a racetrack REBaCuO magnet which is suitable for the magnetic levitation train.The main research contents and results are as follows,?1?Building the model of REBaCuO coil and calculating AC loss of the coil.The AC loss of coils by slitting the tape in different winding positions was analyzed.The result indicates that because the magnetic field of the coil is not evenly distributed along the radial direction,coil with slitting in the outer radial turns can effectively reduce the AC loss,especially in the case of high current load.For A104-turn coil,when running in the current with 80 A amplitude,slitting in only 40turns of outer coil can effectively reduce AC loss.?2?The REBaCuO Helmholtz coil model with radius of 50 mm was built based on the joint-free REBaCuO superconducting coil,and the excitation process,current density distribution and magnetic field distribution were calculated.Under the excitation of 8 mT in the field,REBaCuO coils generated a stable trapped field of2.6 mT.The geometric structure of the coil is designed symmetrically to improve the uniformity of magnetic field distribution.The y component deviation value of the magnetic field was ameliorated from from 0.12 mT to 0.004 mT.Furthermore,the model of axial arrangement of four coils was further built.In the central spherical space area with a diameter of 30 mm,the magnetic field unevenness was reduced from 2.5%to 1.1%.?3?Based on the joint-free REBaCuO superconducting coil,a magnetic shielding coils consist of internal and external coils connected in series was designed.By using the zero resistance characteristic of joint-free coil,the high shielding effectiveness of coils in medium and low frequency magnetic field was realized.The3D simulation model of magnetic shielding coil was built,by adjusting the number of turns of the shielding coil and the ratio of inner and outer radius,optimized single coil structure in magnetic shielding was got.Then built a dual-coil electromagnetic shielding model with axial alignment and the best shielding effect and maximum shielding space are obtained by adjusting the distance between coils.Compared with other superconducting shielding coils with joint resistance,its low frequency magnetic field shielding capability is particularly excellent.Within the frequency range of 0.00001 Hz to 1000 Hz,the shielding factor of coils in applied field of 10?T can reach 0.01%.Moreover,the shielding factor is lower than 1%in the central spherical space area with a diameter of 40 mm.?4?A racetrack magnet based on REBaCuO superconducting tape was designed.The magnet was composed of four double-pancake coils.A 3D simulation model was built to calculate the magnetic field distribution of the magnet and analyze the axial magnetic field attenuation.At 20 K ambient temperature,the rated operating current of the magnet is 153 A,the central magnetic field reaches 2 T,and the axial distance from the central point is 80 mm.The magnetic field can be kept above 0.9T.The AC loss of the magnet in the process of excitation is calculated to be 159 J,and the AC loss of the magnet in the varying magnetic field of 20 mT and 680 Hz is0.016 W in the stable operation of the magnet.