| High-temperature superconducting(HTS)magnets are widely recognized and ex-pected for the wide range of operating temperature,excellent performance in magnetic field and good thermal stability.The recent research of HTS magnets applied in field magnets,rotating machines and magnetic energy storage(SMES)has achieved prelimi-nary results.However,with the development of practical and large-scale HTS magnets,some key technical problems have caused attentions in the industry,such as the structure optimization aiming at cost control,the influence of screening current on field quality,and the large electromagnetic stress in high-field magnets.In this study,the multiphysics performance design of the HTS magnet is theoretically and practically studied in view of the above-mentioned issues.Firstly,the optimal design method of HTS magnet is discussed.Based on the design principle of rotating machine and the anisotropy of HTS tape,a case study of HTS magnet for 100-kW generator is presented.The magnet design with stepped geometry is obtained,which can provide a maximum air gap flux density of 2.0 T at 30 K.The unique stepped-shaped design saves 8%of HTS materials compared to the general one.Aiming at HTS magnet with uniform magnetic field,the influence of shielding current on magnetic field quality is investigated by numerical simulation.Based on the characteristics of the HTS magnet and the superconducting physics,the screening current field in the outer-notched REBCO magnet with 2528 turns was calculated.It is found that the screening current caused a relative error of 3 × 10-3 on the central field,and field uniformity of 1-2%on the axis of the magnet.The analysis shows that the error field is mainly cause by the reverse current in tape near the ends of the magnet,and it can be suppressed by exciting magnet to near critical current.The screening current field in the layer-wound REBCO magnet is also studied,and it is found that the coupling effect of the adjacent tapes in the magnet will affect the amplitude of the screening current field.According to the theoretical analysis,it is suggested to use reinforcing overbanding structure with high strength and high elastic modulus to reduce the hoop stress in the solenoid.In this work,the design method of solenoidal HTS-SMES with reinforcing overbanding structure is studied.Parametric scanning method which takes energy capac-ity,critical current and the maximum hoop stress into consideration,was used to optimize the design of the 40-dm3 solenoidal SMES with reinforcing overbanding structure.It is suggested that the large-aperture thin-walled solenoid is the economical geometry for SMES,and the reinforcing overbanding structure needs to be optimized to achieve high energy storage density.Based on the research above,a 30-K/4-kJ REBCO-SMES magnet is designed as high performance power source.The design of the cryogenic system is carried out according to the basic principle of heat transfer.The cryo/SN2-cooled solenoidal SMES magnet with an inductance of 120 mH is designed to be operated in 30 K,and its energy capacity achieves 4.2 kJ with operating current of 266 A.The loss in the magnet during charging and discharging was evaluated by numerical method. |
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