Optimal Design of a Compound Magnetic Shielding Based on Fe-Based Nanocrystalline Alloy

The magnetic field inside the analyzed double-stator high-temperature-superconducting machine (DS-HTSM) has the characteristics of rich harmonics and non-negligible amplitude, which will seriously reduce the critical current I_c of HTS-excitation coil. Therefore, a new compound magnetic shielding (CMS) is proposed in this paper, which is composed of a copper shield layer and a combined flux diverters (FDs) including the silicon steel sheet (SSS) FD and the Fe-based nanocrystalline alloy (FNA) FD. The key is that the iron loss of SSS FD located in the inner Dewar can be reduced due to the flux pre-diversion of the FNA FD on the outside. In addition, the FEA model based on the T - A formula for HTS-excitation coil is built, based on which the optimal design of proposed CMS is conducted. The results show that the critical current I_c of HTS-excitation coil in the analyzed DS-HTSM can be improved by 36% after using the proposed CMS.