Bending Characteristics of a Quasi-isotropic HTS Conductor with High Engineering Current Density
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ORIGINAL PAPER
Bending Characteristics of a Quasi-isotropic HTS Conductor with High Engineering Current Density Jiuke Wang 1 & Yinshun Wang 1 Received: 26 March 2020 / Accepted: 27 June 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract A high-temperature superconductor (HTS) with high engineering current density and flexibility has recently been proposed and tested. The conductor is suitable for fusion magnets because of its high carrying current capacity in high field. However, the accumulated strain during the conductor fabrication and coil winding may cause irreversible degradation of the conductor critical current. Therefore, it is important to study the bending characteristics of the conductor and the accumulated winding strain and twisting strain on the HTS tapes during the conductor fabrication process. In this paper, the finite element method is used to study the bending characteristics of the conductor, and the degradation extent of the conductor critical current under different bending radii was calculated. Bending experiment was carried out, and the conductor critical currents at 77 K in self-field under different bending radii were measured. The experimental and finite element analysis results presented in this paper are useful in application of the conductor in high-field and large-scale magnet. Keywords Bending characteristics . High-temperature superconductor (HTS) . Finite element method (FEM) . Quasi-isotropic strand (QI-S) . Strain accumulation
1 Introduction In recent years, great progress has been made in the research of second-generation (2G) high-temperature superconductor (HTS) tapes, and some companies have the ability to fabricate 2G HTS tapes with piece lengths of several hundred meters [1]. Compared with low-temperature NbTi and Nb3Sn materials, HTS materials have higher thermal stability, higher current carrying capability, and stronger mechanical properties [2, 3]. In addition, the high field tolerance of HTS materials at low temperatures potentially expands the range of operation for fusion magnets (B>18T) [4]. These excellent properties make the HTS materials suitable for making the large current conductors needed in the operation of fusion magnets and power transmission.
* Yinshun Wang [email protected] Jiuke Wang [email protected] 1
State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
Because REBCO-coated conductors are only available as tapes, multiple tapes must be connected in parallel for practical applications. Therefore, a variety of cabling methods have been proposed internationally, including Conductor on Round Core (CORC) [5], Twisted Stacked-Tape Cables (TSTC) [6], Roebel Assembled Coated Conductor (RACC) [7], and Quasi-isotropic Strand (QI-S) [8]. Other cabling methods for 2G wires are also under development for fusion magnet [9]. The main differences among these various cabling concepts are the transposition and assembly methods of the
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