SNF Issue No. 45, August 2018

In this Issue:

  • Science and Technology Highlights

Simulation and Experimental Assessment of the Electromagnetic-Thermal Behavior of an Inductive-Type Fault Current Limiter

STH57 HP132 Fig 1
June 8, 2018 (STH57, HP132).  The study of the electromagnetic-thermal phenomena of superconducting fault current limiters operating in electrical grids is often neglected in transient simulations due to extensive simulation times or unavailability of commercial software easily addressing the coupling between electromagnetic and thermal phenomena [1, 2]. Recently, in [3], we have presented a fast simulation methodology to predict the dynamical electromagnetic-thermal behavior of an inductive-type limiter, namely: line current, primary linked flux as well as temperature and current in superconducting secondary. Simulations have been compared to experimental results from a laboratory scale prototype, depicted in Fig. 1 [3, 4].

Fig. 1.  Laboratory scale prototype (dimensions in millimeters) [3].

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Robust High Je RE-Ba-Cu-O Symmetric Tape Round (STAR) Wire for Accelerator Magnets

Soumen Kar, Wenbo Luo, Anis Ben Yahia, Xiaofen Li, Goran Majkic, Venkat Selvamanickam

April 8, 2018 (STH56, HP131).  AMPeers and University of Houston have jointly developed an innovative approach to fabricate round REBCO wires with high Je and good bend strain tolerance [1]. These wires are only 1.6 to 1.9 mm in diameter and are made by winding narrow REBCO tapes on an AWG 18 (1 mm diameter) copper wire former. Such small diameter wires are possible by the use of symmetric tapes where the REBCO film is positioned at the geometric center, close to the neutral axis as shown in figure 1. Such asymmetric tape architecture is achieved by a strategic selection of the thickness of the copper stabilizer to match the thickness of the Hastelloy substrate. The substrate itself is made thin, about 22 µm, so as to enable good tolerance to bend strain. The overall thickness of the REBCO tape is about 45 – 60 μm including the copper stabilizer. Symmetric Tape Round (STAR) wires have been fabricated with six to eight of these REBCO tapes, each about 2-3 mm in width, wound on AWG 18 copper wire former.  The optimized STAR wires are found to be mechanically robust and retain 97% of its critical current of over 500 A at 77 K, self-field even when bent to a small radius of 15 mm as shown in figure 2 (photo top left of article)

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