Performance Improvement of YBCO Coil for High-Field HTS-SMES Based on Homogenized Distribution of Magnetically-Mechanically Influenced Critical Current

Abstract

Generally speaking for a HTS coil, perpendicular magnetic field to conductor's broad surface should be suppressed as small as possible in relation to the magnetic anisotropy. This is a reason why toroidal coil with relatively many elementary coils is expected for HTS-SMES. On the other hand, from the point of view of the homogenization of critical current distribution in the coil, perpendicular field and parallel field should be balanced corresponding to the ratio of the magnetic anisotropy. This means that a certain level of the perpendicular field is effective to reduce local heat generation in the coil. Furthermore, this concept is especially reasonable for a high-field coil with usual winding method (flat-wise winding) because the perpendicular field does not induce hoop stress which decreases the critical current. In this paper, we show these findings through an optimal design of a MOCVD-YBCO toroidal coil for 2 GJ class SMES taking account of magnetically and mechanically influenced characteristics. Index Terms-Hoop stress, mechanical strain, optimal design, SMES, YBCO coated conductor. I. INTRODUCTION I N JAPAN, the applicability of YBCO coated conductor to SMES has been explored under a national project by NEDO since FY2004. As a part of the project, we carried out a conceptual design of a high-field (over 10 T) YBCO coil at 20 K, and suggested that YBCO coated conductor could realize a very compact SMES magnet compared with a conventional one using Nb-Ti conductor [1]. Furthermore, it was also indicated that such a high-field coil could be realized not only by good transport characteristics of the YBCO material against magnetic field but also by high mechanical strength of Hastelloy substrate against hoop stress.

Longitudinal inhomogeneity of DC current transport properties in Gd-system HTS tapes – Statistical approach for system design

“…Such calculations are repeated 100 times for above-mentioned E l,m and W t in order to realize the statistical process. Note that to examine both E l,m and W t are important for the control of the hot-spot and the total heat generation of the coil, respectively [21][22][23][24][25] . Fig.…”

“…The first author's group has also performed the analytical study with the use of the above-mentioned model for HTS coils [19][20][21][22][23][24][25] and HTS cables 26,27) . In this paper, variables T i and e i are not subjected to the consideration.…”

Longitudinal Inhomogeneity of DC Current Transport Properties in Gd-system HTS Tapes

“…(1) Electric field E (μV/m) [19][20][21][22][23][24][25][26][27] ࠾࠸࡚᭱ಙᆇᛶࡢ࠸ ো౯ᘧࡋ࡚ᮌᅢࡢ࣮ࢥ࣮ࣞࢩࣙࣥഴ⛣ࣔࢹࣝ [14][15][16] ⏝ࡋ࡚ࡁࡓࠋࡋࡋ࡞ࡀ ᭱Ǻⓗࡣୖঠࣔࢹࣝ ( )…”

Development of High Strength Pancake Coil With Stress Controlling Structure by REBCO Coated Conductor

“…T OWARD the realization of GJ (giga-joule) class large capacity superconducting magnetic energy storage (SMES) system for power system control, high reliability and durability of superconducting coil are essential [1], [2]. High strength and high field coil is needed to increase the electric power capacity.…”