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http://dx.doi.org/10.9714/psac.2017.19.2.048

"Leak Current" correction for critical current measurement of no-insulation HTS coil  

Song, Jung-Bin (Laboratoire National des Champs Magnetiques Intenses, CNRS)
Hahn, Seungyong (Department of Electrical and Computer Engineering, Seoul National University)
Publication Information
Progress in Superconductivity and Cryogenics / v.19, no.2, 2017 , pp. 48-52 More about this Journal
Abstract
Discrepancy between a power supply current and an actual "spiral" coil current makes the conventional 4-probe measurement of a critical current ($I_c$) of a no-insulation (NI) high temperature superconductor (HTS) coil inaccurate and time-consuming. This paper presents a fast and accurate approach for $I_c$ measurement of NI HTS coils. With an NI HTS coil energized at a constant ramping rate, a complete analytic expression for the spiral coil current was obtained from a first-order partial differential equation that derived from an equivalent circuit model of the NI coil. From the analytic solution, both spiral coil current and radial leak current can be obtained simultaneously, which enables fast and accurate measurement of the NI coil $I_c$. To verify the proposed approach, an NI double-pancake (DP) coil, wound with GdBCO tapes of $6mm{\times}0.1mm$, was constructed and its $I_c$ was repeatedly measured with various ramping rates in a bath of liquid nitrogen at 77 K. The measured results agreed well with the calculated ones, which validates the proposed approach to measure $I_c$ of an NI HTS coil.
Keywords
Critical current measurement; HTS coil; Leak current; No-insulation;
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