A wide range E − J constitutive law for simulating REBCO tapes above their critical current

Abstract

When modeling superconducting devices based on rare earth barium copper oxide (REBCO) tapes and operating near or above the critical current value I c , the power-law is not always accurate. In our previous works, we proposed the overcritical current constitutive law, based on a combination of fast pulsed current measurements and finite element analysis. The overcritical current constitutive law was provided in the form of look-up tables and was validated experimentally. We showed that the overcritical current constitutive law could better reproduce experimental measurements than the power-law, and that the power-law predicts a faster quench than the overcritical current constitutive law. In this contribution we use a mathematical expression based on the collective pinning model to analytically describe the overcritical current regime of REBCO tapes based on measurements performed between 77 and 90 K in self-field conditions. The wide-range constitutive law is verified by comparing DC fault measurements with the results of numerical simulations using the overcritical current constitutive law to represent the electrical resistivity of the superconducting layer of REBCO tapes.

Numerical investigation of current distributions around defects in high temperature superconducting CORC® cables

“…Equation ( 3) is assumed to capture the bulk behavior of the tape cross section, however some studies have explicitly modeled the copper stabilizer in parallel with the superconducting layer [21]. This assumption limits our model to cases where the tapes are not driven well above the critical current [25]. All simulated defects consist of a local reduction in I C across two superconducting elements (1.14 mm).…”

Understanding the current–voltage characteristic in high-temperature superconducting wires and bulks is of continuing interest to the modelling community

“…Therefore, understanding the wide range E-J characteristic extended to the overcritical current region is of particular interest for HTS modellers even though the original E-J power law, the critical state model or its approximations, for example the Campbell model or other models based on artificial E-J constitutive laws, often give reasonable AC losses or other magnetization results [13][14][15][16][17]. Recently, Riva et al characterized the ReBCO CCs in the overcritical current regime by combining fast pulsed current measurements and finite element analysis (FEA) and introduced an eta-beta ρ ηβ (I, T) constitutive law at 77-90 K in self-field conditions [18,19]. More extensive measurements under background magnetic fields and in a wider temperature range were scheduled.…”