Numerical Analysis of Dynamic Resistance and Total Loss in REBCO-Coated Conductors at Low Temperature Under High Perpendicular AC Magnetic Fields

Abstract

In several applications of high-temperature superconductors (HTS), a REBCO-coated conductor (CC) carries a DC current under varying magnetic fields. This generates AC loss which can be an important factor to consider in the thermal design of the application. In this work, the dynamic resistance (Rdyn), and total loss in a 4 mm wide Superpower REBCO CC are numerically investigated for AC perpendicular magnetic fields ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> m) up to 1 T and temperatures ranging from 30 K to 50 K. For <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dc</sub> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c0</sub> > 0.1 (where Idc is the DC current level and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c0</sub> is the self-field critical current of the conductor), either of the previously developed equations, the non-linear or the simple linear expression for determining B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> (threshold magnetic field), can be used to predict R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dyn</sub> . Finite dynamic loss is observed even below the B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> points due to the emergence of resistance. The resistance arises from the superposition of subcritical shielding and transport currents which introduces a finite electric field in the CC. The total loss at higher fields decreases as the temperature increases from 30 K to 50 K for all current values, except for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dc</sub> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c0</sub> = 0.9. A lift-off in the total loss is evident for fields around 1 T for all temperatures investigated.