AC Loss Properties of Stacked REBCO Superconducting Tapes

Abstract

REBCO superconducting tapes have excellent critical current properties even at high temperature and high magnetic field. Many projects for the research and development of superconducting machines and devices with REBCO tapes are in progress worldwide. The important problem to realize them is the ac loss reduction of REBCO superconducting tapes since the most part of thermal load of cryocoolers is the ac loss. The evaluation of the induced ac loss in the windings is also quite important to design the superconducting system, especially the cooling system. In this study, we investigated the applicability of the scaling law to the stacked tapes using the currently fabricated REBCO superconducting tapes. We defined the number of stacked tapes as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> , and the temperature as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T </i> . The ac loss for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\rm{B}}_{{\rm{m}}}\,{\rm{&lt; \,B}}_{{\rm{pe}}}$</tex-math></inline-formula> decreased with increasing <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> due to the influence of diamagnetic field, whereas the ac losses for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX"> ${\rm{B}}_{{\rm{m}}}\,{\rm{&gt; B}}_{{\rm{pe}}}$</tex-math></inline-formula> agreed with each other regardless of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$n$</tex-math></inline-formula> . By defining <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_c</i> around zero field at the respective temperature, in the respective number of stacked tapes as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\rm{Ic0(T,\,n)}}$</tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX"> ${\rm{I}}_{{\rm{c}}}$</tex-math></inline-formula> -B normalized by using <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX"> ${\rm{Ic0(T,\,n)}}$</tex-math></inline-formula> . The normalized <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX"> ${\rm{I}}_{{\rm{c}}}\hbox{-}{\rm{B}}$</tex-math></inline-formula> curves coincided with one master curve for every <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$n$</tex-math></inline-formula> regardless of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T$</tex-math></inline-formula> . The normalized M-H curves and ac loss curves against the field amplitude by using <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\rm{Ic0(T,\,n)}}$</tex-math></inline-formula> also coincided with one master curves for every <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> regardless of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> . It was verified that the scaling law of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> and ac loss was available even if the REBCO tapes stacked into multilayers.