扭绞和宽厚比对Bi-2223超导带交流损耗的影响

Effect of Twisting and Aspect Ratio on AC Losses of Bi-2223 Superconductor Tape

在77K及在外磁场下,对具有不同扭矩的多芯Bi-2223超导带的交流损耗进行测量。该研究中所使用的样品(扭矩6～12mm)具有扭绞芯线和非扭绞芯线。在频率范围为3.33～2430Hz的正弦变化的外磁场下,对交流磁场损耗进行了测量。研究了扭绞对Bi-2223超导带的临界电流和交流损耗影响。研究发现,临界电流随扭矩的减小而减小。另外,可以观察到,在平行场下,由于扭绞带芯线的退耦,造成扭绞带中平行磁场损耗也随之减小。在垂直场下,芯线的扭绞对垂直磁场损耗的减小是不明显的,通过运用小的扭矩和选择小的宽厚比的带材,能够明显减小交流损耗。

AC losses measurements on multifilament Bi2223 tape conductors with different twist pitches are performed at 77 K in magnetic field. The samples used in this study were with twisted （twist pitches 6～12 mm） and untwisted filaments. AC magnetic loss measurements were performed in a sinusoidally varying external magnetic field, at the frequency range of 3.33～2430 Hz. The effect of twisting on critical current and AC losses of Bi-2223 superconductor tapes were researched. It was observed,the critical current of the tapes decreased with decreasing pitch. In addition, it was observed that parallel magnetic field losses of the twist tapes were reduced due to that the effect of decoupled filament of twisted tape in parallel field. As a reduction of perpendicular magnetic field losses due to that filament twist is not apparent, AC losses can be reduced evidently by the application of a small twist length and by the choice of the small aspect ratios tape.