多芯Bi2223／Ag带材30K温区的临界电流密度和交流损耗

本文研究了３０Ｋ温区和工频下８１芯Ｂｉ２２２３／Ａｇ带材的临界电流特性和没背场下的交流损耗，临界电流是用ＳＱＵＩＤ磁化法和标准四引法测量；交流损耗理在样品通以正弦电流情况下采用电测法进行测量，结果发现交流损耗随背场的增加而增大，同时与频率的关系是非线性的，并且偏离基于Ｂｅａｎ模型所预言的结果；表明３０Ｋ温区多芯带材Ａｇ基中的涡流损耗的芯间的耦合损耗不可忽略。     

4.5K下的Bi2223／Ag多芯带材的磁化和磁滞损耗

本利用临界态模型Ｊｃ＝βＢ＾－ｐ叙述了长柱矩形或圆形截面Ｂｉ２２２３／Ａｇ１９芯高温超导带材在温度４．５Ｋ和与柱轴平行外场下的磁化行为，临界电流密度和磁滞损耗，并与实验结果进行比较。     

临界电流测量中的影响因素的研究

我们采用直流四引线法对银包套的Ｂｉ２－ｘＰｂｘＳｒ２Ｃａ２Ｃｕ３Ｏｙ,（Ａｇ－Ｂｉ２２２３）带材进行了临界电流的测量研究了外加磁场和电流扫描速度对临界电流的影响结果表明,电流扫描速度和磁场增加使临界电流减小,并且磁场增加使Ｖ－Ｉ曲线对加电流速度的敏感程度发生变化利用电动力学方程和磁通玻璃态蠕动机制对实验结果进行了解释,将磁场、温度、磁通钉扎强度对约化临界电流的影响归结成单一的临界电流参数ｎ的影响,和实验结果符合得比较满意．１引言 临界电流密度Ｊｃ是表征技术应用超导材料性能的主要参量之一,也是表征…     

4.5K下Bi2223/Ag多芯带材的磁化和磁滞损耗

本文利用临界态模型Ｊｃ＝βＢ－ｐ（β，ｐ为与材料特性和温度有关的常数）叙述了长柱矩形或圆形截面Ｂｉ２２２３／Ａｇ１９芯高温超导带材在温度４．５Ｋ和与柱轴平行外场下的磁化行为、临界电流密度和磁滞损耗，并与实验结果进行比较．     

1kA级铋系高温超导模型电缆的研制

我们研制了一根１０００Ａ级铋系高温超导模型电缆。电缆由不锈钢波纹管骨架、导体层、层间绝缘和外绝缘绑扎带组成。电缆的导体层由６层共１７１根Ｂｉ－２２２３／Ａｇ多芯带材绕制而成，电缆外径为４５．２ｍｍ，长度为１ｍ。在液氮下的通电实验表明，电缆的临界电流超过１１８０Ａ（１μＶ／ｃｍ判据），接头总电阻小于０．０６μΩ，均超过设计指标。经两次热循环实验，电缆的临界电流仅退化２．７％，在半小时传输电流１ｋＡ的     

银基Bi系2223相带材临界电流比对循环测试（RRT）的实验结果和分析

在国家超导中心主持下，国内六个实验室成功的开展了银基Ｂｉ系２２２３相带材临界电流循环比对测试实验。有２４个样品在各实验室间进行了并联循环测试，４个样品进行了串联循环测试。在零磁场，液氮温度和１μＶ／ｃｍ判据下，样品临界电流Ｉｃ测量的最大变化系数小于２．５％。液氮温度是影响ＩＣ测但值     

Bi系高温超导带材交流传输损耗的研究和分析

本文研究了Bi-2223高温超导带材的交流传输损耗和频率及运行电流的关系, 调查了热循环过程对交流传输损耗的影响. 实验中, 使用了Lock-in 放大器, 利用四引线法来测量带材交流传输损耗. 实验在温度为77K频率从45Hz到135Hz下进行. 在调查损耗和频率及运行电流的关系时, 发现在运行电流幅值小于临界电流时, 每周传输损耗和频率无关, 说明这时的损耗主要来源于磁滞损耗, 实验结果和Norris椭圆模型的计算结果很接近. 在研究交流传输损耗和热循环的关系时, 发现随着冷热循环次数的增加, 交流损耗也在增加. 这种损耗的增加来源于冷热循环过程中产生的应力, 这种应力的释放减弱了晶粒间的Josephson连接, 使临界电流下降, 从而造成了交流传输损耗的增加.     

高温超导多芯带材中电流受限的机理

Ａｇ包套Ｂｉ－２２２３多芯带材是目前高温超导（ＨＴＳ）强电应用的最佳选择．在美国和日本已有数家公司可以生产长度为１ｋｍ、弯曲性能类似于光纤的这种ＨＴＳ带材,其自场临界电流密度Ｊｃ（７７Ｋ）＝５４ｋＡｃｍ－２（对全体ＢＳＣＣＯ截面平均）．然而,这个值仅...     

低氧压对Bi—2223／Ag复合带组织与性能的影响

本研究了０．１２ｍｍ×４．５ｍｍ的Ｂｉ－２２２３／Ａｇ试样在Ｐｏ２＝０．２１，０．１３，０．０８，０．０４ａｔｍ气氛中于Ｔ＝７８５￣８４０℃中处理５０小时后，带材显微组织与超导性能的变化。实验发现低氧压下带材熔化温区大幅度降低，低氧压与Ａｇ共同作用促进了２２２３相的形成与取向，在低氧压下烧结氧化芯中心的第二相生长受到抑制，改善了带材截面的均匀性，低氧压烧结＋空气中退火，提高了临界电流密度，且改善     

基于改进电测法的Bi-2223/Ag高温超导带的交流损耗研究

研究了B i-2223/Ag高温超导带材的交流传输损耗与频率及运行电流的关系。采用锁相放大器激励,内参考方式,首先对纯阻性相位进行定标的改良电测法,对带材的交流传输损耗进行测量。实验在温度77K,频率45-200Hz的范围内进行。实验结果显示:当运行电流幅值小于临界电流时,传输损耗与电流的关系式(P-In)中,指数n介于2-3之间,说明这时的损耗除来源于磁滞损耗外,涡流损耗的作用也不可忽略。鉴于电测法测得的交流损耗与Norris模型的理论计算值差别较大,分析了这种差别产生的原因,并与另一种B i系高温超导带的交流损耗情况进行了对比;此外还对实验误差的大小进行了理论估测。     

Bi2223/Ag高温超导带的侧向弯曲率对载流能力的影响

Bi2 2 2 3银包套超导带材是研制高温超导磁体和高温超导强电应用的基础。文中就对高温超导磁体最大运行电流有重要影响的 Bi2 2 2 3银包套带材侧向弯曲形变进行了初步探讨 ,就不同的侧向弯曲率对超导带载流能力的影响进行了实验测试 ,并提出了提高 HTS磁体最大运行电流的方法。     

Frequency dependence of AC loss in Bi(2223)Ag-sheathed tapes

The AC self-field loss in Bi(2223)Ag-sheathed tapes with different number of filaments has been measured between 59 and 2500 Hz by means of a dual lock-in amplifier. Due to the wide frequency range of the measurements, we have been able to dissociate quantitatively the different self-field loss contributions: hysteretic, eddy current and resistive loss (near I_c). This is an important advantage compared to single frequency measurements where such loss dissociation is only qualitative. The hysteresis losses of the different tapes fall between Norris' predictions for elliptical and strip cross-section. The relative weight of eddy current loss is found to be inversely proportional to the current ratio—the higher the i, the less is their contribution. Frequency-independent resistive loss due to flux-creep is observed for high currents at low frequencies; this loss becomes quickly negligible with the increasing frequency.     

Temperature dependence of transport ac losses in Bi-2223/Ag multifilamentary tapes

Temperature dependence of transport ac losses in two Bi-2223/Ag multifilamentary tapes with different dc current–voltage characteristics was measured using a lock-in technique at power frequencies. At each temperature, different criteria for critical current determination were used. Comparisons of normalised ac losses with predictions of theoretical models for a tape with elliptical cross-section and a thin strip were made. It was found that the form of the current–voltage characteristic and the critical current criterion play an important role in comparison with theoretical data. A new normalisation procedure of ac loss data is proposed.     

Effect of the sheath resistivity and tape geometry on eddy current loss in Bi(2223) tapes

We have made a software electromagnetic simulation of eddy current effects in Bi(2223)Ag sheathed tapes with applied AC transport current in a broad frequency range. We have used simple models of monocore and multicore tapes. Calculated is the power distribution (W/m³) within the metal sheath using the geometry of real tapes. The numerical simulation is carried out with Finite-element-method software. The paper also describes the influence of the tape cross-sectional architecture and the sheath resistivity on the eddy current loss.     

Bi2223/Ag带小型高温超导实验磁体设计

Bi2223／Ag带材的强各向异性决定了其临界电流对垂直于带材表面的磁场非常敏感，这是该带材在高温超导磁体等强电应用方面的不利因素。我们从减小磁体最大径向场BRmax对磁体运行电流的影响、充分利用超导材料的原则出发，讨论了高温超导磁体的设计方法。在小型Bi2223／Ag实验磁体的设计中，根据对径向磁场的计算、分析，确定了磁体的工作点。     

AC losses in multifilamentary HTS-composite tapes based on BiPbSrCaCuO

Some results of AC loss measurements are presented for 19, 61, 127-filamentary Bi-2223/Ag tapes prepared by the ‘powder-in-tube' method. All measurements have been made at T=77 K under sinusoidal transport current with frequency in the range of 30–600 Hz and the current amplitude up to 30 A. The measurements have been carried out both in self field conditions and at the external magnetic field applied to the tape at the different angles. The dependencies of the AC losses on current amplitude and frequency have been obtained. It is found that for all tapes the current amplitude dependencies of the AC losses show good agreement with the Norris prediction for an elliptical or strip geometry. The AC loss dependencies on frequency were linear. The measurements of AC losses in external magnetic field show that the change of AC losses is only through the change of the critical current. So the transport AC losses in the tapes are the ‘saturation losses' that is they are different from classic hysteresis losses.     

45 kVA单相高温超导变压器交流损耗特性研究

本文研究以多芯不锈钢加强Bi2223/Ag带材绕制的45 kVA单相高温超导变压器的交流损耗特性.变压器绕组置于具有室温孔径的环形玻璃钢杜瓦内,铁芯穿过杜瓦室温孔径以保证铁芯与绕组分离并工作于室温环境.在77 K和工频下,基于Bean模型和绕组中的磁场分布计算了绕组的交流损耗,计算结果与传统电测法和热测法测量的变压器交流损耗结果一致;表明在77K绕组中交流损耗以磁滞损耗为主,涡流损耗和耦合损耗可以忽略不计.     

准绝热环境下Bi-2223/Ag带材在工频过电流冲击下的失超及恢复特性实验研究

本文对工频过电流冲击下准绝热环境中的Bi-2223/Ag不锈钢加强多芯带的失超及恢复特性进行了实验研究.通过实验测量了在液氮温度(77K)、自场下Bi-2223/Ag超导带在幅值为100 A至1 015 A,时间为300 ms的工频电流冲击下,超导带材两端的电压,电流及带材表面温度的变化,得到冲击期间各参量的变化规律.另外,还比较了冲击电流相同、正常载流不同时,带材的温升及失超恢复时间,结果表明正常载流大时,则带材温升较高,失超恢复时间长.正常载流为60A＜0.5Ic时,带材失超恢复时间为冲击时间的21倍.     

Bi—2223带材在拉伸应力下的临界电流

研究了不锈钢加强的Bi-2223/Ag高温超导带材在不同的拉伸应力下临界电流的变化情况。采用改造后的拉伸设备,在温度77K下对超导带材施加拉伸应力的同时,利用四引线法测量带材的临界电流,得到了超导带材的应力—应变曲线以及临界电流—应变曲线。利用理论公式计算了应力对超导带材临界电流的影响,与实验结果进行对比,并对两者的差别进行了分析。     

Reduced filament coupling in Bi(2223)/BaZrO3/Ag composite tapes

Multifilamentary Bi(2223)/Ag tapes often exhibit AC loss levels comparable to those measured in monofilamentary samples, which is partly due to the large coupling currents induced in the low resistive sheath material. Surrounding the individual filaments by electrically insulating barrier layers suppresses these currents and strongly reduces the coupling. We demonstrate this effect with various types of magnetic and self-field AC loss measurements on a series of Bi(2223)/BaZrO₃/Ag tapes. We also discuss the influence of barrier thickness, twist pitch length and filament arrangement on the measured losses in these composite conductors.