损耗对CICC导体设计影响的模拟研究

聚变装置上低温超导磁体的管内电缆导体(Cable-in-Conduit Conductor,CICC)运行在大电流和快速变化磁场环境中,导体的合理设计是其能否稳定运行的关键。由于工程上CICC导体的设计是一个多次尝试和优化的过程,为此提出了基于稳定性和损耗机理的导体设计思想;推导了关于CICC导体结构参数矩阵方程;建立了导体数值仿真的基本设计模型。同时进行了导体的模拟设计,并将仿真设计结构与工程设计情况进行了比较和分析,结果证明二者吻合的较好。     

HTS交流电缆导体层电流的测试

在完成30m,三相,35kV/2kA高温超导(HTS)交流电缆系统的研制过程中,为了优化电缆导体结构设计,需要测量导体层电流分布.为此,我们探索了一套测量导体层电流分布的方法,该方法基本原理是利用自己绕制的Rogowski 线圈,耦合层电流产生的磁场,来测量每层导体所流过的电流值.为了验证该方法的可行性,我们研制了一套测量装置,利用这套装置对3m,6层HTS交流电缆模型进行了测量,测量结果表明这种测量方法和测量装置是行之有效的.     

基于高温超导带材的三通道导体载流特性的仿真研究

本文基于三通道扭曲堆叠导体和准各向同性导体, 提出了三通道准各向同性导体. 在有限元仿真软件中使用自洽模型对两种导体进行建模, 分析并对比了两种三通道导体的临界电流、 临界电流各向异性、 工程电流密度与导体半径之间的关系. 仿真结果表明三通道准各向同性导体在背景场条件下具有使用价值, 同时也为提高两种三通道导体工程电流密度提出了建议。     

铜导体CFETR氦冷固态包层及屏蔽中子学设计与分析

根据铜导体CFETR设计要求,对铜导体CFETR固态包层和屏蔽进行了中子学设计与分析,提出了套管结构的氦冷固态包层设计方案。包层设计和屏蔽分析结果表明,基于套管的氦冷固态包层的氚增殖比(TBR)达到了1.25, 满足铜导体CFTER氚自持设计要求;环向场线圈绝缘层在堆寿期内不会出现显著的辐射感应电导率(RIC)与辐射引起的电气性能退化(RIED)效应。     

铜导体CFETR氦冷固态包层及屏蔽中子学设计与分析

根据铜导体CFETR设计要求,对铜导体CFETR固态包层和屏蔽进行了中子学设计与分析,提出了套管结构的氦冷固态包层设计方案。包层设计和屏蔽分析结果表明,基于套管的氦冷固态包层的氚增殖比(TBR)达到了1.25,满足铜导体CFTER氚自持设计要求;环向场线圈绝缘层在堆寿期内不会出现显著的辐射感应电导率(RIC)与辐射引起的电气性能退化(RIED)效应。     

基于能量裕度和温度裕度CICC导体数字模拟设计

CICC(Cable-in-Conduit Conductor)超导体是大型低温超导磁体的首选导体,在大电流和快速变化磁场环境中以及给定稳定性裕度、温度裕度、空隙率等条件下,开展CICC超导体结构的优化设计及稳定性分析是非常重要的。因此,文中针对CICC导体设计问题,提出数字模拟设计的想法;推导了关于CICC导体结构矩阵参数的算法;建立了导体数字模拟的模型;同时将数字模拟设计情况与工程设计值进行了比较和分析,结果二者基本吻合。     

高温超导大电流导体临界电流特性研究

YBCO带材在高磁场下仍有好的通流性能,可以用多根高温超导带材构成大电流导体用于高场磁体。为减小导体的交流损耗,大电流导体有多种结构形式,缠绕型和扭转堆叠是其中的两种结构形式。临界电流是高温超导大电流导体的重要指标之一。文中采用四引线法对这两种导体结构在液氮、自场环境下的临界电流特性进行了实验测量,分析并总结了其临界电流特性与结构的关系。     

CFETR TF导体的管内压降分析

目前管内电缆导体(CICC)压降的实验结果都是高空隙率(～35%)下测得的,而CFETR纵向场(Toroidal Field,TF)导体的设计偏向于较小的空隙率(～29%),压降实验数据方面的短缺,使得需要重新考虑目前Katheder关系式能否用于CFETR TF的压降估算。在CFETR TF导体的压降分析中,分别采用了修正的Katheder关系式和多孔介质模型对导体的压降进行比较,获得了更为保守的压降预测。     

具有不同扭距的堆叠扭绞型复合导体临界电流特性分析

根据高温超导堆叠扭绞型复合导体的结构参数,研究堆叠带材根数及扭绞节距对其临界电流特性的影响。首先阐述了堆叠扭绞型复合导体的结构特点,据此设计并制作实验样品。在77K、自场下,对采用不同根数超导带材复合而成的导体样品,分别测试其在多个扭绞节距下的临界电流。通过实验测试可得,随着扭转角度的增大,导体的临界电流不断衰减,且堆叠带材的数量越多,导体的临界节距越大。     

6kA气冷二元电流引线优化

为了开展高温超导导体实验研究,中国科学院等离子体物理研究所正在建设背场达6 T,最大测试电流为30 kA的超导导体测试装置。在进行高温超导导体测试时,要为背场磁体提供约6 kA的电流。为了减少电流引线的漏热,设计了自洽气冷二元电流引线,主要由铜换热器段及高温超导段组成。并以电流引线低温端漏热最小及低温端漏热使得的液氦蒸发量等于冷却电流引线所需的氦气量为依据,采用自编c程序对电流引线的尺寸进行优化。同时从简化结构、增加对流换热系数的角度出发,设计出换热效率高、满足换热需求的铜换热器。     

Influence of the multilayer HTS-cable conductor design on the current distribution

The work presents the basic principles of the multilayer cable conductor design to achieve the maximum current-carrying capacity and the minimum losses in a superconductor and constructive cable elements. The multilayer conductors of two to ten layers are analyzed. The results show that the traditional core design with alternative winding directions from layer to layer is useful only for two-layer conductor. The conductor with more layers must have either the layers wound in one direction but with different pitch lengths or two layer groups wound with different pitch lengths. Only for these cases, the balanced design can be realized and current distribution will be uniform. In such balanced design, the interlayer electrical voltage and as a result, the coupling losses, are absent and interlayer electrical insulation is not needed. The recommendations to achieve the maximum critical current as a function of conductor dimensions are derived.     

Radial electric potential in a metallic wire carrying a steady current

A radial electric potential is established in a metallic wire carrying a steady current. The steady current induces a magnetic field inside the conductor. A resultant Lorentz force drives a moving electron to distribute on the surface of the wire. An electric potential deference between two points along a radial direction in the conductor is proportional to a quadratic of the current.     

CFETR馈线导体设计与热稳定性分析

CFETR馈线导体设计采用NbTi超导线材管内电缆(CICC)结构,其中超导电缆主要由6个花瓣形状的电缆和一个中间铜芯绞制而成,而花瓣形状的电缆由NbTi超导线材与铜线沿顺时针方向通过4级绞制而成,导体外部采用不锈钢铠甲结构。计算分析了运行工况下导体结构的热稳定性参数。结果显示,在95.6kA的最高载流下,分流温度低于6K,热点温度低于250K,满足设计要求。     

The transport current redistribution between the core layers on the models of HTS cables

The multilayer conductors with insulated and non-insulated layers are analyzed. The space–time current redistributions between the layers of the conductor are investigated for the next parameters: values of electric resistance at the current leads, transverse contact electric resistance between the layers, the model length, time, the conductor dimension, the current—its peak value, the change law and the ramp of the total current input. Most of the published test results for short (from 1 to 10 m) conductor models do not reflect the true current distribution of the real long length cable conductors. The criterion of experimental model constructions and, in particular, the calculation of its minimum length are presented. The calculations demonstrate the electromagnetic processes in real cable conductors.     

Computation of AC losses in high-temperature superconductors

A formulation for the computation of AC losses in technical HTS conductors by using commercial FEM packages developed for two-dimensional computation of electromagnetic problems is presented. The formulation takes into account the real current density–electric field characteristic of a conductor and the spatial dependence of the current density. Having presented the formulation, example runs comparing transport current loss behaviour between HTS and LTS conductors are given.     

CICC型超导体运行电流的设计

使用超导电性恢复温度模型分析了 CICC型超导体的稳定性与界限电流的关系 ,推导出表明导体运行电流位于下界限电流区域的门限临界电流的表达式 ,给出了 HT- 7U极向场 PF线圈导体的一种设计方案的计算结果。     

Numerical calculation of current density distributions in high temperature superconducting tapes with finite thickness in self field and external field

The current density distribution of high temperature superconducting (HTS) tapes is modeled for the combined case of an alternating self and applied magnetic field. This numerical analysis is based on the two-dimensional Poisson equation for the vector potential. A one-dimensional current (z-direction) and a one-dimensional applied field (y-direction) are assumed. The vector potential is rewritten into an equation of motion for the current density J(x,y,t). The model covers the finite thickness of the conductor and an n-power E–J relation. The magnetic field dependence of J_c is also included in this E–J relation. A time-dependent two-dimensional current distribution that is influenced by the aspect ratio of the conductor and the material properties in E=f(J,B) is calculated numerically. The numerical results are compared with the experimental results for the AC loss of a tape driven by a transport current. Finally, a total AC loss factor is given for two cases in magnetic field direction, perpendicular and parallel to the conductor broad side.     

便携式光纤电流互感器传感头设计

针对电解铝工业中大电流测量现场环境复杂的难题,在传统光纤电流互感器的基础上提出一种便携式光纤电流互感器.对设计安装过程中由于柔性传感头光路不闭合和导体偏心引起的法拉第相移误差进行分析和有限元仿真计算,结果表明:法拉第相移相对误差随传感头不闭合度角度线性增加,随导体到非闭合点的距离增大而减小,且增加传感头匝数能减小法拉第相移误差.由于便携式光纤电流互感器准确度随导体到非闭合点的距离增大而提高,设计了一种使传感头非闭合点向一端延伸且易拆装的结构,实验测试得到该便携式光纤电流互感器的全温准确度为0.86%,满足电解铝厂准确度1%的使用要求.     

Reprint of : Correlated voltage probe model of relaxation in two Coulomb-coupled edge channels

A phenomenological correlated voltage probe model is introduced to mimic the effects of inelastic scattering between particles in different conduction channels of a phase coherent conductor. As an illustration, the non-equilibrium distribution functions of two noisy co-propagating chiral edge channels of the integer quantum Hall effect are calculated and compared with recent experiments. The method is further applied to calculate the linear response current noise through an interacting Mach–Zehnder interferometer.     

Indirect measurement of AC current distributions in HTS tapes by a pickup coil method

It is necessary to develop HTS conductors with a large current capacity and low AC loss characteristics for practical use of HTS power devices. For large capacity power applications, HTS tapes such as Bi-2223 tapes and YBCO coated conductors are assembled. So, it is important to evaluate the characteristics of current distributions in such assembled HTS tapes. However, an adequate measurement method has not been established. In this study, we have tried the development of an indirect measurement method to evaluate the current distributions in stacked HTS tapes. In this method, the current distributions are indirectly found from the results of the field distributions measured by a pickup coil located around the surface of the sample tapes. To confirm the accuracy and the sensitivity of this method, current distributions in a test conductor made of copper tapes are measured. Numerical and measured current distributions are compared. Using this method, the current distributions in stacked Bi-2223 tapes are measured at room temperature and 77 K. On the basis of the obtained results, the characteristics of the AC current distributions in the HTS tapes are discussed.