Transient multi-physics behavior of an insert high temperature superconducting no-insulation coil in hybrid superconducting magnets with inductive coupling

A transient multi-physics model incorporated with an electromagneto-thermomechanical coupling is developed to capture the multi-field behavior of a single-pancake(SP)insert no-insulation(NI)coil in a hybrid magnet during the charging and discharging processes.The coupled problem is resolved by means of the finite element method(FEM)for the magneto-thermo-elastic behaviors and the Runge-Kutta method for the transient responses of the electrical circuits of the hybrid superconducting magnet system.The results reveal that the transient multi-physics responses of the insert NI coil primarily depend on the charging/discharging procedure of the hybrid magnet.Moreover,a reverse azimuthal current and a compressive hoop stress are induced in the insert NI coil during the charging process,while a forward azimuthal current and a tensile hoop stress are observed during the discharging process.The induced voltages in the insert NI coil can drive the currents flowing across the radial turns where the contact resistance exists.Therefore,it brings forth significant Joule heat,causing a temperature rise and a uniform distribution of this heat in the coil turns.Accordingly,a thermally/mechanically unstable or quenching event may be encountered when a high operating current is flowing in the insert NI coil.It is numerically predicted that a quick charging will induce a compressive hoop stress which may bring a risk of buckling instability in the coil,while a discharging will not.The simulations provide an insight of hybrid superconducting magnets under transient start-up or shutdown phases which are inevitably encountered in practical applications.

Current Sharing Technology in Transmission Conductors of Cold Dielectric High Temperature Superconducting Cables Using Second-generation HTS Wires

冷绝缘高温超导电缆的导电层一般设计为多层结构以满足大电流载流特性，但伴随层数的增加，超导体上的集肤效应会引起电缆输电导体各层电流分布不均匀的问题，从而造成电缆损耗增加和传输性能下降。采用基于动态惯性权重因子的粒子群优化算法，提出了电缆导体层电流层间均流优化的设计方法。应用第2代高温超导材料钇钡铜氧涂层导体，通过建立超导电缆的等效电路模型，考虑电场、磁场等约束因素，对一根1km长，110kV／3kA等级的冷绝缘高温超导电缆进行优化设计，获得了电缆本体结构参数及输电导体层和屏蔽层的电流分布。比较优化前后层电流的结果可知，优化后超导电缆各导体层电流与平均电流相比最大不平衡率小于3．5％，各屏蔽层电流达到均布，较好地实现了电缆各导体层电流均匀分布的优化目标。最后，超导模型样缆载流特性实验也验证了优化设计方法的有效性。

Induced current of high temperature superconducting loops by combination of exciting coil and thermal switch

With its commercialization, the second-generation(2G) high temperature superconducting(HTS) RE–Ba–Cu–O(REBCO, RE is rare earth) tape is extensively applied to the superconducting magnets in the high magnetic fields. However,unlike low temperature superconducting(LTS) magnets, the HTS magnet cannot operate in the persistent current mode(PCM) due to the immature superconducting soldering technique. In this paper, an exciting method for two HTS sub-loops,so-called charging and load loops, is proposed by flux pump consisting of exciting coil and controllable thermal switch.Two HTS sub-loops are made of an REBCO tape with two slits. An exciting coil with iron core is located in one sub-loop and is supplied with a triangular waveform current so that magnetic field is generated in another sub-loop. The influence of magnetic flux on induced current in load loop is presented and verified in experiment at 77 K. The relationship between the induced magnetic flux density and the current on the sub-loops having been calibrated, magnetic flux density, and induced current are obtained. The results show that the HTS sub-loops can be excited by a coil with thermal switch and the induced current increases with magnetic flux of exciting coil increasing, which is promising for persistent current operation mode of HTS magnets.

High Temperature Superconducting Magnetic Energy Storage and Its Power Control Technology

High temperature superconducting （HTS） power inductor and its control technology have been studied and analyzed in the paper. Based on the results of simulations and practical experiments, a controlled release scheme has been proposed and verified for developing a practical HTS SMES prototype.

Numerical simulation of the mechanical behavior of superconducting tape in conductor on round core cable using the cohesive zone model

Cables composed of rare-earth barium copper oxide(REBCO)tapes have been extensively used in various superconducting devices.In recent years,conductor on round core(CORC)cable has drawn the attention of researchers with its outstanding current-carrying capacity and mechanical properties.The REBCO tapes are wound spirally on the surface of CORC cable.Under extreme loadings,the REBCO tapes with layered composite structures are vulnerable,which can lead to degradation of critical current and even quenching of superconducting devices.In this paper,we simulate the deformation of CORC cable under external loads,and analyze the damage inside the tape with the cohesive zone model(CZM).Firstly,the fabrication and cabling of CORC are simulated,and the stresses and strains generated in the tape are extracted as the initial condition of the next step.Then,the tension and bending loads are applied to CORC cable,and the damage distribution inside the tape is presented.In addition,the effects of some parameters on the damage are discussed during the bending simulations.

Announcing a Special Issue of the Journal of Electronic Science and Technology of China on High Temperature Superconductivity

Submission Deadline: 15 February 2008 Journal of Electronic Science and Technology of China (JESTC) invites manuscript

Announcing a Special Issue of the Journal of Electronic Science and Technology of China on High Temperature Superconductivity

Journal of Electronic Science and Technology of China (JESTC) invites manuscript submissions in the area of High Temperature Superconductivity (HTS). This special issue of

Announcing a Special Issue of the Journal of Electronic Science and Technology of China on High Temperature Superconductivity

Submission Deadline: 15 February 2008 Journal of Electronic Science and Technology of China (JESTC) invites manuscript submissions in the area of High Temperature Superconductivity (HTS). This special issue of JESTC will focus on recent experiment, theoretical, and application progress in HTS. It is intended to highlight and summarize the major developments that have occurred over the past few years. Topic scopes related to HTS to be covered include:

高温超导磁浮车水平曲线通过适应性研究

针对高温超导磁浮车刚性悬浮架曲线通过性差,文章提出了一种具有一定点头和摇头自由度的半解耦悬浮架结构,将高温超导的悬浮力和导向力简化为线性特性,建立了高温超导磁悬浮车辆的动力学理论模型,通过UM软件,在周期性激励的作用下,对理论模型进行了动力力学响应的仿真验证,证明了动力学理论模型的合理性。文章进一步利用UM软件分析了高温超导磁浮车的水平曲线通过性能,对比了悬浮架不同垂向扭转刚度、横向扭转刚度、空气弹簧垂向刚度对杜瓦的横向位移、垂向位移的影响。仿真结果表明,释放一定点头自由度和摇头自由度的半解耦悬浮架,能够更好地适应曲线轨道的线路弯曲和线路扭曲,减少了构架对悬浮系统的不利影响,充分发挥了高温超导钉扎效应的特性,提高了车辆的曲线通过性能,同时合理的空气弹簧刚度能够很好地抑制杜瓦的振动,使车辆运行平稳。最后提出了满足车辆安全运行的悬浮架方案,高温超导磁悬浮车辆曲线通过性能有明显的提升。

接头电阻对CORC电缆交流损耗的影响分析

采用第二代高温超导(HTS)带材绕制的CORC电缆具有载流能力高、力学性能好等优点,是制造核聚变磁体的理想电缆之一。然而,当由CORC电缆制造的核聚变磁体闭环运行时,现有的工艺很难保证每根CORC电缆的超导带材的接头电阻完全相同,这会对CORC电缆的交流损耗等电气特性产生重要影响。因此,该文搭建了含接头电阻的CORC电缆的三维有限元模型,分析了接头电阻对CORC电缆交流损耗的影响。结果表明,当CORC电缆传输交流电流时,不均匀的接头电阻将导致CORC电缆三根超导带的电流分布不均匀,进而增加了电缆的总体交流损耗。此外,得到了CORC电缆的交流损耗总是随着接头电阻不均匀程度的增加而增大的分析结果。

基于YBCO高温超导线圈的新型无线供电悬浮系统电能传输特性研究

近年来,以氧化钇钡铜(YBCO)为代表的第二代高温超涂层导体以其在20~77K温区下极高的载流能力以及优越的力学性能和电磁性能,被广泛应用于电力、医疗、交通、军事、能源等领域。该文设计并构造了一种基于YBCO高温超导线圈的小型充电悬浮系统,该系统可以同时实现无线充电和自稳定悬浮功能,可应用于为小型物体无线供电悬浮展示。通过理论推导和有限元仿真分析发现,将低电阻、高载流密度的高温超导线圈引入无线充电系统中,可使系统的输出功率和输出效率都有显著的提高,最大分别提高了3倍和2.6倍,在低频段提升效果尤为明显。此外,实验表明该系统在10 mm悬浮高度范围内可以保持稳定悬浮和负载电压的高效输出,解决了现有电磁悬浮和电动悬浮技术中需要设计特定磁路结构和安装内置电池或电源而导致装置复杂及持续供电时间较短等问题,为超导无线电能传输技术的应用开辟了新方向。

高温超导电缆应用场景与产业发展

高温超导电缆具有容量大、损耗低、自限流、环境友好等突出优点,是解决城市电网升级难题、实现高效率电力传输、赋能大容量电力应用的新兴解决方案,探讨相关产业发展兼具基础研究与工程应用价值。本文剖析了高温超导电缆的技术特点与应用要素,凝练了超级开关站、大电流专线、数据中心供电、基于新能源的电解铝与电解水制氢、集中型充电站、城市轨道交通、大容量直流电网等高温超导电缆的应用场景;从国际、国内两方面总结了高温超导电缆的研制及应用进展,尤其是全面梳理了我国的关键产品研制、关键技术研究、工程项目实施情况。进一步探讨了加强运维技术、攻克大型制冷机技术、降低工程整体造价、与传统电网设施的耦合、形成收益共享机制等高温超导电缆产业未来发展挑战,并针对性地提出了发展建议。相关内容可为高温超导电缆产业高质量发展研究提供参考。

A Permanent Magnet Linear Synchronous Motor Drive for HTS Maglev Transportation Systems

A permanent magnet linear synchronous motor （PMLSM） for a high temperature superconducting （HTS） maglev system has been studied, including the motor structure, control strategy, and analysis techniques. Finite element analysis （FEA） of magnetic field is conducted to accurately calculate major motor parameters. Equivalent electrical circuit is used to predict the drive＇s steady-state characteristics, and a phase variable model is applied to predict the dynamic performance. Preliminary experiment with a prototype has been made to verify the theoretical analysis and the HTS-PM synchronous driving technology.

Structural Parameter Optimization of Multilayer Conductors in HTS Cable

In this paper, the design optimization of the structural parameters of multilayer conductors in high temperature superconducting （HTS） cable is reviewed. Various optimization methods, such as the particle swarm optimization （PSO）, the genetic algorithm （GA）, and a robust optimization method based on design for six sigma （DFSS）, have been applied to realize uniform current distribution among the multilayer HTS conductors. The continuous and discrete variables, such as the winding angle, radius, and winding direction of each layer, are chosen as the design parameters. Under the constraints of the mechanical properties and critical current, PSO is proven to be a more powerful tool than GA for structural parameter optimization, and DFSS can not only achieve a uniform current distribution, but also improve significantly the reliability and robustness of the HTS cable quality.

Compact ultra-narrowband superconducting filter using N-spiral resonator with open-loop secondary coupling structure

A novel N-spiral resonator with open-loop secondary coupling structure(OLSCS) is proposed to realize a compact ultra-narrowband high temperature superconducting(HTS) filter. The coupling strength and polarity between the resonators can be significantly reduced and changed by introducing OLSCS, thus the required weak coupling can be achieved in a very compact size. A six-pole superconducting filter at 1701 MHz with a fractional bandwidth of 0.19% is designed to validate this method. The filter is fabricated on Mg O substrate with a compact size of 15 mm × 10 mm. The measured insertion loss is 0.79 d B, and the return loss is better than 17.4 d B. The experimental results show a good agreement with the simulations.

行波磁场中高温超导电动悬浮磁体的热性能研究

地面线圈的交变磁场会在超导电动悬浮磁体中感应出涡流,产生涡流损耗,导致磁体温度上升。该文研究地面推进线圈产生的行波磁场对车载高温超导磁体热性能的影响,首先介绍高温超导磁体和推进线圈结构,分析行波磁场空间分布特征;搭建高温超导磁体热性能测试平台,测量行波磁场激扰下超导磁体内关键组件的温度分布,揭示各组件温度耦合关系;最后探究行波磁场频率和峰值对磁体温升的影响规律。结果表明,行波磁场激扰下,超导线圈的温升可忽略不计,但辐射屏温升显著,进一步使超导电流引线温度升高,增大电流引线失超风险,为此提出2种方法来限制电流引线温升。该研究成果可为高温超导悬浮磁体低温结构和电流引线的设计提供参考。

跑道型高温超导磁体的磁场解析计算模型

基于均匀电流密度假设和毕奥-萨伐尔定律,该文建立了三种计算跑道型高温超导磁体磁场的解析模型。通过有限元仿真和实验测量验证了解析模型的有效性,对比分析了三种解析模型的计算精度和效率。基于解析模型,探究了椭圆段和电流密度穿透深度对跑道型超导磁体磁场分布的影响,揭示了自洽模型的磁场边界大小对超导磁体临界电流估计值的影响规律。该文建立的磁场解析模型能够准确快速地计算复杂形状超导磁体和常导磁体的磁场,可进一步应用于磁体电感、临界电流、交流损耗和电磁力等参数的计算,以提升磁体电磁设计效率。

500 kV限流器高温超导磁体的制作与测试

超导限流器是对超高压输电线路短路故障电流实现快速、有效限制的一种新型电力装置。近年来随着国民经济的发展,用电负荷增长和供电可靠性需求增加,电网短路电流水平已经逼近甚至超过传统开关设备的开断能力,成为超高压电网发展和安全、稳定运行的重要制约因素之一。然而,电网结构调整等传统限流措施降低了电网的安全性和灵活性,亟需研制适用于超高压电网的限流装置。超导限流器集短路故障检测、触发和限流功能于一身,是电力系统最理想的限流装置。依托高电压等级限流器用超导磁体系统的研制项目,完成500 kV限流器用高温超导磁体系统制作与测试工作。该超导磁体的室温孔径为1660 mm,总高度为1960 mm,液氮量为2000 L,中心最大磁场为0.45 T,额定励磁安匝数为468000安匝,由3组线圈共计88个双饼组成,运行电流分别为220 A(YBCO线圈)/1000 A(Bi2223线圈)/220 A(YBCO线圈),杜瓦注入液氮后抽空减压至72 K稳定运行。经过绕制、接线、组装、焊接、检测等工序,完成磁体系统集成,降温后进行整体测试,一次性励磁成功,没有失超。整个系统绝缘等级大于10 kV、真空漏率优于10^(-6)(Pa·L)/s、液氮蒸发量小于70 L/d,指标均达到设计目标。

热开关和多脉冲励磁的类比特高温超导模型磁体的捕获磁通及电磁特性研究

高温超导磁体因其体积小、高实用性、高场强等优点,在科学研究等领域具有广泛的应用。然而,高温超导带材之间焊接技术的不成熟,很难实现持续电流模式。该文提出一种利用RE-Ba-Cu-O(RE为稀土元素,REBCO)超导片堆叠组成的类比特高温超导模型磁体,该模型磁体不但没有焊接电阻的影响,而且实现持续电流模式。该文说明单片REBCO超导片和由超导片堆叠而成的类比特高温超导模型磁体的结构细节,介绍采用热开关和多脉冲励磁的方法,说明通过COMSOL模拟利用热开关和多脉冲电源对超导片以及类比特高温超导模型磁体进行励磁的过程,证明其能够实现持续电流模式,并对其在持续模式下运行的捕获磁通和电磁特性进行仿真分析以及实验验证。结果表明,热开关和多脉冲励磁的方法可以激励类比特高温超导模型磁体。与传统高温超导磁体相比,由多个超导片堆叠而成的高温超导模型磁体可在无电流引线的情况下实现闭环运行,避免无阻焊接的技术瓶颈。

Development and test in grid of 630 kVA three-phase high temperature superconducting transformer

A 630-kVA 10.5 kV/0.4 kV three-phase high temperature superconducting(HTS)power transformer was successfully developed and tested in a live grid.The windings were wound by hermetic stainless steelreinforced multi-filamentary Bi2223/Ag tapes.The structures of primary windings are solenoid with insulation and cooling path among layers,and those of secondary windings consist of double-pancakes connected in parallel.Toroidal cryostat is made from electrical insulating glass fiber reinforced plastics(GFRP)materials with room temperature bore for commercial amorphous alloy core with five limbs.Windings are laid in the toroidal cryostat so that the amorphous core operates at room temperature.An insulation technology of double-half wrapping up the Bi2223/Ag tape with Kapton film is used by a winding machine developed by the authors.Fundamental characteristics of the transformer are obtained by standard short-circuit and no-load tests,and it is shown that the transformer meets operating requirements in a live grid.