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1.
高温超导(HTS)带材的基带可以改变带材的磁场分布,从而影响到带材的交流损耗。从实验和数值分析两个角度计算了不同高温超导带材的自场损耗,并分析了不同基带对带材自场损耗的影响。利用不同高温超导带材制作了多个单层高温超导电缆模型,并从磁性基带的角度分析了各模型的交流损耗特性。结果显示非磁性基带不影响带材的交流损耗。对于超导电缆模型而言,当磁性基带位于模型外侧时,模型外部空间不存在损耗磁通。此外BSCCO模型和YBCO模型的交流损耗特性相似,NY模型和YN模型的损耗相比前两个模型偏大。尤其在低电流区域,YN模型的交流损耗最大。  相似文献   

2.
对高温超导带材YBCO的交流损耗进行了仿真分析。运用有限元FEM方法,基于Maxwell方程组的数值建模,引入了基于实验数据的power-law对交流损耗进行计算。首先对自场下的交流损耗值进行了仿真计算并分析了带材的电流密度与磁场分布情况,并通过与实验测量数据做比较验证仿真方法的有效性。其次分别对不同幅值下的平行场与垂直场下的交流损耗进行了计算,将自场、平行场以及垂直场下的电流密度与磁场强度的分布以及交流损耗值进行了对比分析。  相似文献   

3.
随着高温超导YBCO带材载流能力的不断提高和成本的逐渐降低,YBCO线圈及磁体的应用将日益广泛。文中利用有限元方法研究了YBCO线圈的交流损耗特性,计算了50Hz下线圈的瞬时交流损耗,分析了每匝带材中的电流和磁场分布。仿真结果表明,线圈内侧承受的磁场最大,但线圈中部每周期的交流损耗最大,且线圈中始终存在未被磁场穿透的区域。除此之外,文中实验测量了YBCO线圈的临界电流和交流损耗,实验结果良好地验证了仿真方法的正确性。  相似文献   

4.
超导电缆具有载流能力强、损耗低等优势,是电力输送的良好选择。但是,超导电缆需工作于低温环境。液氢温度为20K,可为超导电缆提供低温条件,将超导电缆输电与液氢燃料输送相结合,可解决超导电缆在输电中的瓶颈问题。开展了液氢替代液氮后高温超导带材的传输交流损耗研究。针对美国超导公司提供的黄铜加强YBCO带材,采用H法有限元模型,仿真分析了液氢、液氮冷却时超导带材的传输交流损耗。结果表明采用液氢作为超导带材的冷却介质时,带材正常金属产生的涡流损耗和磁性基底产生的铁磁损耗对总损耗的影响程度较小。所得结果可为液氢温区超导电缆的设计和运行提供参考。  相似文献   

5.
《低温与超导》2021,49(5):25-29
高温超导复合缆线的运行温度直接决定其载流性能,超导带材交流损耗计算的准确性对缆线的温升计算至关重要。面向具有铜骨架和双层高温超导带材结构的高温超导复合缆线,通过改进利兹线(Litz-wire)涡流损耗计算模型,将导电层作为利兹线结构中由多股线按一定节距扭转的束级结构的并联,分别计算了49.9 Hz和60 Hz下复合缆线的集肤效应损耗和邻近效应损耗。通过分析高温超导带材的平行磁场分量和垂直磁场分量,计算了复合缆线的磁滞损耗。最后,基于超导样缆交流损耗补偿测量系统,对0.2 m、110 kV/1.5 kA铜骨架高温超导复合缆线的交流损耗进行了测量,得到工频下1 200 A载流时的交流损耗为1.21 W。研究发现,在不同频率下,铜骨架高温超导复合缆线的交流损耗随传输电流的增大而增大。通过对比仿真和实验结果,验证了铜骨架高温超导复合缆线交流损耗计算结果的准确性。  相似文献   

6.
随着高温超导技术的发展,超导材料的损耗成为制约其大规模应用的一个重要因素。目前已开展了许多关于Bi-2223带材交流损耗的研究。在应用过程中,外场下的交流损耗是影响超导电力设备运行的极为重要的部分。利用交流磁化率测量装置,测量出Bi-2223带材在平行场和垂直场下的交流磁化率,然后通过计算得到Bi-2223带材在平行场和垂直场下的交流损耗。分析了在平行和垂直外场下,Bi-2223带的耦合损耗时间常数与宽厚比的关系,以及不同宽厚比带材的交流损耗和频率之间的关系。研究发现平行场下,耦合损耗时间常数随宽厚比的增加而增加。而在垂直场下耦合损耗时间常数随宽厚比的增加而减小。  相似文献   

7.
钇系超导带材(YBCO)由于载流能力强、不可逆场高,是近年来高温超导材料领域的研究热点,并在电力行业实现示范应用。YBCO超导带材由基底、缓冲层、超导层和保护层组成,可通过电镀铜工艺实现保护层的制备。目前,有关电镀铜对YBCO超导带材临界电流的影响还鲜有报道。因此,本研究对比了镀铜前后YBCO超导带材的表面形貌和临界电流。实验结果表明:电镀铜在提高带材机械强度的同时,对其超导电性并无明显影响。  相似文献   

8.
介绍了交流损耗测量理论,搭建了高温超导带材的电测法测量平台,并分别测量不同频率下AMSC和Super Power两家公司生产的YBCO带材的交流损耗。将测试结果进行了归一化处理,并与计算结果和Norris模型进行比较,从两种带材材料层面分析了测量结果与计算结果存在微小差别的原因。实验结果表明测量结果与计算结果基本一致,并且和Norris模型吻合较好,说明该测量系统可以很好地测量不同频率下YBCO带材的交流损耗。  相似文献   

9.
高温超导带材在磁场中传输交变电流时,将受到电磁力的作用而产生机械振动,振动对带材的交流损耗将产生影响.本文讨论了振动情况下交流损耗的测量方法,在平行于带面的直流磁场下,测量了Bi-2223/Ag高温超导带材在不同振动情况下的交流损耗.结果显示:当传输电流频率偏离样品的共振频率时,振动对带材的交流损耗影响不大;只有当电流频率在共振频率附近时,样品产生剧烈振动,交流损耗才有明显的增加;另外,带材振动时的交流损耗随频率变化曲线的斜率比不振动时略有增加.  相似文献   

10.
高温超导磁体临界电流磁矢量分析法准确地预测了BSCCO高温超导磁体的临界电流,为了进一步验证该方法预测YBCO高温超导磁体临界电流的准确性,文中作者用9.3m二代高温超导YBCO带材绕制了一个内径为70mm,外径为100mm,共35匝的单饼,测试了单饼5-15匝,15-25匝,25-35匝和5-35匝在77K下的临界电流,并用磁矢量分析法进行了仿真分析。通过对比发现,仿真分析和实验结果的误差在5%左右,最大误差是6.75%,最小误差是4.77%,验证了磁矢量分析法在预测YBCO高温超导磁体临界电流时的准确性。  相似文献   

11.
An attempt is made to introduce the concept of magnetic moment and magnetic induction directly from observed mechanical interactions between magnets, without bringing in the idealized notion of isolated magnetic poles.  相似文献   

12.
In situ magnetic hysteresis measurements of magnetic tips in a magnetic force microscope (MFM) are demonstrated using alternating gradient force magnetometry. The measured magnetic moments of MFM tips are estimated in the range from 10−6 to 10−5 emu by this technique and the whole MFM tips in cantilevers are considered to be measured from the value of measured magnetic moments. The relationship between the magnetic hysteresis loops of MFM tips and those of coated magnetic films is discussed.  相似文献   

13.
磁性材料的磁结构、磁畴结构和拓扑磁结构   总被引:2,自引:0,他引:2       下载免费PDF全文
张志东 《物理学报》2015,64(6):67503-067503
首先简要地介绍了磁性材料中磁结构、磁畴结构和拓扑磁结构以及相互之间的关系. 一方面, 磁畴结构由材料的磁结构、内禀磁性和微结构因素决定; 另一方面, 磁畴结构决定了材料磁化和退磁化过程以及技术磁性. 拓扑学与材料物理、材料性能的联系越来越紧密. 最近的研究兴趣集中在一些拓扑磁性组态, 如涡旋、磁泡、麦纫、斯格米子等. 研究发现这些拓扑磁结构的拓扑性质与磁性能密切相关. 然后从尺寸效应、缺陷、晶界三个方面介绍国际学术界在磁结构、磁畴结构和拓扑磁结构方面的进展. 最后介绍了在稀土永磁薄膜材料的微观结构、磁畴结构和磁性能关系、交换耦合纳米盘中的拓扑磁结构及其动力学行为方面的工作. 通过对文献的评述, 得到以下结论: 开展各向异性纳米复合稀土永磁材料的研究对更好地利用稀土资源具有重要的意义. 可以有目的地改变材料的微结构, 可控地进行磁性材料的磁畴工程, 最终获得优秀的磁性能. 拓扑学的概念正在应用于越来越多的学科领域, 在越来越多的材料中发现拓扑学的贡献. 研究磁畴结构、拓扑磁性基态或者激发态的形成规律以及动力学行为对理解量子拓扑相变以及其他与拓扑相关的物理效应是十分重要的. 也会帮助理解不同拓扑学态之间相互作用的物理机制及其与磁性能之间的关系, 同时拓展拓扑学在新型磁性材料中的应用.  相似文献   

14.
The intrinsic radial magnetic field(B r) in a tokamak is explored by the solution of the Grad–Shafranov equation in axisymmetric configurations through an expansion of the four terms of the magnetic surfaces. It can be inferred from the simulation results that at the core of the device, the tokamak should possess a three-dimensional magnetic field configuration, which could be reduced to a two-dimensional one when the radial position is greater than 0.6a. The radial magnetic field and the amzimuthal magnetic field have the same order of magnitude at the core of the device. These results can offer a reference for the analysis of the plasma instability, the property of the core plasma, and the magnetic field measurement.  相似文献   

15.
The response of the spin system has been investigated by numerical simulations in the case of a nuclear magnetic resonance (NMR) experiment performed in inhomogeneous static and radiofrequency fields. The particular case of the NMR-MOUSE was considered. The static field and the component of the radiofrequency field perpendicular to the static field were evaluated as well as the spatial distribution of the maximum NMR signal detected by the surface coil. The NMR response to various pulse sequences was evaluated numerically for the case of an ensemble of isolated spins (1/2). The behavior of the echo train in Carr-Purcell-like pulse sequences used for measurements of transverse relaxation and self-diffusion was simulated and compared with the experiment. The echo train is shown to behave qualitatively differently depending on the particular phase schemes used in these pulse sequences. Different echo trains are obtained, because of the different superposition of Hahn and stimulated echoes forming mixed echoes as a result of the spatial distribution of pulse flip angles. The superposition of Hahn and stimulated echoes originating from different spatial regions leads to distortions of the mixed echoes in intensity, shape, and phase. The volume selection produced by Carr-Purcell-like pulse sequences is also investigated for the NMR-MOUSE. The developed numerical simulation procedure is useful for understanding a variety of experiments performed with the NMR-MOUSE and for improving its performance. Copyright 2000 Academic Press.  相似文献   

16.
17.
朱晔明  王思慧  周进 《大学物理》2006,25(4):58-59,63
对地磁水平分量测量实验加以改进,将其扩充为能够测量亥姆霍兹线圈磁场分布和磁针的转动惯量以及磁针磁矩的实验.使其成为一个综合性较强,适用于开展研究性实验的项目.  相似文献   

18.
Magnetic dipole(MD) transitions are important for a range of technologies from quantum light sources and displays to lasers and bio-probes. However, the typical MD transitions are much weaker than their electric counterparts and are usually neglected in practical applications. Herein, we experimentally demonstrate that the MD transitions can be significantly enhanced by the well-developed magnetic metamaterials in the visible optical range. The magnetic metamaterials consist of silver nanostrips and a thick silver film, which are separated with an Eu~(3+):polymethyl methacrylate(PMMA) film. By controlling the thickness of the Eu~(3+):PMMA film, the magnetic resonance has been tuned to match the emission wavelength of MDs. Consequently,the intensity of MD emission has been significantly increased by around 30 times at the magnetic resonance wavelength, whereas the intensity of electric dipole emission is well-preserved. The corresponding numerical calculations reveal that the enhancement is directly generated by the magnetic resonance, which strongly increases the magnetic local density of states around the MD emitter and can efficiently radiate the MD emission into the far field. This is the first demonstration, to the best of our knowledge, that MD transitions can be improved by an additional degree of magnetic freedom, and we believe this research shall pave a new route towards bright magnetic emitters and their potential applications.  相似文献   

19.
We investigate theoretically the magnetization dynamics of a conducting magnetic nanoparticle weakly coupled to source and drain electrodes, under the assumption that all relaxation comes from exchange of electrons with the electrodes. In the regime of sequential tunneling, the magnetization dynamics is characterized by a relaxation time t(1), which strongly depends on temperature, bias voltage, and gate voltage. While a direct measure of a nanoparticle magnetization might be difficult, we find that t(1) can be determined through a time resolved transport measurement. For a suitable choice of gate voltage and bias voltage, the magnetization performs a bias-driven Brownian motion regardless of the presence of anisotropy.  相似文献   

20.
The concentration dependence of the specific magnetic moment value at room temperature in dilute semiconductor titanium oxides doped with either Co or Fe has been investigated. This value was found to increase sharply at small concentrations of magnetic impurity. The magnetic moment of 22.9 μB per impurity atom has been revealed for TiO2 doped with 0.15 at% Co, not yet reported in any semiconductor oxide systems. We conclude the observed giant magnetic moments are caused by the crystal lattice polarization at small impurity concentrations. The comparison with published data point to different types of the magnetization concentration dependence for various semiconductor matrixes that is probably related to the dielectric permittivity of the environment.  相似文献   

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