Levitation-Force Investigation of High-Temperature Superconducting Maglev System Under Different Variations of the Vertical Displacement

In the practical application of high-temperature superconducting (HTS) maglev vehicle, the vehicle body ascends and descends in the vertical direction frequently with the passengers on and off boarding, such vertical movement may change the levitation performance but this influence have not been researched. In this article, the influence of the vertical movement on the levitation force in two different types of permanent magnet guideway (PMG) and different movement displacements was experimentally analyzed. We found that the levitation force drastically decays first, and then decays slightly, which is similar to the relaxation phenomena. Meanwhile, the experimental results indicate that the levitation force decay trends to enlargement with the decrease of the working height (WH) and with the increase of the vertical displacements. These phenomena can be ascribed to the magnetic hysteresis loss in the bulk high-temperature superconductor (HTSC).     

Vibration Reduction Using Eddy Current Damper in High-Temperature Superconducting Maglev System

Journal of Superconductivity and Novel Magnetism - The high-temperature superconducting (HTS) maglev system has great potential to become a new type of rail transit due to its unique...     

Measurement Method to Evaluate the Practical Levitation Force of Onboard Bulk Superconductor in the High-Temperature Superconducting Maglev Vehicle System

As the basic parameter in the design of high-temperature superconducting (HTS) magnet levitation (maglev) vehicle system, the levitation force data are usually obtained by experiments, so a reliable measurement method is needed to know the practical levitation force of onboard bulk superconductor. Considering in the actual operation the vehicle will experience some small vertical or lateral movements, especially during the passenger going on or off the vehicle, the usual measurement method for levitation force, in which force with gap and force relaxation are measured, cannot be able to predict the levitation force change due to the vertical or lateral movements. So a measurement method is presented regarding effects of force with gap, relaxation, vertical and lateral movements. Compared with a former measurement method, the presented method may support more reliable levitation force data for the HTS maglev vehicle design.     

磁浮轨检车横向振动及其对磁浮轨道几何参数测量精度的影响

磁浮轨检车是用来检测磁浮轨道几何参数,保证磁浮列车安全运行的轮式特种车辆。建立了磁浮轨检车横向振动二自由度模型,研究了在磁浮轨道随机路面激励下横向振动幅值的大小及其对激光三角法测量磁浮轨道几何参数精度的影响,结果表明该影响在所要求的测量精度范围之内。     

Characterization Method of the V-shaped High-Temperature Superconducting Maglev Module for Transport System Applications

Journal of Superconductivity and Novel Magnetism - It is now recognized that high-temperature superconducting (HTS) technology has a significant potential for future magnetic levitation (Maglev)...     

Numerical Study of the Speed-Related Behavior of the Magnetic Force in the HTS Maglev System Based on a 3-D Model

Based on the 3-D model, we recently proposed to investigate numerically the performance of the HTS maglev system. The speed-related behavior of this kind of maglev system is further studied in this article. The 3-D model is firstly briefly introduced: the 3-D governing equations are established with current vector potential (T) as the state variable, and the special anisotropic behavior and the nonlinear E?CJ characteristic of the HTS were taken into account by an elliptical model and power-law model, respectively. Using a translational symmetry levitation system, which is composed of a rectangular HTS and a permanent magnet guideway (PMG) as an example, the speed-related behavior of the magnetic force in three different cases??i.e., the levitation force (LF) versus gap relation under the vertical movement, the time evolution of the LF, the guidance force (GF) versus lateral displacement relation under the transverse movement??are investigated. The result indicates that, with the increase of the speed, both the LF and GF increase but the rate of increase is reduced and finally saturates when the speed is large enough. We also find that the commonly used speed of 1 mm/s to investigate the magnetic force of the bulk HTS in the experiment is reasonable because both the LF and GF tend to saturate at this speed. For the time evolution study of the LF, although the peak value of the LF is largest when the speed is largest, the LF decay in the relaxed process is most serious, and consequently the final LF at different speeds is almost identical after relaxation. Therefore, the magnetic force cannot be enhanced by simply increasing the speed in the practical application.     

Calculation of Levitation Force between Small Superconducting Cylinder and Magnetic Ring in the Critical State

Levitation force between a small superconducting cylinder in the mixed state and a magnetic ring was calculated using the critical state model. The dependence of the levitation force on the size of the superconductor as well as the magnet was investigated. The finite size effect of the superconductor is included by demagnetizing factor approximation. The stiffness for the levitating system was calculated. The position of the maximum levitation force depends on the size of the superconductor and the magnet. Trend of the calculated force is in agreement with the experimental results.      

On the Scaling Law of the Pinning Force in MgB2 Superconducting Composites with Magnetic Nanoinclusions

Dense superconducting composites with magnetic nanoparticles were prepared by spark plasma sintering. In addition to structure and magnetic properties, we focused on the pinning properties as described by the field and temperature dependence of the scaled pinning force analyzed. We found that the pinning force does not obey any scaling law and attributed this effect to the anisotropy of the MgB₂ and the almost random distribution of the orientation of the superconducting grains within the polycrystalline sample.     

Magnetic Interaction Force and a Couple on a Superconducting Sphere in an Arbitrary Dipole Field

The calculation of the magnetostatic potential and levitation force due to a point magnetic dipole placed in front of a superconducting sphere in the Meissner state is readdressed. Closed-form analytical expression for the scalar potential function that yields the image system for an arbitrarily oriented magnetic dipole located in the vicinity of a superconducting sphere is given. Analytic expression for the lifting or levitation force acting on the sphere is extracted from the solution for a general dipole. A special case of our expression where the initial magnetic dipole makes an angle with the z-axis is derived. Our expression for the force in this particular case shows that a recently obtained result (J. Supercond. Nov. Magn. 21:93–96, 2008) for an arbitrary dipole is incorrect. A brief discussion of another erroneous result (J. Supercond. Nov. Magn. 15:257–262, 2002) for a transverse/tangential dipole–sphere configuration, corrected elsewhere recently, is reproduced. Correct expressions for the interaction energy with some limiting cases are also provided. The result derived here demonstrates that the value of the levitation force for a dipole that makes an angle with z-axis lies between the values for a radial dipole–sphere and transverse dipole–sphere configurations providing upper and lower bounds. It is found that for a magnetic dipole making an angle with z-axis, there exits a second force component along the negative y-direction, which influences a couple acting on the superconducting sphere. It is also shown that the couple is proportional to the second force component and that both the couple and second force components vanish for a radial dipole–sphere and transverse dipole–sphere configurations, respectively. These results appear to be new and have not had received due attention in the context of superconductivity.     

Influence of Work Height on Guidance Force Decay of HTS Bulk Exposed to AC Magnetic Field Perturbation in a Maglev Vehicle System

Bulk superconductors have great potential for various engineering applications, especially in superconducting maglev vehicle systems using high-temperature superconducting bulks. In such a system, the HTS bulks were always exposed to AC external magnetic field, which was generated by the inhomogeneous surface magnetic field of the NdFeB guideway. In our previous work, it was observed that the guidance force of the YBCO bulk over the NdFdB guideway used in the high-temperature superconducting maglev vehicle system was decayed by the application of the AC external magnetic field. In this paper, we investigate the influence of the work height on the guidance force decay of HTS bulk exposed to an AC field perturbation in the maglev vehicle system and try to adopt a method to suppress the decay. From the experimental results, it was found that the decay rate of the guidance force was smaller at higher work height in the case of the same field-cooled height. So we could suppress the guidance force decay of HTS bulk exposed to AC external magnetic field perturbation in the maglev vehicle system by increasing the work height of the bulk.     

Influence of Thermal Conductivity on Guidance Force Decay of HTS Bulk Exposed to AC Magnetic Field Perturbation in a Maglev Vehicle System

Bulk superconductors have great potential for various engineering applications, especially in a high-temperature superconducting (HTS) maglev vehicle system. In the vehicle system, the stable levitation can be achieved without any complex control system owed to the pinning effect of the bulks. However, the HTS bulks in the vehicle system were always exposed to the time-varying external magnetic field, which was generated by the inhomogeneous surface magnetic field of the NdFeB guideway. In our previous work, we studied the guidance force decay characteristics of the YBCO bulk over the NdFdB guideway used in the HTS maglev vehicle system by an experiment in which the AC external magnetic field generated by an electromagnet was used to simulate the time-varying external magnetic field caused by the inhomogeneity of the guideway, and calculated the guidance force decay as a function of time based on an analytic model. In this paper, we investigated the influence of thermal conductivity on the guidance force decay of HTS bulk exposed to AC field perturbation in the maglev vehicle system and tried to adopt a method to suppress the decay. From the results, it was found that the guidance force decay rate was higher for the bulk with the lower thermal conductivity. So, we could reduce the guidance force decay of the HTS bulk exposed to the AC external magnetic field perturbation in the maglev vehicle system by improving the thermal conductance of the bulks.     

Influence of Critical Current Density on Guidance Force Decay of HTS Bulk Exposed to AC Magnetic Field Perturbation in a Maglev Vehicle System

Superconducting maglev vehicle is one of the most promising applications of HTS bulks. In such a system, the HTS bulks are always exposed to AC external magnetic field, which is generated by the inhomogeneous surface magnetic field of the NdFeB guideway. In our previous work, we studied the guidance force decay of the YBCO bulk over the NdFdB guideway used in the High-temperature superconducting maglev vehicle system with the application of the AC external magnetic field, and calculated the guidance force decay as a function of time based on an analytic model. In this paper, we investigated the influence of the critical current density on the guidance force decay of HTS bulk exposed to AC field perturbation in the maglev vehicle system and try to adopt a method to suppress the decay. From the results, it was found that the guidance force decay rate was higher for the bulk with lower critical current density. Therefore, we could suppress the guidance force decay of HTS bulk exposed to AC external magnetic field perturbation in the maglev vehicle system by improving critical current density of the bulk.     

Characteristic of the Guidance Force in the High-T c Superconducting Levitation System with Pre-Load Process

The stable levitation above permanent magnet is an important characteristic of the bulk high-T _c superconductor (HTS). When an external force pushes the bulk HTS up, down or sideways, or tries to tilt it, a restoring force can return it to its initial position. The HTS Maglev relied on this characteristic can overcome the external force from wind or pass the curve lines successfully. The change of guidance force (GF) during many times lateral movement is studied. Experiments show that GF increases during the lateral movement, no matter what kind of PMG or HTS is used, and the change of the GF slows down after 5 times lateral movement. The pre-load method can reduce the levitation force decay during lateral movement. So the influence of GF by the pre-load method is needed to be studied. It is found that the pre-load method can increase GF and reduce the change of the GF during lateral movement. The Halbach permanent magnetic guideway (PMG) can offer much more GF but the change is larger just as the levitation force decays. The GF of cylindrical bulk HTS increases more than of the rectangular bulk HTS in the pre-load case. The characteristics of the GF during the lateral movement are explained. These results are important for further HTS Maglev vehicle system designs.     

Influence of the Vertical Inclination of Permanent Magnet Guideway on Levitation Characteristics of Hts Maglev System

In the application of high temperature superconducting (HTS) magnetic levitation (maglev) system under vertical inclination of permanent magnetic guideway (PMG), the component of the total weight of levitation body above the PMG will be changed. Therefore, the influence of the vertical inclination of PMG on levitation characteristics of HTS maglev system cannot be ignored, such as the levitation gap, the levitation force, guidance force and driving force of the linear motor. In order to investigate the influence of the vertical inclination angle on levitation characteristics of the HTS maglev system, a HTS maglev launch platform has been designed and fabricated for the investigation the influence of vertical inclination angle between the range of 0° and 18° on the levitation and guidance and driving force parameters of the HTS maglev launch platform. Experimental results show that the levitation gap was the main levitation characteristic for HTS maglev system under vertical inclination of PMG, which increased with increment of the vertical inclination angle. However, the levitation force, and the driving force of the linear motor decreased. The guidance force could not be influenced by the increment of levitation gap. The experimental results are helpful toward improving the running performance of the HTS Maglev launch system.     

Effects of Parameters of High-Temperature Superconductor Levitation System on the Vertical Force in Zero-Field Cooling when a Permanent Magnet Is Laterally Traversing

The vertical force on a rectangular permanent magnet above a cylindrical high-temperature superconductor during lateral traverses is simulated in zero-field cooling. The calculations agree well with the previous experimental data, on the basis of which, the effects of initial cooling conditions, physical parameters, levitating height during lateral traverses and geometrical parameters on the vertical force are presented.     

浅谈航空发动机叶片几何参数测试计量保障体系

对航空发动机叶片几何参数进行了定义和分类,基于叶片几何参数精密测量的重要性、型面参数测量的复杂性和叶片几何参数测量评价的现状,详细介绍了航空发动机叶片几何参数测试计量保障体系构建的需求,提出建立覆盖航空发动机叶片几何参数的测试计量保障体系,并对该体系的内涵和架构思路进行了阐述,为航空发动机装备叶片零部件数字化设计制造、...     

Interplay of Magnetic and Superconducting Subsystems in Ho-Doped YBCO

Journal of Superconductivity and Novel Magnetism - Superconducting and paramagnetic contributions to the magnetization of polycrystalline Y1?xHoxBa2Cu3O7?δ samples were...     

基于超导磁场环境真空测量电离规磁屏蔽结构仿真研究

聚变装置超导磁场环境下真空测量电离规因灯丝变形、带电粒子轨迹变化等物理机制导致真空测量精度不高,不能满足工程精确测量的需求。基于磁屏蔽的理论,构建了半封闭式和开放式的两种多层磁屏蔽结构模型,利用Maxwell有限元软件,仿真研究了结构材料层不同厚度和不同磁场方向等条件下磁屏蔽效能的变化规律。结果表明,屏蔽效能随铁层材料径向厚度的增加而增大,铁层材料端部厚度对其影响较小;超导材料层厚度对屏蔽效能影响较小;磁场方向角在0°~90°范围内,屏蔽效能先减后增,并在90°(屏蔽结构轴向与磁场方向平行)时达到最大值。为电离规在复杂磁场应用条件下的屏蔽结构工程设计提供了依据。     

Magnetic Brake Considerations for the High-<Emphasis Type="Italic">T</Emphasis><Subscript>c</Subscript> Superconducting Maglev Vehicle System

Levitation, guidance and driving/braking are three indispensable parts for a high temperature superconducting Maglev vehicle system. To maintain the advantage of a passive, non-contact levitation system, a magnetic brake based on a discontinuous permanent magnet guideway (PMG) is introduced. Its feasibility is verified by the experimental investigations on the behavior of a levitated bulk high temperature superconductor (HTSC) moving towards the broken-off PMG. When the bulk moves towards the broken-off PMG, a braking force will be generated to hold back the bulk due to the inhomogeneous field distribution. That is to say, this magnetic braking mechanism can act as a safe-protection function. The magnetic brake just makes use of the existing PMG, which is very simple with no extra components needing to be added. This makes it very economical and practical for the future application of the HTS Maglev vehicle system.