Superconductor Permanent Magnet Research Articles

Research on Levitation and Guidance Characteristics of DSSC HTS-PMG Maglev System Integrating Upper Suspension and Down Hanging

The maglev train has great application potential in the field of high-speed transportation, which is based on high-temperature superconductor-permanent magnet guideway (HTS-PMG) maglev system. In order to break through the bottleneck of insufficient performance of the conventional upper HTS-PMG maglev system, it is of great value to explore a higher performance maglev configuration. In this article, the mechanical characteristics of the upper suspension and the down hanging type are studied through numerical simulation and experimental methods, and a new type of double-sided strongly coupled (DSSC) HTS-PMG maglev configuration is proposed based on the PMG concentrating magnetic field through the iron plate in the middle. The results show that the upper suspension and down hanging type complement each other in the characteristics of levitation force and guidance force, that is, when the levitation force (guidance force) of the upper suspension type increases (weakens) with the increase of cooling height, the hanging force (guidance force) of the down hanging type exhibits the opposite changing behavior, and vice versa. For the coupled system, within a certain levitation gap range, its levitation force and guidance force can be approximated as the linear superposition of the upper suspension and the down hanging, and the coupling degree of the system increases with the decrease of the levitation gap. Through optimization, the levitation force and guidance force are significantly improved. When the upper cooling height (UCH) and the down cooling height (DCH) are fixed at 20 and 5 mm, at the upper working height (UWH) of 15, 10, and 5 mm, the levitation force is respectively increased by 267.7, 105.7, and 46.8% compared with the upper suspension type. When the UCH is 20, 25, and 30 mm, the guidance force is, respectively, increased by 181.4, 201.2, and 188.2% at the lateral displacement ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LD</i> ) of 20 mm compared with the upper suspension type. The above research results provide a design reference for the development of higher-performance HTS-PMG maglev train.

Vertical Magnetic Field Distribution Characteristics of Triple-Peak Halbach Array PMG and Its Engineering Application in HTS Maglev Train

The maglev train has a broad application prospect in the field of high-speed transportation, which is based on the high-temperature superconductor permanent magnet guideway (HTS-PMG) maglev system. The optimized design of the permanent magnet guideway (PMG) configuration is of great significance to improve the overall performance of the system and reduce the cost. In this article, a triple-peak Halbach array PMG is proposed, which is suitable for the HTS-PMG maglev system based on square single-seed melt-texture YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7-</sub> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">_x</i> block with a width of 40 mm. Through theoretical calculations, the influence of structural parameters of triple-peak Halbach array PMG on the vertical magnetic field distribution characteristics is revealed, that is, increasing the proportion of horizontally magnetized permanent magnet (vertically magnetized permanent magnet) is conducive to enhancing the vertical magnetic field in the regions close to (far away from) PMG. Furthermore, combined with the engineering application of HTS-PMG maglev train, an optimized triple-peak Halbach array PMG sample is fabricated. And the reliability of the theoretical model of triple-peak Halbach array PMG is verified by simulation and experimental measurements. Based on the optimized PMG, a full-scale HTS-PMG maglev train test line with a length of 22 m and a standard gauge of 1.435 m (in China) is built up, and the manned test is successfully carried out, which shows the feasibility of the triple-peak Halbach array PMG in large-scale engineering application of the HTS-PMG maglev train.

Levitation behaviours of an eccentric SC-PM system with multi-degree-of-freedom motion

The high temperature superconducting (HTS) magnetic levitation is actually a self-stable levitation with multi-degree-of-freedom (DoF). However, the research of HTS magnetic levitation focuses on the axial or radial levitation behaviour with single-DoF motion independently. This article mainly discusses the 3-D modelling and the levitation behaviours of an eccentric superconductor-permanent magnet (SC-PM) system with multi-DoF motion. Firstly, the Power-Law E − J relation is used to obtain the relationship of equivalent conductivity-electric field strength for the superconductor. Then, a 3-D finite element model (FEM) of SC-PM system is established and calculated in software MagNet. At the same time, the result of the simulation is verified by the experimental measurements. The axial levitation behaviour is analysed by establishing and solving the 3-D FEM in eccentric SC-PM system with different multi-DoF motions. The results show that the maximum axial levitation force decreases with the increase of the static eccentricity distance. When the PM rotor exhibits dynamic eccentricity, the axial levitation force presents periodic fluctuations of which the amplitude and period are related to the dynamic eccentric distance and speed.

Dynamic Characteristics in the Horizontal Direction for New Type SMB Using SC Bulk and SC Coil

Superconducting magnetic bearings (SMBs) are usually composed of superconducting (SC) bulk and permanent magnet (PM). These SMBs are based on pinning forces between SC bulk and PM. In this paper, new type SMBs composed of SC bulk, SC coil and PM are proposed. In order to compare SMB Type-I with Type-II, impulse responses in the horizontal direction are performed. Then, natural damped vibration curves for impulse responses are observed. The damping coefficient for the SMB Type-II is very larger than the Type-I. The damping coefficient depends on the position of SC coil.

The Effect of Cone Additional Permanent Magnet Thickness on Magnetic Field Distribution and the Levitation Force of Single Domain GdBCO Bulk Superconductor

It has been investigated that the interaction force between truncated cone permanent magnet (PM) and a GdBCO bulk (HTSC) superconducting permanent magnet (SCPM) magnetized by a truncated cone permanent magnet in their configurations at 77K. The influence of two configurations in different thickness of truncated cone permanent magnets of single domain GdBCO bulk capture field and superconducting magnetic levitation force results. The maximum superconducting magnetic levitation force first increases as H increase, and then decreases with H when it reaches a certain value, from 5.7N to 16.6N at first, and then it decreases to 3.8N. The vertical component of the magnetic field intensity on the top surface (h=2mm) of truncated cone permanent magnet first increases, and then decreases also, from 0.20T to 0.54T, and then decrease to 0.25T. These results indicate that the levitation force of high temperature superconductor bulk can be effectively improved by scientific choosing of shape and size of permanent magnet, and reasonable designing of the system configurations, which is very important during the practical design and applications of superconducting magnetic levitation system.

Comparison of Electromagnetic Performance of SCPM Wind Power Generators With Different Topologies

This paper focuses on the comparison of electromagnetic performance of the superconducting permanent magnet (SCPM) generators with two different topologies. The torque capabilities of the two generators are first investigated. The peak torque is largely restricted by the material characteristics of the superconducting (SC) and the permanent magnet. The SCPM generators with iron-cored rotor and iron-cored stator topology (IRIST) is superior to the one with iron-cored rotor and air-cored stator topology in terms of torque capability. Furthermore, the flux density, line electromotive force, torque and its torque ripple, and the efficiency of the designed generators are evaluated by using numerical model. The simulation results confirm that IRIST has higher output torque and efficiency with the penalty of higher harmonics and torque ripples.

Proposal of New Superconducting Magnetic Bearing Using High &lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$T_{c}$ &lt;/tex-math&gt; &lt;/inline-formula&gt; Superconducting Bulk and Coil

Superconducting magnetic bearings (SMBs) are usually composed of superconducting (SC) bulk and permanent magnet (PM). These SMBs are based on pinning forces between SC bulk and PM. In this paper, new SMBs composed of an SC bulk, an SC coil, and a PM are proposed. In order to compare Type-I and Type-II SMBs, impulse responses are performed. Then, damped free vibration curves for impulse responses are observed. The damping coefficient for the SMB Type-II is very larger than the Type-I. From the experimental results, both stiffness and damping coefficient for the SMB Type-II are better than the Type-I.

Simplified calculation for the radial levitation force of radial‐type superconducting magnetic bearing

It is usually difficult to obtain the radial levitation force of the radial-type superconducting magnetic bearing (SMB) due to the massive numerical calculations and the sophisticated experimental measurements. This study presents a method for fast calculating the radial levitation force of radial-type SMB, which is based on the infinitesimal method and the 2D finite-element method. During the modelling, the radial-type SMB is assumed to be composed circumferentially of infinite superconductor-permanent magnet (SC-PM) infinitesimals with shape of rectangular thin slice. The dependence of levitation force for the SC-PM infinitesimal on the air-gap length between the SC stator and the PM rotor can be obtained using the 2D finite-element model established in Cartesian coordinate system. Moreover, a simplified analytical model of calculating radial levitation force is developed based on the infinitesimal method and the circumferential distribution formula of non-uniform air-gap when the PM rotor exhibits radial eccentricity. The results of theoretical calculation and experimental measurement of radial levitation force show a good agreement, which verifies the feasibility of the proposed method. It has the advantages of fastness and easiness, and can be used as a theoretical tool for the design, optimisation and performance prediction of the radial-type SMB.

The effect of additional permanent magnet magnetizing methods on magnetic field distribution and the levitation force of single domain GdBCO bulk superconductor

It has been investigated that the interaction force between a cubic permanent magnet PM1 and a GdBCO bulk (HTSC) superconducting permanent magnet (SCPM) magnetized by a cubic permanent magnet PM2 under different configurations at 77 K. Two configurations were used for the magnetization of the GdBCO bulk, one is that the North pole of the PM2 is in upward direction, the other is in downward direction, so that the North pole of the SCPM is in two states SCPM↑ and SCPM↓; the vertical distance between the bottom surface of PM1 and the top surface of SCPM is kept as a constant value, but the PM2 can be fixed at any positions (x) along a diameter of the GdBCO bulk during the magnetization process. It is found that: for the PM1↓-SCPM↑ configuration, the maximum levitation force is increasing from 16.7 N to 23.1 N when x increases from –15 mm to 0, and then decreases to 16.6 N when x further increases to 15 mm; but for the PM1↓-SCPM↓ configuration, the maximum levitation force is decreasing from 17.7 N to 7 N when x increases from –15 mm to 0, and then increases to 17.6 N when x further increases to 15 mm. These results are not only much different in the two configurations, but also much different from the maximum levitation force 17.1 N of the sample under zero field cooled condition, which is closely related with the trapped field distribution of the SCPM at different x values. These results indicate that the levitation force of high temperature bulk superconductors can be effectively improved by introducing additional permanent magnet based on scientific and reasonable designing of the system configurations, which is very important during the practical design and applications of superconducting magnetic levitation systems.

Local model for magnet–superconductor mechanical interaction: Experimental verification

Several models exist for calculating superconducting repulsion forces in the Meissner state that are based on the method of images. The method of images, however, is limited to a small number of geometrical configurations that can be solved exactly, and the physical interpretation of the method is under discussion. A general local model based on the London equations and Maxwell’s equations has been developed to describe the mechanics of the superconductor-permanent magnet system. Due to its differential form, this expression can be easily implemented in a finite elements analysis and, consequently, is easily applicable to any shape of superconductor in the Meissner state. It can solve both forces and torques. This paper reports different experiments undertaken in order to test the model’s validity. The vertical forces and the angle of equilibrium between a magnet and a superconductor were measured, and a positive agreement between the experiments and theoretical calculations was found.

Influence of some metallic additives on the flux trapping ability of high temperature superconducting ceramics

By applying magnetic fields on high temperature superconducting (HTS) bulks, superconducting permanent magnets (SPMs) can be produced. Two relevant factors influencing the properties of the SPMs have been investigated: 1. The external magnetic field to be trapped by HTS bulks—that depends on the mode of the magnetization (static or pulse form). 2. The flux trapping ability of the HTS bulks (that is, which percentage of the external magnetic field can be trapped by the HTS materials)—that depends on and can be controlled by the composition and the preparation technique of the HTS bulks. YBaCuO base single domain bulks with CeSn and Ce + Ag additives were prepared aiming at the analyse of the influence of these additives on the flux trapping ability of Y 1Ba 2Cu 3O 7− x (Y123) superconducting bulks. In the reported stage of our long term R&D work we focused on the pulse magnetization of these superconducting bulks. A pulse generator equipped with set of magnetizing coils have been designed and built for supplying various pulse forms for magnetizing the bulks. Using this pulse magnetization equipment, a magnetic flux density as high as 4.0 T could be created by discharging a capacitor bank through ignitron switches into the magnetizing coil. The equipment is capable to generate variable pulse shapes. The YBCO bulk samples were magnetized in zero field cooled (ZFC mode). For cooling the samples, liquid nitrogen was used. The pulse magnetized bulks were measured and tested by field mapping.

Stiffness and energy losses in cylindrically symmetric superconductor levitating systems

Stiffness and hysteretic energy losses are calculated for a magnetically levitating system composed of a type-II superconductor and a permanent magnet when a small vibration is produced in the system. We consider a cylindrically symmetric configuration with only vertical movements and calculate the current profiles under the assumption of the critical state model. The calculations, based on magnetic energy minimization, take into account the demagnetization fields inside the superconductor and the actual shape of the applied field. The dependence of stiffness and hysteretic energy losses upon the different important parameters of the system such as the superconductor aspect ratio, the relative size of the superconductor–permanent magnet, and the critical current of the superconductor are all systematically studied. Finally, in view of the results, we provide some trends on how a system such as the one studied here could be designed in order to optimize both the stiffness and the hysteretic losses.

Stability and hysteretic losses in superconductor–permanent magnet levitation systems

From the calculations of the levitation force, the stiffness and the hysteretic energy losses are studied in a cylindrical system composed of a permanent magnet and a type-II superconductor (SC) of finite shape. By including demagnetization effects in the calculations, we analyze the dependence of those magnitudes on the aspect ratio of the SC.

A scheme of Maglev vehicle using high T/sub c/ bulk superconducters

High T/sub c/ superconductors are highly attractive because they can operate at liquid nitrogen temperature. The high performance of high T/sub c/ bulk superconductors is exciting to people in the application research work on superconducting magnetic levitation (Maglev) vehicle. The Maglev concept using high T/sub c/ bulk superconductors has been demonstrated by the Beijing Small Model. In this paper, schemes relating to the use of high T/sub c/ YBaCuO superconducting bulk materials for Maglev vehicle are discussed. First, the YBaCuO bulk superconductors are arranged above the rail using NdFeB permanent magnets. The second scheme is the electromagnetic suspension (EMS) Maglev vehicle using high T/sub c/ superconducting permanent magnets (SCPM) or high T/sub c/ superconducting wire. The third is the EMS Maglev using high T/sub c/ SCPM. The third scheme is chosen after making a comparison. The key problems of the EMS Maglev vehicle using high T/sub c/ SCPM are discussed.

高温超電導体と軟磁性体を用いた磁気浮上

This paper describes a novel suspension technique using high-Tc superconductors and magnetic materials. For a field-cooled superconductor and an adjacent magnetic material, it has been found that the usual inverse relationship between the attractive magnetic force and gap distance switches to a direct relationship for small gap lengths under certain conditions. This phenomenon was found for even soft magnetic materials possessing a minimal coercive force. Thus, stable, noncontact suspension is possible within a certain gap range. When compared to a conventional superconductor-permanent magnet combination, both reduced cost and increased mechanical robustness can be expected since permanent magnets are not needed. Since remarkable switching in the force-gap relationship has been observed for magnetic materials with diameters much smaller than that of the effective pinned area, it was considered that the pinned flux is subject to a “gathering effect” in the magnetic material. Stable contactless suspension of a 180-g carbon steel weight under a superconductor has been performed previously. In continuing work, suspension of a 1.4-kg superconductor vehicle under a 1.8-m silicon steel rail was achieved by an extension of this technique.