Permanent Magnet Guideway Research Articles

Vertical Dynamic Response Analysis of HTS Maglev Vehicle Excited by a Designed Coreless-Typed PMLSM

High-temperature superconducting (HTS) pinning maglev has the potential for high-speed application because of its advantages of passive self-stabilization, energy conservation, environmental protection, and no inherent magnetic resistance along the forward direction. The HTS pinning maglev can realize non-contact levitation and guidance. Permanent magnet linear synchronous motor (PMLSM) is suitable for HTS pinning maglev to realize non-contact drive. However, in addition to the longitudinal driving force for the HTS pinning maglev train, the PMLSM also produces the normal force which will cause additional excitation on the maglev train and affect its levitation height and vertical dynamic response. In this paper, a coreless-typed PMLSM is designed for HTS pinning maglev driving system, and the driving force and normal force characteristics of the motor under different air gaps are calculated. Then, a vertical dynamic model of the HTS pinning maglev vehicle is established. The vertical dynamic response of the HTS pinning maglev vehicle excited by the normal force of PMLSM and permanent magnet guideway (PMG) irregularity is simulated and analyzed. This work can provide a reference for the study of the electromechanical coupling effect between the HTS pinning maglev levitation system and linear motor driving system.

Vertical and lateral random vibration of high-temperature superconductor maglev under high-speed operation conditions

High-temperature superconductor (HTS) maglev systems shows significant potential to be applied to high-speed rail transportation based on its passive stable levitation owing to the coupling between the HTS bulks and permanent magnetic guideway (PMG). As one of the key factors to guarantee the safe and stable operation of HTS maglev, the dynamic characteristics of the HTS bulks reflecting the operational performance of the HTS maglev system under high-speed running conditions should be focused on. Therefore, this paper, based on H-formulation, established a finite element model of an HTS-PMG system, and assessed its feasibility by experiments. Moreover, the random free vibration of the HTS bulk caused by guideway random irregularity at high speed is also studied by this validated model. The random vibration characteristics and temperature variation of the HTS bulk at three high speeds (600 km h−1, 800 km h−1, and 1000 km h−1) under vertical vibration, lateral vibration, and vertical-lateral coupling vibration, respectively, are compared. The results show that at high speed, vertical vibration can only cause the fluctuation of levitation height, while lateral vibration and vertical-lateral coupled vibration will affect both lateral offset and levitation height. Compared with the mere vertical or lateral vibration mode, the levitation height attenuation and temperature rise of the coupling vibration mode is greater due to more energy loss caused by magnetic flux motion, but it can aid in the suppression of the vibration in the vertical and lateral directions. The increase of velocity intensifies the vibration strength of the HTS bulk and increases the fluctuation of the levitation height, lateral offset, and temperature rise. However, vibrations at a certain high speed causes a limited temperature rise and thus a limited influence on the bulk performance, and the HTS bulk is still in the safe operating range at a maximum speed of 1000 km h−1. These conclusions are anticipated to provide some references for future high-speed applications of the HTS maglev system.

Permanent Magnet Guideway Irregularity Measurement and Characterization by Single Dewar HTS Pinning Maglev System

Permanent Magnet Guideway Irregularity Measurement and Characterization by Single Dewar HTS Pinning Maglev System

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.

Dynamic guidance performance of HTS bulk under varying external magnetic field

With the unique flux pinning characteristics, high temperature superconducting (HTS) bulk can stably levitate above the permanent magnet guideway (PMG). Moreover, owing to its advantages of environmental protection, frictionless and pollution-free, the HTS maglev has shown significant potential in high-speed rail transit. At present, HTS maglev technology is at a critical moment from laboratory research to engineering application. Among the numerous parameters related to its engineering application, the curve negotiation ability determined by the guidance performance of the HTS bulk superconductors is crucial to the safety and stability of its operation. Thus, in this paper, we experimentally investigated the dynamic guidance force of the HTS bulks under different operational conditions including different rotational speeds, maximum lateral displacement (MLD), field cooling height (FCH), and working height (WH) based on a customized HTS maglev dynamic measurement system (SCML-03). In addition, the dynamic guidance force of HTS bulk under long-time operation was studied. It is concluded that FCH, WH, and MLD are intimately associated with the dynamic guidance performance of the HTS bulk, while the rotational speed of the circular PMG has little influence on it. Namely, to improve the dynamic guidance performance of the HTS bulk, reducing the FCH and increasing the WH properly can be regarded as an effective method. Eventually, this research also verifies the long-term lateral stability of the HTS maglev system during dynamic operation.

Double-layer quasi-Halbach guideway with NdFeB and ferrite materials for HTS Maglev

In the high-temperature superconducting (HTS) pinning magnetic levitation system, permanent magnet guideways (PMG) need to be laid along the line as an essential part, and currently the guideways are all made up of NdFeB permanent magnets containing rare earth elements. To reduce the dependence on the rare-earth materials and to reduce the cost of the guideway, a double-layer double quasi-Halbach guideway has been designed and fabricated. The design is based on the finite element simulation using Maxwell equations. PMG model is based on the magnetic remanence and relative magnetic permeability of material, and bulks model is based on the power law model. The performance of the quasi-Halbach guideway is intermediate between that of the one-polar guideway and the Halbach guideway. Under the same conditions, a group of array of quasi-Halbach guideway has fewer permanent magnets and a larger vertical maximum magnetic field than a Halbach array. In this paper, a convex double quasi-Halbach multi-peak guideway has been designed by multiplexing NdFeB and ferrite material while taking PMG structure and NdFeB consumption into account. The new guideway utilizes 35% less NdFeB than the traditional Halbach guideway. Compared with Halbach guideway, there is no decrease in levitation capability at key place and only 25% decrease of guidance capability. The concept of double-layer quasi-Halbach multi-peak guideway significantly reduce the PMG's reliance on rare earth materials and then save a large amount of system expense.

A High-Temperature Superconducting Maglev Turnout Based on a Permanent Magnet Device

Turnouts are an important part of the engineering application of high-temperature superconducting (HTS) maglev. Compared with railway turnout, the strong magnetic force between segments of the permanent magnet guideway (PMG) used in the HTS maglev system makes it inconvenient to switch. By replacing part of the permanent magnets (PMs) at the turnout area, the switching magnetic poles with excitation can change the magnetic field distribution above the PMGs and guide the levitating HTS bulks to complete switching. This paper presents a novel turnout design that consists of switching magnetic poles and the attached permanent magnet device (PMD). In particular, the PMD can reduce the turnout volume and avoid coil heating. Based on the system, the simulation data indicates that the switching magnetic poles could replace PMs to create a similar magnetic field distribution, meanwhile feasible for design and manufacture. This work provides references for future design in non-mechanical PMGs turnouts.

Numerical Studies of Dynamic Characteristics of a Stack-Type HTS Maglev System Based on H-Formulation

High temperature superconducting (HTS) magnetic levitation (maglev) is a promising technology for future high-speed transit systems. Superconducting magnetic bearings are made of a permanent magnet guideway and HTS bulks (bulk-type) or stacks of 2G HTS tapes (stack-type). If the dynamic behavior of bulk-type HTS maglev systems has been well reported, there is little literature about the dynamics of stack-type HTS maglev system. To fill the gap, we built here an electromagnetic-mechanical model of a stack-type bearing. We used a segregated <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> -formulation finite element model to account for the nonlinear resistivity. The multi-layer structure of the HTS tape is either homogenized or modeled in detail. We studied the bearing dynamic response when subjected to different time-varying external magnetic fields mimicking the guideway irregularity and the vehicle speed. The results show that the induced current in the copper layer negatively impacts the stability. By extension, since it cannot account for the copper layer, the homogenized model is not suitable for such analysis. This work contributes to finding viable measures for improving the stability of stack-type HTS maglev systems.

The Simulation on Thermal-Electromagnetism of High-Tc Superconducting Bulks Under Stochastic Excitations

High temperature superconducting (HTS) maglev utilizes the magnetic flux pinning characteristics of vehicle's high temperature superconducting bulk to achieve the stable suspension. During the operation, ac losses will occur inside the HTS bulks due to the irregularity of the permanent magnetic guideway (PMG), causing the change of the temperature, which directly affects the stability of the suspension system. In this article, the magnetic-thermal-guideway coupled model of two-dimensional HTS bulks YBCO, liquid nitrogen (LN) and PMG is established by using COMSOL Multiphysics. The test track irregularity spectrum of high-speed railway is introduced and added to the PMG to simulate the magnetic field fluctuation caused by its arrangement irregularity. The characteristics of the HTS bulks’ power loss, the average current density distribution over the cross section and the temperature rise of the bulk, LN, and suspension gap (SG) are studied respectively under four conditions of excitations: lateral coupled with vertical excitations, lateral excitations, vertical excitations, and nonexcitations. Meanwhile, by comparing and analyzing with the model without considering the temperature, the influence of the temperature on the current density is studied. These results provide certain references for the safe and stable operation of HTS suspension system.

Different directional random excitation's influence on the thermal-electromagnetism of HTS bulks with the real-time coupling method

High-temperature superconducting (HTS) maglev, owing to its unique characteristic, has a wide range of engineering application. Researches on the dynamic response, mostly affected by the irregularity of permanent magnetic guideway (PMG), is the top priority. In order to detailly find out the influence of the irregularity of PMG in lateral/vertical direction on the dynamic response of the HTS bulks respectively, this paper introduces the different directional random excitation and employs a real-time mechanic-electromagnetic-thermal coupling method to study the HTS bulks’ dynamic response. The results show that the different directional excitation has a more significant effect than the temperature does. This study makes a detailed understanding of the HTS bulks’ dynamic response under the random excitation in different directions, providing an effective reference for the HTS bulks’ dynamic analysis.

A method for evaluating levitation performance of electromagnetic guideway

The levitation force can directly reflect the levitation performance of high temperature superconducting (HTS) maglev. In the previous studies, the permanent magnet guideway (PMG) was used as the favorite guideway type, whose levitation performance has been studied through many theoretical calculations, simulations, and experiments. In recent years, the feasibility of electromagnetic guideway (EMG) has been proposed and studied. Continuing to use the levitation force calculation method designed for PMG to cope with EMG will cause some problems. In this study, we improved a levitation force calculation method for E-shaped EMG prototypes, whose width of the center pillar was set as a variable to generate different field distributions. The levitation force was then measured under the condition that magnetic fluxes in a certain levitation region were the same. Subsequently, the levitation forces were calculated according to the equivalent model method and compared with measurement results. Afterward, the causes of errors were discussed, and the calculation method was improved with two correction approaches. Finally, factors affecting calculation accuracy were analyzed. The above research results may be helpful for the prediction of levitation performance and structural design of EMGs in an HTS maglev system.

Dynamic guidance performance of GdBaCuO and YBaCuO bulk single grain superconductors under a varying external magnetic field

High temperature superconducting (HTS) maglev technology has attracted considerable attention from researchers around the world. It provides a new direction of development for urban rail and high-speed rail transit due to its considerable advantages of frictionless transportation, low noise, and environmental protection. HTS bulk materials are able to provide a significant performance advantage to maglev technology and are a key component to achieving both levitation and vehicle guidance. HTS bulk samples with enhanced flux pinning characteristics can enable improved curve negotiating ability and lateral stability for the maglev vehicle. This paper reports the results of experiments on the dynamic guidance force of single grain Y–Ba–Cu–O (YBCO) and Gd–Ba–Cu–O (GdBCO) bulk HTS single grains in order to explore their potential for enhanced maglev guidance performance. A customized HTS maglev dynamic measurement system (SCML-03) with a rotating, circular permanent magnet guideway (PMG) was employed to simulate the dynamic operation of the HTS vehicle above the PMG at different translational speeds. It was observed from the experimental results that the GdBCO bulk superconductor is more able to resist the attenuation of the dynamic guidance force compared to YBCO under the same operational conditions. In addition, the GdBCO bulk single grain is more able to return to the original equilibrium position following exposure to an external displacement. It is concluded that the GdBCO bulk single grain offers greater potential than YBCO for practical application in HTS maglev given its enhanced guidance performance. The results of these tests provide an important benchmark for the future design of HTS maglev transportation systems.

The SCML-05 Developed for Studying the 3D Force and PMG Irregularities Characteristics of HTS Maglev

In order to promote the application of high temperature superconducting (HTS) maglev vehicle, the series of superconducting maglev (SCML) measurement devices — 01, 02 & 03 have been developed in Southwest Jiaotong University. During the course of research, the importance of three-dimensional (3D) study of the interaction between HTS bulks and permanent magnet guideways (PMGs) has become evident. More specifically, when the HTS vehicle is moving at a high speed, small irregularities of the PMG's magnetic field become the source of vibration. Therefore, in order to study the 3D force and the characteristics of HTS maglev under PMG irregularities, a new measurement device called SCML-05 was designed, constructed, and validated. This newly developed measurement device consists of two major parts. The first one is a closed-loop sliding platform providing 3D motion. The second part is measurement and data acquisition system with the software developed for this purpose. In addition, a laser displacement sensor is used to measure the geometry irregularities of the PMG. Overall, the SCML-05 is flexible and light. The force characteristics of the HTS bulks placed above the PMG can be precisely investigated by means of this system. Additionally, the PMG irregularities including geometry and magnetic field irregularities can be measured. These parameters are required to analyze the relationship between the PMG irregularities and the force of HTS maglev vehicle. The test process and typical results obtained by this system are presented in this paper.

Measurement and Characterization Method of Permanent Magnetic Guideway Irregularity in HTS Maglev System

Measurement and Characterization Method of Permanent Magnetic Guideway Irregularity in HTS Maglev System

High-temperature superconducting guidance force enhancement by a novel permanent magnet guideway for maglev curve negotiation

In order to enhance the guidance force, adding the high-temperature superconducting (HTS) bulks and permanent magnets in lateral direction is the simplest way especially in curve negotiation situations. However, as the core component of maglev system, permanent magnet guideway (PMG) consists of a huge amount of NdFeB magnets along the operation line. Hence, it means a huge construction cost to add the magnets in lateral direction. To help solving this issue, this paper discusses a PMG improvement methodology based on the widely-used two-pole Halbach PMG. This proposed novel PMG can enhance the guidance force by only adding air intervals between neighbor magnets and the flux-concentration irons and raising the onboard HTS bulks’ width accordingly. Firstly, a 2D electromagnetic theoretical model of the HTS bulk-PMG maglev system was built in the COMSOL Multiphysics. Then, under the different external magnetic fields of the PMGs with different air intervals, levitation and guidance performances of the typical onboard HTS bulk array at typical working conditions were discussed. The results showed that, with the suitable HTS bulks’ width, the guidance force can increase with the intervals increasing in a range. And the HTS maglev system adopting this idea can achieve a guidance force growth of about 41%. This PMG idea is appropriate for curve negotiation situations because of its higher ratio of the guidance force to the levitation force, without changing the basic magnetic circuit and the magnet block number of the previous linear PMG.

A high-pinning-Type-II superconducting maglev for ICF target delivery: main principles, material options and demonstration models

Abstract Nowadays, inertial confinement fusion (ICF) research related to noncontact positioning and transport of free-standing cryogenic targets is playing an increasingly important role in this field. The operational principle behind these technologies is the magnetic acceleration of the levitating target carrier (or sabot) made from Type-II, high-temperature superconductors (HTSCs). The physics of interaction among levitation, guidance and propulsion systems is based on a quantum levitation of high-pinning HTSCs in the mutually normal magnetic fields. This paper discusses current target delivery strategies and future perspectives to create different permanent magnet guideway (PMG) systems for ICF target transport with levitation. In particular, several PMG building options for optimizing both suspension and levitation of ICF targets using an HTSC-sabot will be analyzed. Credible solutions have been demonstrated for both linear and round PMGs, including the ones with a cyclotron acceleration process to realize high-running velocities of the HTSC-sabot for a limited magnetic track. Focusing on physics, we describe in detail the main aspects of the PMG building and the results obtained from computations and proof of principle experiments. High-pinning HTSC magnetic levitation promises a stable and self-controlled levitation to accelerate the ICF targets placed in the HTSC-sabots up to the required injection velocities of 200 m/s and beyond.

Stiffness characteristic of high temperature superconducting upper maglev system

High temperature superconducting (HTS) magnetic levitation (maglev) train, by virtue of its passive stabilization, has the potential to become the next generation high-speed rail transit mode. For the further practical HTS maglev dynamic study and design, the levitation stiffness between the superconductors and the permanent magnet plays a significant role. Due to the nonlinear characteristics and the hysteresis phenomenon of the levitation force, the levitation stiffness is a variadic value. This varying stiffness complicates the vibration reduction design. And the violent vibrations caused by the lack of reasonable design can endanger the safety and comfort of the vehicle. In this paper, the levitation stiffness of a YBaCuO superconductor vessel levitating above a permanent magnetic guideway (PMG) in Halbach-array was measured and analyzed. First, a quasi-static experiment was designed to measure the levitation stiffness, which will be assessed during different vessel movement, separately. Subsequently, the natural frequencies of the levitation system under different working loads were measured by a series of dynamic experiments, and the levitation stiffness calculated by vibration was compared with the test result of the quasi-static experiment. Finally, a systematic differential equation was proposed to describe the levitation stiffness varying phenomena, and its dynamic characteristics were analyzed and verified by simulations as well. The result of this paper shows that the levitation stiffness does not have a strong regular relation with the levitation height as prediction but has a linear relation with the levitation force in the limit space above the PMG. And the studies about the stiffness characteristics with the proposed stiffness model in this paper can provide reference for engineering application and relative dynamic calculations.

A reconstructed three-dimensional HTS bulk electromagnetic model considering J c spatial inhomogeneity and its implementation in a bulks’ combination system

High-temperature superconducting (HTS) bulks in HTS Maglev systems are always arrayed in a combination to make full use of the applied magnetic field of the permanent magnet guideway (PMG). An excellent combination scheme improves the overall levitation and guidance performance significantly. In this paper, a three-dimensional (3D) electromagnetic model of the real HTS-PMG maglev system with an HTS bulk array was established. This model comprehensively expresses the influence of various factors on the E – J relationship and the 3D spatial distribution of J c, including internal factors such as the inhomogeneity and anisotropy of electromagnetic characteristics, as well as external factors such as applied magnetic field and working temperature. A ternary function was proposed to describe the uneven distribution of J c caused by the bulk’s growth process, which is an interesting phenomenological modeling attempt. In the simulations of the bulks’ combinations, perfect magnetic conductor boundary conditions were applied on the contact surface to simulate two bulks touching each other. Besides, the research target includes reproducing the shapes, the orientations, and the combination scheme of HTS bulks in the real PMG magnetic field. The calculation results of levitation force of the cylindrical bulk under different spatial orientations above the PMG were compared with the experimental results, through which the accuracy of the model was verified. On this basis, the influence of the magnetic field generated by the superconducting current on the nearby bulk was further explored. It was found that this magnetic field has a small contribution to the total levitation force and a relatively obvious influence on the guidance force. When the lateral displacement is large, such as 5 mm, the magnetic field generated by the superconducting current slightly increases the total guidance force stiffness. According to more simulated conditions, some optimization strategies on bulk combinations were proposed. This work provides not only a 3D descriptive model for fitting the real multi-bulk-combination maglev scenarios but also some optimization strategies for the HTS maglev transportation applications.

The magnetic and levitation characteristics of single-grain YBaCuO and GdBaCuO-Ag bulk superconductors in high magnetic fields

In principle, high-temperature superconducting (HTS) flux-pinning maglev has the advantage of self-stable levitation and is therefore a good development prospect as a new rail transit technology. The magnetic field intensity is one of the key factors affecting the levitation performance of single-grain bulk superconductors in the HTS maglev system. To date, however, most researchers have focused on the levitation performance of HTS bulk superconductors in magnetic fields within a permanent magnet guideway (PMG) configuration. The magnitude of the external working magnetic field provided by a PMG is limited to about 0.5 T at 77 K, given that the superconductor usually levitates at a typical working height of 10 mm above the PMG. Therefore, the weak magnetic fields generated by the PMG significantly limits the levitation performance of HTS maglev systems to that of the permanent magnet (PM). In this article, a superconducting magnet test bench was utilized to provide a 0–3 T external magnetic field (B) environment for the study of the levitation force in HTS single grains. The difference in levitation performance between YBaCuO (YBCO) and GdBaCuO-Ag (GdBCO-Ag) bulk superconductors under large, changing magnetic fields was studied systematically. The relationships between levitation force and magnetic field characteristics, including vertical magnetic field component (Bz), transverse magnetic field component (Br), and vertical magnetic field variation (ΔBz) were investigated. The result of variation curves about YBCO and GdBCO bulks' levitation forces under different ΔBz shows that the levitation force of the bulk, single-grain superconductors will reach saturation under a varying ΔBz environment (0.72 and 1.5 T). The values of ΔBz corresponding to the saturation positions are found to be independent of the sizes of the HTS samples. At the same time, GdBCO-Ag exhibits a levitation force that is 112.8% greater than YBCO in B = 3 T magnetic environment. As a result, it is demonstrated that the levitation potential of single-grain HTS bulks can be better exploited by optimizing the distribution of the magnetic field.

The Single-peak and “V” Shaped Combined Permanent Magnet Guideway for High-Temperature Superconducting Magnetic Levitation

With the merits of the excellent self-stabilization, the high-temperature superconducting (HTS) magnetic levitation (maglev) system is relatively appropriate for high-speed railway transportation. The suspension force and guidance force are mainly produced by the interaction between the HTS bulks and the permanent magnet guideway (PMG). Before the HTS bulks turn into the superconducting state, it will capture the magnetic field generated by the PMG and interact with the magnetic field of PMG after turning into the superconducting state, which creates the suspension phenomena. Therefore, the research of the magnetic flux density of external magnetic fields excited by the PMG is very significant to an intensive discovery of HTS maglev properties. However, the previous single-peak guideway needs to be improved to supply HTS maglev with sufficient vertical magnetic fields gradients. Otherwise, it might cause the guidance force to be not great enough for practical engineering application. Hence, this paper proposed a better “V” shaped PMG, by combining the single-peak and “V” shaped PMG. Under the typical work condition of 30 mm field cooling height, 10 mm work height and 10 mm lateral displacement, the levitation force and guidance force of HTS bulks could attain 6779 N and 2778 N, respectively. Compared to the levitation force and guidance force produced by using single-peak PMG, these two forces increase by 12.6% and 137%. As a result, the new “V” shaped PMG will provide HTS maglev with more adequate guidance performance and load capacity.