Halbach Permanent Magnet Guideway Research Articles

Enhancing dynamic stability of HTS maglev systems with preloading method

High temperature superconducting (HTS) bulks have strong flux pinning capabilities and are widely used in various fields. Their self-stabilizing characteristics also provide new ideas for ultra-high-speed rail transit. For HTS maglev systems, operational stability, curve negotiation and safety when subjected to external forces are very important. Due to the hysteresis effect of superconducting bulks, they do not always return to their initial positions after deviating from the levitated position in an alternative external magnetic field. In some cases, the levitation system can be destroyed. Studies have shown that preloading can enhance quasi-static levitation performance. Therefore, this paper conducts a detailed analysis of the quasi-static levitation and guidance forces of HTS bulks above a Halbach permanent magnet guideway (PMG) under conditions with and without preloading. Additionally, the dynamic responses of the HTS bulks under lateral or vertical pulsed excitations are studied, with a particular focus on the final equilibrium position offset after disturbance. The results indicate that preloading can suppress the attenuation of the levitation force, enhance the guidance performance, and raise stiffness in both lateral and vertical directions. It also effectively suppresses position deviation from disturbance and increases the maximum excitation force threshold for system instability. This study provides practical insights for HTS maglev applications.

Orientation optimization of the Halbach PMG for the levitation and guidance performance of the HTS maglev system

High-temperature superconducting maglev technology has great application potential in rail transit applications due to its advantages such as passive stable levitation and green environmental protection. As one of the key components of the HTS maglev system, the Halbach-type permanent magnet guideway (PMG) enhances the magnetic field on one side of the guideway and weakens that on the other side. Optimizing the PMG, including the geometry and magnetic properties of the magnet, is an effective method to improve the levitation and guidance performance of the system. In addition, since NdFeB permanent magnets are expensive, optimizing the design of the PMG for the HTS maglev system is also an important work to reduce the application cost. In this paper, the Nelder–Mead Simplex method (NMS) in the optimization solver in COMSOL software is used to optimize the geometric parameters of the Halbach PMG according to the different objective requirements of the HTS maglev system. The optimization objectives include the maximum levitation force and guidance force under the constraint of the maximum cross-sectional area of the PMG, as well as the minimum cross-sectional area of the PMG with a minimum levitation force constraint. The results indicate that the NMS method is effective. By comparing four PMGs during the optimization process, it is found that this method can fully improve the utilization of the magnetic field by changing the geometric parameters of the Halbach PMG. This study can provide a valuable reference for the optimal design of the PMG for HTS maglev systems in the future.

Investigation of saturation levitation force and optimization of permanent magnet guideway based on multi-seeded superconducting bulks model

After more than 20 years of research, the superconducting maglev has advanced to the engineering research stage. In engineering applications, multi-seeded superconducting bulks have been widely used in high-temperature superconducting (HTS) maglev systems, but there remains a deficiency in terms of the theoretical model description of multi-seeded superconducting bulks. In this paper, the fully coupled, partially coupled, and uncoupled models of the multi-seeded superconductor are presented to simulate HTS multi-seeded bulk. Then, the levitation performance and trapped field of three kinds of HTS bulks were experimentally tested, revealing a saturation levitation performance on the permanent magnet guideway (PMG). Therefore, the levitation force and trapped field of HTS bulks with different critical current density are further studied by 3D simulation. Taking the 90% and 95% of the maximum levitation force as the benchmarks, the corresponding critical current density of HTS bulks are respectively 4.6 × 108 A m−2 and 6.1 × 108 A m−2. Further, a mapping coupled boundary method was adopted to automatic optimize the PMG to increase the levitation force above the PMG. After optimization, the levitation force under a unit of the permanent magnet is increased by 19%, while the maximum levitation force above multi-period Halbach PMG is increased by 9.23%. This study provides a general multi-seeded superconducting bulk simulation model and levitation force optimization method, which can serve as a reference for selecting suitable superconducting bulk.

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.

Design Optimization of the Electromagnetic Turnout by Using a Compensation Coil

The creating of the ideal turnout switch for a highly branched Maglev system is still a challenging task, because the turnout is one of the most important and indispensable devices involved in the Maglev system. The unmovable electromagnetic turnout can easily move the Maglev vehicles running one way to another, by replacing the permanent magnets (PMs) with electromagnets. But there is still a difference between the normal permanent magnet guideway (PMG) and the area of the turnout switch, which cannot be used in real operation at high speeds. Thus, this paper introduces the possible way to improve the design optimization of the electromagnet used in the electromagnetic turnout of the high temperature superconducting (HTS) Maglev systems. In particular, the use of a compensation coil between magnetic poles was suggested and proved. An equivalent circuit of the electromagnet with compensation coil was built, the criteria for the identity of the magnetic circuit are used to compare with the proposed variant. The parameters of the magnetic field in the electromagnet were calculated and the graph of the magnetic induction was given. Consequently, further direction for improving the electromagnet was described which means this work provides valuable references for the future ideal design of the electromagnet as a crucial element of an electromagnetic turnout for Halbach PMG.

Dynamic performance of HTS maglev and comparisons with another two types of high-speed railway vehicles

In order to explore the potential advantages of HTS maglev vehicles, the dynamic response of HTS maglev vehicle-bridge coupling system model under different speeds and track beam spans is calculated by using Universal Mechanism (UM) software, which is further compared with two existing high-speed train systems, the high-speed EMS vehicle and wheel-rail vehicle. Before establishing the dynamic model, first a simplified mathematical model of levitation force of HTS maglev is extracted based on the experimental results of three YBCO bulks on a Halbach permanent magnet guideway (PMG). The results of simulation show that the HTS maglev vehicle can fully meet the requirements of current high-speed railway operation index on the acceleration of car body and its influence on track beam. The comparisons show that HTS maglev vehicle has some advantages over high-speed EMS vehicle and wheel-rail high-speed vehicle, especially in the acceleration of the car body and the impact on the track beam under high-speed operation. This makes a better understanding of the dynamic performance of HTS maglev vehicle, and provides an effective reference for the selection of high-speed railway system types and related indicators in the future.

Determination of magnetic levitation force properties of bulk MgB2 for different permanent magnetic guideways in different cooling heights

Abstract In our study as different from the literature, the magnetic levitation force between a bulk MgB2 and two different permanent magnetic guideway (PMG) arrangements, which are Halbach and Conventional PMGs, were investigated in different cooling heights (CHs) and Field-Cooled (FC) condition at the temperatures of 37 K and 33 K. The cylindrical bulk MgB2 superconductor was fabricated by in-situ solid state reaction process with the diameter of 18 mm and the height of 5 mm. The XRD data indicates well developed MgB2 phase and the Jc value was obtained as 68 kA/cm2 at 30 K in the self-field. Experimental results show that MgB2 bulk above the Halbach PMG can exhibit better load capability at all the cooling heights between the bulk MgB2 and the PMG due to a more suitable magnetic field distribution. The maximum levitation force for Halbach PMG corresponds to 16.86 N whereas the conventional PMG shows 9.02 N at 37 K in cooling height of 77 mm. Additionally, the maximum levitation force increases while the CH increases because flux exclusion is more effective for larger CHs. It is considered that the experimental results obtained in study are very useful for future Maglev applications, because there are limited number of studies on magnetic levitation force of MgB2 bulk for different MgB2-PMG arrangements.

Optimization study of the Halbach permanent magnetic guideway for high temperature superconducting magnetic levitation

Due to the combined advantages of no-contact friction and self-stable levitation, high temperature superconducting magnetic levitation (HTS Maglev) has significant potential for rail transit applications. In order to further improve the carrying capacity of the HTS maglev system, it is necessary to optimize the permanent magnet guideway (PMG). In this paper, the original Halbach PMG was optimized and a new PMG with better performance was designed and manufactured. The magnetic field and magnetic forces were calculated by the finite element method, and the size and magnetization direction of each PM in the PMG were optimized. Then, the magnetic field above the optimized PMG were measured and compared with the original Halbach PMG as well as the levitation and guidance force of the bulk high temperature superconductors. Experimental data show that the magnetic field above the optimized PMG is effectively enhanced and the levitation and guidance force of the superconductors increase by 12.2% and 11.3%, respectively. This study can provide the foundation for the further optimization of PMGs and the research of large load HTS Maglev technology.

Dynamic Simulation of the HTS Maglev Vehicle-Bridge Coupled System Based on Levitation Force Experiment

In this paper, we built a high-temperature superconducting (HTS) maglev vehicle-bridge coupled system model by Universal Mechanism (UM) software, and analyzed the vertical dynamics. The UM model is composed of two parts, the train subsystem involved three vehicles, and the flexible bridge with simple-supports. In the UM modeling system, the expression of levitation force and the parameters related to the maglev vehicle-bridge were indispensable. The levitation force of maglev vehicle was described by an exponential analytical expression simplified by the experimental results of four YBCO bulks above a Halbach permanent magnetic guideway. The parameters related to the maglev vehicle-bridge are based on experimental prototype. Based on the UM model, the vertical dynamic was simulated and analyzed with different bridge spans under different operating velocities. This subject is a basic study for understanding the unique dynamic characteristic of the HTS maglev vehicle-bridge system. The simulation results provided reference for the further design of the HTS maglev vehicle-bridge coupled system in different speed ranges.

Magnetic Field Test on an Electromagnetic Turnout Prototype System for High-T c Superconducting Maglev

Due to the strong magnetic force between segments of the permanent magnet guideway (PMG), the unmovable electromagnetic turnout becomes one of the most possible choices for high-temperature superconducting (HTS) maglev systems. Meanwhile, it has advantages of quicker response and smaller volume compared with mechanical turnout. A complete turnout system is vital for further evaluating feasibility. Based on the previous studies in ASCLab of Southwest Jiaotong University, a complete electromagnetic turnout prototype system is introduced in this article, which consists of two electromagnets, a Halbach type PMG, a control system, and a maglev vehicle model with a single-domain YBaCuO cylindrical bulk superconductor. In order to guarantee the stable running of vehicle at the turnout area, electromagnets are necessary to provide a similar magnetic field compared with the normal Halbach PMG. Based on the system, the measurement on the magnetic field was done and indicates that the electromagnet could replace permanent magnets of guideway to create a similar magnetic field distribution. The magnetic field experiment on this prototype system further certifies the applicability of the Halbach electromagnetic turnout. For future HTS maglev transportation, the electromagnetic turnout could be widely used in low-speed application such as railway station, switchyard, and laboratory.

Magnetic levitation and guidance performance of Y–Ba–Cu–O and Gd–Ba–Cu–O bulk superconductors under low ambient pressure

The high-temperature superconducting Maglev-evacuated tube transport (HTS Maglev-ETT) system has significant potential for practical applications. In order to employ HTS bulks in an ETT system, it is necessary to study the magnetic levitation and guidance performance of bulk superconductors under low ambient pressure conditions that are representative of those inside the tube. As a result, we have investigated the Maglev performance of Y–Ba–Cu–O (YBCO) and Gd–Ba–Cu–O (GdBCO) single grain, bulk superconductors under different ambient pressures of 100 kPa, 60 kPa and 20 kPa using a bespoke pressure-controlling platform, in which the superconductors were positioned above a Halbach permanent magnet guideway. The levitation forces under conditions of field-cooling (FC) and zero-field-cooling (ZFC) have been measured and analyzed. The guidance force for the FC case and the levitation force relaxation for the ZFC case were also measured. It was found from the experimental results that the Maglev performance of both types of bulk superconductor improves significantly by reducing the ambient pressure in their immediate working environment. The levitation forces of YBCO and GdBCO bulk superconductors were observed to increase by 11.6% and 4.4% in the case of FC, and by 20.3% and 13.7% in the case of ZFC, respectively, as the ambient pressure changed from 100 kPa to 20 kPa. An improvement of the guidance force and an inhibition of the levitation force relaxation were also observed for these materials. The supercooled liquid nitrogen cryogen in the low-pressure environment further reduces the temperature, which, in turn, increases the critical current density Jc of the bulk superconductors and improves their levitation performance. These results provide further evidence of the significant advantages of combining HTS Maglev with evacuated tube technologies as a key enabling feature of the HTS Maglev-ETT system. The data further indicate that YBCO bulk superconductors tend to be more sensitive to ambient pressure and temperature variation than GdBCO bulk superconductors. This difference essentially reflects the dependence of Maglev performance of HTS bulk superconductors on Jc when operating in a low-pressure environment.

Guidance Force and Its Hysteresis of YBCO Bulks Under a Low-Pressure Environment

High temperature superconducting (HTS) maglev train running in the evacuated tube is a new kind of transportation with great potential. The HTS bulks are core component of the HTS maglev train, and its guidance performance is crucial to the ability of curve-passing. Therefore, it is necessary to study the guidance force of YBCO bulks under a low-pressure environment. Based on the test system of magnetic levitation characteristics under low-pressure environments, the super-cooling state of liquid nitrogen is realized by the method of evacuation. The guidance force of YBCO bulks moving laterally above a Halbach permanent magnetic guideway was measured under different pressure values (100, 60, 40, 20 kPa). Results show that decreasing pressure is beneficial to improve the guidance performance of YBCO bulks. When the field cooling height (FCH) is under 35 mm, the guidance force increases with the decrease of the pressure. However, when the FCH is more than 35 mm, the guidance force decreases with the decrease of the pressure. Furthermore, decreasing FCH and pressure value can decrease hysteresis of guidance force and enhance the lateral stability of the HTS maglev system.

Levitation Force of Bulk YBaCuO and GdBaCuO Under a Low-Pressure Environment

The high-temperature superconducting (HTS) bulk is the core component of HTS maglev systems. For the potential application of evacuated tube transportation, it is necessary to verify the loading capacity of the bulk under a low-pressure environment. Based on a home-made pressure-reducing platform, we investigated the levitation force of two kinds of typical bulks, that is, the same sized YBaCuO and GdBaCuO, above a Halbach permanent magnet guideway under different pressure conditions. The levitation force in the cases of zero-field-cooling (ZFC) and field-cooling (FC) were measured and analyzed. Experimental results show that the reduced air pressure can significantly improve the levitation force of the two kinds of bulks. The levitation force of YBaCuO and GdBaCuO has increased by 11.6% and 4.4% in the FC case, 20.3% and 13.7% in the ZFC case under 20 kPa compared with the atmospheric pressure (100 kPa), respectively. This universal phenomenon was explained by the increasing critical current density Jc of HTS bulks due to cooler liquid nitrogen under the low-pressure condition. It is interesting to find that the YBaCuO bulk was more sensitive to the pressure variation compared with the GdBaCuO bulk. This difference reflects the improvement extent of levitation force of HTS bulks with different Jc performance working in a low-pressure environment.

Levitation and guidance force relaxations of the single−seeded and multi−seeded YBCO superconductors

The stable levitation and guidance forces at higher force levels are important parameters for technological applicability of high temperature superconductors (HTSs) in Maglev and Flywheel energy storage systems. In this study, we have investigated the levitation and guidance force relaxation of both the single-seeded and multi-seeded YBCOs for different (HTS)−permanent magnetic guideway (PMG) arrangements in different cooling heights (CH). The measured saturated force values of Halbach PMG arrangements are bigger than the maximum force values of other PMGs. It is determined that the normalized magnetic levitation force (MLF) and normalized guidance force (GF) relaxation rate values decrease while the relaxation rates increase with increasing magnetic pole number and the effective external magnetic field area for both the single−seeded and multi−seeded YBCO. Also it can be said that the force stability at the higher force value of Halbach PMG arrangement indicates that the relaxation quality of Halbach PMG is better than that of the others. Additionally, it can be said that both the MLF and GF relaxation qualities of the multi−seeded YBCOs are better than that of the single−seeded ones. This magnetic force and relaxation results of the single−seeded and multi−seeded YBCOs are useful to optimize the loading capacity and lateral reliability of HTS Maglev and similar magnetic bearing systems.

Levitation Performance of YBCO Bulks in Supercooling Condition Under a Low-Pressure Environment

Taking the influence of low pressure on levitation performance of high temperature superconducting (HTS) maglev into account, we established a simple super-cooling platform based on pumping method to study the levitation performance of YBCO bulks above the Halbach permanent magnet guideway (PMG) under different pressure conditions. Through measuring the temperature of liquid nitrogen (LN2) during the decreasing process of pressure, it is known that the LN 2 would turn into a super-cooling state as the pressure reduction. Measurements of the levitation force versus vertical motion and the force relaxation were performed both in case of zero-field-cooling (ZFC) and field-cooling (FC). The experimental result showing that the decreasing pressure is beneficial to improve the levitation performance of HTS bulks, and the maximum force increase up to 23.5% and 22.1% were realized in ZFC and FC compared with the atmospheric pressure, respectively. Moreover, the low pressure could also reduce the hysteresis loop area and restrain the relaxation decay of levitation force. These results imply that, the low pressure environment in evacuated tube will be beneficial to the levitation performance of HTS maglev system.

Magnetic superelevation design of Halbach permanent magnet guideway for high-temperature superconducting maglev

To improve the curve negotiating ability of high-temperature superconducting (HTS) maglev system, a special structure of magnetic superelevation for double-pole Halbach permanent magnet guideway (PMG) was designed. The most significant feature of this design is the asymmetrical PMG that forms a slanting magnetic field without affecting the smoothness of the PMG surface. When HTS maglev vehicle runs through curves with magnetic superelevation, the vehicle will slant due to asymmetry in magnetic field and the flux-pinning effect of onboard HTS bulks. At the same time, one component of the levitation force provides a part of the centripetal force that reduces lateral acceleration of the vehicle and thus enhances its curve negotiating ability. Furthermore, the slant angle of magnetic superelevation can be adjusted by changing the materials and the thickness of the added permanent magnets. This magnetic superelevation method, together with orographic uplift, can be applied to different requirements of PMG designs. Besides, the applicability of this method would benefit future development of high-speed HTS maglev system.

Levitation performance of different bulk YBaCuO arrays above a permanent magnet guideway for HTS maglev systems

Abstract In order to promote the performance of present high-temperature superconducting (HTS) Maglev systems, the interaction between applicable HTS bulk arrays and an applied Halbach permanent magnet guideway (PMG) was investigated. Ten rectangular multi-seeded YBaCuO bulks were used to find an optimal arrangement for maximum levitation forces by combing the double-layer bulk array pattern and the c-axis direction design of HTS bulks. The studies were implemented in both zero-field-cooling and field-cooling conditions. The experimental results indicate that the present levitation force can be improved remarkably by optimizing the bulk array above the PMG. Compared with single-layer bulk array, Maglev performance can be improved significantly by simply adopting a double-layer bulk array. In addition, by setting the c-axis direction of HTS bulks parallel or perpendicular to the PMG field, we can obtain large levitation force or guidance force, respectively. In the optimization process, the width ratio between the HTS bulk array and the PMG is also an important factor; by designing the bulk array to cover the entire PMG width, we can improve the utilization of the applied magnetic field. Finally, an optimal bulk array pattern was recommended by taking the levitation performance and economic cost into consideration. The experimental data will be used as reference for designing the new HTS Maglev system.

Study on the Magnetic Field Inhomogeneity of a Halbach Permanent-Magnet Guideway Due to Different Defects

The track regularity of a permanent-magnet guideway (PMG) is an important issue to ensure the riding comfort and running stability of high-temperature superconducting (HTS) maglev vehicles. Compared with defects of typical railway tracks, similar defects on PMG could affect the magnetic field at the levitation height and then influence the running performance and the riding comfort of the maglev system. In this paper, the influence of four kinds of Halbach PMG defects on magnetic field distribution was investigated by a finite-element simulation method. According to the calculation results, it is found that the sensitivity of the magnetic field inhomogeneity varies with each kind of defect. The vibration experiments found that the magnetic field inhomogeneity does bring vibration to HTS maglev vehicles. The results could provide significant references for future PMG design in the HTS maglev system.

Levitation and guidance force efficiencies of bulk YBCO for different permanent magnetic guideways

The development of superconductor Maglev systems depends on various disciplinary studies due to the inherent composition of available technologies. Because the fabrication cost is very effective on the Maglev, the requirement of the efficiency improvement focuses the researchers on the design considerations. In this study, the guidance force, the magnetic levitation force (MLF) and magnetic stiffness of different permanent magnetic guideway (PMG) arrangements were investigated in different cooling heights (CH) to enhance the efficiency of Maglev system. The single domain cylindrical bulk YBCO superconductors fabricated by top seeding method with the diameter of 45mm and the height of 15mm were used as HTS. Magnetic field distributions of the PMGs were calculated by finite element method to determine optimum HTS–PMG arrangements. We have used auxiliary onboard permanent magnets with YBCOs to improve the MLF of three pole Halbach PMG arrangements. It is seen that the efficiency of Maglev systems can be improved by using suitable HTS–PMG arrangements. In this study cost efficiency of the integrated levitation and guidance force ((Fz)max(Fx)max/(SPMG∗Cost)) was also determined. It is inferred from this study that the cooling height and PMG–HTS arrangement are key parameters for guidance force, levitation force, magnetic stiffness and efficiency of Maglev systems. It is believed that this study will supply useful references for practical application of HTS Maglev systems.

Investigation of the Lateral Reversible Region of YBCO Bulk above a Permanent Magnet Guideway

The lateral reversible region of the high-T c superconductor (HTSC) bulk YBCO above a permanent magnet guideway (PMG) is investigated experimentally in this study. The dependence of the lateral reversible region upon selected parameters, such as Field Cooling Height (FH), Working Height (WH), and magnetic field structure, is studied. Results show that the lateral reversible region of the HTSC bulk is not only proportional to the magnitude of the guidance force or guide-force hysteresis, but closely related to the external applied magnetic field structure, FH, WH, and the size and shape of the HTSC bulk. A conclusion that the lateral reversible region of an HTSC bulk over the single peak symmetrical PMG prior to multipeak Halbach PMG is drawn. The results may be helpful to the design and optimization of maglev systems composed of a permanent magnet guideway and HTSCs.