Magnet Guideway Research Articles

Enhancing magnetic levitation and guidance force and weight efficiency of high‐temperature superconducting maglev systems by using sliced bulk YBCO

AbstractWe aimed to enhance the magnetic force efficiency of Maglev systems without increasing total weight. For this aim, we divided YBCO bulks into three slices horizontally to utilize the YBCO‐permanent magnetic guideway (PMG) interaction surface as much as possible. We used whole YBCO above PMGs with different magnetic pole directions (PMG‐A and PMG‐B) in two lying positions of transversal and longitudinal and investigated levitation and guidance force performances. It is determined that levitation and guidance forces by using YBCO in transversal lying mode are bigger compared to the longitudinal mode. For sliced YBCO, the maximum levitation force increased by 69% and 78%, while the guidance force enhancements are determined as 212% and 91%, compared to the whole YBCO above PMG‐A and PMG‐B, respectively. The levitation and guidance force density with respect to the total mass of unit a set of slices YBCO increased by 92% and 106%, respectively, compared to the whole YBCO above PMG‐B in transversal mode. Since the higher levitation force and the lower total weight of the onboard unit are important parameters in point of the energy efficiency in Maglev and other levitation applications, the result of this study supplies useful data for the engineers and industrial partners.

Dynamic Identification of HTS Maglev Module for Suspended Vehicle by Using a Single-Degree-of-Freedom Generalized Bouc–Wen Hysteresis Model

The energy dissipation phenomenon of a high-temperature superconducting (HTS) magnetic levitation (Maglev) transport system is investigated by using a single degree of freedom generalized Bouc–Wen hysteresis model. The Maglev system under test consists of a bogie with HTS skaters, which interacts with permanent magnets distributed on the guideways; thanks to a passive and self-balanced magnetic interaction, the vehicle is suspended and guided in all phases of the motion, including zero speed. The response of the HTS skate is tested under pseudo-static cyclic load in the vertical and lateral directions. The parameters of the generalized Bouc–Wen (GBW) model are calibrated on the experimental hysteresis loops using an ordinary least squares–based algorithm. The vertical dynamics of the levitating HTS skate is affected by the magnetic field discontinuities of the guideway. The dissipated hysteretic energy is simulated to assess the dependence on the velocity and pattern of the magnetic field. The displacement response is obtained by solving the nonlinear differential equation representative of the moving HTS skater, modelled as a single degree of freedom system, whose interactions with the magnetic guideway are described by the identified GBW hysteresis law.

Mobile HTS Bulk Devices as Enabling Ton-Force Technology for Maglev Trains

The status of bulk superconductor magnetic levitation (Maglev) train technique is evaluated. Existing industrial magnetic trains (electromagnetic, electrodynamic) point to key performance factors as load, speed, efficiency, and environmental protection. On that basis, a feasibility analysis of trapped-field train demonstrators should be attained. HTS bulk trapped field experiments at lower temperatures up to 6.8 T were performed and the HTS mass production capability is indicated. For increasing the transport load, a new generation of robust and mobile LN 2 vacuum cryostat type is developed. The new device is designed and scaled up according to the technique and practical experience of a smaller cryostat with 250 kg load and 30-40 h operation time. A test vehicle levitated by four cryostats on a magnetic guideway is presented. It is capable of levitating more than 1 ton. The new cryostat consists of 30 tiles 3-seed YBCO bulks, it levitates up to 0.5 ton at 10 mm distance, and with 5 l LN 2 stored it achieves an operation time of up to 2 days. We report about the integration of YBCO bulks, thermal insulation, LN 2 refilling, and mechanical construction. With the new development, we obtain evidence to manage higher train forces of several tons.

Experiments of Superconducting Maglev Ground Transportation

We report about the use of trapped-field HTS bulk Maglev above a PM guideway. Guideway and superconductors need a robust design and safe operation at LN2 cryogenic temperatures. Cryogenic refrigeration in compact cryostat design has been successfully proved. First generation of 40-cm-long bulk vacuum cryostats are capable to suspend mechanical loads up to 2.5 kN per module 1 cm above a magnetic guideway. The self-weight-to-load ratio is about 15, and thermal losses are reduced to 2.5 W, allowing one-day operation without refilling LN2. More than 40 cryostats are now in successful operation. Thousands of people did ride many hundreds of kilometers in three larger Maglev train systems. We review and analyze the present PM biasing concepts and measure the parameters of a new flat cryostat type. Using FEM calculations and experiments, we propose universal PM biasing conditions for optimum track dimensions. The overall technical performance of the developed and fabricated vacuum cryostats is described.

Study on the effect of transition curve to the dynamic characteristics of high-temperature superconducting maglev

High temperature superconducting (HTS) maglev technology is becoming more and more mature, and many key technologies have been deeply studied. However, the transition curve plays a key role in HTS maglev system, and related studies have not been carried out. In this paper series of simulations were conducted to test the lateral and vertical vibration of HTS maglev when passing through curves. Two magnetic guideways, of which one has transition curves but the other does not, are designed to test the vibration characteristics of a mini HTS maglev model running though curves. Results show that after adding transition curves between straight line and circular curve the vibration of HTS maglev model in lateral and vertical directions are all weakened in different degrees. It proves that adding transition curve into HTS maglev system is favorable and necessary.

Tests on a Superconductor Linear Magnetic Bearing of a Full-Scale MagLev Vehicle

A full-scale MagLev vehicle prototype has been developed by the team of the Laboratory for Applied Superconductivity from the Federal University of Rio de Janeiro. This vehicle is named MagLev-Cobra (cobra means snake in Portuguese), because it is composed by several modules and its motion in curves resembles the movement of a snake. The suspension technology proposed for this vehicle is the levitation of bulk superconductors above a rail made with Nd-Fe-B magnets and steel. The main advantages of the MagLev-Cobra vehicle are low energy consumption, negligible noise emission, curvature radius of 45 meters and capability to ascend ramps of 15%. These properties allow the vehicle to be perfectly adjusted to big cities layout and to be constructed along roads and rivers. One of the most important parts of this project is the superconductor linear magnetic bearing (SLMB) development for the MagLev. In this work, some new results of the SLMB are presented. Measurements of the vertical levitation force of the SLMB and the effect of the flux creep on this force are presented. Also, some tests were made to investigate the influence of the load variation on the levitation force and the SLMB levitation gap. Finally, some tests were made to measure the levitation force and torque in the cryostat for an angular displacement between it and the magnetic guideway. These tests simulate the vehicle operation in real conditions.

Towards an Optimized Magnet-Superconductor Configuration in Actual Maglev Devices

There is an intense research in maglev technology for providing convenient and safe transportation. In particular, several projects are being carried out worldwide -particularly in Germany, Brazil, and China- for constructing full-scale maglev trains. They are based on the levitation of superconducting pellets over magnetic guideways. The optimization of their geometrical parameters and the properties of both superconducting and magnetic parts become very important. Theoretical simulations capturing the essential physics of the superconducting levitation become a very useful tool for understanding and improving the devices. In this work, we extend previous numerical models to incorporate new features in order to simulate closer to actual maglev designs. In particular, we analyse how the levitation and guidance forces are modified when the superconducting part is composed of several superconductors as compared with a single one.

HTS Magnetic Bearings in Prototype Application

ATZ Company has successfully developed high temperature superconducting (HTS) magnetic bearings for power energy application and high-speed machinery. Journal-type design and improved HTS magnetic properties increasingly fulfill industrial prototype requirements. Maximum load up to 1.1 ton, stiffnesses in 3-4 kN/mm level, simultaneous self-stabilization in axial and radial directions, largegap operation of 5-6 mm and reliable machine cooling in the 50-60 K region characterize the present progress of HTS magnetic bearings. A 200 mm HTS bearing of 10 kN load capacity is fabricated and integrated in a 5 kWh/250 kW flywheel energy storage system. We report about a new large-gap HTS magnetic coupling system ensuring 300 mm wafer treatment inside a closed processing chamber in semiconductor industry. A linear MAGLEV transport system consisting of four modular cryostat units have been recently fabricated in a prototyping process. The four HTS cryostats can carry almost 1 ton at 10 mm magnetic gap above a magnetic guideway with a force density of about 5 N/cm2. Due to perfect thermal insulation each cryostat operates more than 24 hours without refilling LN2.

Experimental Study and Optimization of HTS Bulk Levitation Unit for Launch Assist

Magnetic levitation and propulsion has been viewed as a safe, reliable, and inexpensive launch assist for sending small payloads into orbit. In order to investigate the feasibility of HTS bulk levitation system for the purpose, an experimental setup was designed and constructed to study the performance of the lifting body above permanent magnet (PM) guideway. The measurements of the levitation force and guidance force were carried out in zero-field-cooled and field-cooled modes for different topologies of HTS bulk arrangements and PM guideway configurations. The results were analyzed with computational simulations. An optimal design was discussed for the levitation system for launch assist

Lift and guidance forces by using iron-magnetic track with side rims interacting with passive HT C superconducting plate: Experimental analyses

The paper presents the results of levitation tests carried out by an experimental ring device employing a cooled high critical temperature superconducting ring interacting with magnetic field generated by a circular track with side rims. The track is composed of toroidal iron structure on which convex surface three homopolar ring sets of permanent magnets (PM) are arranged to exalt the flux density in the top side of track. The experimental device is conceived and constructed to reproduce, by analogy, the static and dynamic behaviour of a passive superconducting “runner” of levitated vehicle riding above the magnetic guideway. In a wide range of work conditions, lift and guidance performances of system have been tested. Moreover, a two-dimensional finite element parametric model of experimental device has allowed carrying out several numerical analyses.

Comparison of the Lift and Guidance Performances of Two Guideways, with and without Magnetic Side Rims, Interacting with HTC Superconductor

The paper reports the results of levitation tests carried out by using an experimental ring device employing a cooled high critical temperature superconductor ring interacting with magnetic field generated by two different types of circular tracks. The tracks are composed of homopolar permanent magnets arranged in loose soft iron slot with and without magnetic side rims. The experimental device reproduces, by analogy, the magneto-dynamic behaviour of a magnetically levitated vehicle with superconductors on board, riding above a magnetic guideway. Two types of inductors have been replaced on the experimental device achieving two different configurations of system that are described and examined. Lift and guidance forces have been tested in a wide range of work conditions and the levitation performances are compared and discussed.