D. H. N. Dias

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.

Optimization of a Linear Superconducting Levitation System

The Laboratory for Applied Superconductivity of the Federal University of Rio de Janeiro (LASUP) has been developing a superconducting magnetic levitation urban train named MagLev-Cobra. It is a kind of light rail vehicle where the conventional wheel-rail track is substituted by a rail of Ne-Fe-B magnets and carbon steel interacting with superconductor bulks installed in the vehicle to promote levitation. The main cost of this levitation system is the magnetic rail. Therefore, any improvement in the shape and configuration of magnets and iron has a significant budgetary impact. In this paper, the optimizations carried out with the feasible direction interior point algorithm, extensive search, and genetic algorithm of magnetic rails are presented. The objective is to find the geometry that minimizes the total cost, for a given levitation force, considering some practical restrictions. The levitation force restriction is calculated using a finite-element method. During the optimization process, the superconductor null permeability model is used. Finally, the results are checked with the Bean model and verified experimentally. Measurements of the levitation force and the field mapped over the magnetic rails are presented. Significant reduction of soft and hard ferromagnetic materials was reached.

Experimental and Theoretical Levitation Forces in a Superconducting Bearing for a Real-Scale Maglev System

A numerical model based on the critical-state approximation and on a magnetic-energy minimization procedure is presented to simulate the levitation of a system composed of two isolated infinitely long superconductors levitating over permanent-magnet guideways. Three different sets of magnetic guideways are simulated and compared with experimental tests of a linear superconducting magnetic bearing for a prototype of a real magnetic levitation vehicle. In spite of the complexity of the permanent-magnet guideway design, the model serves as a first approach to calculate the vertical levitation force of these superconducting bearings. The measured and calculated force results validate the model applied to study these systems, in addition to some limitations caused by simplifications considered in the theoretical model.

Experiments in a real scale maglev vehicle prototype

A Brazilian real scale magnetically levitated transport system prototype is under development at the Federal University of Rio de Janeiro. To test this system a 180 m long line has been projected and it will be concluded by the end of 2010. A superconducting linear bearing (SLB) is used to replace the wheels of a conventional train. High temperature superconductor bulks placed inside cryostats attached to the vehicle and a magnetic rail composes the SLB. To choose the magnetic rail for the test line three different rails, selected in a previous simulation work, were built and tested. They are composed by Nd-Fe-B and steel, arranged in a flux concentrator topology. The magnetic flux density for those magnetic rails was mapped. Also, the levitation force between those rails and the superconductor cryostat, for several cooling gaps, were measured to select the best rail geometry to be used in the real scale line. The SLB allows building a light vehicle with distributed load, silent and high energy efficient. The proposed vehicle is composed of four modules with just 1.5 m of length each one and it can transport up to 24 passengers. The test line having two curves with 45 m radius and a 15% acclivity ramp is also presented.

A Full Scale Superconducting Magnetic Levitation (MagLev) Vehicle Operational Line

This paper describes the construction and main components of a full-scale superconducting magnetic levitation vehicle. The prototype, comprising four 1.5-m-long wagons, will travel a short test line of 200 meters, connecting two buildings inside the campus of the Federal University of Rio de Janeiro. The efforts to implement this technology started thirteen years ago with a small-scale prototype in an attempt to prove the concept. The second step was the construction of a functional prototype that could levitate more than one Ton. The actual stage of this project is the construction of an operational prototype mentioned above, designed to transport up to 24 passengers. This work has been reported in several previous editions of the ASC conference. New details about the elevated test line, the permanent magnetic (Nd-Fe-B) guideways, the cryostats with YBCO high critical temperature superconductors, the energy conditioning, the linear induction motor and its regenerative braking, as well as the automatic supply system of liquid nitrogen will be presented in the proposed paper. Tests with this operational prototype demonstrate the technology feasibility.

Tests With One Module of the Brazilian Maglev-Cobra Vehicle

Approximately a decade ago, superconducting maglev train prototypes started to be developed. Researchers from China, Germany, and Brazil have built prototypes carrying people based on superconducting levitation technology. The Brazilian MagLev project, named MagLev-Cobra, started in 2000 with a small-scale prototype that was concluded in 2006. After that, efforts toward a full-scale test vehicle for 30 passengers began. This vehicle will be composed of 4 modules, each one 1.5 m long, with six levitation cryostats and a linear induction motor. The first module and 12 m of test track are already constructed and this paper will describe the following tests: air gap as a function of load, temporal air gap stability, linear motor traction force, and vehicle acceleration. The paper will also describe the construction details of module, linear motor, and the rail.

Simulations and Tests of Superconducting Linear Bearings for a MAGLEV Prototype

The complex microstructure of melt grown YBCO bulk material and the non-linear electromagnetic behavior makes it difficult to determine their thermal, electrical and magnetic properties. The knowledge of these parameters is essential to design superconducting magnetic bearings (SMB) for various applications. The main characteristic of a SMB is the levitation force that arises between the superconductor and the magnetic source. The availability of simulation tools can greatly simplify the design of new prototypes. An algorithm based on the critical state model and the Finite Element Method (FEM) was developed. This method is based on the determination of the current density profile within the superconductor due to the penetration of the flux lines. This algorithm showed satisfactory to simulate the levitation force for a rotational magnetic bearing used in a flywheel prototype. In the present paper, this method is used to simulate a linear bearing and to design the optimal geometries for a magnetic rail that is being developed for a MAGLEV vehicle prototype. The linear bearing consists of two parts: a rail assembled with Nd-Fe-B magnets and YBCO bulks mounted inside a cryostat. Some simulated bearings were mounted and tested. The simulation results agree with the measurements.

Superconducting Levitation Using Coated Conductors

The second-generation (2G) YBCO wire has been used for several applications, such as electric power transmission and distribution cables, fault current limiters, MagLev vehicles, electric machines, high field magnets, superconducting magnetic energy storage, etc. The main advantages of 2G wires are: high critical current density values, large scale production, lower manufacturing cost than first generation, and superior performance under high magnetic fields. This work presents a preliminary study of superconducting magnetic bearings (SMB) using 2G wires as passive levitators. A superconducting block using stacked 2G wires was built to evaluate the behavior of coated conductors in the SMB application. The levitation and lateral force between the 2G block and a permanent magnet guideway was measured and compared with the results for an YBCO bulk with approximately the same dimensions. The results indicate that 2G wires have potential for applications with superconducting levitation, but its economic feasibility still depends on the coated conductors price decreasing.

Emulation of a Full Scale MagLev Vehicle Behavior Under Operational Conditions

Based on the magnetic characteristics of HTS superconductors, the group of the Laboratory of Applied Superconductivity from COPPE/UFRJ in Brazil has proposed and developed a full-scale superconducting MagLev vehicle. The levitation system of this vehicle consists of a superconducting magnetic linear bearing, which is composed of a permanent magnetic guideway (PMG) and YBCO bulks superconductors. The levitation and guidance forces that appear due to the interaction between the superconductor and the PMG keep the vehicle passively levitating in a stable equilibrium point. However, under operational conditions, which include the entry and exit of passengers, vibrations and curves performed by the vehicle, this equilibrium point may be changed. One of the critical consequences caused by this change is the reduction in the levitation gap of the superconductor in relation to the PMG. In order to emulate the vehicle operation, the superconducting bearing is submitted to a series of vertical and horizontal displacements around the equilibrium point and the levitation gap and guidance position are monitored. These movements are controlled by time-variant reference forces that reproduce the operational conditions and the behavior for the levitation gap and guidance position are shown. These measurements are essential to the development process of a full-scale superconducting MagLev vehicle.

MagLev Cobra: Test Facilities and Operational Experiments

The superconducting MagLev technology for transportation systems is becoming mature due to the research and developing effort of recent years. The Brazilian project, named MagLev-Cobra, started in 1998. It has the goal of developing a superconducting levitation vehicle for urban areas. The adopted levitation technology is based on the diamagnetic and the flux pinning properties of YBa2Cu3O7−δ (YBCO) bulk blocks in the interaction with Nd-Fe-B permanent magnets. A laboratory test facility with permanent magnet guideway, linear induction motor and one vehicle module is been built to investigate its operation. The MagLev-Cobra project state of the art is presented in the present paper, describing some construction details of the new test line with 200 m.