R. de Andrade

Magnetic Bearing Sets for a Flywheel System

This paper presents a magnetic bearing set developed to work in a flywheel energy storage system. The bearing set is composed of a permanent magnetic bearing (PMB) and a superconducting magnetic bearing (SMB). A new configuration of a PMB having Nd-Fe-B magnet rings and a back yoke is proposed and compared with an existing one. Finite element method (FEM) simulations were used to design two different PMB configurations. Measurement results of axial and radial forces were carried out in zero field cooling (ZFC) and field cooling (FC) processes in two SMB topologies. These measured force results are presented and discussed in order to discover which configuration is more promising for the proposed application.

Flywheel Energy Storage System Description and Tests

This paper presents test results of a flywheel energy storage system (FESS) prototype. The bearing system is composed of a superconducting magnetic thrust bearing (SMB) and a permanent magnet bearing (PMB). The SMB was built with Nd-Fe-B magnet and YBCO superconducting blocks. The PMB has the function of positioning radially the switched reluctance machine (SRM) used as motor/generator and reduce the load over the SMB. The SRM drive is responsible to convert electrical into mechanical energy, and vice versa. The prototype still operates at low speeds, but the dynamical simulations of the SRM drive showed that the system can work at high speed, supplying the required energy during disturbances. In the tests performed with the FESS prototype, the system took or delivered energy from/to the grid when requested.

Halbach array superconducting magnetic bearing for a flywheel energy storage system

In order to develop a new magnetic bearing set for a flywheel energy storage prototype, it was designed and simulated some configurations of Permanent Magnetic Bearings (PMB) and Superconducting Magnetic Bearings (SMB). The bearings were assembled with Nd-Fe-B permanent magnets and the simulations were carried out with the Finite Element Method (FEM). The PMB was designed to reduce the load on SMB and provide radial positioning of the whole set. SMB were designed with YBCO superconductors and an assembly of permanent magnets. Several configurations of permanent magnets were simulated, trying to maximize the magnetic flux gradient in direction orthogonal to the movement and flux density in the surface of the superconductors. Early experiments have shown an increasing stiffness and levitation force with increasing field gradient and intensity. It was also a goal to reduce the stray field outside the bearing. The levitation force of the SMB using a flux shapers configuration was measured and compared with FEM simulation, showing very good agreement. The simulation of a SMB using Halbach array configuration shows that it increases the levitation force and reduces the stray field.

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.

Simulations and Tests of MCP-BSCCO-2212 Superconducting Fault Current Limiters

Superconducting fault current limiters (SCFCLs) represent a promising solution to the problem of increasing short- circuit currents in the grid. The SCFCL is based on the fast transition from the superconducting state to the normal state, causing a sudden increase in the impedance of the network. In this paper, we simulate the behavior of resistive-type SCFCL modules. The SCFCL modules are based on MCP-BSCCO 2212 coils. The superconductor acts as a nonlinear resistance that varies with the current and the temperature. The behavior of the simulated curves is consistent with the experimental results. Short-circuit currents as high as 37 kApeak were limited to about 10% of their peak values in the first half cycle.

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.

Voltage sags compensation using a superconducting flywheel energy storage system

This paper presents a voltage sag compensator, which uses a flywheel energy storage system with superconducting magnetic axial thrust bearing (SMB) and a permanent magnet radial bearing (PMB). The SMB was built with Nd-Fe-B magnet and YBCO superconducting blocks, refrigerated with liquid Nitrogen. The magnets are assembled with magnetic flux shapers in order to increase the levitation force and the stiffness. The radial PMB is used to positioning the vertically arranged switched reluctance machine (SRM) used as motor/generator. Simulations of the power electronics and SRM show that the system can work up to 30,000 rpm supplying the required energy during disturbances.

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.

Levitation force and stability of superconducting linear bearings using NdFeB and ferrite magnets

Abstract In the frame of a project on the development of a reduced-scale-levitating rail-vehicle prototype, the performance of two different permanent magnets have been tested in linear bearings using YBa2Cu3O7−y bulk superconductors. The levitation forces, the stiffness and the vibration damping have been measured using two different rail assemblies: one mounted with NdFeB magnets and another with ferrite ones. The levitation force of the NdFeB rail is more than one order of magnitude larger than that of the ferrite one. The stiffness of those linear bearing and the vibration damping were measured for several cooling heights from the rail. The stiffness increases with the decrease of the cooling height and is larger in the NdFeB rail. The vibration damping is rather low in both systems. Finally, we conclude that the NdFeB magnets are the most suitable for applications on linear levitating bearings.

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.