This paper describes the present status of high temperature superconductors (HTS) and of bulk superconducting magnet devices, their use in bearings, in flywheel energy storage systems (FESS) and linear transport magnetic levitation (Maglev) systems. We report and review the concepts of multi-seeded REBCO bulk superconductor fabrication. The multi-grain bulks increase the averaged trapped magnetic flux density up to 40% compared to single-grain assembly in large-scale applications. HTS magnetic bearings with permanent magnet (PM) excitation were studied and scaled up to maximum forces of 10 kN axially and 4.5 kN radially. We examine the technology of the high-gradient magnetic bearing concept and verify it experimentally. A large HTS bearing is tested for stabilizing a 600 kg rotor of a 5 kWh/250 kW flywheel system. The flywheel rotor tests show the requirement for additional damping. Our compact flywheel system is compared with similar HTS–FESS projects. A small-scale compact YBCO bearing with in situ Stirling cryocooler is constructed and investigated for mobile applications. Next we show a successfully developed modular linear Maglev system for magnetic train operation. Each module levitates 0.25t at 10 mm distance during one-day operation without refilling LN2. More than 30 vacuum cryostats containing multi-seeded YBCO blocks are fabricated and are tested now in Germany, China and Brazil.

http://iopscience.iop.org/article/10.1088/0953-2048/25/1/014007/pdf

Superconductor bearings, flywheels and transportation

A 45-m-long high-temperature superconducting (HTS) Maglev ring test line, named “Super-Maglev,” has been successfully developed in Chengdu, China, in February 2013, 12 years after the birth of the first man-loading HTS Maglev test vehicle. The Maglev vehicle (2.2 m in length, 1.1 m in width) is designed for one passenger with a levitation height of 10–20 mm; the permanent-magnet guideway (PMG) (45 m in length, 0.77 m of track gauge) is a racetrack shape with a curve radius of 6 m; the driving is accomplished by a linear induction motor with a maximum running speed of 50 km/h. The linear motor is composed of four submotors installed at one straight section in the middle of the double PMGs, and the total length is 3 m. This second-generation HTS Maglev vehicle system is highlighted by the cost-performance and the wireless multiparameter onboard monitoring function. The current same-level load capability has been achieved over a small-section low-cost PMG whose cross-sectional area is only 3000 mm
 2
. On the vehicle, parameters of levitation weight, levitation height, running speed, acceleration, lateral offset, online position, and total running distance of the vehicle are real-time monitored and displayed on the onboard tablet computer. The system component and test data are reported in detail in this paper.

A High-Temperature Superconducting Maglev Ring Test Line Developed in Chengdu, China

As a bellwether transportation mode, albeit with hot controversy, evacuated tube transport (ETT) can dramatically reduce air friction, and incorporating Maglev technology could also thoroughly eliminate wheel-rail friction. It is not difficult to imagine that incorporation of these two technologies could establish an innovative transportation system, with particular advantages in terms of high speed, safety, energy saving, and environmental protection. The integration of these two technologies has been a great challenge, however, due to the composite technology. To realize this revolutionary idea, we have successfully developed the first proof-of-principle prototype of a 45-m-long high-temperature superconducting Maglev evacuated tube transport (HTS Maglev-ETT) test system, called the “Super-Maglev,” based on the passive self-stable HTS Maglev conceived in our group in 2000. The system mainly consists of three parts: an HTS Maglev-vehicle-guideway coupling system with 1-t load capability at a levitation gap of 10 mm, a 45-m-long racetrack-type evacuated tube with a 2-m-diameter circular cross section pumped by a hybrid air extraction system, and a 3-m linear induction motor to provide sectional propulsion. The system can achieve a pressure as low as 2.9 kPa in the tube. Experiments show that air drag on the vehicle is greatly reduced at that low air pressure, and a maximum speed of 50 km/h was recorded on the 6-m-diameter test guideway. Theoretically, the reduction of the aerodynamic consumed power could reach as high as to 90% under 10 kPa. This “Super-Maglev” strongly demonstrates the feasibility and potential merits of the HTS Maglev-ETT transportation concept.

A High-Temperature Superconducting Maglev-Evacuated Tube Transport (HTS Maglev-ETT) Test System

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.

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

We review the modeling progress of the magnetic response of hard type-II superconductors (SCs) using the critical-state model (CSM). We focus on magnetization loops when a uniform field is applied to the SC and on the levitation forces that appear when the applied field is nonuniform. Different analytical and numerical solutions of the CSM are discussed, and the main characteristics and parameters of the magnetization loops and levitation forces are reviewed. Although this paper does not pretend to be an exhaustive review of the modeling of type-II SCs or of the superconducting levitation studies, a general overview of some important theoretical models used to understand the hard type-II SC macroscopic behavior is presented.

Macroscopic Modeling of Magnetization and Levitation of Hard Type-II Superconductors: The Critical-State Model

SupraTrans is an innovative transportation concept based on the principle of superconductive magnetic levitation. The aim of the project is to create a fully working prototype, which proves its ability for passenger transport by explicit consideration of the compatibility between systems for propulsion, safety, positioning, power supply, transport logistics and the levitation system itself. The SupraTrans technology uses the flux pinning in high temperature superconductors (HTS) to stabilize the lateral and vertical position of the vehicle on the magnetic track. This self-stabilizing system is the main advantage of the superconductive levitation in comparison to all other levitation systems, which need electronic control and power to keep a constant distance between the train and the track.

U. Funk

Papers

Superconductively levitated transport system - the SupraTrans project