Superconducting magnetic bearing
A superconducting magnetic bearing is a bearing (machine element that picks up another element or guides moving parts in the intended direction), especially a magnetic bearing in which the Meissner-Ochsenfeld effect of superconducting materials and the relationships described by Lenz's rule are used To guide or carry objects without contact.
Abbreviations are in German SML (Superconducting Magnetic Bearing), HTS-Lager (HTS or HTSL for high temperature superconductors ), in English SMB (Superconducting Magnetic Bearing).
principle
The approach of the magnetic field from a permanent magnet generates eddy currents in a superconductor as in other conductors , which in turn generate a magnetic field that is opposite to the triggering magnetic field. This creates repulsive forces, which, however, quickly subside with conventional electrical conductors. However, since the electrical resistance of superconductors is zero, the induced eddy currents persist and, together with the magnetic field, generate an inherently stable Lorentz force that has a restoring effect.
Compared to mechanical plain bearings or ball bearings , this bearing , which has not yet been used commercially, has the advantage that there are no losses resulting from friction . However, it must be noted that there is an accompanying energy expenditure for cooling the superconducting materials.
In contrast to the active magnetic bearing (e.g. Transrapid ), the superconducting magnetic bearing does not require any control mechanisms as long as the boundary conditions of temperature and the strength of the exciter magnetic field are not exceeded.
Applications
With the development of materials that become superconducting above 77 K (the temperature of liquid nitrogen , corresponds to approx. −196 ° C) ( high-temperature superconductors, HTSL ), it now seems to be more worthwhile to develop such magnetic bearings.
Use in high-speed applications such as B. turbo machines, rotating energy storage (flywheels, flywheel storage ) and linear transport systems.
literature
- Siems, SO, High-temperature superconductor magnetic bearings for high-speed machines, IMAB Annual Report 2000, Institute for Electrical Machines, Drives and Railways, TU Braunschweig (2000)
- Siems, SO, May, H., Portabella, E., Canders, W.-R., Application of HTSC-Bearings for High Speed Machines, 7th International Symposium on Magnetic Bearings (ISMB-7), Zurich (2000)
- F. Werfel et al., IEEE Trans. Appl. Supercond. 2003, 13 (2), 2173 (2003)