Electrodynamic Passive Magnetic Bearing With Planar Halbach Arrays

Active magnetic bearings are finding an increasing number of practical applications. However, system costs are still high. Passive contact free magnetic bearings need no sensors and no electronic control, such systems could therefore open up new application fields such as e.g. flywheels. Furthermore, today’s active magnetic bearings have small air gaps between stator and rotor (some few tenths of millimeters) and therefore do not allow for large rotor deviations from the nominal position. The presented passive magnetic bearing uses permanent magnet rings as radial bearings and an electrodynamic system as the axial bearing. The latter is composed of two planar Halbach arrays and of twosets of short-circuited coils. The total rotor weight is magnetically compensated. For axial stabilization at the rest or at low speeds two mechanical touch-downbearings are provided. If a certain moderate rotational speed is exceeded then the complete rotor levitation will be achieved. The clearance of air gaps is so ample that the rotor can spin about its principal axis of inertia without touching the stator. For rotor stabilization no electronics is needed.