Wide-Gap, Electro-Permanentmagnetic Bearing System with Radial Transmission of Radial and Axial Forces

Abstract

The unique features and applications of this magnetic bearing essentially result from two facts: (1) The only bearing components attached to the rotor are non-laminated ferromagnetic steel collars or cylinders; (2) all radial as well as axial forces are transmitted via radial gaps. The stator assembly needs no axially overhanging components that might impose restrictions on the rotor design and axial mobility. Due to the use of flux modulation technique wide radial gaps (25 mm are realised) can be provided at virtually zero-power conditions. The large gaps allow for effective encapsulation and shielding of rotors at elevated (or low) temperatures, corrosive environment, voltage potentials, and pressure. A 2-kg X-ray rotary anode was operated under high-vacuum conditions at + 100 kV anode potential, 600°C temperature at the bearing collars and speed 18,000 r.p.m. with 13 mm radial gaps. The complete X-ray tube is easily exchangeable by removing it from the stator assembly along the axial direction. Similar handling conditions were achieved with hollow cylindrical rotors (up to 500 m/s periphal speed at the bearing gap), spin turbines and choppers (up to 90,000 r.p.m.), and with long-stroke supporting shafts for crystal pulling plants.