ARRAY OF PERMANENT MAGNETS FOR THE ROTOR OF A MAGNETIC BEARING AND METHOD OF ASSEMBLY OF THE ARRAY

摘要

Stray magnetic fields created by asymmetric magnetization of permanent magnets in a rotating magnet array of a magnetic bearing assembly when used in a turbo molecular pump can cause significant problems in devices such as scanning electron microscopes. In order to minimize the stray field, at least the dipole and tetrahedron moments of each magnet in the array are measured first. Next, the magnets in the array are arranged relative to each other such that the dipole and quadrupole moments are minimized, thereby minimizing the stray field when the magnet array is rotated in the turbo-molecular pump.