Three Axis AMB High Speed Micro Motor

This contribution investigates possibilities and limitations of high speed rotation of small rotors supported on active magnetic bearings (AMBs). A sub-millimetric spherical steel ball has reached 2.88 million rpm in partial vacuum. The AMB system actively stabilizes the three translations of spherical rotors with diameters varying from 1 mm down to 0.4 mm. In addition, an interesting method to measure rotational speed is introduced.