Design aspects of a large scale turbomolecular pump with active magnetic bearings

Abstract

A large scale 5-axis magnetically levitated turbomolecular pump is designed and fabricated in this paper. The rotor is supported by two radial active magnetic bearings (AMBs) and an axial AMB, and driven by a high-speed brushless DC Motor with a ring permanent magnet. The considerations discussed are described by design of an actual magnetic levitation turbomolecular pump with rated high-speed vacuum pumping speed of 4100L/s and ultra-high vacuum of the order of 1.8 × 10−7Pa. The vacuum, stress, modal, and electromagnetic aspects are put equal weight in the design of a large scale turbomolecular pump supported by AMBs. The thermal assembly technology of the ring PM, sleeve, and shaft for the turbo rotor is proposed. Finally, the suggested design methodology for designing a large scale turbomolecular pump with AMBs is presented.