Integrated magnetic levitation and rotation system

摘要

A rotary motor and a rotary magnetic bearing are integrated in a compact assembly that is contact-less. A stator assembly surrounds a ferromagnetic rotor with an annular air gap which can accommodate a cylindrical wall, e.g. of a chamber for semiconductor wafer processing. The stator assembly has a permanent magnet or magnets sandwiched between vertically spaced magnetic stator plates with plural pole segments. The rotor is preferably a ring of a magnetic stainless steel with complementary pole teeth. The stator assembly (i) levitates and passively centers the rotor along a vertical axis and against tilt about either horizontal axis, (ii) provides a radial position bias for the rotor, and (iii) establishes a motor flux field at the rotor poles. Polyphase coils wound on the stator plates produce a rotating flux field that drives the rotor as a synchronous homopolar motor. A rotor without pole teeth allows operation with an asynchronous inductive drive. A controller energizes control coils wound on each stator pole segment in response to a sensed physical position of the rotor. The control coils provide active radial position control and can actively damp tip and tilt oscillations that may overcome the passive centering.