INTEGRATED MAGNETIC LEVITATION AND ROTATION SYSTEM

摘要

A rotary motor and a rotary magnetic bearing are integrated in a compact assembly (10) that is contactless. A stator assembly (16) surrounds a ferromagnetic rotor (18) with an annular air gap (20) which can accommodate a cylindrical wall (12e), e.g. of a chamber, for semiconductor wafer processing. The stator assembly (16) has a permanent magnet (38) or magnets sandwiched between vertically spaced magnetic stator plates (36) with plural pole segments (36a). The rotor is preferably a ring of magnetic stainless steel with complementary pole teeth (18c). The stator assembly levitates and passively centers the rotor along a vertical axis and against tilt about the either horizontal axis (26, 28), provides a radial position bias for the rotor, and establishes a motor flux field at the rotor poles. Polyphase coils (40) wound on the stator plates (36) 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 (54) energizes control coils (42) wound on each stator pole segment (36a) in response to a sensed physical position of the rotor. The control coils (42) provide active radial position control and can actively damp tip and tilt oscillations that may overcome the passive centering.