Browse Prior Art Database

Original Publication Date: 1992-Aug-31
Included in the Prior Art Database: 2004-Apr-06

Publishing Venue

Xerox Disclosure Journal


An electromagnetic bearing for supporting rotating or reciprocating shafts is disclosed. The electromagnetic bearing shown in Figures 1A (cross sectional) and 1B (axial) consists of magnetic iron pole pieces 10, 12, 14, 16 wound with wire coils 18, 20, 22, 24, a magnetic iron shaft 26 (or iron insert), position sensor 28 (one of two shown) and an electromagnetic feedback circuit. The electromagnetic bearing operates as follows: If sensor 28 indicates shaft 26 is too low, coil 18 is energized by the electronic feedback circuit, pulling shaft 26 upwards. If shaft 26 is too high, coil 22 is energized. Left and right coils 24 and 20 operate in a similar manner. The electromagnetic feedback circuit maintains shaft 26 in a centered position by providing proper actuation signals for coils 18, 20, 22 and 24. The inputs to the electromagnetic feedback circuit are signals from two position sensors (only 26 shown), which identify the upidown and leftiright position of shaft 26. The outputs of the electromagnetic feedback circuit are four currents to coils 18, 20, 22 and 24. A bias force is applied at each pole piece by having a small current flow in each coil. The bias helps linearize the force from the electromagnetic bearing and provides stiffness when shaft 26 is centered. Note that only three iron pole piece are required to support shaft 26. Four pole pieces 10, 12, 14, 16 are used however to simplify the electromagnetic feedback circuit.