Patent ID: 7719151

Claim:
An active magnetic bearing with autodetection of position, the bearing comprising a stator comprising at least first and second opposing electromagnets, said stator disposed about a ferromagnetic body forming a rotor held without contact between said electromagnets, the first and second electromagnets each comprising a magnetic circuit essentially constituted by a first portion comprising a first ferromagnetic material and co-operating with said ferromagnetic body to define an airgap, together with an excitation coil powered from a power amplifier whose input current is servo-controlled as a function of the position of the ferromagnetic body relative to the magnetic circuits of the first and second electromagnets, the position of the ferromagnetic body being measured from the inductance detected between the two electromagnets in response to simultaneous injection into both opposing electromagnets of a sinusoidal current at a frequency that is greater than the closed loop passband of the system, the bearing being characterized in that the magnetic circuit of each electromagnet further includes a second portion comprising a second ferromagnetic material having magnetic permeability that is lower than that of the first ferromagnetic material and electrical resistivity that is higher than that of the first ferromagnetic material so as to encourage the passage of the high frequency magnetic fields that are generated in the bearing, wherein the second portion is located between the first portion and the excitation coil, and wherein said first ferromagnetic material comprises a plurality of ferromagnetic laminations stacked in a direction parallel to an axial length of the rotor.