Electromagnetic device for reducing vibration in a rotary machine fitted with fluid bearings

Claim 1

An electromagentic device for reducing vibration in a rotary machine comprising a rotor mounted in a casing via at least one fluid bearing, the device comprising: at least one compensation ring disposed in the vicinity of the fluid bearing and mounted relative to the rotor by means of an active radial magnetic bearing; a position detector for detecting the position of the compensation ring relative to the rotor; at least two vibration detectors disposed on the casing of the machine and having nonparallel axes of sensitivity which are perpendicular to the axis of the rotor; said active radial magnetic bearing having electromagnetic windings which are controlled as a function of the signals delivered by said position detector and said vibration detectors; wherein the signals delivered by the vibration detectors are applied to a high-gain narrow-band selective feedback circuit having a central frequency synchronized with a reference frequency and including means for integrating the signals from the vibration detectors, and filter means for eliminating transient signals at frequencies unrelated to the reference frequency, thereby causing the compensation ring to exert a rotary compensation force on the rotor via the radial magnetic bearing, said compensation force being equal to the centrifugal force due to the out-of-balance mass of the rotor but being phase-shifted by 180° relative thereto.