Abstract: A device is disclosed for compensating synchronous disturbances in the magnetic suspension system of a rotor which is supported by a radial electromagnetic bearing and which has means associated therewith for detecting the radial position of the rotor, comprising a servo-circuit for connection between the detecting means and windings of the electromagnetic bearing and including a circuit for the control of the current supply to the windings in response to signals from the detecting means to keep the rotor in a pre-determined radial position. The servo-circuit is provided with means for filtering the signals supplied by the detecting means between the latter and the control circuit, the filtering means having at least one band rejection filter centered on a frequency which is a direct function of the speed of rotation of the rotor.