Inductances and forces of a three phase permanent magnet biased radial active magnetic bearing in dependence on the rotor eccentricity

The paper discusses a novel arrangement of a permanent magnet biased radial active magnetic bearing with three poles. The control currents of the three poles produce a heteropolar distribution of the magnetic field whereas the permanent magnets cause a homopolar configuration of the magnetic field. Therefore, 3D finite element analyses have to be used to accurately obtain the steady-state parameters such as inductances and electromagnetic forces. With the intent of finally using a position-sensorless control algorithm for the hybrid magnetic bearing, in particular the dependence of the electromagnetic parameters on the rotor position is of great interest. The presented results are focussed on the inductances of the three coils carrying the control currents and the electromagnetic forces acting on the rotor in dependence on the various eccentric rotor position.