Effect of nonlinear permeability on attractive force and counter torque in a magnetic bearing model

This paper deals with the eddy current problem in a magnetic bearing model, with the object of clarifying the effects of nonlinear permeability. Eddy currents induced in the rotating shaft show both demagnetizing effect and cross-magnetizing effect on the main flux of electromagnets. We treat these effects for the case when nonlinear permeability material is used as a shaft. For the two assumed magnetizing characteristics, flux distributions, attractive forces and counter torques are calculated and examined. In addition to the permeability effect, exciting current effect on eddy currents has also been clarified. For the benefit of comparison, we also show flux distribution diagrams for linear permeability case.