Three-dimensional finite element modeling of active magnetic bearings considering eddy current losses in laminated rotor

Active Magnetic Bearing (AMB) had proven good suitability to several applications over conventional bearing. They can best fit in oil lubricant free applications, extreme temperature environments and maintenance free requirements. Several industrial application are adopting smaller, higher speed and higher power density machines. In this paper homogenization approach which had been used successfully to emulate the macro electric and magnetic characteristics of transformer laminations is being applied to AMB rotor lamination structure. In such approach the rotor lamination region is defined as bulk anistropic material where the electric conductivity (σ) and relative magnetic permeability (μ_r) are defined with deferent values in the direction perpendicular to the lamination plan relative to their values in the directions parallel to it. Two FE models are developed for heteropolar and homopolar AMB. The calculated losses results are validated against experimental data. in addition to that the braking torque is obtained through Maxwell stress tensor and through run down method. Once the model is validated, it is then can be used in order to get an optimized design for the AMB targeting the minimum eddy current losses.