Analysis of eddy-current loss for design of small active magnetic bearings with solid core and rotor

As the size of rotors levitated by active magnetic bearings (AMBs) gets smaller, it becomes increasingly difficult to make laminated cores and rotors that have low eddy-current loss, and solid cores and rotors have to be substituted. Thus, accurate modeling of eddy-current loss is important for small-size AMB systems with solid cores and rotor. In this paper, we propose a new eddy-current loss model for AMB systems, based on the eddy-current brake concept. We show that the eddy-current loss in AMBs strongly depends on the arrangement and size of poles. We compare test results for hetero- and homopolar AMBs having nonlaminated cores and rotor to analytical findings based on the eddy-current loss model. The experimental results confirm that the eddycurrent loss in small homopolar AMBs with nonlaminated cores and rotor can be greatly reduced by optimizing the arrangement and size of poles.