Effect of magnetic pole arrangement on core loss in laminated high-speed magnetic journal bearings

Power losses in magnetic journal bearings as compared to rolling element or fluid film bearings are very low and normally negligible. However, as operating conditions become more severe, the power losses in magnetic bearings must be considered. This paper examines the effect of magnetic pole arrangement on the core loss of a magnetic journal bearing at high-speed and high-flux-density operation. Experimental core loss results are presented for rotational speeds up to 3.1 million DN and flux densities up to 1.60 T. These results are for a magnetic bearing constructed of cobalt iron. The results are compared to existing results for low-speed operation of silicon iron magnetic journal bearings. Results show that a paired pole arrangement gives a slightly less core loss than an alternating pole arrangement, and that this advantage is not necessarily negligible at high speeds and high flux densities for the cobalt iron bearing.