Scaling of magnetically levitated homopolar hollow-shaft machines

In this paper, we analyze scaling issues that arise when the size of a magnetically levitated hollow-shaft machine is varied, but the output power is kept constant. Reducing the size by a factor of two leads to a required increase in speed by a factor of about three. Because the losses of previously used topologies did not scale well we suggest and analyze a different topology: the combined homopolar magnetic bearing (CHB). The proposed design methodology has been experimentally verified in a prototype product.