Design Considerations for 2-Level Bearingless Homopolar Motors

The simple rotor structure of 2-level bearingless homopolar motors provides a high mechanical and thermal robustness due to its saliency-based design without permanent magnets. The lack of permanent magnet materials in the rotor significantly reduces costs, but results in lower torque densities. To provide a qualitive overview of viable motor topologies for different stator and rotor pole combinations, this paper provides force and torque performance factors for 2-level bearingless homopolar motors with combined windings. The effects of different tangential displacement angles between the top and the bottom rotor level on the performance factors are investigated and numerically evaluated. Additionally, measurement results of a selected prototype are presented in the bearingless operation.