Exact Torque and Force Model of Bearingless Electric Machines

This paper proposes and develops a new and exact analytic electric machine model that has several potential advantages. The model can be used to address levitation performance requirements by developing exact force/torque regulation methods to precisely calculate commands to current regulators. This allows relaxing constraints during the design stage and has the potential to enable consideration of higher performance bearingless machines. Furthermore, analogous to torque enhancement in conventional electric machines, the proposed model can be used to identify options for suspension force enhancement by controlling multiple magnetic field harmonics. This paper provides a detailed derivation of the model and shows how it can be used to improve force regulation accuracy and enhance force density.