Novel structure of bearingless flux-switching motor for improvement of levitation force characteristics

Due to the temperature sensitivity and the cost issue of permanent magnets, the application of electrical machines with permanent magnets on the rotor are limited in spaces with high-temperature as well as disposable fields. To deal with these problems, bearingless flux-switching motor, which is a kind of electrical motors with permanent magnets located in the stator, is studied in this paper. Firstly, the principle of levitation force generation and its characteristics are illustrated and analyzed respectively. Then the mathematical model and levitation control strategy are derived under the assumption of large air-gap length. However, even if with the assumption of large air-gap, it still has unsymmetrical DC components in levitation current, which brings about complicated control effort. In addition, large air-gap length must lead to the reduction of density of levitation force and torque. Aiming at improvement of the characteristics of levitation force and simplification of the control strategy without under larger air-gap length assumption, a novel topology of bearingless flux-switching motor with paralleled structure is proposed. Detailed performance analysis and evaluation are performed by FEM for verification the effectiveness of the proposed topology.