Thrust Characteristics Improvement of a Circular Shaft Motor for Direct-Drive Applications

This paper presents a semicircular tubular linear machine model, which is called a circular shaft motor (CSM), with trapezoidal magnets. For a conventional CSM system, the stator is difficult to construct as designed, and the thrust characteristics are not high enough. The proposed CSM model includes trapezoidal magnets that are magnetized in the axial direction. This structure can facilitate the construction of the stator and decrease the thrust ripple. In addition, the magnetic flux characteristics are shown as new results of a CSM. Magnetic field is related to thrust characteristics closely. By investigating magnetic distribution characteristics, it is shown that the proposed model can improve magnetic field characteristics. In this paper, the structure of the proposed CSM model is described. The improvement in the thrust characteristics is verified by magnetic field analysis. The thrust characteristics of the proposed CSM system are verified in a thrust characteristics test. The magnetic flux characteristics of the proposed CSM system are compared with those of a conventional CSM system to evaluate the thrust characteristics.