Transverse-flux motor for enhanced torque and reduction of torque ripple

Windings are significant factors affecting the manufacturing cost and reliability of motors. For use in electric vehicles, motors should be highly efficient, inexpensive, and highly reliable; moreover, high efficiency and reliability are major requirements for wind generators. Unfortunately, the armature windings of such motors are difficult to manufacture with automated techniques and are not very reliable. Thus, to obtain a motor at a low cost and with high reliability, we investigated a transverse-flux motor (TFM) containing a torus coil. In this study, we propose a novel TFM capable of increasing torque and discuss its basic characteristics and reduction of torque ripple. The rotor comprises radially magnetized permanent magnets, and the stator comprises torus coils and axial 9-shaped cores. The stator core is alternately arranged in the circumferential direction and has radial and axial air gaps. Furthermore, each core component of the same phase unit of the stator is arranged so as to shift the relative angular position to other core components to reduce torque ripple. The results of our analysis confirm that the enhanced TFM produces a high torque per motor volume of 4.88 kN·m/m³ and reduces the torque ripple up to 7%.