Reduction of the torque ripple and magnetic force of a rotatory two-phase transverse flux machine using herringbone teeth

The transverse flux machine (TFM) is a promising driving machine, especially for the low-speed applications, because it has greater power density, torque, and efficiency than the conventional electrical motors. However, the TFM has a complicated structure, a large torque ripple, and, occasionally, an unbalanced magnetic force. This paper investigates the effects of teeth geometry on torque ripple and unbalanced magnetic force in a rotatory two-phase TFM using the 3-D finite element method, and proposes a rotatory two-phase TFM with herringbone teeth to reduce the torque ripple and eliminate the unbalanced magnetic force. Index Terms--Herringbone teeth, torque ripple, transverse flux machine (TFM), unbalanced magnetic force.