Transverse-Flux Motor Design With Skewed and Unequally Distributed Armature Cores for Reducing Cogging Torque

Transverse-flux motors have an advantage on realizing high torque density owing to their compatible design of a large number of poles and large magnetomotive force. However, many permanent magnets are required with increasing number of the poles, and that results in a big exertion for building magnet arrays. Thus, we have studied transverse-flux motors with a consequent-pole rotor having almost half amount of magnets compared with conventional magnet rotors. However, the consequent poles cause large cogging torque due to their deformed flux-density distribution. This paper presents magnetic-pole configuration for effectively reducing the cogging torque and its verification by magnetic analysis even though axially skewed configuration, commonly used, is difficult to be applied to transverse-flux motors due to their axially non-uniform structure. In this paper, radially skewed and unequally distributed configurations are introduced to the armature cores for eliminating the two most dominant harmonic components of the cogging torque. Analysis result indicates each configuration can eliminate the harmonic components selectively and effectively, and magnitude of the cogging torque decreases by 97.6%. These configurations can be applied to a wide variety of transverse-flux motors for eliminating any harmonic order of cogging torque, and can be considered to be promising techniques for realizing high torque density.