Comparative study of rotor PM transverse flux machine and stator PM transverse flux machine with SMC cores

With the adoption of 3D magnetic flux material and global ring windings, permanent magnet transverse flux machine (PMTFM) with soft magnetic composite cores can output relatively high torque density and only requires easy manufacturing process. For the PMTFM, there are two ways to put the permanent magnets (PMs). One is to put the PMs on the rotor side which is the traditional rotor PM TFM and the other is to put the PMs on the stator side which is the stator PM TFM. In this paper, the design methods and operation principle for both kinds of PMTFM will be presented and discussed. Four different TFMs (benchmark rotor PM TFM with NdFeB, stator PM TFM1 with ferrite magnet and stator PM TFM2 and TFM3 with NdFeB) have been designed, and the magnetic parameters and the main performance will be comparatively studied to show the main difference between stator PM TFM and rotor PM TFM. It can be seen that the stator PM TFM has better performance, and the stator PM TFM1 with ferrite magnets can have the same torque ability as that of the rotor PM TFM with NdFeB magnet but with very low material cost. With the adoption of NdFeB, the stator PM TFM2 can have two times higher torque ability than the rotor PM TFM, and the stator PM TFM2 can have the same torque ability as that of rotor PM TFM but with much smaller volume. As for the power factor and efficiency, it can be seen that the adoption of ferrite magnet will reduce both of them, and there is no much difference for the place where the PMs are installed.