Optimal design of partitioned primary linear switched flux PM machines

Due to the high efficiency and force density, linear switched flux permanent magnet machine (LSF-PMM) is gaining more and more attention in direct drive technology. For conventional LSFPPM, the structure enables the PMs and windings to be arranged on the same side, which largely reduces the manufacture cost. However, with the insert of PMs into adjacent teeth, limited by the volume of primary, the slot area has to be reduced. That is to say, the trade-off between PM and winding space should always be taken into consideration. This paper proposes a new structure of LSFPMM, in which primary is divided into two parts, one containing windings and the other containing PMs, and the shape of secondary is also different from conventional ones. A 9 primary/10 secondary poles LSFPMM is investigated to validate the new structure. The 3D schematic and 2D cross section views of the new structure are shown. It can be seen that the primary is divided into two parts: windings and magnets are separately arranged so that slot area can be larger; also, magnet can be thicker in the magnetized direction at the same time. Since the total height increases compared with conventional structure, the lamination width is reduced correspondingly to maintain the total volume of the machine.