Design and Analysis of a New Separated Type Permanent Magnet Machine Based on Bidirectional Field Modulation Effect

This article proposes a new separated type permanent magnet (ST-PM) excitation machine (STPMM) based on bidirectional field modulation effect, which has the merits of high quality output torque and high power density. ST-PM can be designed by separating rotor surface-mounted PM into one piece radially excited outer PM and two pieces circumferentially excited inner PMs. This design takes advantage of high airgap flux density, which can be achieved by extending the length and adjusting the rotating angle of inner PMs. The operating principle and design method of the proposed STPMM are provided including the key design parameters. The analytical modeling considering rotating angle of inner PMs in STPMM and bidirectional field modulation effect is presented. The electromagnetic performances of the proposed STPMM are evaluated using finite-element analysis (FEA) and compared with the conventional designs. The FEA-predicted results show that the proposed STPMM exhibits high quality electromagnetic performances. The prototype of the proposed STPMM is manufactured and tested, then, the experimental result confirms the advantages of the new machine topology.