Torque Improvement in Spoke-Type Interior Permanent Magnet Motors Using Resin-Unit-Type Shaft Fastening Structures

This paper presents a novel rotor structure for spoke-type interior permanent magnet motors. In the proposed motor, the rotor is fastened to the shaft using a resin unit. Thus, the inner-side core, which is the leakage path for the magnetic flux, can be eliminated. As a result, the torque density of the proposed motor can be improved compared with that of conventional motors without increasing the magnet volume. A numerical verification was performed using the finite element method to validate the effectiveness of the proposed structure. Moreover, the proposed structure was experimentally verified using a prototype motor. The results of numerical and experimental verifications indicate that the proposed structure could improve the torque density without increasing the magnet volume.