Development of IPMSM with rare earth and ferrite magnets

This paper presents our development of an interior permanent magnet synchronous motor (IPMSM) that reduces the amount of rare earth magnets required for its operation by changing the rotor structure. For comparison, as a standard, we employ a conventional IPMSM that uses only rare earth magnets. We introduce 2 types of rotor structures and analyze the average torque and torque ripple using the three-dimensional finite element method (3D-FEM). Compared to that in the conventional model, the quantity of rare earth magnets in the proposed rotor structures can be reduced by 58%. Instead of solely using rare earth magnets, we combine their use with a properly arranged ferrite magnet in the rotor to offset the reduction in magnetic flux. As a result, one of the proposed models shows the same average torque as that of the conventional model. Consequently, we confirm that the average torque in the final model is approximately equal to that in the conventional model and that the torque ripple is also improved.