Additively Manufactured Ferrite Permanent Magnet Rotor with 3D Flux for Efficient Utilization of the Overhang Volume and Enhanced Performance

Abstract

Additive manufacturing (AM) is an emerging manufacturing approach that offers improved sustainability metrics and high geometric design freedom. In addition, it enables magnetic flux guidance in three dimensions while maintaining high magnetic permeability and mechanical strength. This study leverages AM to propose a new spoke-type ferrite permanent magnet (PM) rotor that offers enhanced electromagnetic performance beyond traditional laminated designs within a fixed frame size. The proposed concept deliberately exploits the rotor overhang region to accommodate a larger volume of low-cost ferrite PM and create a strong fluxfocusing effect via guided 3D flux paths. This concept is particularly advantageous in designs with low-cost non-rarearth PMs, which generally exhibit low air-gap flux density. An analytical model that accounts for the 3D features of the rotor is also developed to reduce computational time in the initial design stage. Moreover, a comprehensive comparison with a traditional laminated rotor under identical frame size, current, and air-gap is conducted. The analysis indicates that the proposed 3D printed design delivers significantly higher air-gap flux in a fixed frame size, leading to a 47% increase in back-emf and a 35% increase in torque, along with improved power factor and efficiency. To validate the concept, the proposed rotor is printed via laser powder bed fusion and tested against a laminated prototype.