Additively Manufactured Spoke-type Permanent Magnet Rotors: Solutions to Multidisciplinary Design Challenges and Comparison with Traditional Design

Abstract

Sustainability in electrical machines demands minimizing material waste, eliminating rare-earth permanent magnets (PMs), and improving efficiency and reliability. Additive manufacturing (AM) offers a promising pathway toward these goals by enabling near-zero material waste, streamlined production, and enhanced design freedom. This study leverages the compatibility of spoke-type rotor configurations with nonrare-earth PMs and the unique advantages of AM to achieve a highly sustainable design. The paper proposes innovative solutions to address the existing challenges of using AM for developing ferrite PM rotor topologies and provides a comprehensive comparison with traditional laminated topology. A novel technique is presented, reducing torque ripple from 42% to 16%, and voltage THD from 11% to 5%. The proposed solution not only maintains the average torque but also avoids added manufacturing complexity and cost, unlike skewing techniques. Moreover, a new grooving technique is implemented, reducing the eddy current loss in the bulk rotor by more than 40%. A spoke-type design with open bridges is selected over the closed-bridge design, and a comprehensive multidisciplinary analysis is conducted. Two spoke-type rotors are 3D printed, and one traditional laminated rotor is manufactured. The experimental comparisons show that the proposed 3D printed rotors outperform the laminated design in terms of torque ripple, voltage THD, and material usage, while offering comparable power rating and back-emf.