Soo-Bum Kim

This paper presents the integrated design and experimental verification of a ferrite spoke permanent magnet motor with rib core skew for semiconductor process pump drives. Conventional induction motors are widely used in industrial pump systems because of their robustness and cost-effectiveness; however, rotor copper loss and limited output capability under a restricted installation envelope remain practical limitations. To address these issues without rare-earth magnets, a flux-concentrating ferrite spoke rotor is applied. The proposed design procedure considers the baseline induction motor envelope, electric and magnetic loadings, manufacturable winding specifications, voltage and current density limits, irreversible demagnetization, and post-assembly magnetization feasibility. An 8-pole/12-slot topology is selected because it enables one-shot post-assembly magnetization, unlike the 10-pole/12-slot alternative requiring segmented magnetization. Rib core skew and stator tooth shoe chamfer geometries are then applied to reduce cogging torque and load torque ripple. A prototype is fabricated and tested. At 1000 rpm, the measured no-load line-to-line voltage is 21.6 V_rms. At 7000 rpm, the prototype achieves 4.028 kW output power and 93.1% efficiency. The measured post-assembly magnetization ratio is 98.7%, and the maximum winding temperature recorded during an approximately 50 min water-cooled test at 6.68 A/mm² is 57.4 °C. These results confirm the feasibility of the proposed design procedure.

This paper presents the integrated design and experimental verification of a ferrite spoke permanent magnet motor with rib-core skew for semiconductor process pump drives. Conventional induction motors are widely used in industrial pump systems because of their robustness and cost effectiveness; however, rotor copper loss and limited output capability under a restricted installation envelope remain practical limitations. To address these issues without rare-earth magnets, a flux-concentrating ferrite spoke rotor is applied. The proposed design procedure considers the baseline induction-motor envelope, electric and magnetic loadings, manufacturable winding specifications, voltage and current-density limits, irreversible demagnetization, and post-assembly magnetization feasibility. An 8-pole/12-slot topology is selected because it enables one-shot post-assembly magnetization, unlike the 10-pole/12-slot alternative requiring segmented magnetization. Rib-core skew and stator tooth-shoe chamfer geometries are then applied to reduce cogging torque and load torque ripple. A prototype is fabricated and tested. At 1000 rpm, the measured no-load line-to-line voltage is 21.6 V_rms. At 7000 rpm, the prototype achieves 4.028 kW output power and 93.1% efficiency. The measured post-assembly magnetization ratio is 98.7%, and the maximum winding temperature is 57.4°C at 6.68 A/mm². These results confirm the feasibility of the proposed design procedure.

Axial Flux Permanent Magnet Synchronous Motor (AFPMSM) offers high power density in structures with short axial lengths and large radial dimensions, making it attractive for applications that require thin structures, such as in-wheel motors. This study proposes an AFPMSM design process applicable under fixed inner/outer diameter and axial length constraints. The proposed process is presented as step-by-step procedures: selection of pole/slot combinations, adjustment of slot depth, determination of stator/rotor dimensional ratios, and slot structure design. It is universally applicable to both bobbin-type rectangular wire windings and shoe-type round wire windings. The validity of the proposed process was verified through finite element method (FEM) analysis, and the differences between the two winding structures were examined through post-processing of the results. By presenting an AFPMSM design methodology that can be consistently applied under constrained spatial conditions, this study provides practical design guidelines for the development of in-wheel motors for next-generation mobility applications.