Conference: The 16th Joint Conference on Magnetism and Magnetic Materials and Intermag (2025 Joint MMM-Intermag)
Authors: Seung-Hun Lee, So-Yeon Im, Byeong-Cheol Bae, Myung-Seop Lim
DOI:
Coaxial magnetic gear (CMG) offers many advantages over mechanical gear, such as high torque density, high efficiency, low noise, and no tooth wear. To predict the performance of CMG through finite element analysis (FEA), it is essential to know the magnetic properties of the electrical steel sheets. The Epstein frame test (EFT) is widely used to obtain magnetic properties. However, for small geometry rotating machines or solid cores, the ring specimen test (RST) is preferred due to its simplicity and geometric similarity. Fig. 1 shows the fabricated ring specimens and magnetic properties data obtained by RST. Using this magnetic property data, the performance of the CMG is predicted through three-dimensional (3D) FEA. In 3D FEA, the high-speed rotor (HSR) and the low-speed rotor (LSR) are analyzed separately using EFT data and RST data, respectively. During this process, the pole piece is held constant using EFT data. As shown in Fig. 2, the 3D FEA results using EFT data indicate torques of 2.47 Nm (HSR) and 17.2 Nm (LSR), with an iron loss of 1.15 W. Using RST data, the torques are 2.44 Nm (HSR) and 16.9 Nm (LSR), with an iron loss of 1.59 W. Finally, to validate the CMG performance predicted based on the 3D FEA results, experiments are conducted. The experimental setup and results are shown in Fig. 2. The experimental results show that the HSR torque is 16.8 Nm and the LSR torque is 2.45 Nm. The torque prediction errors compared to the experimental results are 1.57 % for HSR and 2.38 % for LSR using EFT data, and 0.31 % for HSR and 0.6 % for LSR using RST data. This demonstrates that the accuracy of CMG performance predictions is superior when utilizing RST data compared to EFT data.