## 4 Comparative Evaluation of Magnetic Gear Core Materials
### Powder Metallurgy
However, due to its high electrical conductivity, Vacodur 50A may suffer significant eddy current losses when used in bulk form under varying magnetic fields. Therefore, it is recommended to apply fine laminations when using this material in such systems. With proper lamination, these losses can be reduced to a tolerable level while maintaining high magnetic performance. On the downside, Vacodur 50A's high cost and processing difficulties are limiting factors for widespread industrial use. M400 50A electrical steel offers a more balanced profile, providing moderate saturation flux density (2.10 T) and high manufacturability (90/100). When evaluated from a cost-performance perspective, it emerges as a suitable candidate for mass production-focused industrial applications. However, due to its high electrical conductivity, it may also experience elevated eddy current losses in variable magnetic field environments unless laminated [90]. \begin{table}
\begin{tabular}{l l l l l} \hline \hline
**Material** & **Production Method** & **Prototype** & **Mass Production** & **Average** \\ \hline \multirow{4}{*}{M400-50A} & Machining & 85 & 75 & \multirow{4}{*}{59} \\  & Wire EDM & 80 & 40 & \\  & Investment Casting & 30 & 60 & \\  & Powder Metallurgy & 40 & 65 & \\ \hline \multirow{4}{*}{Somaloy 700 HR 5P} & Machining & 25 & 10 & \multirow{4}{*}{22} \\  & Wire EDM & 10 & 0 & \\ \cline{1-1}  & Investment Casting & 0 & 0 & \\ \cline{1-1}  & Powder Metallurgy & 40 & 90 & \\ \hline \multirow{4}{*}{Vacodur 50A} & Machining & 50 & 30 & \multirow{4}{*}{36} \\  & Wire EDM & 70 & 25 & \\ \cline{1-1}  & Investment Casting & 20 & 55 & \\ \cline{1-1}  & Powder Metallurgy & 15 & 25 & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Core material manufacturing feasibility scores (0–100). Somaloy 700 HR 5P, on the other hand, offers significant advantages in low core loss, low density, and ease of production in complex 3D geometries through powder metallurgy. Although it exhibits lower values in relative permeability and magnetic saturation parameters, its extremely low electrical conductivity (\(\approx\)10\({}^{-4}\) S/m) enables manufacturing in a solid form. This feature allows for the creation of low-loss structures without lamination, particularly in applications exposed to varying magnetic fields where eddy current losses must be avoided. Thus, SMC materials offer strategic advantages for transverse flux machines, magnetic gears, and compact 3D magnetic circuits. In summary, the radar chart reveals that Vacodur 50A is well-suited for high-performance, specialized applications; M400 50A is ideal for general industrial use; and Somaloy 700 HR 5P is preferred for niche applications requiring low losses and flexible production capabilities. The multidimensional comparisons based on the radar chart provide crucial insights into the general performance profiles of the materials. However, to further deepen this evaluation, it is essential to analyze the fundamental magnetic characteristics of these materials. For this purpose, the B-H characteristic curves and permeability curves of the materials are presented and discussed below. Figure 14 illustrates the B-H characteristics of M400-50A, Somaloy 700 HR 5P, and Vacodur 50. These curves reveal the materials' tendencies to reach magnetic saturation flux density (Bs) and their magnetic permeability behavior. Vacodur 50 achieves the highest saturation level at 2.35 T, offering a significant advantage in applications requiring high magnetic flux density. Although Somaloy 700 HR 5P exhibits a relatively lower saturation level, it stands out due to its low core loss characteristics. Studies on the performance of materials used in magnetic gear systems have particularly compared SMC and steel-based core materials. Experimental and numerical analyses have shown that SMC cores are  
Figure 13: Performance comparison of materials using normalized radar chart). (**a**) Electrical steel (M400 50A), (**b**) Cobalt steel (Vacodur 50A), (**c**) Iron powder (Somaloy 700 HR 5P).