# Design of Magnetic Concrete for Inductive Power Transfer System in Rail Applications
## 4 Results and Discussion
### Thermal Analysis in IPT Systems  
The thermal analysis of the IPT systems, conducted using the Ansys simulation package, evaluates the thermal behavior of various coupler designs to ensure efficient system operation under diverse conditions while maintaining thermal stability and performance integrity. The temperature distribution for the coupler design with ferrite bars (referred to as Coupler Design 1) is presented in Figure 12. The color-coded scale illustrates temperature variations, with red indicating the highest temperatures and blue representing the lowest. The thermal simulation of this design provides a detailed temperature profile across the coupler, closely aligning with experimental tests conducted on the current design, thereby confirming the accuracy and reliability of the Ansys simulation package for thermal analysis in IPT systems. \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Parameter** & **W-I ferrite Cores** & **Magnetic Concrete** & **Normal Concrete** \\ \hline Coupling & & & \\ Coefficient, k & 0.236 & 0.232 & 0.193 \\ Power Efficiency, \% & 90.85 & 89.71 & 84.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Simulation results for power efficiency comparison with different materials. \begin{table}
\begin{tabular}{l l l} \hline \hline
**Parameter** & **W-I ferrite Cores** & **Magnetic Concrete** \\ \hline Power Efficiency, \% & 89.17 & 88.12 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Experiment results for power efficiency comparison with different materials. This study also explores the temperature distributions for the coupler design with magnetic concrete (Coupler Design 2) and a design utilizing normal concrete (Coupler Design 3), as shown in Figures 13 and 14, respectively. These simulations were performed under identical operating conditions, including a 12.7 cm air gap between the transmitter and receiver coils, a frequency of 85 kHz, and an output power of 3 kW. The analysis highlights localized hotspots, particularly in areas with high magnetic flux density. Notably, the inclusion of magnetic concrete in Coupler Design 2 demonstrates improved thermal behavior, with a more uniform temperature distribution compared to the ferrite and normal concrete designs. This improvement is attributed to the enhanced thermal conductivity and magnetic properties of magnetic concrete. The results for Coupler Design 3 (Figure 14) reveal increased localized heating and less efficient heat dissipation, which may lead to higher thermal stress and material degradation. These findings underscore the limitations of standard concrete as a coupler material in high-power IPT systems and highlight the advantages of magnetic concrete in addressing these challenges. Figure 12: Thermal distribution for Coupler Design 1 using ferrite cores. Figure 13: Thermal distribution for Coupler Design 2 with magnetic concrete. Due to the amount of ferrite powder added to the magnetic concrete, the influence on temperature increase is less significant when compared to the electromagnetic effects. This is evident when comparing Figures 13 and 14, where the maximum temperature increases due to magnetic concrete comprising less than 0.3%. The incorporation of magnetic concrete into IPT systems is expected to provide a more uniform temperature distribution and reduced hotspots due to its higher thermal conductivity and magnetic properties. Experimental thermal imaging further validates these findings, as shown in Figure 15. The thermal images show the actual temperature distribution across the system during operation, highlighting the lower temperatures and more evenly distributed heat in the transmitter coil employing magnetic concrete. Even though no quantitative assessment has been performed on the full-size IPT transmitters, the findings of this study, nonetheless, validate the feasibility of magnetic concrete as a material for high-power wireless power transfer applications.