## 3 Design and Preliminary Verification
### LCT Structure Design  
LCTs are generally designed with circular, square or rectangular structures. According to [26], square coils have higher mutual and self-inductance than circular coils of the same diameter. Moreover, the mutual inductance of square coils is more stable under horizontal offset, but the current at the corners of the square coils is typically uneven due to collector and proximity effects. To avoid the impact of the corners on the current and reduce loss, a rounded corner design can be selected. Therefore, both the transmitting coil \(L_{\text{p}}\) and the receiving coil \(L_{\text{s}}\) of the proposed LC/S compensated IPT system adopt a square coil structure with rounded corners. The specific parameters of the coils \(L_{\text{p}}\) and \(L_{\text{s}}\) are shown in Table 1.  
Since there is compensation inductance \(L_{1}\) on the transmitter side, it will generate unnecessary coupling interference with \(L_{\text{p}}\) and \(L_{\text{s}}\), which complicates the design and affects the efficiency of system energy transmission. Therefore, this article considers the decoupling design of the series compensation inductor \(L_{1}\) and LCT. According to [27], unipolar coils and bipolar coils placed in parallel have no coupled mutual inductance in case of alignment. Figure 4 shows the magnetic field distribution diagrams generated by unipolar and bipolar coils. \(B\) and \(I\) in the figure represent the magnetic field and current of the coils respectively. Generally, unipolar coils generate a magnetic field away from the center of the magnetic field, while bipolar coils produce a magnetic field distributed along the axis (long axis or width axis). When the unipolar coil and the bipolar coil are coaxially placed in parallel, since the magnetic flux generated by the bipolar coil is symmetrical along the space, the magnetic flux flowing into the unipolar coil is equal to the magnetic flux flowing out of the bipolar coil. Therefore, the unipolar coil and the bipolar coil are decoupled from each other, i.e., there is no coupled mutual inductance between them. This decoupling design can maximize the space utilization of the magnetic coupling coil, reduce the size of the IPT system, and ensure that the transmitting coil \(L_{\text{p}}\) transmits power only to the receiving coil \(L_{\text{s}}\), improving the transmission efficiency and stability of the system. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameters** & **Transmitting Coil \(L_{\text{p}}\)** & **Receiving Coil \(L_{\text{s}}\)** \\ \hline Outer diameter & 210 mm & 280 mm \\ Internal diameter & 156 mm & 196 mm \\ Turns of coils (n) & 9 & 14 \\ Specifications of Litz wire & 400 strands & 400 strands \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Dimensional parameters of the designed LCT. Figure 4: The magnetic field distribution diagram of the coils: (**a**) unipolar coil topology; (**b**) bipolar coil topology. To verify the correctness of the decoupling design according to the structural parameters in Table 1, a model of the compensation inductance \(L_{1}\) and LCT was created using the electromagnetic simulation software Maxwell, as shown in Figure 5. The compensation inductor \(L_{1}\) uses a bipolar (DD) coil, whereas the coils \(L_{\text{P}}\) and \(L_{\text{s}}\) employ square unipolar coil structures with rounded corners. Wherein \(L_{\text{P}}\) is placed immediately on \(L_{1}\), \(L_{\text{s}}\) is positioned directly above \(L_{\text{P}}\), and the three coils are placed coaxially and parallel. The ferrite is placed outside the coil to reduce series impedance and enhance electromagnetic performance.