## 4 Results and Discussion
### Differences in System Transmission Performance  
In this section, we compare the differences in transmission performance between the HTS-Cu and Cu-Cu systems when azimuthal misalignment occurred under coaxial alignment conditions, as well as under different lateral misalignment conditions with azimuthal misalignment.  
In order to investigate the performance improvement of WPT systems using HTS coils, and to make a quantitative comparison analysis of their transmission performance, we defined the increase in transmission efficiency (\(\Delta\)PTE) as follows:  
\[\Delta PTE=PTE_{\text{:}HTS-Cu}-PTE_{\text{:}Cu-Cu} \tag{9}\]  
Similarly, following reference [8], the increase ratio of LOP (\(\xi_{\text{P}}\)) can be expressed as:  
\[\xi p=\frac{P_{out\text{:}HTS-Cu}\ -\ P_{out\text{:}Cu-Cu}}{P_{out\text{:}Cu-Cu}} \tag{10}\]  
Figure 8 illustrates the \(\Delta\)PTE and \(\xi_{\text{P}}\) of HTS-WPT and Cu-WPT systems under coaxial alignment of the coils. It can be observed that when the azimuthal misalignment angle between the coils is 90\({}^{\circ}\), the minimum value of \(\Delta\)PTE is 0.13%, indicating that when the transmitting and receiving coils are completely perpendicular to each other, the mutual inductance between the systems tends to be zero, and the improvement of the superconducting WPT system on the transmission efficiency is very limited. When the azimuthal misalignment angle is 70\({}^{\circ}\), the maximum value of \(\Delta\)PTE is 12.3%, and the \(\Delta\)PTE of the systems corresponding to other azimuthal misalignment angles can be stabilized at 9.4\(-\)12.3%, which indicates that the superconducting coil has a higher quality factor and lower electromagnetic loss. At the same time, it can be observed that the power enhancement of the WPT system with superconducting coils is much more significant than \(\Delta\)PTE. In the full range of azimuthal misalignment from 0\({}^{\circ}\) to 90\({}^{\circ}\), \(\xi_{\text{P}}\) values are between 61.9% and 71.0%, which means that the HTS system is more sensitive to changes in transmission power. Therefore, by introducing high-Q HTS coils, both the output power and efficiency have been significantly improved.  
Figure 9 shows the \(\Delta\)PTE and \(\varepsilon\)P of the HTS-WPT and Cu-WPT systems under lateral misalignment distances of 4 cm and 8 cm. For the case of \(\blacktriangle=4\) cm, it can be observed that, except for the azimuthal misalignment of 90\({}^{\circ}\), where the minimum value of \(\Delta\)PTE is 6.11%, the values of \(\Delta\)PTE are stable and mostly within the range of 8%\(-\)9.8% for any other azimuthal misalignment angles. Additionally, the \(\varepsilon_{\rm p}\) value reaches its minimum of 60.2% at an azimuthal misalignment angle of 50\({}^{\circ}\) and its maximum of 66.3% at an azimuthal misalignment angle of 70\({}^{\circ}\). For the case of \(\blacktriangle=8\) cm, the minimum value of \(\Delta\)PTE is 7.4% at a deviation angle of 0\({}^{\circ}\), and the maximum value is 11.1% at a deviation angle of 80\({}^{\circ}\). Unlike the completely aligned and laterally displaced by 4 cm cases, at a deviation angle of 90\({}^{\circ}\), \(\Delta\)PTE can still reach a relatively high value of 10.6%, indicating that the HTS coil can still maintain a strong electromagnetic coupling with the WPT system under this condition due to its larger mutual inductance compared to the previous two cases. For \(\varepsilon_{\rm p}\), its range of values is between 64.6% and 84.3%. Overall, the experimental results demonstrate that replacing copper coils with HTS coils can significantly improve the transmission efficiency and transmission power of the WPT system.  
Figure 9: APTE and \(\underline{\varepsilon}\), with different deflection angles: (**a**) lateral misalignment of 4 cm; (**b**) lateral misalignment of 8 cm.