## 5 Experimental Investigations  
The developed static and dynamic inductive charging stations were tested at power \(P=10\)-\(5\) kW, frequency \(f=18\)-\(25\) kHz, vertical air gap between transmitting and receiving coils \(50\)-\(200\) mm, and horizontal misalignment up to \(\pm 200\) mm. In dynamic infrastructure four primary coils were built into a road and one for static infrastructure (see Figure 9) [9]. The main parts of the charging station are a full bridge AI with ED (Figure 7) and an IPT module presented in Figure 1 using the dimensions in Table 2. During the design of the primary and secondary coils, important tests were made for shielding the coils against electromagnetic field exposure. These design measures have respected the proper Directive of EC and its latest version from 2013. It is closely based on the guideline published by ICNIRP in the case of power and frequencies (ICNIRP 2010) [4; 16; 17]. Figure 9: Real tests: (**a**) static and (**b**) dynamic charging of of electric vehicles (EV). Figure 10 presents a characteristic, taken experimentally, of the HF power supply using the principle of energy dosing. This characteristic demonstrates the dependence of the output voltage and the power on the load resistance. It is evident that, when the load resistance Z increases, the voltage rises sufficiently to keep the power constant. When the load is in a state close to short circuit and idle running, the power naturally drops. The voltage in the case of a short circuit also decreases, and in idle running, it increases, but not as much as with the conventional circuits of autonomous inverters [7; 19; 20; 21; 22]. These results have been used to plot the load characteristic of AI with ED in case of battery charging. Figure 11 presents either of the studied modes of battery charge at two charging power values (current values) until the charge level SOC = 90%, when the process ends. The initial points in both charging scenarios start from SOC = 10% and SOC = 50%. At the beginning of the process of charging (0-500 s), the AI with ED maintains constant power and gradually increases in current value from 0.8\(I_{DC}\) to reach \(I_{DC}\). For the battery LiFePO4, the charging voltage can be calculated by following relationship:  
\[U_{BAT\ f}=U_{BAT\ 90\%}-I_{DC}R_{BAT}=310+0.9(374-310)-I_{DC}R_{BAT} \tag{30}\]  
where \(U_{BATf}\) is battery voltage in the end of charging process and \(U_{BAT\ 90\%}\) is battery voltage at SOC = 90%. From the implemented tests, it can be concluded that the charging source works most efficiently while maintaining maximum charging current or/and output power. Depending on the type of battery used, there is a maximum value of SOC, to which the charging process can be carried out--typically, SOC = 80 \(\div\) 90%. The time required for charging the battery depends on its SOC and the power of the charge station. As the transmitting coils are operating in pulse mode, they can be overloaded in order to \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \(\mathbf{x}\) & \(\mathbf{x_{0}}\) & \(\mathbf{x_{1}}\) & \(\mathbf{x_{2}}\) & \(\mathbf{x_{3}}\) & \(\mathbf{y}\) & \(\mathbf{y_{0}}\) & \(\mathbf{y_{1}}\) & \(\mathbf{y_{2}}\) & \(\mathbf{y_{3}}\) & \(\mathbf{z_{0}}\) & \(\mathbf{z}\) \\ \hline
920 & 800 & 175 & 450 & 60 & 820 & 700 & 175 & 350 & 60 & 90 & 50–200 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: IPT dimensions (all dimensions are in mm). Figure 10: Load characteristic of AI with ED. achieve shorter charging zone. At the other hand on highways there could be special lane for electric vehicles--by driving in it they can add a certain charge to their batteries and proceed to the nearest charge station. The expressions obtained from the circuit analysis and tests results allow to plot charging characteristics for different batteries. They define the area in which AI with ED can support constant output current and/or power.