## 5 Experimental Investigations
It should also be noted that changing the dosing capacitor value \(C_{d1}\)--\(C_{d3}\) leads to a proportional change of the output power in accordance with Equation (25). Furthermore, operating zero current switch (ZCS) mode of the switches is maintained (Figure 12). The research conclusion is that changing the power value by electronic switches might be acceptable as one of the directions to be followed in creating a special HF power supply for EV charging stations. By changing the values \(E\), \(C_{d}\), or \(f\), it is possible to regulate the output voltage or to fix an assigned level for it. \[U_{LOAD}=\sqrt{C_{d}}\Big{[}E\sqrt{4 fR_{L}}\Big{]}/cos\varphi_{L} \tag{31}\]  
Equation (31) suggests that the output voltage can be maintained at a constant if the \(C_{d}\) capacitor value is varied when the load and/or input DC voltage are changed. Another very important advantage about flexibility of the developed charging station is that load matching can be controlled with a suitable selection of primary matching capacitor value (15), by electronic switches, during the charging process. The test results are summarized in Figure 13. They represent the electrical parameters \(L_{1}\), \(L_{2}\), \(M\), \(k\) as a function of the distance between the transmitting and receiving coils (50-200 mm) and horizontal misalignment (0/0-200/200 mm). The condition is to maintain resonance at the HF inverter output in the whole range of possible coil positions. In accordance with the required capacitor values, matching is proposed to be affected with three capacitors--one main capacitor with capacity of 1.1 \(\upmu\)F, and two additional ones with capacities of 0.1 \(\upmu\)F and 0.2 \(\upmu\)F. Figure 13 shows the algorithm for selection of the right capacitor values using appropriate shading. The accuracy and range of this method of dynamic matching depends on the number of electronic switches and capacitors values. It is important to note that, with different capacitor values, the transistors switch on and off at zero current, and the transient processes do not generate transistor current and voltage overload. Figure 14 shows the current through transistors at the variation of matching capacitors from 25% \(C_{1}\) to 100% \(C_{1}\) and from 100% \(C_{1}\) to 25% \(C_{1}\). It should be noted in both cases that the transient processes finish for one or two periods, ensuring the transistors' safe operating conditions. Figure 12: The current through AC diagonal of AI with ED at different dosing capacitor: 1–100% \(\text{P}_{\text{RATED}}\); 2–75% \(\text{P}_{\text{RATED}}\); 3–50% \(\text{P}_{\text{RATED}}\); 4–25% \(\text{P}_{\text{RATED}}\). The optimal matching at different positioning between the two coils is related to maximum efficiency, in accordance with Figure 13. Therefore, the range of operational air gap and horizontal misalignment of the IPT system must be selected very carefully. Figure 15 presents the dependence of efficiency as a function of horizontal misalignment between the coils and a vertical distance between them of 100 mm. These measurements are valid for static and dynamic charge, as the configuration of the contactless module remains unchanged. In order to assess the losses, the magnitudes of the currents and voltages and the phase angle between them are measured, as are the input and output of the HF inverter and the IPT module. In addition to this, the IPT module has been tested in short circuit and with no load in order to calculate the parameters of its equivalent circuit. The abovementioned measurements were performed in order to precisely define the equivalent parameters and the losses in each part of the wireless charge station. The total max efficiency of the charging station from the mains to the battery at zero misalignment is 90-92%.