# A Multi-Domain Model for Variable Gap Iron-Cored Wireless Power Transmission System
## 5 Experimental Validation and Results Comparisons
### The Experimental Apparatus  
The experimental apparatus used during the dynamic analysis of the campaign is reported in Figure 9. Figure 10 shows a schematic representation of the two main measured circuits. The two reported schematics essentially present the same component connection, with the only exception being a capacitor on the load side. Figure 10a identifies the  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{4}{c}{**Lumped Parameters**} \\ \hline
**Description** & **Parameter** & **Value** & **Unit** \\ \hline Measured DC resistance of the emitter side coil & \(R_{\text{DC1}}\) & 0.514 & \([\Omega]\) \\ Measured DC resistance of the receiver side coil & \(R_{\text{DC2}}\) & 0.9370 & \([\Omega]\) \\ Measured inductance of the stand-alone emitter inductor & \(L_{\text{11}}\) & 11.74 & \([\text{\mu F}]\) \\ Measured inductance of the stand-alone receiver inductor & \(L_{\text{22}}\) & 38.14 & \([\text{\mu F}]\) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Measured values of the stand-alone inductors.  
Figure 8: Wireless power transfer device under analysis.  
schematic used for the validation of the co-simulation model under the time domain, while Figure 10b depicts the circuit used for the frequency domain validation. The apparatus is composed of a function generator that introduces an AC sinusoidal voltage excitation on the emitter side, sampled through so-called Channel 1 of the oscilloscope. The current circulating in the primary side is measured by the Channel 2 probe through the voltage drop across a shunt resistor. The introduced excitation induces a voltage through the coupled WPT that is measured across the receiver via the probe called Channel 3. Depending on the measuring circuit, this induced power is absorbed by the load side, which can only consist of a resistor or a parallel between a resistor and a capacitor. The most significant features of the electric parameters are reported below in Table 2.  
Finally, in order to provide an appropriate explanation of the used experimental apparatus, it is important to describe the controlled gap mover device. The main body of the system consists of a stationary frame and a mobile frame guided by two parallel round  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **Lumped Circuit Parameters** & \\ \hline
**Component** & **Value** & **Unit** \\ \hline Function generator amplitude range & 0–10 & [V] \\ Function generator frequency range & 0–1 & [MHz] \\ Rshunt1 & 22 & [\(\Omega\)] \\ Rshunt2 & 600 & [\(\Omega\)] \\ Cloud & 1 & [nF] \\ \hline \hline \end{tabular}
\end{table}
Table 2: Nominal value properties of the components used during the experimental campaign.  
Figure 10: (**a**) Equivalent schematic of the experimental circuit for the time domain analysis; (**b**) equivalent schematic of the experimental circuit for the frequency domain analysis.  
Figure 9: Experimental apparatus.  
rail lines. The mobile part is driven by a nut-screw coupling which, through a controlled rotation of the lead screw, allows the fine adjustment of the air gap. This parameter is measured using a centesimal dial indicator, which is mounted on side A of the device (Figure 11a). On the other hand, on side B (Figure 11b) the two cored coils are mounted one on the stationary frame and one on the mobile frame, respectively. This WPT coupling resonator is fed and tested by the previously described experimental set-up.