# Research on Three-Phase Wireless Power Transfer System
## 3 Experiment and Analysis
### Laboratory Experiment  
In order to verify the effectiveness of the proposed method and the simulation results, a laboratory experimental platform is constructed based on the proposed three-phase wireless power transfer system to verify the feasibility and performance of the system. The laboratory experimental platform is shown in Figure 12. The laboratory experimental platform consists of a power supply part, a control circuit, a transmitting part, and a receiving part. The power supply part includes a power module, DSP, and inverter circuit. The power module provides the required direct current, and DSP is used to control the inverter circuit to convert the direct current into three-phase alternating current. The IXFH160N15T2 switch tube is used in the inverter circuit. The transmitting part includes a transmitting coil and a resonant capacitor. The receiving part includes a receiving coil, a resonant capacitor, a rectifier circuit, and a load. The inductance of the primary side coil and the secondary side coil is 31 \(\upmu\)H, the compensation capacitance of the primary side and the secondary side is 0.36 \(\upmu\)F, the secondary side load uses a resistance box, and the resistance is set to 2 \(\Omega\). The detailed parameters of the system are shown in Table 3.  
Figure 11: The output phase voltage and current waveform at the receiving end. Figure 10: Three-phase transmitter input line voltage and current waveform. Figure 13 shows the experimental waveform of line voltage and phase current under power transmission of 200 W. From the resulting diagram, it can be seen that the output voltage has positive and negative symmetry, with some jagged ripples. These fluctuations can be further reduced by adjusting the circuit parameters and resonant frequency. However, the overall control effect is relatively stable. The control signal of the switch tube is the same as the control strategy, which indicates that the inverter circuit can effectively generate symmetrical AC voltage output. The output current is sinusoidal, which indicates that the system can effectively convert DC energy into AC energy and transmit it to the receiving end through the electromagnetic coupling coil. The phase relationship between voltage and current is consistent, which indicates that the power transmission is effective, and the phase relationship between voltage and current is in line with theoretical expectations. In addition, the experimental results show that the sinusoidal symmetry of the output current is good, the output voltage is stable, and the smooth waveform also shows that the power transmission efficiency of the system is high and the energy loss is small, which further proves the good performance of the system. By comparing the experimental results with the Simulink simulation results in Figure 10, it can be found that they are basically the same, which further verifies the effectiveness and reliability of the system in power transmission. We measured the DC input power of 200 W and calculated the output power to be about 166.05 W. However, by measuring the control part of the circuit, there is a loss of 20 W: the switching frequency of the control system is 47.5 kHz, the switching time is 50 ns, and the dead time is 600 ns. The higher switching frequency may lead to more switching losses, and the dead time also affects the efficiency of the power converter. The total loss of this part is 15 W, plus the loss of the control circuit, on-resistance, and driving circuit is 20 W, so the AC-AC efficiency of the three-phase system reaches 92.25%. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Symbol** & **Value** \\ \hline Power supply & \(U_{dc}\) & 50 V \\ Transmitting coil & \(L_{p}\) & 31 \(\mu\)H \\ self-inductance & \(C_{p}\) & 360 nF \\ Resonant capacitor & \(L_{s}\) & 31 \(\mu\)H \\ Resonant capacitor & \(C_{s}\) & 360 nF \\ Load & \(R_{L}\) & 2.5 \(\Omega\) \\ Frequency & \(f\) & 47.5 kHz \\ Power supply voltage & \(U\) & 52.7 V \\ \hline \hline \end{tabular}
\end{table}