## 3 Operation of AC Power Router  
First, we verify the function of the single prototype AC power router for expected conditions experimentally. For this verification, we use two input ports 1 and 2, and two output ports A and B in the power router. Thus, we can select from two circuit topologies, _i.e._, \"1 and A\" and \"2 and B\" are connected or \"1 and B\" and \"2 and A\" are connected. After detecting the instance when the input voltages coincide with each other, the CPU in the power router sends a switching command signal to power switches in the routers to change the circuit topology. By causing the circuit to switch close to the equipotential instance, namely, _equipotential switching_, inrush current and surge voltage are suppressed [10]. However, it is inevitable to encounter some hard switching because of the delay between sending the switching signal and accomplishing the switch.  
To confirm the operation of the AC power router, two experiments are performed with two input power voltage sources as follows:  
\[\begin{array}{ll}\text{Experiment I.}&\text{input 1: 60 Hz/100 V}_{\mathrm{rms}},&\text{input 2: 60 Hz/90 V}_{\mathrm{rms}}\text{ with no phase difference}  
The power voltage sources connected to inputs 1 and 2 are a commercial power and an independently simulated power source, respectively. The independently simulated power voltage source can be operated at an arbitrary frequency, amplitude and phase. In the above-mentioned experiments, we assume the simulated source as distributed power sources with and without phase synchronization of the commercial power source. Here, incandescent bulbs are set as loads.  
Figure 4 shows the measured output voltage and the current waveforms of the power router, respectively, under the phase synchronized condition, _i.e._, Experiment I. The lower boxes in (a) and (b) show the switching command signals. Conversely, Figure 5 shows these waveforms under out of phase synchronization, _i.e._, Experiment II.  
From these results, it is determined that the power router succeeds in exchanging the lines after detecting the equipotential instance under both conditions. Moreover, the inrush current and surge voltage occur, especially in the out of phase synchronized condition. This is because there is a time  
Figure 4: Output waveforms of circuit switching operation with no phase difference between two inputs: (**a**) output voltage waveforms; and (**b**) output current waveforms.  
Figure 5: Output waveforms of circuit switching operation with 120\({}^{\circ}\) phase difference between two inputs: (**a**) output voltage waveforms; and (**b**) output current waveforms.  
delay between the detection of the equipotential instance and switching. This delay is essential to executing an algorithm in the CPU. The surge voltage and inrush current might prevent the switching from occurring. However, we confirmed that circuit switching can be performed successfully for the experimental parameters. The results show that the delay of the switching operation does not cause a switching failure in this case. An improvement of the algorithm in the CPU can obviously shorten the delay, so that the surge can be suppressed. Improvements to suppress the surge influence at the switching time and the quantitative evaluation of harmonics are inevitable in practical applications.