**3. Experimental Verifications**

Based on the design described, a prototype was built. When the line voltage in the three-phase input was 220 V, namely, the phase voltage was 127 V, the switching frequency 40 kHz, and the output load 7 kW, then the measured waveforms for three-phase V*RN*, V*SN*, V*TN*, line voltage and the line current were at low line and full load. The current waveform, as in Figure 7, is practically sinusoidal with low THD and a high power factor (the A-THD is shown in Figure 8 and power factor is shown in Figure 9).

**Figure 7.** Measured waveforms of input voltage and input current at full load.

**Figure 8.** A-THD measured results.

**Figure 9.** Power factor measured results.

Figure 10 shows the simulation waveforms using Isspice at half load and full load. It can be seen that the main switches *S*4 and *S*2 on the bottom sides turned on when their *VX* was down to zero by the resonant circuit, after the auxiliary switch *SA* was turned on.

Measured waveforms of the gate drive signals and voltage across the main switch are shown in Figure 11. The captured waveforms indicate the need to turn on the auxiliary switch *SA* before the turning on the main switches *S*4 and *S*2 to achieve ZVS.

As shown in Figure 12, when the current *i*1 of resonant inductor *LR* decreases to zero, the auxiliary switch *SA* can be turned off under ZCS conditions.

**Figure 10.** Simulation of key waveforms of the main switch voltage *VX* and current *il* at (**a**) half load and (**b**) full load.

**Figure 11.** Measured waveforms of drive signal and voltage for the main switch of the soft-switched rectifier.

**Figure 12.** Measured waveforms of drive signal and resonant current for the main switch of the soft-switched rectifier.

A comparison between the hard-switched and proposed soft-switched rectifier was performed at a load of 7 kW over an input voltage range of 190–250 V. The hard-switched rectifier was tested by simply disabling the soft-switch assist circuitry. Figure 13 shows the efficiency improvement from the soft-switched rectifier. The largest efficiency difference between hard-switch and soft-switch rectifier was 2.55% when the input line voltage was 220 V, and Figure 14 shows the soft-switched rectifier efficiency from 1–7 kW.

**Figure 13.** The efficiency comparison between hard-switching and soft-switching rectifier at 7 kW load.

**Figure 14.** Measured efficiency from 1 to 7 kW with the soft-switched rectifier.
