## 4 AC/DC/AC Power Supply  
The converter power system consists of three devices: (1) AC/DC/AC converter, (2) matching transformers, (3) ignition module (Figure 3).  
The converter power supply system of a plasma reactor consists of two converters: (1) AC/DC input (mains), (2) DC/AC output (Figure 4) [4]. The converter parameters are given in Table 2.  
The AC/DC network converter is a three-phase transistor bridge in 6T + 6D. It is a typical voltage inverter structure. An integral part of the AC/DC converter are L\({}_{\text{S}}\) line chokes connected in a series to the three-phase circuit input. The role of the AC/DC converter is to maintain a constant, preset \(U_{\text{dc}}\) voltage at the DC output. It works as a boost converter. A boost of the AC/DC converter output voltage causes the DC/AC output inverter powered from the higher \(U_{\text{dc}}\) voltage to form the first voltage harmonic of the higher amplitude at its output. This translates into a higher voltage supplying the plasma reactor. The AC/DC converter output has a parallel capacitive filter.  
The DC/AC output converter is designed as a six-phase inverter system. Because the receiver, which is a plasma reactor, is of a non-linear character for the correct operation of the reactor and safe operation of the converter, the method of controlling the operation with a closed, non-linear current control loop (delta-modulation method) was adopted. The DC/AC converter has been designed as a six-phase inverter system in which the output voltages (currents) in individual phases are equal in amplitude and shifted by 60 (Figure 5A). The converter can also be considered as two independent three-phase inverters. Then, the output voltages (currents) have the same amplitudes for each three-phase system and the phase shift between them is 120. Two three-phase converters also allow for shaping output voltages (currents) with any phase shift between the two three-phase systems (Figure 5B).  
The voltage at the AC/DC/AC converter output is too low to initiate ignition and hold the discharge in the plasma reactor. The voltage is adjusted to the plasma requirements using three single-phase transformers. Conventional voltage booster transformers with lower and upper voltage winding coaxially wound on one column are used. Single-phase transformers were used in order not to magnetically connect through the transformer's phase core, as would be the case if one three-phase  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Operating Data** & **Converter** & **Transformer** & **Ignition System** \\ \hline Input power & 10.38 kVA & 4.6 kVA & 60 VA \\ Primary voltage & 230 V & 230 V & 230 V \\ Primary current & 15 A & 20 A & 0.25 A \\ Secondary voltage & 300 V (1 st harm.) & 1.5 kV & 15 kV \\ Secondary current & 0 \(\div\) 10 A (1 st harm.) & 3 A & 40 mA \\ Output frequency & 10 \(\div\) 200 Hz & - & 20 kHz \\ \hline \hline \end{tabular}
\end{table}
Table 2: Parameters of the power supply system.  
Figure 3: GlidArc Plasma Reactor Power Supply System: AC/DC/AC—converter, Tr W—booster transformer, Tr I—ignition system, PR—plasma reactor.  
transformer was used. Such an approach eliminates the problem of interference transfer between phases. The parameters of the transformers are given in Table 2.  
Figure 4: Plasma reactor power supply diagram by AC/DC/AC converter.  
Figure 5: Six-phase converter output voltage vector system (**A**), or two three-phase converters with angle adjustment \(\gamma\) (**B**).  
Electronic voltage boosting modules were used to power the ignition electrodes of the plasma reactor. Such a module consists of a circuit of a high-frequency generator and a transformer that increases voltage [5]. The module's task is to generate low-power electric sparks. The parameters of the modules are given in Table 2.