# Supply Systems of Non-Thermal Plasma Reactors. Construction Review with Examples of Applications
## 3 Transformer Power Supply Systems for Plasma Reactors
### Integrated Power Supply Systems
The ignition transformer TR I is connected to a voltage that is induced between the PEN and N terminals of the primary side of the power transformers because of the non-linearity of the magnetization characteristics of their magnetic circuits. The UI voltage at the output of the ignition transformer having a 150/180 Hz frequency, is sufficient to ionize the inter-electrode space, enabling ignition of the discharge between power transformers, which are designed and built for a voltage several times lower than the ignition voltage--Figure 2a. Three times higher frequency of the ignition  
Figure 1: Integrated power supply system (IPSS) for dielectric barrier discharge (DBD) plasma reactor (PR) (**a**) and for gliding arc discharge (GAD) PR (**b**), where: Tr W—power transformer, VR—voltage regulation, Tr I—ignition transformer, WE—working electrodes, IE—ignition electrode, YNd-3-phase transformer with star-delta connection with neutral wire (N) on the primary side, YNyn-3-phase transformer with star-star connection with neutral wires on the both transformer sides [43; 48; 49; 50; 51]. voltage in relation to the power voltage frequency improves the ignition reliability and reduces power failure. Courses of working electrodes' voltages are shown in Figure 2b. Figure 3 presents courses of electrode current, phase voltage, and instantaneous power recorded for a three-electrode GAD plasma reactor fed from transformers with cores made of metallic glass (**a**) and a conventional transformer sheet (**b**). According to the oscillograph from Figure 3, the material of the power supply transformer core has a significant impact on the instantaneous phase voltage of the GAD PR. In the case of a core material made of metallic glasses, it will carry much more harmonics that come from ignition discharges systems. Reducing the content of higher harmonics in a system with amorphous cores is possible by using an ignition system operating at a technical frequency of 50 Hz. In the case of transformer sheet cores, higher harmonics are suppressed by the power supply's magnetic circuit and do not occur in phase voltages--Figure 3b. Figure 3: Oscillographs of electrode current I\({}_{\text{GAD}}\), phase voltage U\({}_{\text{GAD}}\) and discharge power p\({}_{\text{GAD}}\)(t), when feeding the GAD reactor from transformers with cores made of: (**a**) Amorphous glass, (**b**) transformer sheet; on both oscillographs frequency of ignition voltage is equal to 20 kHz, process gas—Argon, flow rate 1 m\({}^{3}\)/h, RMS voltage U\({}_{\text{GAD}}\) = 250 V, RMS current I\({}_{\text{GAD}}\) = 2.2 A, supply voltage frequency f = 50 Hz. Figure 2: (**a**) Characteristics of the IPSS (A-B ignition voltage characteristic, B–C operating voltage characteristic); (**b**) phase voltages u\({}_{\text{f1}}\)(t), u\({}_{\text{t2}}\)(t) and u\({}_{\text{t3}}\)(t) on the 3-electrode GAD reactor during the discharge in air at flow rate of 10 lit/min, supply voltage frequency f = 50 Hz. IPSS can also be used in three-wire network without an available neutral point, then the role of the neutral point is played by an artificial star point (N2), which can be implemented from three capacitors connected in a star (Figure 4). Other integrated circuit solutions for feeding six and nine-electrode reactors are shown in Figure 5a,b [5; 43]. Power supply system from Figure 5b owing to the three-stage connection of working electrodes--two of three working electrodes and one ignition electrode in each stage--allows to enlarge the space covered by the discharge and can be used to utilize exhaust gases at high flow rates, so as to extend the residence time of contaminated gas in the plasma space, which means its better decontamination.