# Supply Systems of Non-Thermal Plasma Reactors. Construction Review with Examples of Applications
## 4 Power Electronics Supply Systems for NTPR
### Micro-Gliding Arc Discharge (\(\mu\)GAD) Power Supply System with Push-Pull Inverter  
Two electrode micro-gliding arc discharges (\(\mu\)GADs) have found recently applications for agricultural and biomedical solutions [24; 25; 26; 27; 28; 29]. They can be used for treatment and bactericidal decontamination of surfaces not resistant to high temperatures, like TEFLON, paper or materials for the packaging of food products, for seed germination and plants grow support as well for biomedical applications, like blood coagulation, wound healing, sterilization of tissues and medical equipment, in dermatology and even skin cancer therapy [18; 19; 57; 58]. In the Figure 16 results of final temperature measurements on the surface of the sample with _E-coli_ droplets in the function of gas composition are presented. Evidently, the _E-coli_ bacteria colony was exterminated because of the plasma process, but not the heating process [59; 60; 61]. Figure 14: Scheme connection of the AC/DC/AC power supply system of the sixth electrode GAD rector for decomposition of volatile organic compounds (VOCs) emitted during industrial processes [55]. Figure 15: Discharge voltage (blue signal) and current (yellow signal) waveforms while energized form AC/DC/AC inverter: (**a**) In the current source regime—current is sine; (**b**) in the voltage source regime—voltage is sine; process gas—Argon at flow rate 2 m\({}^{3}\)/h. Power suppliers with push-pull topology are well-known, but their uses for supplying plasma reactors are relatively rare [62; 63]. The supply shown on Figure 17 owes its beneficial properties to its topology. It has also the special feature of not having the switching overvoltages totally extinguished, as it happens in typical push-pull inverters. The overvoltage peaks that are dangerous for the transistor are the only ones to be cut off and the remaining ones move to the secondary coil. The correctly shaped overvoltages are used for improvement of ignition in GAD reactor [45; 64]. The power supply with the block diagram shown in Figure 11 has a modular structure, whose mutual location is shown in Figure 17a. Development of the discharge is presented in Figure 17b. As can be seen from Figures 17 and 18, the AC/DC bus (1) consists of two components: a rectifier with protective elements and a filter, which is equipped with a DC side capacitor pre-charging system, twin current control modules on the primary side (2) contain IGBTs with special drivers in their structure. Their inputs first of which has a 0\({}^{\circ}\) phase and the second one 180\({}^{\circ}\). They constitute links of the power path, and at their output alternating voltages V\({}_{\text{AC}}\)' and V\({}_{\text{AC}}\)' are obtained with the frequency and duty cycle values set by the PWM control system (3). PWM controllers are implemented as two-output astable generators. Depending on the set value, pulse width modulation, and dead times, they perform the function of frequency control and soft start function. This module also has an error amplifier used in the feedback loop. With its help, the signal d\(i\) can be used to influence the PWM value and control the primary current of the high frequency transformer. Block 4  
Figure 16: (**a**) Final temperature in degrees centigrade on the surface of the sample in function of gas composition—N\({}_{2}\), O\({}_{2}\), and CO\({}_{2}\) and their mixtures—, (**b**) _E-coli_ bacteria samples treated by \(\upmu\)GADs, distance between the top of electrodes and the sample 21 mm [59]. Figure 17: (**a**) Block diagram of the of NTP power supply for 2 electrode GAD reactor, based on push—pull topology, 1—AC/DC bus with, 2—twin current control modules, 3—PWM control system, 4—auxiliary DC voltage, 5—HV and HF transformer with divided primary winding, (**b**) development of the \(\upmu\)GAD in air at flow rate 450 dm\({}^{3}\)/h—above photo and below image recorded with a fast speed camera [64]. is an auxiliary DC voltage source.