# Analysis of Plasma Reactor Interaction with the Power Grid Depending on the Power Supply Design
## 5 Test Results
Despite superior argon characteristics, significant distortion of the output voltages of the tested power supplies is observed in the obtained oscillograms. Particularly large distortions are seen in the output voltage of the PCS power supply. In the case of the ITPS power supply, high value overvoltages are observed in the form of peaks accompanying the ignition of the reactor discharge. In the case of this power supply, distortion of the arc current is also evident. Poorer performance of the power packs with the plasma reactor is obtained when helium is used as the plasma-generating gas. The plasma-generating gas that is most problematic in the interaction of the investigated power packs with the plasma reactor is nitrogen. Nitrogen is a gas with a high  
Figure 11: Current and voltage waveforms of PCS power supply, 1—input voltage, 2—input current, 3—output voltage, 4—output current, plasma gas: argon, flow: 2.8 m\({}^{3}\)/h. Figure 10: Current and voltage waveforms of the IFCTPS power supply, 1—input voltage, 2—input current, 3—output voltage, 4—output current, plasma gas: argon, flow: 2.8 m\({}^{3}\)/h. ignition voltage and discharge support. Co-operation of power supplies with a reactor in which the discharge burns in nitrogen is unfavourable due to high discharge instability, a large number of disturbances in the voltage and current waveforms, and poor control characteristics. Slightly better performance is obtained with air as the plasma-forming gas. These problems arise for several reasons: (1) the design of power supplies with the assumption that the main plasma-generating gases will be argon and helium, (2) the adoption of an output voltage of power supplies not much larger than the ignition voltage of the discharge in nitrogen, (3) the limitation of the value of the discharge current which translates into a low arc temperature, (4) the susceptibility of the arc discharge to stochastic changes in position and length, and/or (5) the disturbance of the gas flow through the reactor discharge chamber caused by the reactor structural elements and the electrical discharge, worsening locally and temporarily the conditions for ignition and burning of the discharge [32; 33]. Figures 12-15 show the control characteristics of the reactor supplied from the test power supplies when the discharge burns in argon, helium, nitrogen and atmospheric air. The characteristics were obtained for a volumetric gas flow rate through the plasmotron nozzle of 1.6 m\({}^{3}\)/h. Figure 12: Control characteristics of the tested power supplies loaded with plasma reactor, plasma gas: argon, volumetric flow rate: 1.6 m\({}^{3}\)/h. Figure 13: Control characteristics of the tested power supplies loaded with plasma reactor, plasma gas: helium, volumetric flow rate: 1.6 m\({}^{3}\)/h. In the case of an electric discharge burning in argon, all power supplies tested showed good regulation properties (Figure 12). The IFCTPS and TPS power supply have the widest range of discharge current regulation. The worst performer in this respect is the PCS converter power supply. This power supply is also characterised by the highest value of the voltage at which the discharge in the plasma reactor burns. The value of the discharge burning voltage when the reactor is supplied from the PCS power supply is about 4 times higher compared to the IFCTPS power supply. The low voltage values at which the discharge in the reactor burns, together with the high excess voltage supplying the working electrodes of the reactor provided by the TPS, ITPS and IFCTPS power supplies, allows the power supplied to the plasma reactor to be regulated using an autotransformer. The wide current control ranges available with these power supplies allow the plasma temperature to be influenced to suit the requirements of the plasma process being carried out. The low voltage and current values at which the discharge burns when the reactor is supplied from TPS, ITPS, and IFCTPS power supplies make it possible to obtain the low-temperature plasma required in many plasma-chemical processes.