Electrode Phenomena in Plasma Torches

The performance of most plasma generators using electric arcs is determined by the design of the electrodes. While the cathode design is the dominant factor in determining the limitations in torch operating current and power level as well as life between maintenance, the anode design dominates the functional performance for most torches, i.e. the heat and momentum transfer to the materials to be processed. Plasma torch electrodes are conveniently divided into the following categories: (1) thermionic cathode, (2) non‐thermionic (cold) cathode, (3) anode with arc axis and flow perpendicular to the surface, and (4) anode with the arc axis and the flow parallel to the surface. All possible combinations are encountered in commercially available torches. In this review, the performance characteristics of each of these electrode types are discussed.