Study of high-current arcs and its interaction with side walls and layers

Summary form only given. The interaction of arcs with materials e.g. of the electrodes or of side walls are key issues of the functionality in many arc applications. An electrode configuration with a stable and reproducible arc operation as well as with optical access is preferable for the experimental analysis and fundamental study of such interactions. A setup with copper electrodes under ambient atmosphere in distances of several centimeters is used in this study. Arcs with currents of several kA are operated for few milliseconds between the electrodes which are placed inside ceramic nozzles to fix the arc attachment area. The electrode erosion promotes a stable arc operation. Electrical measurements and optical emission spectroscopy of copper lines are used to characterize the arc properties. Radiation transport and a simple arc power balance are utilized to estimate the arc temperature and the energy transport to the arc surrounding or to side walls. The interaction of the arc with materials is studied by mounting plates parallel and in distances of several millimetres to the arc axis. Beside pure materials, ceramic plates coated with oxide or hydroxide powder layers of approximately 1 mm thickness with simple binding agents are considered. The erosion of the materials and layers is qualitatively studied by high speed imaging of the fume formation. The thermal impact of the arc is analysed by pyrometric measurements at the back and the front side of the test plates. First results demonstrate the appropriability of powder layers to protect side walls from thermal load and destruction.