This report describes attempts to discover a method for starting a water walled argon arc at high pressure. It is demonstrated that addition of small amounts of acetylene to the argon causes a very small reduction of breakdown voltage at pressures of about 3 atmospheres. Droplets of distilled water and of KC1 solution are shown to effectively increase the breakdown potential of a gas. A calculation of static fields before arc ignition is presented, and alternative starting circuit tests are done. Parallel starting pulse injection is found inferior to the normally used series injection. An auxiliary discharge is found to aid starting slightly, and a drastic decrease in the breakdown potential due to removal of the water wall is discovered. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The power balance equations for the column of a 500 A DC vortex stabilized arc in argon have been solved numerically to give predicted values for the temperature profile, radiative power and heat transport to the wall. These quantities have also been measured using spectroscopy and calorimetry, and compared with the theoretical results so as to refine our understanding of the heat transport processes in the arc. Further study is required to predict convective effects accurately, especially at low power levels, but the results show that the behaviour of the column is predictable at high power levels. Forced convection has been shown to play an important role in the arc column. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This study investigated the heat transfer within the anode material moving through and heated by an electric arc. The arc was a low current (< 16 A) atmospheric electric discharge between a carbon rod cathode, and a moving carbon felt anode. The carbon arc was a low current(<16 A) electric discharge between a cathode constructed of a carbon rod, and a moving carbon felt anode. The thermal profile within the anode material was predicted by a system of differential algebraic equations, adapted from the model developed by (Stark and Fricke, 1993). This set of equations was run using the software MATLAB R2011b, using a numerical integrator with consideration taken for sparsity. The change in degree of graphitisation was then predicted using the thermal profiles developed. This indicated that while the graphitisation of the surface of the felt exposed to the arc increased (from about 10% to about 99%) this effect did not penetrate far into the felt. At a depth of 0.3 mm there was very little increase in graphitisation (about 7% increase at slow movement rates, negligible at standard rates), indicating that this gaphitisation degree was unlikely to explain the improvement of battery cells produced using this material compared to non–arc treated material. Vaporisation of carbon due to the arc was then investigated as a possible explanation. With a similar activation energy to graphitisation a similar profile was obtained.

No description available.

No description available.

Le disjoncteur modulaire protège les installations électriques basse-tension contre les défauts de court-circuit. L’arc électrique, généré dans la chambre de coupure du disjoncteur lors de l’ouverture du circuit, est fractionné en plusieurs arcs dans un assemblage de multiples plaquettes métalliques, afin de limiter l’intensité du courant et d'isoler le défaut. Le travail exposé dans ce document se concentre sur la phase de limitation de l’intensité du courant de court-circuit. Une chambre d’arc modèle représente de façon simplifiée l’environnement de l’arc électrique durant cette phase. L'arc est amorcé par une impulsion haute-tension entre deux plaquettes métalliques fixes, l'onde de courant est transitoire et de forte intensité. La pertinence du montage expérimental est validée par la confrontation des phénomènes qu'il permet d'observer à ceux rencontrés dans le disjoncteur. Une attention particulière est portée à la tension d'arc, qui est une caractéristique déterminante pour la performance de la limitation. L’influence du matériau des électrodes est étudiée, en distinguant le substrat d’un éventuel revêtement. / The modular circuit breaker protects low-voltage lectrice installations against short-circuit faults. The electric arc generated in the arc chamber of the circuit breaker upon opening of the circuit is divided into several arcs in an assembly of multiple metallic plates, in order to limit the current and isolate the fault.The work set out in this paper focuses on the short-circuit current limitation phase. A model arc chamber represents in a simplified way the environment of the electric arc during this phase. The arc is initiated by a high-voltage pulse between two fixed metal plates, the current wave is transient and of high intensity.The relevance of the experimental setup is validated by comparison of the phenomena that it allows to observe with those encountered in the circuit breaker. Particular attention is paid to the arc voltage, which is a determining feature for the performance of the limitation. The influence of the material of the electrodes is studied, distinguishing the substrate from a possible coating.

Thesis (MTech (Mechanical Engineering))--Peninsula Technikon, 1999. / Word processed copy. Summary in English. Includes bibliographical references (leaves 66-68). Also available online.

Mémoire (M.Ress.Renouv.)-- Université du Québec à Chicoutimi, 1993. / Résumé disponible sur Internet. CaQCU Document électronique également accessible en format PDF. CaQCU

Inaug.-diss.--Göttingen. / Lebenslauf.

Thesis (MTech (Mechanical Engineering))--Peninsula Technikon, 1999 / The simulation of Plasma Arc Cutting is presented in this study. The plasma arc cutting process employs a plasma torch with a very narrow bore to produce a transferred arc to the workpiece. A technique for modelling plasma arc cutting has been developed by applying the thermo-metallurgical model to the process and integrating a model of material removal to this model. The model is solved using the finite element method using the FE package SYSWORLD, more specifically SYSWELD. The objective is to determine the minimum energy required to cut a plate of some thickness using this virtual model. The characteristics of the cut need to exhibit the characteristics of a "high quality cut". The model presented can predict the kerf size given certain process variable settings. The numerical results obtained are assessed by conducting experiments. By maintaining Ill1rumum energy input cost savings can be made through energy savings, limiting additional finishing processes and reducing expense of shortening the electrode and nozzle lifetimes. The modelling of the PAC process using virtual design techniques provides a cost-effective solution to the manufacturing industries with respect to process specification development. This plays an important role in South Africa's transition into a competitive global market. It is envisaged that the model will provide an alternative more efficient, non-destructive means of determining the optimum process variable settings for the plasma arc cutting process.