Constriction dynamics of high-current vacuum arcs

• Applicant: Dr. Sergey Gortschakow
• Subject Area: Electrical Energy Systems, Power Management, Power Electronics, Electrical Machines and Drives ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 448727250

Constriction of discharge plasma is an important physical phenomenon, which has the relevance to various applications. The fundamental processes leading to the constriction of diffuse plasma have different nature for various types of discharge. In case of glow discharges increasing impact of stepwise processes, approaching of electron velocity the equilibrium distribution and increase of gas temperature (thermalisation) cause the formation of thin plasma channel, as well as the formation of localized attachment on the electrodes - cathode and anode spots. The constriction mechanisms in the vacuum arcs are quite different. The discharge medium formed by electrode material evaporation is already hot enough; the plasma species have significant velocities. Furthermore, the cathode spots are present from the beginning of the discharge formation, as they are the plasma source. In this situation, two phenomena can influence the constriction behavior, namely the self-induced magnetic field and the electrode processes (evaporation).The arc constriction has different meaning in various applications. This phenomenon is highly undesirable in low power operating devices (thrusters, on-load tap changers), surface coating devices, circuit breakers with axial magnetic field contact systems. In other applications, like e.g. circuit breakers with transversal/radial contact systems and vacuum spark gaps an arc constriction a standard working situation and it is desirable to control both the constriction behavior and the arc motion in order to reduces the local thermal load of the electrode.The present project is devoted to study of constriction processes in high-current vacuum arcs. Detailed investigations will be performed for dynamics, spatial structure and charge state distribution in arc plasma column during its constriction. The role of various factors such as electrode material, geometry of the discharge gap, self-induced and external magnetic fields will be analyzed. Parameters of the post-arc plasma, in particular vapor density, expansion of the cathode layer will be studied in dependency on constriction dynamics and thermo-physical processes on the electrode surface. Formation of constricted channel in interaction with external magnetic field will be characterized.Results of investigations can contribute to improvement of parameters of power apparatus based on high-current vacuum arcs.Following results can be expected especially for the switching applications:- scientifically optimized electrode system configurations approved for control of both constriction process and arc motion under the action of applied magnetic field will be developed;- new configurations of electrode systems based on hybrid of vacuum circuit breaker and spark gap which provides the arc motion from arc initialization region to arc extinction region where an efficient arc termination occurs.

• DFG Programme: Research Grants
• International Connection: Russia
• Partner Organisation: Russian Foundation for Basic Research
• Cooperation Partner: Dr. Alexander Batrakov