| In many state-of-the-art pulsed power machines,the limiting component is the switch.This is due to the fact at some point,the switch transfers all of the energy in the system.Two-electrode gas switch with excellent electrical performance and thermal stability is one of the suitable choices for all kinds of high energy pulsed power systems.Frequently,the switch requires the most maintenance or replacement after a short time.Replacing and repairing switches in a complicated circuit is time consuming and costly.For this reason,the ablation of the switch electrode under the action of a large current arc has been studied in great detail and has provided much information on the usage of electrode materials and switch configurations.However,there are relatively few studies on the mechanical effect caused by the discharge arc.At strong current,high power,and large energy discharge conditions,the impact of the impulse discharge arc may directly lead to the cracking of the discharge switch or cause fatigue damage to the switch structure,effecting reliability and shortening the service life of the discharge switch,after long time and repeated work.The lack of mechanical analysis caused by the discharge arc will limit the flow capacity of a single structure switch,and cannot meet the requirement of larger energy transfer.In this paper,a high power,high current gas switch is used as the site of the impulse discharge arc.The generation process of shock wave induced by high-current impulse discharge arc is analyzed based on the thermodynamic equilibrium of the arc channel and the shock wave physics theory.The explosion wave theory and the arc channel energy balance equation are introduced to analyze the decay process of the shock wave overpressure caused by impulse discharge arc expansion,and the demarcation point of the arc channel is given,from which the energy of the arc channel is no longer converted into shock waves.With reference to the current parameters of the impulse discharge arc flowing through the gas switch in the capacitor storage pulsed power supply,the shock wave overpressure generated by impulse discharge arc with different current parameters is simulated and compared.Through the analysis and calculation,it is found that the magnitude of the shock wave overpressure caused by impulse discharge arc expansion is closely related to the arc current rising rate.The arc shock wave overpressure will undergo a slow decay process and then decay rapidly.Aiming at the problem that how to reduce the mechanical effect of the impulse discharge arc on the electrode of GW-hundreds kA gas switch,electromagnetic force,gas thermal expansion force and shock wave overpressure is discussed in this paper.The theoretical calculation expression for the maximum electromagnetic force and shock wave overpressure that the electrode may withstand is given.The COMSOL Multiphysics is used to simulate the temperature distribution under the condition of local thermal equivalence.Theoretical analysis and simulation results show that the shock wave overpressure generated by the expansion of high current impulse discharge arc channel is the main component of the pressure on the switch electrode.Under the condition of constant discharge current,by adjusting the gap distance and pressure of the gas switch,the shock wave overpressure on the electrode can be reduced.The study of this paper can be used to explain the damage effect of shock waves induced by the high current arc.In the engineering application,it can provide the theoretical basis for the development of the switch with stronger flow capacity. |
