Mechanism of mass expulsion from the surface of a pure tungsten cathode during dc arc initiation

Abstract

In this work the destruction mechanism of a pure tungsten cathode during the initiation of direct current arc is studied. The experimental work shows that the cathode resides in liquid form during the initiation of the arc, and the process of its destruction happens by ejecting droplets from its surface with the following explosion. The average speed of the ejection and the temperature at the explosion points microseconds before the explosion were registered. A mathematical model is proposed explaining the reason behind the droplets formation.

Analysis of processes leading to explosive phenomena on the surface of a liquid cathode at the time of the dc electric arc ignition

“…This work is a continuation of research [2,7,8] in the field of stationary arc discharges of atmospheric pressure in argon. The process of formation of the liquid channel and steps that happened before the explosion are discussed in detail in our previous work [2].…”

“…This work is a continuation of research [2,7,8] in the field of stationary arc discharges of atmospheric pressure in argon. The process of formation of the liquid channel and steps that happened before the explosion are discussed in detail in our previous work [2]. Here we consider the development of several instabilities in order to determine which one is responsible for the explosion of a liquid channel on the surface of a pure tungsten cathode formed at the initial moment of arc ignition.…”

“…Introduction. -The destruction of the cathode in an arc discharge can occur both in the stationary mode of combustion [1] and in the non-stationary mode, due to the processes of ignition and extinguishing of the arc [2]. The measure of destruction is the amount of material carried away from the cathode surface during the passage of an electric charge and is expressed by the value kg/C.…”

“…In industry, as a rule, a value at the level of ∼ 10 −10 kg/C is considered satisfactory [1]. At the same time, as shown in recent works on the example of atmospheric pressure arc burning in an argon medium with a tungsten cathode, the destruction rate at the moment of ignition reaches ∼ 10 −7 kg/C [2]. Such a large value is due to explosions on the cathode surface in the region of the arc attachment.…”

“…Such a large value is due to explosions on the cathode surface in the region of the arc attachment. One of the possible reasons for the formation of the tip and the dynamics of its development was discussed in [2], where a comparison with experiment is also presented. The authors of this work have not previously encountered detailed experiments that study the destruction of cathodes in arc discharges during the initiation of the arc.…”