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Break the arc generation process and the mechanism of action

Arc generation
In the closing or breaking circuit, due to the arc on the electric “contact material input energy generated by the thermal-force effect, so that the electrical contact surface melting or even gasification, melting the metal in the electromagnetic stirring force and mechanical force, etc. in the form of small droplets from the electrical contact surface melt pool spattered out, which is the arc erosion. Arc erosion can be divided into the commissioning circuit process and the breaking circuit process of arc erosion, the arc time when the circuit is connected mainly depends on the duration of the electrical contacts due to the reaction force and bounce; breaking circuit arc generally from the moment of contact separation has been continuously burning until the end of the breaking process. Usually the arc erosion in the process of breaking the circuit is much larger than the arc erosion in the process of turning on the circuit.
Figure 1-1 to Figure 1-3 shows a schematic diagram of the arc generation during the breaking of a circuit [25]
According to the physical process occurring between the two electrical contacts during the breaking process, it can be considered that the arc generation during the breaking process goes through five stages [26]
(1) As shown in Figure 1-1 (a), when the two electrodes begin to gradually separate, the contact area between them is also gradually reduced, at this time the current is concentrated in one or several conductive spots through the conductive spots in the vicinity of the conductive spots will produce a large contraction resistance thermal effect, can make the electrical contact surface metal melt.

(2) As the distance between the two electrodes further increases, the molten liquid metal is pulled out between the two electrodes to form a “metal-liquid bridge” phenomenon. As the diameter of the “liquid metal bridge” decreases, as shown in Figure 1-1(b), the contraction resistance will increase and cause the temperature to rise sharply, when the temperature of the “liquid bridge” exceeds the boiling point of the contact material, the molten metal starts to vaporize and the “liquid metal bridge” is pulled off. The “liquid metal bridge” is pulled off.
(3) After the “liquid metal bridge” is pulled off, the voltage between the two electrodes rises rapidly and the metal vapor fills the gap between the two electrodes rapidly. The “mound” on the cathode acts as an extremely strong source of cathodic electron emission – field electron emission.
(inter-polar electric field strength up to 106~107V/cm) and hot electron emission (cathode emission spot instantaneous temperature up to 5000K) become the arc root of the arc, the electrons emitted from the cathode under the action of the inter-polar electric field to the anode in the process of high-speed movement will inevitably occur inelastic collision with metal atoms, resulting in its cationization and the generation of more electrons, the occurrence of electron “avalanche” effect. At this point the metal vapor temperature will rise sharply, the arc is ignited, forming a metal arc, as shown in Figure 1-2. In the metal arc stage, the metal vapor in the generation of electric

(2) As the distance between the two electrodes further increases, the molten liquid metal is pulled out between the two electrodes to form a “metal-liquid bridge” phenomenon. As the diameter of the “liquid metal bridge” decreases, as shown in Figure 1-1(b), the contraction resistance will increase and cause the temperature to rise sharply, when the temperature of the “liquid bridge” exceeds the boiling point of the contact material, the molten metal starts to vaporize and the “liquid metal bridge” is pulled off. The “liquid metal bridge” is pulled off.
(3) After the “liquid metal bridge” is pulled off, the voltage between the two electrodes rises rapidly and the metal vapor fills the gap between the two electrodes rapidly. The “mound” on the cathode acts as an extremely strong source of cathodic electron emission – field electron emission.
(inter-polar electric field strength up to 106~107V/cm) and hot electron emission (cathode emission spot instantaneous temperature up to 5000K) become the arc root of the arc, the electrons emitted from the cathode under the action of the inter-polar electric field to the anode in the process of high-speed movement will inevitably occur inelastic collision with metal atoms, resulting in its cationization and the generation of more electrons, the occurrence of electron “avalanche” effect. At this point the metal vapor temperature will rise sharply, the arc is ignited, forming a metal arc, as shown in Figure 1-2. In the metal arc stage, an electric arc is generated in the metal vapor, and the charged particles are mainly electrons (emitted from the cathode spike and produced by inelastic collisions with metal atoms), metal ions, and metal atoms. The electrons that gain energy from the electric field move from the cathode to the anode and will impact the anode, resulting in electron sputtering. The impact of electron impact at the cathode leads to the deposition of metal ions at the cathode. Therefore, in the metal vapor phase, the material is transferred from the anode to the cathode.

(4) As the distance between the two poles continues to increase, metal cations on the one hand, the electrode between the electric field in the role of continuous deposition in the cathode, on the other hand, also in the diffusion to the atmosphere, resulting in the two poles between the metal vapor density decreases, between the two poles gradually filled by the atmosphere. At this time, if there is sufficient voltage to break through the atmosphere, will produce a large number of gas cations, instead of metal cations to become the main body of the arc conductivity, the formation of gas arc, as shown in Figure 1-3
shown. In the gas arc stage, the dominant role is played by gas ions, gas molecules/atoms and metal atoms. In this phase, when the gas ions bombard the cathode, the gas ions sputter, a phenomenon equivalent to the sputtering of electrons that occurs in the metal phase. Then, the sputtering particles (metal atoms) have enough energy to transfer to the anode and undergo deposition due to the higher binding force between the same particles. Therefore, in the gas arc phase, the material transfer is from the cathode to the anode. According to the PSD model, during the arc parting stage
first occurs from the anode to the cathode material transfer (metal arc), if the necessary conditions are met to generate the gas arc
If the necessary conditions are met to produce a gas arc, material transfer from the cathode to the anode (gas arc) will occur. Therefore, for each disconnection operation, the net transfer of material corresponds to the balance of mass gain and loss at the cathode and anode during the metal and gas arcs.

(5) The distance between the two poles is further enlarged, the arc between the two poles disappears, the circuit is split, and over time, the spacing between the electrodes increases, and the discharge process is insufficient to produce positive and negative ions due to the lack of electron emission or power supply, which eventually leads to arc extinction. Thus, if the necessary conditions are met, the opening arc first produces metal vapor, followed by a transfer from the metal phase to the gas phase, and finally ends. It is important to note that if during the initial phase
or arc phase, even if power is supplied or sufficient electrons are emitted, the arc will not be generated or will be extinguished immediately after it is generated. Finally, during a single disconnection operation of the electrical contact material, arc erosion is the result of a combination of evaporative loss of electrode contact material (mainly metal phase arcing) – spattering loss of electrode contact material particles – spattering or evaporative deposition of electrode contact material.

Author

Hello, my name is Eva Xia, and I am currently the Marketing Manager at Yueqing Weup Technology Co., Ltd, located in Wenzhou, Zhejiang, China. With over a decade of experience in the accounting field, I have developed extensive knowledge and skills that enable me to excel in my role. Additionally, I have spent two years working as an English teacher, which enhanced my communication abilities and instilled discipline within me.

Having gained more than three years of valuable experience in overseas sales, I have had the opportunity to expand my horizons and develop a deeper understanding of the commercial landscape. This exposure has nurtured my business understanding and allowed me to navigate diverse markets confidently.

However, despite my accomplishments thus far, I remain dedicated to continuous growth and learning. My current area of focus revolves around electronic switches. It is a fascinating and dynamic field that constantly evolves with technological advancements. By delving deeper into this realm, I aim to enhance my professional knowledge and stay ahead of industry trends.

In summary, as a Marketing Manager at Yueqing Weup Technology Co., Ltd., I bring forth a wealth of experience in accounting coupled with the valuable skills honed during my time as an English teacher. Furthermore, my extensive overseas sales expertise has sharpened my business acumen. With a relentless thirst for knowledge and a specific interest in electronic switches, I strive to enhance my professional capabilities further while contributing positively to our organization’s success.

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Eva Xia,
Marketing Manager at Yueqing Weup Technology Co., Ltd

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