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![Calculation model of melting and evaporation of molten metal bridge and arc generation [Colour figure can be viewed at wileyonlinelibrary.com]](publication/363209509/figure/fig3/AS:11431281174322792@1689182538191/Calculation-model-of-melting-and-evaporation-of-molten-metal-bridge-and-arc-generation.png)
Calculation model of melting and evaporation of molten metal bridge and arc generation [Colour figure can be viewed at wileyonlinelibrary.com]
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As the mileage of the electric railway increases, the unevenness of the contact wire may separate the contact wire and the contact strip. Simultaneously, a disconnection arc discharge is generated by the molten metal bridge. This causes the contact wire to melt and evaporate causing it to break. A few studies have conducted experiments to prevent t...
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Citations
... In chronological order, molten metal bridges are first generated while the electrodes begin separating; then, the molten metal explodes, resulting in arc discharge. The authors use numerical simulations to mimic this series of phenomena to elucidate the mechanisms of wear of the contact strip and contact wire with the aim of reducing maintenance costs [1]. Therefore, the authors implement separation experiments between contact strips and contact wire using materials with different polarities and measure the radius and length of the molten metal bridge immediately before arc discharge. ...
Numerical simulations are commonly used to elucidate the arc phenomenon in electrical railways and analyze its physical property variations. However, the initial conditions of the molten metal bridge must be set to accurately mimic the arc phenomenon. Therefore, the radius and length of the molten metal bridge are experimentally measured immediately before arc generation for four different contact strip materials as the cathode and copper contact wire as the anode. It found that the radius and length of molten metal bridge both proportional to the current regardless of the contact strip material. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.
The liquid metal bridge generated at the microspot of the contact has a crucial role in the formation of the arc, which provides the initial energy distribution for the ignition of the arc when the dc air circuit breaker is interrupted. A transient model of microspot thermal process which includes solid, liquid, and gas phase transition of liquid metal bridge during dc air circuit breaker contact separation was established in this article. The key parameters such as temperature, electric potential, and melting voltage of the material during liquid metal bridge formation process were analyzed, and the effects of different microspot surface topographies and contact materials on the liquid metal bridge formation process were also considered. The results show that the microscopic contact surface topography affects the contact microspot thermal process. The liquid metal bridge is formed fastest in pin-pin microspot surface topography and slowest in sphere-sphere microspot surface topography. The formation of the liquid metal bridge of the pure silver contact is the fastest and that of the pure tungsten contact is the slowest at the pin-pin microspot surface topography. A reasonable choice of contact materials can slow down the formation of liquid metal bridge and reduce contact ablation, which can improve the reliability of the circuit breaker and extend contact service life. This article can provide a reference for further research on the mechanism of arc formation process and exploring of ablation resistance contact materials. It can also provide a complement to the traditional arc magneto-hydro-dynamic (MHD) modeling.
