Numerical Simulation of Thermal Characteristics of Anodes by Pure Metal and CuCr Alloy Material in Vacuum Arc

Abstract

Anode material seriously influences the characteristics of vacuum arc and further affects the performance of medium-voltage vacuum switches when the interruption current is high. There are many materials used for electrode manufacture, and different materials are selected for different switches. For a pure metal, its performance usually cannot satisfy the actual requirement. To improve switch's performance, an alloy is usually used as an electrode material. In this paper, thermal processes of six kinds of metal anodes (including pure metal and alloy anodes) are simulated and researched. The physical parameters of the pure metals all come from experiment results directly or are fitted by the experimental data. The physical parameters of the CuCr alloys are derived from Cu and Cr parameters. Two kinds of temperature calculation methods are used, which are called melting and solidification model and equivalent specific heat method, respectively. Simulation results show that W and Mo anodes have the higher temperature than Cu, Cr, CuCr25, and CuCr50 anodes. A pure Cr anode has the largest melting width and highest saturated vapor pressure and evaporation energy. A Cu anode has the biggest melting depth. A W anode has the smallest melting width and depth. Axial temperature gradient is related to the thermal conductivity, and the Cr anode has the largest axial temperature gradient. The thermal characteristics of CuCr25 and CuCr50 anodes are located between the pure Cu and Cr anodes. There are two melting points appearing in the results of CuCr alloys, and between the two melting points, the alloy anodes are in solid-liquid mixture state.

Numerical simulation and experimental investigation of transient anode surface temperature in vacuum arc

“…where φ sh is the anode sheath potential, W e is the work function, and W z is the mean ionization energy. The energy loss by evaporation is given according to Hertz-Knudsen formula [21,24]…”

“…where f A is the mole fraction of material A in the anode, W ev-A is the latent heat of evaporation of one A atom, and P sat-A is the saturated vapor pressure of material A (A = Cu or Cr). Detailed physical parameters can be found in the previous work [21].…”

“…Shmelev et al [18] built a self-consistent model to analyze the influence of the radiation absorption of the anode on the anode temperature. In our previous work [19][20][21], the anode heating process was also analyzed. However, our previous models were not self-consistent since the vacuum arc and the anode were not coupled with each other.…”

Strengthening Mechanisms and Thermal Models of Chemically Incompatible Metals (Mo/W–Cu): A Review

“…[27] Therefore, reducing the number of internal pores of the materials and improving the density of the materials are the keys to prepare high-quality Mo/W-Cu composites. [28] At present, the commonly used preparation methods of Mo/W-Cu composites include melting infiltration method [14,29] and powder metallurgy method. [25,30,31] Mo/W-Cu composites have a wide application prospect.…”

“…For this part, different switches will choose different materials for better performance. Huang et al [ 28 ] simulated and analyzed the thermal characteristics of Cu, W, and Mo electrodes. Figure shows the physical model of the anode thermal process.…”