In this paper, a three-dimensional non-equilibrium steady arc model is used to investigate the temperature, velocity and electromagnetic field in multi-cathode arc torch, and the formation mechanism of a large-area, uniform and diffused arc plasma is analyzed. The numerical simulation results show that a large volume plasma region can be formed in the central region of the generator during discharge. During this process, the maximum electron temperature appears near the cathode and in the central convergence region, while the maximum heavy particle temperature only appears in the central convergence region. This phenomenon is consistent with the experimental arc images. Near the cathode tip, the arc column is in a contraction state. In the area slightly away from the cathode, the six arc columns begin to join together. In the plasma generator, there is a large-scale current distribution in all directions of X, Y and Z, forming a stable arc plasma with a wide range of diffusion. The calculated electron temperature distribution is in good agreement with the measured electron temperature. The results suggest that the large-area diffused arc plasma in the multi-cathode arc torch is the combined effect of current distribution, convection heat transfer and heat conduction.

本文利用三维非平衡稳态电弧模型研究了多阴极电弧焊炬的温度、速度和电磁场，分析了大面积均匀扩散电弧等离子体的形成机理。数值模拟结果表明，在放电过程中，发生器的中心区域可以形成大体积的等离子体区域。在此过程中，最高电子温度出现在阴极附近和中心会聚区，而最大重粒子温度只出现在中心会聚区。这种现象与实验电弧图像一致。在阴极尖端附近，弧柱处于收缩状态。在稍微远离阴极的区域，六个弧柱开始连接在一起。在等离子体发生器中，X、Y和Z，形成稳定的电弧等离子体，扩散范围广。计算的电子温度分布与测量的电子温度非常吻合。结果表明，多阴极电弧炬中的大面积扩散电弧等离子体是电流分布、对流传热和热传导的综合作用。