三丝焊作为一种高效的焊接方法受到重视，而电弧形态及燃弧特性是反映焊接过程稳定性，决定焊缝成形及质量的重要因素。试验中搭建三丝熔化极惰性气体保护(Metal inert-gas, MIG)焊系统，利用MultDaq电信号采集系统采集焊接电流和电弧电压波形，借助高速摄像系统同步拍摄电弧形态及熔滴过渡过程，实时监测焊接过程。观察不同电弧电压下的焊丝燃弧情况及熔滴过渡方式，研究短路过渡和大滴过渡形式下的交替燃弧机理，以及电弧电压对单电源三丝MIG焊交替燃弧过程的影响。结果表明，当焊接电源供给能量较小时，并联的三根焊丝上的电流分配呈现“此消彼长”的规律而导致电弧在焊丝间交替燃烧，且焊丝在电弧空间中的位置决定了焊丝上的电流分配。随着电弧电压的增加，交替燃弧频率减小。当电弧电压达到34 V时，三根焊丝同时燃弧，无交替燃弧现象，交替燃弧频率变为0 Hz。

As a kind of efficient welding method, triple-wire welding is taken seriously, and the arc shape and arcing characteristics are important factors in reflecting the stability of welding process and determining the weld quality and formation. Triple-wire metal inert-gas(MIG) welding system has been established in the test. In the welding process, the waveforms of welding current and arc voltage are acquired through the MultDaq signal acquisition system while the arc behavior and metal transfer process are monitored by high-speed photography system synchronously. Then the whole welding process can be monitored in real time, the mechanism of alternate arcing in different metal transfer modes and the influence of arc voltage on alternate frequency are studied. The results of experiments show that when the welding power source can only supply less energy, the current distribution on three wires connected in parallel presents the rule of “shift”, which results in alternate arcing among wires. Moreover, current distribution on three wires is decided by the location of wires in the arc space. As the increases of the arc voltage, the alternate frequency decreases. When the arc voltage is up to 34V, the three wires start arcing simultaneously, no alternate arcing, and alternate frequency becomes 0 Hz.