It is the use of both positive and negative poles in an instantaneous short-circuit when the high temperature arc produced to melt the welding electrode solder and welding materials, to achieve the purpose of combining them. The structure of welding machine is very simple, plainly is a high-power transformer, will $number alternating current into low voltage, high-current power supply, can be DC can also be AC. Welding Transformer has its own characteristics, that is, the characteristics of a sharp drop in voltage. After the electrode ignition voltage drop, in the welding machine work voltage adjustment, in addition to a $number voltage conversion, two times coil also has tap conversion voltage, but also useful iron core to adjust, adjustable iron core welding machine is generally a high-power transformer, by using the principle of inductance, the inductance quantity will produce a great voltage change when connected and disconnected, and use the High-voltage arc produced by both positive and negative poles in an instantaneous short circuit to melt the solder on the electrode. To achieve the purpose of bringing them together. Applying voltage between the welding rod and the workpiece, by scratching or contacting the ignition arc, the energy of the arc is fused with the electrode and heating the base material.