The main body of the welding machine is a power supply; but it is a power supply designed according to certain functions; then, the output of the welding machine has two electrodes; then, when the welding machine establishes welding, it is to establish a stable current Circuit; Take the DC welding machine as an example, the current of the welding machine is output from the positive electrode of the welding machine to the welding handle and then back to the negative electrode of the welding machine; this constitutes a complete current loop.