In the whole welding process, it is very difficult to ensure both the welding current and the constant arc voltage. Because in the welding process, the external interference often occurs, which eventually leads to the deviation of the welding current and the arc voltage in the predetermined value. But there are many kinds of disturbances caused by the outside world. The most common ones are the change of arc length and the change of network voltage.

Because of the uneven surface of the weld, irregular groove of the weld, low quality of positioning welding and assembly on the weld path, the arc length is constantly changing because of the welding process. In fact, the arc length of welding is relatively short, so it will lead to the fluctuation of welding parameters. When the voltage of the network changes, the power curve outside the welding will also change differently, which makes the welding parameters change accordingly. If submerged arc welding is carried out on low alloy structural steel, the arc voltage and welding current are stipulated, otherwise the formation of weld will be difficult to control.

Through practice, it is concluded that under normal conditions, the interference of arc length will directly affect the stability of welding process. Therefore, if the parameters of arc welding are adjusted, the main purpose is to eliminate arc length. Arc welding can be divided into two main ways: automatic regulation of arc voltage and self-regulation of arc. According to different principles of regulation, welding and arc voltage can be designed and adjusted.