Observations of abnormal arc voltage phenomena in AC/DC pulsed MIG welding

Arc stability in AC/DC pulsed MIG welding is mostly determined by the performance of the arc length control system. This system detects the arc voltage as arc length information for feedback purposes and varies the output of the welding power source so that the arc voltage is equal to the voltage set point. For example, at a high arc length, the arc voltage increases. The pulse frequency is reduced in response, the wire melting rate is reduced and the arc length is returned to normal.