To make the apparent arc length constant by setting the period of counting the number of times of short circuits and the target number of times of the short circuit, starting welding and controlling the output voltage value so that the detected number of times of the short circuits becomes the target number of times of the short circuits.
In order to obtain the suitable apparent arc length La, the suitable ranges of the target number Nr of times of the short circuits and the period Tr of counting the number of times of the short circuits, are set. In a small current zone, a middle current zone and a large current zone, the count periods Tr are set to the same of 1 sec and also, the output voltage value Vt is controlled so as to become the target number Nr of times of the short circuits corresponding to the average value Ia of welding current or the pulse frequency (f) defining this average value. In the small current zone which sets the frequency to low, the Nr is set to e.g. 4 times, and at the time of controlling the Vt so that the number of the short circuit becomes 4 times, the number of times of the short circuits and the number of times of peak current synchronously become the same of 4 times and the La becomes the suitable value. In the same way, the Nr is set to 6 times in the middle current zone, and 8 times in the large current zone, and then, the suitable La can be obtd.
NISHIKAWA KAZUICHI
KAMIYAMA TOMOYUKI
TAKEDA TSUNEO
DO KOUGUN
