METHOD AND DEVICE FOR CONTROLLING POWER SOURCE FOR SHORT CIRCUIT TRANSFER WELDING

摘要

PURPOSE:To prevent generation of a spatter and to improve quality of welding by detecting exactly the time when a welding wire is contracted and controlling the electric current on the welding wire. CONSTITUTION:A resistance detector 111 calculates the resistance between a welding wire 103 and a base metal 106 from the ratio between the output signal from a voltage detector 110 and the output signal from a voltage detector 112. The calculated resistance value is impressed on a differentiating circuit 113. The resistance R calculated by the detector 111 in the circuit 113 is differentiated with a time (t) and dR/dt is outputted. The differential resistance value dR/dt is impressed on a computer 114, which compares the value with the set value set by a setter 115. The comparator 114 impresses the control signal to a welding power source 101 when the differential resistance value is larger than the set value to change over a switch 120 to the setter 121 on a low current side, thereby controlling the output of the power source 101 and decreasing the current on the wire 103. The set value of the setter 115 is determined in accordance with the differential value of the resistance value between the wire and the base metal when the wire is contracted.