DETECTING METHOD FOR DROPLET TRANSFER TIME

PURPOSE:To detect the time when a droplet transfers from a consumable electrode at real time by performing a waveform treatment after differentiating the welding voltage and welding current respectively and by performing the logical operational processing of the signal that the welding voltage and welding current are subjected to a waveform treatment. CONSTITUTION:The welding arc current between an electrode wire 2 and the material 7 to be welded is detected by a shunt 14. A variation is caused on the welding voltage when a droplet is separated into an arc 6 from the tip of the wire 2. A positive pulse is caused at the current rising time and negative pulse at the falling time, when the welding current is differentiated by a differentiation circuit 18 after its amplification by an amplifier 16. On the other hand, a positive and negative pulses are caused at the voltage rising and falling times when the welding voltage is differentiated by differentiation circuit 17 after its amplification by amplifier 15 and positive and negative pulses are caused at the place corresponding to the transfer time of the droplet as well. The differentiated waveforms of the welding current and welding voltage are respectively formed in two positive pulses of square shape by waveform shaping circuits 20, 19 and added to the circuit 21, then the pulse signal equivalent to the droplet transfer time appears on an output terminal 22. Namely the droplet transfer time can be detected.