Patent ID: 7091446

Claim:
An electric arc welding system for creating a first AC welding arc with a first current waveform between a first electrode and a workpiece by a first power supply and a second AC welding arc with a second current waveform between a second electrode and a workpiece by a second power supply as said first and second electrodes are moved in unison along a welding path, said first and second power supply each comprising an high speed switching inverter creating its waveform by a number of current pulses occurring at a frequency of at least 18 kHz with the magnitude of each current pulse controlled by a wave shaper and the polarity of said waveforms controlled by a signal, wherein said first and second AC waveforms have a positive portion and a negative portion and a cycle period of about 10–20 ms, a detector arrangement configured to detect, at any given time, the polarity of the first waveform of the first AC welding arc and the polarity of the second waveform of the second AC welding arc, a comparator arrangement configured to receive and compare the detected polarities of the first waveform and the second waveform and to determine when the polarities are the same, which identifies a pull state, and when the polarities are opposite, which identifies a push state, a first timing circuit for determining the push time of a sustained maintenance of opposite polarity between said waveforms and a waveform adjusting circuit to limit said push time to less than about 5.0 ms.