An Automatic Power Input Control System in High Frequency Electric Resistance Welding

It was found that monitoring the variation in oscillator frequency of welding current enables to detect the optimum welding state that produces the fewest weld defect. Applying this finding, new automatic power input control system was developed. This new system establishes and maintains the optimum welding state rapidly by the feed-forward system and precisely by the feed-back system. Besides the power input, other welding conditions were also optimized. Synthesizing these techniques, it has been possible to produce ERW pipes without weld defect.