AUTOMATIC CONTROL DEVICE OF HIGH FREQUENCY WELDING HEAT INPUT

摘要

PURPOSE:To perform adequately the welding of an electric welded tube by controlling within the target value using a target value output circuit and control circuit the variation in the power source output of high frequency welding detected by a detection/holding circuit. CONSTITUTION:A comparator 21 produces the output corresponding to the phase difference between the input and the output of a voltage control oscillator 23 when the output frequency of a welding power source 11 is inputted into the phase comparator 21 of a detecting circuit 20. This output is outputted to a holding circuit 9 as the amplitude of a low frequency signal through a filter 22. The difference in the target value outputted by a target value output circuit 30 and the frequency variation outputted by the holding circuit 9 controls the output electric power of the welding power source 11. With controlling like this, the measuring circuit for controlling the most suitable heat input is widely simplified.