Control manner and device null of power source for a - ku welding

摘要

PURPOSE:To stably and surely carry out the inversion without generating the excessive transient voltage by changing over a current set value of a current control system right before the inversion of an output current to change an output current value and carrying out the inversion when a prescribed current value is attained. CONSTITUTION:Rectangular wave signals with the advancing phase having repetition frequency and a duty ratio corresponding to set values of a reverse frequency setter 17 and a setter 18 for the ratio of the straight polarity to the reversed polarity are produced from a rectangular wave generator 16. With a current control circuit 13, the output current set value which is compared with a detected value of a current detector 5 at the rise and fall times of a reference rectangular wave signal is changed over from a set value of a first current setter 14 to a set value of a second current setter 15 with a prescribed time constant. When a signal indicating a delay is outputted from a delay circuit 21, a rectangular wave signal with the delay phase is outputted from a rectangular wave generator 23. At the rise and fall times of this rectangular wave signal with the delay phase, the inversion of the output current is carried out via a driving circuit 24. The current control circuit 13 returns the output current set value to the set value of the current detector 14 on receipt of a signal from the driving circuit 24.