| 摘要 |
PURPOSE:To perform stable cutting by giving a stop signal to a driving device to drive a rotating circular plate when a detected value of the quantity of arc electricity is larger than a set value to prevent the rotating circular plate from coming into contact with a piece to be cut. CONSTITUTION:When a current feedback signal If is smaller than a current set signal Is, a PI controller 16 increases output in a time constant. At this time, when the time constant is made sufficiently large, the increasing rate of the PI controller 16 is smaller and the rotating circular plate 2 increases the speed gradually and an arc current also increase gradually. When the arc current increases, the current feedback signal If becomes large and the difference between the feedback signal and current set signal Is becomes small. When this difference becomes small, the increasing rate of the PI controller 16 also becomes small and the difference (Is-If) is made to zero, the increase of the PI controller 16 is stopped and this output is made constant. When the current feedback signal If becomes larger than the current set signal Is, a comparator 17 is made to H and OV is inputted to a servo amplifier 10 by a changeover apparatus 18 and a capacitor of the PI controller 16 is discharged.
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