Importance

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Abstract

In a plasma arc cutter and a method of controlling the same, a rise compensating circuit (39) and a shift compensating circuit (44) both composed of a charging and discharging capacitor and a resistor are respectively inserted in parallel between an electrode-side connection (21) and a nozzle-side connection (35) and between the electrode-side connection (21) and a workpiece-side connection (34), and a diode (33) is provided on the workpiece-side connection in such a manner as to be inserted between a connecting point (36) of the nozzle-side connection and a connecting point (43) of the shift compensating circuit. A detector (31) for controlling a current is provided on the electrode-side connection at a position closer to the electrode side than a connecting point (37) of the rise compensating circuit, and a detector (32) for detecting a shift is provided on the workpiece-side connection at a position closer to the workpiece side than the connecting point (43) of the shift compensating circuit. In addition, to effect cutting after boring, at least one plasma torch ( 14a) for boring and at least one plasma torch (14b) for cutting are provided. Furthermore, the voltage between an electrode (14) and a workpiece (17) or between a nozzle (15) and the workpiece (17) is detected, and the power source is stopped when that voltage exceeds a predetermined value. Consequently, since a shift from a pilot arc to a main arc is facilitated, cutting is performed by the exclusive plasma torch, and the occurrence of a double arc is prevented, cutting precision and cutting efficiency are enhanced.

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