| 摘要 |
PURPOSE:To carry out the large area work and finishing work by setting the electric current restricting resistance in variable ways from a dc power source for detection and applying said resistance between the electrodes during a repose time and detecting the between-electrode impedance and controlling the internal impedance of an electric power source. CONSTITUTION:During a repose time, the voltage less than the arc voltage is applied into between electrodes 1 and 2 from a dc power source 3 for detection by setting an electric current restricting resistor group 8 in variable ways, and the between- electrode voltage or electric current is detected by a detection means 10, and the between-electrode impedance is calculated by a calculating means 11. During the no-loaded time, the internal impedance Rx of an electric power source 3 for work for the supply of the no-load voltage over the electric discharge generating voltage is obtained, and after the generation of the electric discharge is detected by a detector 9, the internal impedance Ry of the electric power source 3 of the flow of a desired working electric current is obtained, and a series of operations for selecting the electric current restricting resistor group 5 through a power transistor group 4 are repetition- controlled after a repose time. Therefore, the optimum no-load electric current and a desired working electric current can be obtained, and the large area working and the work in a finishing work region are permitted.
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