| 摘要 |
PURPOSE:To make both a large area machining and a finish machining possible by detecting an impedance between electrodes and calculating internal impedances of a power source for both a no-load voltage higher than a spark generating voltage during the time of no load and for a required discharge current after starting the discharge. CONSTITUTION:During a pause period of a dc current source 3 for machining, a power source voltage below an arc voltage is applied to electrodes 1 and 2 from a dc power source 7 for detection by means of a restriction resistance 8, a voltage between the electrodes is detected with a detection means 10, and an impedance between the electrodes is obtained with an operation means 11. An internal impedance Rx of a machining power source 3 so as to provide a no-load voltage higher than a spark generating voltage is set for the time of no load, an internal impedance Ry of the power source so as to flow a required machining current after a spark generation is detected with a detection means 9 is set, and a current restriction resistance array 5 is switched and controlled through a switching means 12, a drive circuit 13, and a power transistor array 4. In this way, the optimum no-load current and the required machining current are obtained to make machinings in the areas of both a large area machining and a finish machining possible.
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