| 摘要 |
PURPOSE:To make both a large area machining and a finish machining possible by calculating and controlling internal impedance values of a power source from impedance values between electrodes so as to supply a no-load voltage higher than a spark generating voltage during a time of no load. CONSTITUTION:Obtaining an impedance between electrodes 1 and 2 by detecting a voltage between the electrodes caused with a dc power source 7 for detection by means of a detection means 10 during a time of a pause, by calculating with an operation means 11, and from a mean value of two or more of the impedance values, internal impedances Rx and Ry of a power source 3 for machining are set so as to supply a no-load voltage higher than a spark generation voltage at a time of no load and to supply a required machining current after a spark generation is detected with a detection means 9. After a specified time of the pause, a series of actions of switching a current restriction resistor array 5 through a power transistor array 4 are repeated and controlled. In this way, the optimum no-load current and the required machining current are obtained to make the machinings in areas of both a large area machining and a finish machining possible.
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