| 摘要 |
PURPOSE:To make both a large area machining and a finish machining possible by change-controlling internal impedances of a power source so as to obtain both a constant no-load voltage higher than a spark generating voltage and a required machining current by detecting an impedance between electrodes. CONSTITUTION:Detecting a voltage between electrodes 1 and 2 caused with a dc power source 7 for detection by means of a detection means 10 during a time of a pause, an impedance between the electrodes is calculated with an operation means 11. Based on a mean value of n-piece data or on a maximum value of the calculated impedance, internal impedances Rx and Ry are set so as to supply a no-load voltage higher than a spark generating voltage during a time of no load and to supply a required machining current after a spark generation is detected with a detector 9, According to the impedances Rx and Ry, a series of actions of switching a current restricting resistor array 5 through a power transistor array 4 are repeated and controlled after the time of the pause. In this way, the optimum no-load current and the required machining current are obtained to make machinings in areas of both a large area machining and a finish machining possible.
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