| 摘要 |
A power source apparatus for electrical discharge machining, adapted to accurately detect the starting of normal electric discharge between electrodes, and switch an auxiliary power source to a primary power source. A switch (3) is turned on by a signal S1 from a control unit to apply a voltage of an auxiliary power source (1) between a work (5) and a machining electrode (6), and the voltage Vw between the electrode starts increasing. When the insulation recovery is sufficient, a partial voltage Vwd at the node between voltage dividing resistors (7, 8) exceeds a reference voltage V1, and the level of an output C1 from a comparator (9) becomes high, so that a SR flip-flop (14) is set. When the voltage Vw between the electrodes decreases due to the generation of electric discharge, the partial voltage Vwd becomes lower than a reference voltage V2, and the level of an output C2 from a comparator (10) becomes low, so that the level of the inverted signal C3 from an inverter (13) becomes high. Consequently, the SR flip-flop (14) is reset, and the level of an output C4 changes from high to low. A monostable multivibrator (15) detects the fall of the output C4 and outputs a signal C5 indicating the detection of a discharge.
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