| 摘要 |
PROBLEM TO BE SOLVED: To obtain a power supply unit for a wire electric discharge machine capable of improving a machining speed while exercising zero-voltage control to prevent the occurrence of electrolytic corrosion. SOLUTION: The power supply unit contains two subsidiary power supplies 5, 7 used for OV control as the power supplies to apply a voltage between a wire electrode 1 and a workpiece electrode 2, in addition to a main power supply 3. The first subsidiary power supply 5 applies a positive-polarity voltage when a switch 6 is on between the poles. The second subsidiary power supply 7 applies a negative-polarity voltage when a switch 8 is on between the poles. The switches 6, 8 are controlled to go on and off alternately. A OV control circuit 11a compares, in magnitude, the absolute value of an average value of positive-polarity voltages obtained by an average-voltage detection circuit 10 with the absolute value of an average value of negative-polarity voltages, increases or decreases a greater-polarity voltage application time by a unit time from an initial value or from the last value according to the polarity of an inter-electrode voltage when the average-voltage detection circuit 10 finds the average value, and notifies a discharge control circuit 9a of the determined greater-polarity voltage application time. COPYRIGHT: (C)2010,JPO&INPIT
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