Patent ID: 8586891

Claim:
A wire electrical discharge machining apparatus, in which upper and lower conducting terminals are arranged in sliding contact with a wire electrode that runs in an up-down direction at at least one point of upper position and at at least one point of lower position of the wire electrode, respectively, and a workpiece is arranged to be opposed to the wire electrode between the upper and the lower conducting terminals having a predetermined machining gap between the wire electrode and the workpiece, wherein the wire electrical discharge machining apparatus includes a machining power supply for supplying a discharge current between the wire electrode and the workpiece by applying a discharge voltage to the upper and the lower conducting terminals and the workpiece, wherein the machining power supply includes first and second main discharge power supplies that generate main discharge voltages independently of each other, and a sub-discharge power supply that generates a sub-discharge voltage different from the main discharge voltages, the first main discharge power supply is connected between the upper conducting terminal and the workpiece using a first connection line capable to configure a first round-trip path, the second main discharge power supply is connected between the lower conducting terminal and the workpiece using a second connection line capable to configure a second round-trip path, and the sub-discharge power supply is connected between the upper conducting terminal and the workpiece, and between the lower conducting terminal and the workpiece, respectively using third and fourth connection lines that have higher impedances than the impedances of the first and the second connection lines and are capable to configure third and fourth round-trip paths, respectively, wherein the higher impedances of the third and fourth connection lines block a discharge current from flowing into the lower conducting terminal when the first main discharge power supply generates and supplies the main discharge voltage to the upper conducting terminal and block the discharge current from flowing into the upper conducting terminal when the second main discharge power supply generates and supplies the main discharge voltage to the lower conducting terminal.