Wire electrical discharge machine

An electrical discharge machine for performing electrical discharge machining on a workpiece by applying voltage across an electrode gap formed between a wire electrode and the workpiece, comprising:

• a first voltage applying circuit including a first DC power source connected across the electrode gap so as to apply a positive polarity voltage with a workpiece side being a positive electrode and a wire electrode side being a negative electrode, and a first switch arranged between the first DC power source and the electrode gap and configured to perform on/off switching control of applying the positive polarity voltage across the electrode gap;
• a second voltage applying circuit including a second DC power source connected across the electrode gap so as to apply a reverse polarity voltage with a wire electrode side being a positive electrode and a workpiece side being a negative electrode, and a second switch arranged between the second DC power source and the electrode gap and configured to perform on/off switching control of applying the reverse polarity voltage across the electrode gap;
• and,
• a switch controller configured to perform on/off control of the first switch and the second switch and control the first switch and the second switch such that the first switch and the second switch are not turned on simultaneously,
• wherein the first DC power source and the second DC power source are configured so that an absolute value of the reverse polarity voltage is always lower than an absolute value of the positive polarity voltage.