POWER SUPPLY SYSTEM FOR ELECTRIC DISCHARGE MACHINE AND ELECTRIC DISCHARGE MACHINING METHOD

摘要

A power supply circuit (8) includes a D.C. power supply (8A), a switching device (8B) and a diode (8C). A transformer (12) includes a ring core (13A), a primary winding (13B) and a secondary winding (13C). The switching device (8B) is turned on and off by a signal pulse supplied from a pulse generator (5) and supplies a D.C. current pulse to the primary side of the transformer (12). An inverter (15) inserted between the power supply circuit (8) and the transformer (12) includes switches (151, 152, 153 and 154) and is controlled by a signal from a relay circuit. While the switches (151 and 152) are closed, the switches (153 and 154) are open. The first half wave of an A.C. voltage pulse induced on the secondary side of the transformer (12) is supplied to a machining gap formed between a wire (1) and a workpiece (3) in the direction from the wire (1) to the workpiece (3). The second half wave is subsequently supplied to the machining gap in the direction from the workpiece (3) to the wire (1). At this time, the voltage waveform of the A.C. pulse is biased to the positive side of the potential of the workpiece (3) with respect to that of the wire (1). The workpiece (1) is, desirably, not coated with the material of the wire (1). When the switches (151 and 152) are opened and the switches (153 and 154) are closed, the A.C. voltage pulse induced on the secondary side of the transformer (12) is biased to the negative side.