| 摘要 |
PCT No. PCT/JP95/02624 Sec. 371 Date Aug. 21, 1996 Sec. 102(e) Date Aug. 21, 1996 PCT Filed Dec. 8, 1995 PCT Pub. No. WO96/19311 PCT Pub. Date Jun. 27, 1996A power supply circuit (8) incorporates a DC power supply (8A), a switching element (8B), and a diode (8C). A transformer (12) incorporates a ring core (13), a primary windings (13B), and secondary windings (13C). The switching element (8B) goes ON and OFF on the basis of a signal pulse supplied from a pulse generating device (5), so that a DC current pulse is supplied to the primary side of the transformer (12). An inverting device (15) connected across the power supply circuit (8) and transformer (12) incorporates switches (151), (152), (153), and (154), and is controlled by a signal from a relay circuit. When the switches (151) and (152) are closed, the switches (153) and (154) are open. The first half-wave of the voltage pulse of the current induced on the secondary side of the transformer (12) is supplied to a machining gap formed between a wire (1) and work piece (3) in the direction of the work piece (3). The subsequent half-wave is then supplied to the machining gap in the direction of the wire (1). At this time, the voltage waveform of the current pulse is biased to the positive side in terms of the potential of the work piece with respect to the wire (1). Thus, undesirable coating of the material of the wire (1) onto the surface of the work piece (3) is prevented. When the switches (151) and (152) are opened and the switches (153) and (154) are closed, the AC current pulse induced on the secondary side of the transformer (12) is biased to the negative side.
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