GB1459509A - Supplying electric power for electro-erosion - Google Patents

Abstract

1459509 Electro-erosion S-A E BUTRON 6 March 1974 [6 March 1973] 9997/74 Heading B3V An electro erosion gap 13 is supplied with machining power comprising direct voltage on which are superimposed first and second trains of pulses 1, 3 having an opposite polarity and larger amplitude than the direct voltage, the second pulse train comprising pulses 1 of higher repetition rate and smaller width than the pulses 3 of the first train and being selectively superimposed on the direct voltage for variable time periods. In one embodiment, the electrodeworkpiece gap 13 is connected to a main rectifier 7 fed with power via saturable reactors 5 which are controllable by a regulator 6. Pulses 1 from a high frequency generator 8 and pulses 3 from a low frequency generator 11 are superimposed on the output of the rectifier 7 by transformers 9, 12 such that the polarities of the pulses are opposite to that of the direct current from the rectifier 7. The generators are controlled by a timer 10. A silicon controlled rectifier by-pass 14 is connected across the erosion gap and is triggered by a circuit 15 in response to pulses from the generator 11 to facilitate extinguishing of the erosion arc. The dielectric may be slightly alkaline (soapy) deionized water at a tempera. ture of 90‹ C. In another embodiment (Fig. 4, not shown) a trigger circuit (26) is actuated when a short circuit occurs which causes a silicon controlled rectifier (24) to block the supply of direct current. The by-pass (27) is triggered by one of the pulse generators (28). The electrode (33) comprises individual sections insulated from each other and each connected to each terminal of the main rectifier via a resistor (34, 35). In another embodiment (Fig. 5, not shown) power is supplied to the erosion gap (42) via a pair of transformers (36, 47) having variable output voltages, rectifiers (38, 44) and trans. formers (39, 45) connected to pulse generators (40, 43). Short circuits are blocked by a circuit (41). Suitable examples of pulse generators which may be used are described (Figs. 2 and 6, not shown).