JPS645723A - Power supply for electric discharge processing machine - Google Patents

Abstract

PURPOSE:To simplify construction by changing the internal impedance from large to small during no-load period, storing the value at the time of arc voltage, and adding to its inverted number an inverted number of the internal impedance for obtaining desired discharge current. CONSTITUTION:During no load at the starting time of voltage pulse, the power supply internal impedance is sunk gradually by a group of current limited resistances 5 through a driver circuit 11 in response to a signal from a counter 27, and when a sensing means 10 senses that the arc voltage is attained, the output of counter 27 at the current time is latched in a latching circuit 16. Then this latch data and the internal impedance to obtain the desired discharge current setting value stored previously in a memory 28 are added together in the form of inverted numbers at an adding device 14, and thus the internal impedance for the processing current to flow is determined. When another sensing means 9 senses that discharge is generated between poles 1, 2, a switching means 12 changes over to the output data from the adding device 14. Thus a power supply for discharge processing can be constructed with simple hardware.