PURPOSE: To ease electrode feed control, and also prevent electrode exhaustion due to pulse split during electric discharge and effect given to processing surface roughness by floating capacity in finishing processing for a large processing area by composing a device so that applied D.C. voltage before electric discharge and power source voltage after arc break can be lowered.
CONSTITUTION: In a first control part 10, when the supply of a signal showing the detection of electric discharge is received from an electric discharge detection part 9, a control signal 8a is changed from a high level to a low level to control a first switching element 5a to off. Since the output of a second D.C. power source 3b is cut off when the first switching element 5a is controlled to off, processing voltage applied between an electrode 1 and a pole composed of a work piece 2 is lowered. consequently even when an insulation condition exists between electrodes again due to the occurrence of pulse split, electric energy to be charged in floating capacity becomes small, and current peak to be discharged when electric discharge occurs again can be restrained small.
OZAKI YOSHIO
AKAMATSU KOJI
