Patent ID: 6130816
Filing Date: 2000-10-10
Classification: B23H

Abstract:
An electric discharge machining apparatus for machining a workpiece by supplying a series of voltage pulses to a machining gap formed between the workpiece being machined and a tool electrode, said apparatus comprising:a machining power supply for applying a voltage to the machining gap;a switching transistor connected between the machining power supply and the machining gap for pulsing an output voltage of the machining power supply;a gate pulse generator for generating a gate pulse signal having an ON time and an OFF time to control an on/off switching operation of the switching transistor whereby the switching transistor is in a non-conducting state when the gate pulse signal is OFF;a monitoring power supply monitoring circuit connected in parallel with the switching transistor, and;a faulty transistor detection circuit for determining if the switching transistor has failed by determining if current flows from the power supply monitoring circuit through the switching transistor when the gate pulse signal is OFF.