Realization of high discharge frequency in LC pulse generator for EDM by ignition using transistor circuit

Abstract

Recent research has revealed that the LC pulse generator is able to generate higher rising speed discharge current pulses and high open voltage for EDM by utilizing electromotive force induced by an inductor. However, the discharge probability of LC generators is low because the duration of the open voltage pulse is significantly short in the order of several microseconds, although it usually takes several microseconds or longer for discharge to be ignited. In this paper, the discharge probability of the LC pulse generator was investigated, which was proved to be lower than 20% if the discharge frequency divided by the switching frequency of the LC generator is defined as the discharge probability of the LC generator. An excessively short delay time demonstrates that the gap will be short-circuited, resulting in decreased machining stability. Hence, this paper proposes a modified version of the LC generator, combining a high impedance transistor pulse generator with a conventional LC pulse generator. The high impedance transistor pulse generator is used to cause the ignition in the interelectrode gap, but not to supply energy to remove the workpiece. Triggered by the ignition, the LC pulse generator is activated to supply high discharge energies and unique discharge current shape. This modified LC pulse generator can produce a discharge frequency 2 to 3 times higher than the conventional LC pulse generator.