Study on volt-ampere characteristics of spark discharge for transistor resistor pulse power of EDM

Electrical discharge machining (EDM) is widely used in aerospace industry and difficult-to-machine materials field. But the research on machining mechanism is insufficient and it has become a bottleneck of restricting its further development. In this paper, spark discharge self-sustaining conditions, the effects of pulse power circuit parameters on gap volt-ampere characteristics of EDM, formation of maintaining voltage of spark discharge, frequency and amplitude fluctuation of high-frequency components of maintaining voltage, and stability of spark discharge state are studied. Forming process of maintaining voltage of spark discharge is analyzed through discharge main circuit structure of transistor resistor pulse power. Influence of current-limiting resistor on maintaining voltage of spark discharge is also studied. The effect law of current-limiting resistor on oscillation frequency of maintaining voltage of spark discharge is obtained through spectrum analysis of maintaining voltage of spark discharge by methods of fast Fourier transform (FFT). Gap spark discharge control system is established through discharge circuit model of transistor resistor pulse power and the gap of EDM is replaced by spark discharge gap equivalent form. Input of the control system is the voltage of pulse power and its output is the gap voltage. Influence of current-limiting resistor on stability and response speed of the system is analyzed. The above research is important for revealing the mechanism of EDM, maintaining the stability of spark discharge, and guiding the design of pulse power and selection of processing parameters.