Pulse Power Supply And Equivalent Load For HSWEDM

High Speed Wire Elcetrical Discharge Machining(HSWEDM)is outstanding in processing special materials and precision metal parts.In order to continuously improve the processing quality,the pulse power supply that provides discharge energy is developing towards the direction of low loss,high voltage and current control accuracy and flexibility,digitization and intelligence.In this paper,the special load model of pulse power supply for HSWEDM is studied.A new type of composite pulse power supply is designed based on this model,and a method of load parameter extraction is proposed.In this paper,the equivalent circuit of HSWEDM discharge gap is analyzed firstly.The equivalent load of pulse power supply is obtained by considering the parasitic parameters of various components in the energy transmission circuit.According to typical discharge waveforms,the parasitic parameters in the load are calculated.The result of matching with the discharge waveform is obtained through simulation,which verifies the accuracy of the equivalent load model.Then,combined the equivalent load of HSWEDM pulse power supply and actual processing requirements,a novel pulse power supply is designed,which adopts composite structure of four parallel Buck circuit and a full bridge circuit.Among them,Buck is mainly used to generate high-power low-pulsation rectangular wave current,high-power high-pulsation sawtooth wave current,and medium-power triangle wave current,used for rough and medium processing;Full-bridge with small inductance,inverter characteristics to provide micro-energy triangular wave current and bipolar processing wave current,used for micro machining;When Buck circuits and the full-bridge circuit work in parallel,a current superimposed on a lowfrequency rectangular wave and a high-frequency triangular wave is generated,which can further improve the machining performance.After then,an equivalent load parameter extraction method is proposed.The voltage threshold comparison method is used to judge the pulse state.Combined with the Buck topology,through the no-load waveform and sawtooth discharge waveform,the cable inductance,working fluid resistance,maintaining voltage and other parameters are calculated.It is used to detect changes in load parameters in real time.Finally,a prototype of the composite pulse power supply is designed.Experiments are carried out with physical model of equivalent load in the laboratory,which verifies the feasibility of generating different levels of energy and different processing current waveforms by pulse power supply,and the effectiveness of the parameter extraction method.