The Research Of CO₂ Inverter Welding Machine Controlled By Waveform

The signal detecting circuit, the constant-speed wire-feeding circuit and the programmed control system during the short circuit of CO₂ (Carbon Dioxide) welding are all designed and debugged in the dissertation. The signal of arc voltage without distortion is got by use of photo-coupled isolator 6N136 to insulate signal voltage from arc voltage. And the relative appropriate voltage detecting the signal of short circuit is provided. The liquid bridge shrink detecting circuit based on du/dt is designed. The clipping circuit is applied to eliminate the effect on the liquid bridge shrink detecting circuit from arc voltage successfully, which improves the capability of anti-jamming of it.The control system based on microcomputer 8031 is devised, which can pre-setup the parameters, collect the data and protect itself. The signal of short-circuit which period is too small is eliminated by means of software to ensure the validity of signal processing and improves the capability of anti-jamming of the control system. The circuit model of IGBT (Insulated Gate Bipolar Transistor) during switch is devised after the inversion main circuit of welding machine was analyzed. The voltage waveform from the model has a strong resemblance to the voltage waveform from the experiment, which shows that the model can provide the reference for the research of on-off process of IGBT.Compared the voltage negative feedback wire-feeding speed regulation system supported by current positive feedback with the rotational speed negative feedback regulation system, the equivalent condition of the two systems is obtained. Then, a wire-feeding speed regulation circuit for the CO₂ welding machine is designed based on TL494 chip, which has the self-protective function under the condition of current overloading. In the experiments, when the power voltage varies from 342V to 418V, and the load from 25N to 50N, the variation ratio of the wire-feeding speed is small than 5%, which satisfies the JB/T9533-1999 professional standard.