Development Of Consuming Electrode Gas Shielded Arc Welding Inverter Control System

The arc-welding inverter power supply has the advantages of well controllability, fast dynamic response and having facility in realizing real-time control. It has great potential in performance. So it has been used more and more widely. In long views, arc-welding inverter is the trend of welding power supply. But in contrast to developed countries, our country has a long way to catch up with them.In this thesis, a set of control system is developed for IGBT inverter power supply of consumable-electrode CO2 shielded arc-welding machine. The following studies have been done:① According to the technological requirements of CO2 shielded arc welding machine, a set of control system for are-welding inverter power supply is developed. Due to two work states ---arc burning and short current ---existed in welding process of consumable electrode welding, and different control objectives in these two states, two close-loop feedbacks are designed in the control system: welding voltage feedback and welding current change rate feedback.② The core of the power supply control system is PWM control circuit TL494. Constant output characteristic is performed by voltage feedback, and the dynamic characteristic control of power supply is realized by modifying the reference voltage in di/dt feedback loop. Also there are drive circuit and protective circuit designed in control system. Besides all these, an automatic wire-feeding circuit and its control system are designed for the welding machine is semi-automatic arc welder.③ In order to design the parameter of error amplifier, the small signal model is derived for arc welding inverter using state-space averaging, and frequency-domain analysis is performed to complete the parameter design. Based on the compensated open-loop transfer function, the system stability at the small-signal perturbation and the system response to step signal are analyzed. Analysis result proves that the arc welding inverter works stably either in arc-burning state or in short-current state.④ Because arc welding inverter is working in the large signal perturbation state, a large-signal simulation model is created. And simulation program Matlab is used to study the model. The simulation result proves stability of the power supply and simulation waveform satisfies the technological requirements of CO2 shielded arc welding.⑤ The hardware of arc-welding inverter control circuit is built up. Weldingexperiment is processing, and output characteristic curves are measured. The experiment result proves that the designed arc-welding inverter power supply works stably and has little spatter in welding process, it has realized the required constant output characteristic curve,and has accomplished the requirements of welding procedure.