Waveform Control Of Co <sub> 2 </ Sub> Inverter Welding Machine System Design

The application, history, actuality and foreground of carbon dioxide welding (CO2 welding) in welding field are firstly introduced in the introduction part of this paper. The important specialties of CO2 welding machine and its study evolution are follow set forth.In this paper , researching and producing on current waveform control system of inverter carbon dioxide welding machine is given . The overall plan, the design of hardware structure and software is described in detail. The defects of big welding spatter and making bad welding seam form obstruct the popularization of CO2 welding short circuit transition . In order to achieve the aim of CO2 welding, a suit of IGBT inverter CO2 system is developed. The main circuit is made up of rectifier, filter, high-frenquency transformer, output reactor, and full-bridge inverter, where 4 IGBT are adopted. The key points in designing high-frequency transformer are discussed. At the same time, in order to obtain accurate and real-time control, high performance 16-bit microprocessor 80C196KC is adopted for control kernel. The digital signal from microprocessor are firstly converted into analogy signal, which is then modulated by pulse width modulate (PWM) chip SG3525 into two pulses not overlapped each other. At last the pulses are used to spring IGBT after they are magnified. In this thesis, controlling waveform CO2 system, which take advantage of the waveform control inverter power source characteristic that more parameter can be controlled and controllability is better, put forward to settle the above defects . In addition, the resource distribution of microprocessor and the functions of peripheral circuit are given. The safeguard circuit mainly consists of over-current, over-heat, over-voltage and low-voltage circuits.Through probing into the current waveform control of CO2 welding, one method of short transition is put forward. Based on confirming the method of waveform control and experimenting, the rule that waveform control parameter effect on welding spatter, seam form, arc voltage and welding current is studied . Thus parameters include the time of small current in short circuit propose , rising ratio of short circuit , maximal value of short circuit , big ignition arc current and small ignition arc current.Reliability and noise resistance designs are also covered. Various noises probably appear in the whole system, as well as their causation, are analyzed systematically. Then, in order to reduce their bad affections some hardware and software measures are adopted designing schematic chart and compiling code.At last, some tests are given to the circuit. It shows that control system and software are reasonable in design.