Research On The Reliability Of MMA/TIG Welding Inverter With MCU

The MMA/TIG welding machine is a multi-purpose welding machine which includesthe manual arc welding, DC TIG welding and pulse TIG welding, It has been widely appliedin industrial field, automobile, rolling stock, chemical industry, ship welding and so on. Basedon the research and the development tendency of MMA/TIG welding power source,considering the problem of the MMA/TIG welding machine controlled by80C196KBMCU, we decided study its reliability on the main circuit, control circuit, software programs,anti-jamming. The experiment results showed that the improved MMA/TIG welding machinehas a series of merits such as small volume, simple control circuit, low cost, reliable use andhigher control precision.Firstly, we have introduced the concept of reliability in this thesis. The reliability ofequipment is the capacity to complete the required task under the specified function withinthe given time. For the mass production, all aspects performance of MMA/TIG weldingmachine must meet certain standards, including efficiency, automation, cost and reliability,especially reliability et al. Based on the main circuit structure and working principle, for theproblems in its application, we studied the reliability of main circuit from three aspects.Specifically, the three aspects was the enter and output rectifier, high-frequency transformerand the switching power IGBT respectively.Then the reliability of control circuit was researched on power circuit, parameters preset,display circuit, PWM circuit, data acquisition circuit, drive circuit and protect circuit. In orderto ensure IGBT work in safe, we analyzed the structure and failure mechanisms of IGBT onthe over-voltage, over-current and over temperature appearing in application, and weproposed several protection methods. The results showed that the main and control circuit canall meet the expected reliability. In addition, the data acquisition circuit was modified to becontrolled by MAX530.Secondly, we have analyzed the reliability of the software program structure andanti-jamming. According to the timing requirements of MMA/TIG welding machine, wedesigned the software for control system, highlighted the main program and the interruptservice program, improved parameters preset and display program, and showed the programflow chart and some of the key program. On anti-jamming, we have introduced not onlyseveral common hardware anti-jamming measures, but also the anti-jamming measures takenby the current sampling and the high frequency circuit. Besides, several softwareanti-interference measures, such as WDT, redundancy directive and digital filtering, were taken in designing the software program.Finally, we have done the offline and online debugging for this power source, andprovided the relevant oscillograph traces. The experiment results showed that the improvedMMA/TIG welding machine can be more reliable to meet the request of pulse TIG, directTIG and the manual welding. After the debugging, the specimens have been welded to testthis power source, which proved that this power source is suitable.