Research On Key Technology Of Digital High-Power AC-pulse Submerged Arc Welding Power Supply

Submersed arc welding has been widely used in the field of medium/thick plate and long weld due to its advantages of large welding heat input and high degree of automation.In order to improve the welding efficiency,the process parameters of large current and high speed are usually used in submerged arc welding.However,this will not only increase the probability of defects such as arc magnetic deflection,weld underbite,warm grain and weld porosity,but also lead to the phenomenon of grain coarsening in the welded joint due to excessive welding heat input,which will decrease the mechanical properties of the weld.In order to solve these problems,a new method of AC pulse submerged arc welding is proposed,which integrates the advantages of AC square wave welding and pulse welding to further improves the welding efficiency and quality of submerged arc welding.Based on the actual demand of AC pulse submerged arc welding,this paper combines high-power and high-frequency inverter technology with digital control technology to develop a digital high-Power AC-pulse submerged arc welding power supply.The main research points are as follows:(1)According to the power characteristics of submerged arc welding,a dualcircuit parallel high-power circuit topology is designed.Combined with dual closed-loop digital current sharing technology,which can stabilize current sharing output in multiple welding modes,and the rated output current is up to 1250 A.(2)In order to solve the problem of slow polarity switch in high-power AC output,a coupling inductor is added in the secondary circuit,and the critical short-circuit strategy of the secondary inverter is combined to shorten the AC zero crossing time significantly.(3)Optimize the topology of the main circuit through electrical simulation and modal analysis,and the core components such as IGBT and power transformer are selected.(4)According to the functional requirements of AC pulse submerged arc welding,the ARM Cotex-M4 chip is used as the core to develop the peripheral circuit and software of the control system,including the welding process control system,output signal sampling and processing system,fault detection and processing system,welding parameter real-time display system,CAN communication system,etc.And through the RTOS system and NVIC interrupt to coordinate the welding tasks,to ensure the response speed and working stability of the system.(5)In view of the complex and frequent changes of AC pulse waveforms,a set of waveform control programs was written,and three control optimization methods were proposed,which are separated incremental PID control algorithm,full-bridge inverter staggered control method,and peak current suppression strategy,to further improve the dynamic characteristics of the welding power source,reduce the output ripple,and suppress the current overshoot,steadystate error and waveform oscillation during AC pulse output.The developed AC pulse submerged arc welding power supply is used to build an experimental platform.The results show that the developed AC pulse submerged arc welding power supply has excellent external characteristics,dynamic characteristics and current sharing performance.When the welding experiment,in a low frequency ac frequency and pulse frequency range,ac pulse submerged arc welding the weld penetration of weld width,respectively,with the increase of frequency and pulse frequency communication are presented first increases and then rule,and ac pulse submerged arc welding compared with ac square wave submerged arc welding can restrain better weld bite edge and hole defect occurred.