Research On Interpulse TIG Welding Power Supply Based On SiC Devices

Pulse tungsten inert gas welding(TIG)has been widely used because of its advantages of stable arc,zero spatter,high welding quality and wide weldable metal range.However,traditional pulse TIG arc welding has large heat affected zone and coarse weld grain,and reduces mechanical properties of welded seam due to its low pulse frequency,inconsistent arc energy and large heat input.Interpluse TIG welding can improve arc shrinkage,energy density and arc stiffness.It is hopeful that the shortcomings of traditional pulsed TIG welding methods can be solved,and it has become one of the research hotspots in the field of pulsed TIG welding.However,the Interpluse TIG welding technology will produce strong electromagnetic interference to the welding power supply,especially to the power semiconductor devices,due to the addition of high-frequency current,which will easily lead to unstable welding current and poor arc control effect in high-frequency band.Improving the stability of welding power supply is the key to optimize Interpluse TIG welding.The switching performance of Si power devices is difficult to meet the application requirements of the new generation of high performance welding power supply.The third generation wide bandgap silicon carbide(SiC)power devices are extremely suitable for high temperature,high frequency,high voltage,radiation resistance and high power applications,and have great potential in improving the overall performance of welding power supply.Therefore,SiC power devices are used to develop high performance welding power supply to meet the requirements of Interpluse TIG welding process.Firstly,the research status of Interpluse TIG welding was analyzed in the thesis.Then the main power circuit of Interpluse TIG welding power supply were designed,as well as the supporting digital control system.The arc characteristics of Interpluse TIG welding were simulated and analyzed by finite element software.The test platform of SiC Interpluse TIG welding power supply was set up for the performance test of welding power supply and the welding process experiment.The main works of the dissertation are as follows:1)The overall solution of SiC Interpluse TIG welding power supply was determined.The research status of Interpluse TIG welding was analyzed,and the advantages of Interpluse current welding power source and welding were summarized.The performances of SiC MOSFET,Si MOSFET and Si IGBT were compared and analyzed.The advantages of using SiC power devices were defined.Interpluse TIG welding power supply was designed by using SiC devices with better switching performance to optimize the control effect and response characteristics of the power supply.2)A digital SiC Interpluse TIG welding power supply was developed.According to the requirement of Interpluse TIG welding process,Interpluse current switching circuit,pulse current main circuit and basic current main circuit were designed.The digital control system of SiC Interpluse TIG welding power source was designed based on the Interpluse TIG welding process.3)The shrinkage mechanism of Interpluse arc was discussed.The arc simulation model was established by using finite element software.The characteristics of Interpluse TIG welding power source were studied.The influence of pulse current frequency on arc itself and arc pressure was analyzed.And the arc shape is analyzed by high-speed photography system.4)The performance test of welding power supply and the experiment of Interpluse TIG welding process were carried out.The test platform of SiC Interpluse TIG welding power source was built,and the ability of stable output of Interpluse current of the prototype of SiC welding power source was tested.The welding process of SiC Interpluse TIG welding was tested,and the weld formation under different base current value,main current value,duty cycle of main current and pulse current mode was compared and analyzed.The results show that the developed SiC Interpluse TIG welding power supply can output 20 kHz Interpluse current waveform stably,and the waveform was stable and undistorted during welding.The Interpluse TIG welding process was stable,the weld seam was well formed,and there is no obvious pore defect.Using SiC to develop Interpluse TIG welding power supply can enhance the effect of arc control in high-frequency band,stabilize the output of Interpluse pulsed current,and promote the development of Interpluse TIG welding.