Development Of Power Supply For Precision Medium Frequency Resistance Spot Welding Machine

Affected by science and technology,welding production is developing towards automation and intelligence.As an important welding method,resistance spot welding is widely used in automobile production,electronic technology,aerospace and other fields.Welding current,voltage and power are the main welding process parameters,which not only directly affect the welding process,but also important information for analyzing the quality of solder joints in intelligent production line.At present,most spot welding power supplies only use a single constant current control,which has the disadvantages of poor adjustment effect of welding process parameters,poor control effect of welding accuracy and few application occasions.When the welding current is large,the heat is too high and it is easy to burn through the weldment;When the welding current is small,the ideal welding nugget can not be obtained,and the welding process is discontinuous;The control mode is single and can not adapt to different welding occasions.In addition,the existing constant voltage and constant power control modes have some defects,such as slow response speed,poor stability and so on.Aiming at solving the above problems,this paper focuses on the multimode discharge control of spot welding power supply and how to improve the discharge performance.For the main circuit of power supply,three-phase uncontrolled rectifier circuit,filter circuit and full bridge inverter circuit are designed,and the applicable intermediate frequency transformer is selected.The system uses TMS320F28335 as the control core,and designs the hardware circuits of the control system,such as IGBT driving circuit,auxiliary power supply circuit,current/voltage sampling circuit,communication circuit and protection circuit;The main program of the control system is designed to control the whole welding process,including welding,communication and other subroutines.The welding process subroutine is designed to control the single welding process;The discharge control modes are designed,including constant current mode,constant voltage mode and constant power mode.A welding performance test platform is built by combining software and hardware.At the same time,the correctness of the discharge control system based on fuzzy control theory is verified by MATLAB simulation.The simulation waveform shows that the discharge performance of fuzzy control is obviously better than that of conventional PI closed-loop control.Using the experimental platform,the field welding tests of aluminum,copper and galvanized sheet are carried out in constant current,constant voltage and constant power modes respectively.The test results show that no matter what kind of metal,when using constant current,constant voltage and constant power mode welding,the corresponding welding current,voltage and power can quickly stabilize at the set value,indicating that the control effect is good and the design scheme is feasible.Figure[64]Table[5]Reference[80]...