Research On Alternating Current Magnetron Power Supply Based On 80C196KC

GMAW is one of the welding technology widely used in various metal components,but the conventional GMAW wire depositing efficiency is low,resulting in low production efficiency.The most direct way to solve this problem is to increase the welding current,which will synchronously improve the welding speed and wire melting speed,thereby improving the welding efficiency.However,when the welding current increases beyond the second critical current,unstable rotating spray transfer will be formed,which will increase the welding spatter and worsen the welding quality,resulting in various defects.It is impossible to improve the welding efficiency of GMAW by simply increasing the welding current in welding production.Because of the good conductivity of arc plasma,the external magnetic field can act on the arc and affects the shape and position of the arc.Therefore,the external magnetic field which was applied to GMAW under the condition of high current(exceeding the second critical current)can be considered to have a beneficial effect on the unstable rotating spray transfer.It is possible to improve the welding efficiency by improving the welding current under the action of magnetic field.This project has developed a set of magnetic field generating devices,including digital alternating magnetron power supply and excitation coil.It can adjust the output current from 0 to 20 A,the frequency from 0 to 5000 Hz,and the duty cycle from 0 to 80%.The excitation coil was installed on the GMAW automatic welding torch,which is required to be coaxial with the welding wire.As the load of alternating magnetron power supply,the excitation coil produces a certain intensity and frequency of longitudinal alternating magnetic field,which acts on arc,liquid beam and molten pool.The main circuit of the alternating magnetron power supply adopts the IGBT type double inverter structure.The primary inverter selected the half bridge inverter topology structure to realize the current regulation.The IGBT model which was selected in the half bridge inverter circuit is K30N60 HS.Frequency and duty cycle are adjusted by secondary inverter,and K30N60 HS was also selected as the IGBT model in secondary inverter.The alternating magnetron power supply has designed a digitized man-machine interface,and has the functions of overheating,overcurrent,overvoltage and undervoltage protection.The control system of the magnetron power supply uses a 16-bit 80C196 KC single-chip computer as the main control chip.According to the functions of the magnetron power supply,the minimum system of the main control chip,half-bridge drive system,secondary inverter drive system,human-computer interaction system,excitation current sampling and D/A conversion system,protection system and so on were designed.Each system includes hardware circuits and software programs.With the cooperation of hardware and software,the design index of alternating magnetron power supply was realized.According to the design of main circuit and control system,a prototype of alternating magnetron power supply was developed after making PCB and debugging program.The developed alternating magnetron power supply was provided control power by separate control,and the man-machine interface setting and display was tested in the whole parameter adjustment interval,and the driving waveforms of the half-bridge inverter and the secondary inverter under the given parameters were tested.The test results show that the man-machine interface displays normally in the whole parameter adjustment range of the alternating magnetron power supply,and the driving waveforms meet the requirements.The test system of excitation current and magnetic induction intensity waveform of alternating magnetron power supply was established.The waveform of excitation current and magnetic induction intensity waveform of excitation coil axis at a certain position under different given parameters were tested,and the effective value of excitation current waveform was analyzed.A large number of test data were prepared for subsequent welding process test.The GMAW process test system under longitudinal alternating magnetic field was built.The welding process experiments of MIG/MAG before and after applying alternating magnetic field under high current condition were carried out.The results show that there exists an optimum matching range of magnetic induction intensity and frequency under the action of external longitudinal alternating magnetic field.In this region,the longitudinal magnetic field has certain control on the unstable rotating spray transfer which was formed by MIG/MAG under high current conditions.In this region,the longitudinal magnetic field can improve the weld formation and reduce the spatter which were produced by MAG welding.