Development And Optimal Design Of Alternating Magnetron Power Supply

There are various charged particles in the arc plasma generated in the welding process.When an external magnetic field is introduced,these charged particles will be affected by the Lorentz force,which changes the force state of the arc plasma.This makes it possible to improve the high-current GMAW welding process and increase the welding efficiency by applying an external magnetic field.Magnetron power supply is one of the key equipment in the research of magnetron welding technology,and it has a direct relationship with the mechanism research and quality control of the welding process.Therefore,this paper uses inverter technology to develop a digital dual-inverter magnetron power supply with a 16-bit microcontroller 80C196 KC as the control core.The power supply can output a square wave AC current with adjustable frequency,duty cycle and amplitude.The main circuit of the magnetron power supply adopts a dual inverter structure,and the inverter device selects IGBT.The front-stage inverter selects a half-bridge inverter topology,and the inverter frequency is 20 KHz.This paper uses the current closed-loop feedback control technology to control the turn-on and turn-off of the front-stage IGBT to achieve the adjustment of the magnetron power supply power;The rear-stage inverter adopts a full-bridge inverter topology,In this paper,the frequency and duty cycle of the square wave AC current output by the magnetron power supply are independently adjusted by controlling the alternate conduction of the IGBT in the rear-stage inverter circuit.In this paper,the main component parameters in the main circuit are calculated,and based on the MATLAB/Simulink simulation software,the magnetron power supply simulation model is established.Through the simulation and analysis of the output results of the magnetron power supply model,it provides theoretical guidance for the actual circuit structure and parameter design.At the same time,the input protection circuit,EMI filter,absorption circuit,half-bridge DC blocking capacitor protection and other circuits are designed to optimize the main circuit to protect the switching devices and improve the reliability of the magnetron power supply.The magnetron power supply control system uses 80C196 KC with good real-time performance and rich chip functions as the core of the control system.According to the functions that the magnetron power supply needs to realize,the smallest single-chip microcomputer system,human-computer interaction system,current feedback sampling circuit,D/A conversion circuit,front-stage inverter drive system circuit and back-stage inverter drive system circuit are designed.Combining the working sequence of the magnetron power supply and hardware circuit design,this paper adopts modular programming to improve the efficiency of software design.In order to speed up the response of the magnetron power supply and improve the control accuracy,this paper optimizes the design of the real-time display subroutine.At the same time,in order to improve the ability of the magnetron power supply to resist interference under complex working conditions,software anti-interference technology is also used to improve the software system during program design,and further improve the reliability of the magnetron power supply.The designed main circuit part and control system part were repeatedly debugged and revised,and the whole machine was debugged after ensuring that the modules were correct.And The output excitation current waveform of the magnetron power supply and the magnetic field under the corresponding parameters were tested.The test results show that when the alternating frequency is set low,the excitation current waveform is consistent with the expected design goal,and a symmetrical alternating magnetic field at a given frequency and a certain intensity is obtained,which shows that the designed alternating magnetron power supply has reached the expected design goal.However,when the alternating frequency is set to be high,the actual measurement results show that the inductive resistance generated by the inductive load is too high and the current cannot go up,and the magnetic induction intensity is very low.It is impossible to discuss the influence of the high-frequency alternating magnetic field process on the welding process.Therefore,in the last chapter,an exploratory experiment is done.The idea of ??RLC series resonance is adopted in the high frequency range,and a resonant capacitor is connected in series to the load to offset the reactive power generated by the inductive load.In this way,the power factor of the circuit is improved,and the output power of the power supply is increased,so that the effective value of the excitation current is increased,and the bottleneck problem of the excitation current of the magnetron power supply at a higher frequency is further solved.