Study Of Digital Inverter Welding Machine

ABSTRACT:Digital technology has greatly promoted the development of precise and flexible control of welding power source. Digital control inevitably is the developing direction of welding power.The concept, structure and features of digital welding machine is introduced in the thesis. Combined with the present development of welding machine at home and abroad, the necessity of the study project is put forward.In this thesis, main circuit, in which FB-ZVS-PWM full-bridge inverter topology of IGBT is applied, is made up of input rectifier filter circuit, inverter circuit, IF (intermediate frequency) transformer and output rectifier circuit.Working principle of the main circuit and components design and selection of parameters is introduced, and simulation with MATLAB verifies the feasibility and rationality of main circuit. DSP2407A is adopted in the control system as a core.Four phase-shifting PWM pulse directly generated by the DSP, isolated by the 6N137 optocoupler, is used to drive IGBT after power amplification by the driver IC M57959LDesign of the minimum system of DSP and peripheral function circuits is also described in the thesis.For example, to achieve real-time control, voltage and current sampling processing circuits are designed. And according to the system failure that may occur, the corresponding protection circuit module is designed. High-frequency arc ignition circuit for TIG and corresponding hardware anti-jamming circuits are specially designed.With in-dept understanding of the resources and instruction of DSP, modular programming method is used to write the main program, each function subrountine and interrupt service program to meet the welding control needs.The corresponding gate drive and load tests are taken.Experimental results indicate that the welding power circuit can achieve soft switching in the whole load range, and meet the MMA welding and TIG welding of welding technology. Hardware and software systems can achieve the original design concept and the basic requirements.Finally, a preliminary conclusion of this stage is made, and the further work directions and goals are pointed out.They will make a found ground for future's study of digital welding power.