The Research Of Mid-frequency Inverter Resistance Welding Systems Based On PWM Converter

Thesis main job is around design 3KW mid-frequency inverter resistance welding power source product launch on the basis. Modern inverter resistance welding power source system energy conversion process for:AC-DC-AC-DC, includes a three-phase diode rectifier filtering, H bridge inverter and subprime diode rectifier filter circuit whole wave. Such power system is marked the final output current thousands to tens of thousands of amp, and only a few volts output voltage to dozens of volts.This paper mainly for modern welding inverter system hardware and software of research and analysis, this paper expounds the three-phase voltage source PWM rectifier circuit working principle and control strategy for three-phase diode rectifier and through the PWM rectifier circuit PWM rectifier circuit that comparative simulation can not only overcome diode rectifier brings to the grid of harmonic and pollution, and realize unit power factor control, and makes the dc voltage rectifying output increases, adjustable. Secondly, to H bridge inverter and MOS tube synchronous rectifier principle, and analyzed by simulation confirm the application of synchronous rectifier brings MOS tube of power efficiency than fast recovery power diode to much higher. In the control system software design, according to the different articles in the welding conditions by using fuzzy-PI dual mode control algorithm, switching to use.Finally, on the basis of theoretical study, on the one hand, design 3KW mid-frequency inverter resistance welding system test, the parameters, try to be single-system waveform analysis, finally system is stable, reliable and realize the basic welding function, achieve the design requirements, preliminary design products and production sales; On the other hand to H bridge inverter and MOS tube synchronous rectifier was tested, according to get each data waveform analysis comparison, also shows:the conduction resistance is extremely low MOS tube synchronous rectifier diode rectifier is concerned, compared with power increased the efficiency of the system's power, and circuit design more precise and simple, reliable and control effect is good.