Research On Pulsed Welding Power Source System Ofaluminium Alloy

The rapid development of industrial automation and IT information technology industry constitute a favorable condition for the development of digital welding power source. This paper introduces the characteristics and advantages of digital welding power source. Given the present research state and the difficulty of pulse welding power source, the research on this topic is necessary. This paper provides a preliminary study on aluminium alloy pulse MIG welding by DSP and MCU. The paper mainly researches the following several aspects of contents:This paper firstly designs a voltage-sharing control strategy of the series double-transistor forward converter. The voltage-sharing control strategy adjusts the duty based on adjusting the capacitive charging slope and peak control theory. It makes the dividing capacitor with higher voltage have a smaller charging slope, then the bigger current flows through the load, the corresponding capacitor consumes more charges and the voltage of corresponding module decreases; The dividing capacitor with lower voltage has a bigger charging slope, then the smaller current flows through the load, the corresponding capacitor consumes less charges and the voltage of corresponding module increases. Finally the control strategy achieves voltage-sharing and power equalization of the input series module. The results of simulation and experiment prove the correctness of the voltage-sharing control strategy.And then the arc ignition control strategy of pulsed MIG welding power source system is designed. The arc ignition control strategy includes three phases: the first phase gives a bigger current in order to ensure that the wire can break out at the top of the wire; the second phase gives a smaller current than the first phase so as to avoid the bigger welding spatter; The third phase gives the hot pulses and the arc voltage control loop has formed a closed loop in this step. It can provide enough energy for the process of arc ignition and has the ability of keeping the arc voltage stable. The experiments based on the pulsed MIG welding power source experimental platform prove the validity of the arc ignition control strategy.At last the paper designs the arc length control strategy of pulsed MIG welding power source system. The arc length control strategy achieves the stable arc voltage control based on the fixed frequency arc feedback closed loop control method. The principle of the control strategy is keeping the pulse frequency fixed, adjusting the base current and controlling the size of average current by comparing the real time voltage with the reference voltage, making the melt speed of the wire keep up with the wire feeder's speed by adjusting the melt speed, keeping a stable arc length in order to make the welding process stable. The experiments prove that pulsed MIG system achieves precisely the current control and the arc voltage feedback control.