变极性等离子弧焊换向过程控制方法研究

Research on the Control of Commutation Process in Variable Polarity Plasma Arc Welding

通过试验证实了变极性等离子弧焊换向过程中存在电弧电流谐振现象,且不同极性的电流谐振峰值不同,依据电弧理论分析发现换向期间等效电弧电阻是一个时变量。对换向电路建模分析和仿真结果表明,在换向期间系统阻尼比为时变量,调整系统阻尼比是降低电流谐振峰值的有效途径。又根据变结构控制思想提出了新的换向控制方法,并重新设计了换向电路,显著降低了电流谐振峰值,改善了大电流焊接时换向器件的工作状态,为大功率变极性等离子弧焊电源的研制和开发提供了依据。

Phenomenon of arc resonance current is studied by experiments during commutation in variable polarity plasma arc welding. Analysis based on theory of arc shows that the arc resistance is time variable. Model of commutation circuit is set up and simulated. Results indicate that adjusting damp ratio of system is valid to restrain peak of resonance current. Then a new commutation method is presented based on variable structure control method. The commutation circuit is redesigned to apply new commutation method. Experimental result shows that the peak of resonance current is restrained while commutation speed is unchanged. This research provides the basis for designing high power supply of VPPAW.