变极性TIG焊电弧燃烧稳定性与恒占空比控制
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摘要
电流换向的快速性和稳定性是影响变极性TIG焊接电弧燃烧稳定性的关键因素,尤其是在小电流变极性TIG焊时,极易出现熄弧和电弧燃烧不稳定问题.对电流换向期间的电压/电流波形深入分析发现,一次逆变采用基于PID的电流反馈控制获得恒流输出时,在电流换向结束后易产生焊接电流回调现象,小电流焊接时甚至降至零,从而导致电弧熄灭,这与PID控制中的di/dt项密切相关.提出了一次逆变在电流换向期间采用恒占空比控制新方法.结果表明,该方法可有效提高换向电流的响应速度,防止换向后的电流回调或超调,增强了变极性电流换向过程的稳定性.
The rapidity and stability of current commutation are the key factors that influence the arc burning stability of variable polarity TIG welding.Especially,arc extinguishing and burning instability occur easily when the variable polarity TIG welding is performed under low current value.The waveforms of voltage and current during the current commutation process were deeply analyzed.It was found that the phenomenon of current declination occurred easily after the current commutation process and even arc extinguished welding with low current when the current feedback control based on PID was applied in the primary inverter to obtain constant current output,which was closely relative to the term of di/dt within the PID control.In this paper,a new control method with constant duty cycle was proposed and adopted in the primary inverter during the current commutation process.The experimental results showed that this method improved the response speed of commutation current effectively and prevented the declination or overshoot of current after commutation,which enhanced the stability of current commutation process for the variable polarity TIG welding.
The rapidity and stability of current commutation are the key factors that influence the arc burning stability of variable polarity TIG welding.Especially,arc extinguishing and burning instability occur easily when the variable polarity TIG welding is performed under low current value.The waveforms of voltage and current during the current commutation process were deeply analyzed.It was found that the phenomenon of current declination occurred easily after the current commutation process and even arc extinguished welding with low current when the current feedback control based on PID was applied in the primary inverter to obtain constant current output,which was closely relative to the term of di/dt within the PID control.In this paper,a new control method with constant duty cycle was proposed and adopted in the primary inverter during the current commutation process.The experimental results showed that this method improved the response speed of commutation current effectively and prevented the declination or overshoot of current after commutation,which enhanced the stability of current commutation process for the variable polarity TIG welding.
引文
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[2]柏久阳,林三宝,杨春利,等.铝合金TIG焊变极性参数对阴极清理及钨极烧损的影响[J].焊接,2015(5):9-13.Bai Jiuyang,Lin Sanbao,Yang Chunli,et al.Effects of variable polarity parameters on cathode cleaning and deterioration of tungsten in TIG welding of aluminum alloy full-bridge power converter with zero-voltage and zero-current soft-switching[J].Welding&Joining,2015(5):9-13.
[3]Sarrafi R,Kovacevic R.Cathodic cleaning of oxides from aluminum surface by variable-polarity arc[J].Welding Journal,2010,89(1):1-10.
[4]夏铸亮.软开关变极性埋弧焊电源数字化控制及换流策略研究[D].北京:清华大学,2012.
[5]杨中宇.稳压式变极性焊接电源电流换向控制及电弧稳定性研究[D].北京:清华大学,2017.
[6]夏铸亮,朱志明,陈俊杰.移相控制全桥零压零流软开关功率变换器谐振过程分析和参数设计方法[J].电焊机,2013,43(1):9-14.Xia Zhuliang,Zhu Zhiming,Chen Junjie.Resonant procedure analysis and parameters design approach for phase-shift controlled fullbridge power converter with zero-voltage and zero-current softswitching[J].Electric Welding Machine,2013,43(1):9-14.
[7]朱志明,杨中宇,汤莹莹,等.软开关逆变器谐振过程解耦分析与参数设计[J].焊接学报,2015,36(3):5-8,13.Zhu Zhiming,Yang Zhongyu,Tang Yingying,et al.Decoupled analysis of resonant process and parameters design for softswitching inverter[J].Transactions of the China Welding Institution,2015,36(3):5-8,13.
[8]陈杰.数字化变极性TIG/MIG焊接电源系统研究[D].北京:清华大学,2009.
[9]Yang Zhongyu,Zhu Zhiming,Liu Bo.Reverse voltage generating circuit for rapid commutation of output current polarity in variable polarity arc welding power supply[J].IET Power Electronics,2017,10(12):1609-1616.
[10]丁坤,姚河清,范兴辉,等.变极性TIG焊电弧负载特性及换向控制策略[J].焊接学报,2008,29(9):31-34.Ding Kun,Yao Heqing,Fan Xinghui,et al.Welding arc load characteristics of variable polarity TIG welding and its control strategy at commutation[J].Transactions of the China Welding Institution,2008,29(9):31-34.
[11]杨中宇,朱志明,汤莹莹,等.稳压式变极性焊接电源二次逆变拓扑及控制策略[J].焊接学报,2017,38(9):23-27.Yang Zhongyu,Zhu Zhiming,Tang Yingying,et al.Topology of secondary inverter and its control strategy of variable polarity welding power supply for generating stabilized reverse voltage[J].Transactions of the China Welding Institution,2017,38(9):23-27.