Complete digital PWM controlled AC pulse MIG welding system

Abstract

The invention relates to a full-digital PWM-controlled AC pulse MIG welding system, which belongs to the field of welding equipment and automation. The full-digital PWM-controlled AC pulse MIG welding system comprises a main circuit and a control circuit, wherein the control circuit comprises a kernel control section, a control execution section, etc. The kernel control section comprises a DSP system, a current sampling and filtering circuit, a voltage sampling and filtering circuit, a CPLD system and a protection circuit. The DSP system is respectively connected with the CPLD system, a welding parameter setting signal and a welding parameter display signal in a front panel input and display section, a welding torch switch signal in a wire feeding system, a valve switch quantity signal and a wire feeding setting signal, and the CPLD system is also connected with the protection circuit and a primary inversion drive circuit in the control execution section. By combining the DSP system and the CPLD system, the welding system can achieve full-numerical control, which has flexible control and accurate control in comparison with the analog control manner of D / A+SG3526.

Description

technical field [0001] The invention relates to an all-digital PWM controlled AC pulse MIG welding system, which belongs to the field of welding equipment and automation. Background technique [0002] AC MIG welding is a new welding method that appeared in the 1990s. The key technology is what kind of current output mode to use and how to control the welding current, so as to effectively control the droplet transfer, weld penetration, Forming of weld seams. Tsinghua University researched AC MIG welding earlier in China. It uses a current waveform called "double concave", which has a self-stabilizing arc function when the arc polarity changes. [0003] The characteristic of this AC pulsed MIG welding is that it adopts self-stabilizing arc measures without additional arc stabilizing devices, but the polarity changes during the pulse current period, which increases the burden on the switch tube; there are two polarities in EN and EP. Pulse, easy to cause multiple droplet tran...

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Problems solved by technology

[0003] The characteristic of this AC pulsed MIG welding is that it adopts self-stabilizing arc measures without additional arc stabilizing devices, but the polarity changes during the pulse current period, which increases the burden on the switch tube; there are two polarities in EN and EP. Pulse, easy to cause multiple droplet transfer, it is difficult to achieve precise control of droplet transfer

[0004] Beijing University of Technology used single-chip microcomputer 80C196KC as the control core in the early stage, and successfully developed AC PMIG welding machine. It is controlled by single-chip microcomputer, the data processing capacity is limited, and the available IO interface is not sufficient. PWM is realized by analog DA+SG3526. This analog control It has inherent disadvantages: ① complex circuit, poor reliability, and high cost; ② PWM frequency is determined by RC value, and the precision of capacitors and resistors on the market is not high, which makes it difficult to achieve precise control of PWM signal frequency; ③ SG3526 generates triangular waves Easy to oscillate, which further leads to instability of the PWM signal

④The maximum digital-to-analog conversion time of DAC7625 is 10us, so the PWM signal frequency is limited

There are still some problems in the stability of the equipment. The amplitudes of the base currents of EN polarity and EP polarity are the same and cannot be adjusted separately. The adjustment of welding parameters is very inconvenient. improve

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