Novel Dual-Pulse MIG Welding Power Source with Silicon Carbide Power Devices

Literature Overview

This paper, published in the Welding Journal (Vol. 40, Issue 7, 2019, pp. 94–99) by Zhong Qiming, Xie Fangxiang, and Wang Zhenmin from South China University of Technology, presents the development of a dual-pulse MIG welding power source based on all-silicon carbide (SiC) power devices. The inverter frequency reaches 100 kHz, enabling fine-grained arc control. The control system is built around an STM32F405RGT6 microcontroller, and the welding power source employs an incremental PID algorithm with single-pulse output combined with pulsating wire feed control to achieve dual-pulse welding. The work is supported by the National Natural Science Foundation of China (Grant No. E51875212) and Guangdong Provincial Science and Technology Plan projects.

Technical Architecture and Design Principles

The development of this welding power source addresses a fundamental challenge in advanced arc welding: achieving precise control over the welding arc through high-frequency switching. Traditional welding power sources based on silicon-based IGBTs typically operate at switching frequencies of 20–50 kHz, which limits the resolution of arc current waveform shaping. By employing all-SiC power devices, the inverter frequency is extended to 100 kHz, providing significantly finer control over the arc current pulse profile.

The dual-pulse concept in MIG welding refers to the combination of a main pulse (which provides the primary heat input and metal transfer) with a secondary pulse (which provides additional control over arc stability and metal transfer mode). This dual-pulse approach offers several advantages over conventional pulsed MIG welding:

• Improved arc stability through continuous current delivery
• Enhanced metal transfer control through synchronized dual-pulse timing
• Reduced spatter through optimized droplet detachment dynamics
• Improved weld bead appearance with clear fish-scale pattern

Control System Design

The control system architecture is based on the STM32F405RGT6, a high-performance ARM Cortex-M4 microcontroller with a 168 MHz clock speed. The system comprises three main modules:

1. Main control circuit: Processes welding parameter inputs, executes the incremental PID algorithm, and generates the dual-pulse current waveform commands.
2. Digital panel: Provides user interface for parameter setting, process monitoring, and fault indication.
3. Wire feed control circuit: Implements pulsating wire feed synchronized with the electrical pulse output.

The incremental PID algorithm is chosen for its simplicity and robustness, which are essential for real-time welding control. The incremental form of the PID controller computes only the change in control output at each cycle, which simplifies implementation and reduces computational burden. The dual-pulse welding is achieved through a coordinated strategy: the electrical output provides a single pulse per cycle, while the wire feed speed is modulated in a pulsating pattern synchronized with the electrical pulse. This approach effectively creates a dual-pulse welding effect without requiring complex multi-level current waveform generation.

Performance Evaluation

The experimental results demonstrate that the developed welding power source exhibits rapid dynamic response, which is critical for maintaining arc stability during parameter changes. The coordination between the electrical pulse output and pulsating wire feed is effective, producing weld beads with clear fish-scale patterns and no obvious defects. The fish-scale pattern is an indicator of stable metal transfer and consistent arc behavior, which are hathe writing systemarks of well-controlled pulsed MIG welding.

Engineering Practice Considerations

The use of SiC power devices in welding power sources represents a significant technological advancement with several practical implications:

• SiC devices have higher switching frequencies, lower switching losses, and better high-temperature performance compared to silicon-based devices.
• The higher switching frequency enables faster current response, which improves arc control precision and reduces the risk of arc instability.
• The compact size of SiC-based inverters reduces the overall size and weight of the welding power source, improving portability for field welding applications.
• The digital control architecture based on ARM microcontrollers enables advanced control algorithms, including adaptive control, model predictive control, and data analysis-based optimization.

For welding engineers, the availability of high-frequency SiC-based power sources opens new possibilities for advanced welding processes such as cold wire transfer, hot wire transfer, and dual-pulse welding of thin materials. These processes require precise current waveform control that was previously difficult to achieve with conventional power sources.

Key Questions and Reflections

Several aspects of this work merit further consideration. First, the paper does not provide detailed electrical efficiency data or thermal management analysis for the SiC-based inverter. In practical welding applications, the power source operates at high duty cycles, and thermal management is critical for long-term reliability. Second, the paper does not include a comparison with conventional IGBT-based power sources in terms of welding quality and process stability. Third, the dual-pulse welding concept, while promising, requires careful parameter optimization for each material and joint configuration. The pulsating wire feed synchronization with the electrical pulse is a critical parameter that affects metal transfer stability and weld quality.

The STM32F405RGT6 microcontroller, while capable, has limited computational resources compared to industrial PLCs or dedicated DSPs. For more complex control algorithms or multi-axis robotic welding integration, a more powerful control platform may be necessary.

Study Insights and Outlook

This work demonstrates that the combination of SiC power devices and digital control architecture can enable advanced dual-pulse MIG welding with rapid dynamic response and high-quality welds. The 100 kHz inverter frequency provides a new level of arc control precision that was not achievable with conventional power sources. For welding engineers, this represents a step forward in the development of intelligent, high-performance welding power sources that can support advanced welding processes for aluminum alloys, magnesium alloys, and other challenging materials. The next steps would include detailed efficiency and thermal analysis, comparative welding trials with conventional power sources, and integration into robotic welding systems for automated production applications. The SiC-based welding power source technology has the potential to transform the welding industry by enabling new welding processes and improving the quality and consistency of existing processes.