Development of a New Inverter TIG Welding Power Source

Overview and Context

The 1993 paper by Yang Lijun, Hu Shengsun, Zhao Jiarui, Sun Dong, and Lu Dengping from Tianjin University presents the development of a new inverter TIG welding power source. This work is historically significant as it represents the transition from traditional transformer-based welding power sources to inverter-based technology, which has since become the dominant technology in modern welding equipment. For engineers involved in cladding and pressure vessel fabrication, the inverter TIG power source offers significant advantages in terms of efficiency, portability, and process control.

Core Technical Content

The traditional TIG welding power source uses a transformer to step down the mains voltage and step up the current to the required welding current. This approach results in a bulky, heavy, and inefficient power source. The inverter-based approach, on the other hand, uses high-frequency switching devices to convert the mains voltage to a high-frequency voltage, which is then stepped down by a high-frequency transformer and rectified to produce the welding current.

Power Source Architecture

The inverter TIG welding power source developed by the authors consists of the following main components:

Component	Function	Typical Specification
Rectifier	Converts AC to DC	Three-phase bridge rectifier
DC-DC converter	Steps down voltage, steps up current	IGBT-based full-bridge inverter
High-frequency transformer	Steps down voltage	Operating frequency 20–50 kHz
Output rectifier	Converts AC to DC welding current	Fast-recovery diodes
Control circuit	Regulates welding current and voltage	Microprocessor-based controller
HF ignition circuit	Provides high-frequency arc strike	160–300 kHz oscillator

The key innovation in this power source is the use of insulated-gate bipolar transistors (IGBTs) as the switching devices, which offer a combination of high switching speed and low switching losses. This results in a power source that is significantly more compact and efficient than traditional transformer-based designs.

Performance Characteristics

The authors characterized the performance of the new inverter TIG power source and compared it with a conventional transformer-based power source:

Performance Parameter	Transformer-Based	Inverter-Based
Efficiency	75–85%	85–92%
Power factor	0.6–0.7	0.9–0.95
Weight	150–200 kg	30–50 kg
Welding current range	10–300 A	5–300 A
Current regulation	Slow	Fast (microsecond response)
Duty cycle	60%	80–100%

The improved efficiency and power factor of the inverter-based power source result in lower energy consumption and reduced stress on the electrical supply system. The fast current regulation capability enables precise control of the welding current, which is essential for achieving consistent weld quality in cladding and overlay applications.

Process Control Advantages

The inverter-based power source offers several process control advantages that are particularly relevant to cladding and overlay applications:

Control Feature	Benefit for Cladding
Fast current response	Precise control of dilution rate
Adjustable current waveform	Control of heat input and bead geometry
Pulse current capability	Reduced heat input, improved metallurgy
Soft start and soft stop	Reduced spatter and arc blow
Current limiting	Protection against short circuits and arc blow

The pulse current capability of the inverter TIG power source is particularly valuable for cladding applications. By pulsing the welding current, the heat input can be reduced while maintaining a stable arc, resulting in lower dilution rates and improved overlay quality. The soft start and soft stop features reduce the risk of arc blow and spatter, which are common problems in cladding operations.

Engineering Practice Implications

For engineers involved in pressure vessel cladding and overlay operations, the inverter TIG power source represents a significant improvement over traditional transformer-based power sources. The improved efficiency, portability, and process control capabilities enable more precise control of the welding process, which is essential for achieving consistent overlay quality.

The development of inverter-based welding power sources has enabled the widespread adoption of advanced welding processes, such as hot-wire TIG, pulse TIG, and laser-assisted TIG, which are all based on inverter technology. The work presented in this paper laid the foundation for these advances and has had a profound impact on the welding industry.

Study Insights

This work is a testament to the transformative impact of power electronics on welding technology. The transition from transformer-based to inverter-based power sources has enabled the development of welding processes that were previously impossible, opening up new possibilities for cladding and pressure vessel fabrication. For engineers involved in equipment selection and process development, understanding the capabilities and limitations of inverter-based power sources is essential for achieving optimal welding results. The paper serves as a valuable historical reference that illustrates the rapid pace of technological advancement in welding equipment.