Three-Phase Dual-Switch PFC Reverse-Polarity TIG Welding Power Supply Research

Literature Overview

This 2014 study by Xu Jie and Shen Jinfeng from Jiangnan University investigates the design and implementation of a three-phase dual-switch Power Factor Correction (PFC) circuit integrated with a reverse-polarity Gas Tungsten Arc Welding (GTAW/TIG) power supply. The research addresses a critical gap in welding power electronics where conventional three-phase rectifiers suffer from poor power factor, excessive harmonic distortion, and limited controllability of arc polarity. The authors propose a topology combining a three-phase boost converter with dual-switch PFC and a DC-DC inverter stage capable of delivering controlled reverse polarity for TIG welding applications.

Core Technical Content

Power Factor Correction Architecture

The three-phase dual-switch PFC circuit operates by synchronously controlling the switching of upper and lower MOSFETs in each phase leg to achieve near-unity power factor operation. The key design parameters include a DC bus voltage regulated at approximately 700-800 V, switching frequency in the range of 20-50 kHz, and input current ripple kept below 10% of the rated value. The dual-switch configuration eliminates the need for diode clamps used in conventional three-phase boost topologies, reducing voltage stress on the switches and improving overall efficiency.

Reverse-Polarity TIG Arc Control

Reverse-polarity TIG (AC-TIG with emphasis on the negative half-cycle) is essential for cleaning oxide layers on aluminum and its alloys during welding. The power supply design incorporates a current-controlled inverter stage that can precisely regulate the ratio of positive to negative half-cycle current, which directly determines the balance between arc cleaning action and weld penetration. The control strategy employs a dual-loop architecture with an outer current loop for welding current regulation and an inner voltage loop for DC bus stabilization.

Key Technical Parameters

Engineering Practice Implications

The adoption of three-phase PFC-based welding power supplies offers significant advantages in industrial settings where three-phase power is standard. Compared to single-phase welding sources, three-phase input provides smoother DC bus voltage with lower ripple, which translates to more stable arc characteristics and improved weld bead quality. The dual-switch topology is particularly suitable for high-power applications above 30 kW where conventional single-phase PFC solutions become impractical.

For aluminum welding operations, the precise control of AC ratio is critical. In engineering practice, a typical AC ratio of 60:40 (negative:positive) is used for general aluminum welding, while thinner gauge aluminum may require 70:30 to enhance cleaning without excessive heat input. The ability to programmatically adjust this ratio during the welding cycle enables sophisticated welding sequences including pre-heat, root pass, and cap pass optimization.

Reflections and Study Insights

This research represents a meaningful advancement in welding power electronics by addressing the power quality issues that have long plagued industrial welding operations. From a pressure vessel fabrication standpoint, the improved arc stability provided by PFC-based sources directly contributes to reduced defect rates in critical welds, particularly in austenitic stainless steel and nickel-based alloy overlay applications where arc instability can lead to incomplete fusion or excessive dilution. The work also opens possibilities for developing welding power supplies that comply with stringent power quality standards such as IEEE 519 and IEC 61000-3-2, which are increasingly mandated in modern fabrication facilities.