Resonant Welding Current Source for Safe Contactless Arc Ignition
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Solution Overview
Problem
Existing welding current sources face challenges in safely and cost-effectively igniting an arc between an electrode and a workpiece for welding processes, as they must comply with safety regulations while minimizing circuit complexity and size, especially in TIG welding with non-melting electrodes.
Innovation Solution
A series-parallel resonance converter generates a periodically varying open circuit welding voltage with high-frequency pulses superimposed time-synchronously at voltage maxima, reducing the need for complex circuits and allowing safe, efficient arc ignition within regulatory limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high voltage is used for contactless arc ignition, then ignition reliability is improved, but safety compliance deteriorates
Solution Approach 1:
The welding voltage is designed to vary periodically over time, with voltage maxima occurring at regular intervals. High-frequency ignition pulses are applied synchronously at these voltage maxima moments, creating periodic action that combines safety compliance with effective ignition. This periodic modulation allows the system to achieve high ignition reliability without maintaining continuously high voltage that would violate safety standards.
Solution Approach 2:
The control device detects voltage maxima in advance and triggers high-frequency ignition pulses at these predetermined moments. By preparing and applying ignition energy at the optimal moment (when voltage reaches maximum), the system ensures reliable ignition while keeping the overall voltage profile within safety limits for most of the time.
2Reliability
If auxiliary voltage sources are used to raise output voltage for arc ignition, then ignition capability is improved, but device complexity increases
Solution Approach 1:
The ignition function is merged with the existing welding voltage generation circuitry. Instead of adding separate auxiliary voltage sources, the system uses the welding voltage itself (when modulated to have periodic maxima) in combination with high-frequency pulse generation to achieve ignition. This integration eliminates the need for additional complex circuits while maintaining effective ignition capability.
Solution Approach 2:
High-frequency pulses serve as an intermediary mechanism that bridges the gap between the welding voltage and arc ignition. Rather than directly raising the welding voltage with complex auxiliary circuits, the high-frequency pulses mediate the ignition process by providing the necessary energy at critical moments, simplifying the overall circuit design.
3Productivity
If high-frequency pulses are superimposed on welding voltage, then ignition efficiency is improved, but circuit complexity increases
Solution Approach 1:
The control device generates high-frequency pulses in a periodic manner, synchronizing them with the periodic voltage maxima of the welding voltage. This periodic action ensures that ignition pulses are applied only when needed (at voltage maxima), maximizing ignition efficiency while minimizing the duty cycle and complexity of the pulse generation circuitry.
Solution Approach 2:
The system changes the temporal parameters of the welding voltage by introducing periodic modulation with distinct voltage maxima. This parameter change creates optimal moments for ignition without requiring fundamental changes to the voltage generation circuitry, achieving high ignition efficiency through parameter optimization rather than circuit complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures safe and cost-effective arc ignition with minimal additional circuit complexity, allowing for economic application of welding current sources, while maintaining compliance with safety regulations and improving ignition properties.
Implementation Method 1
Resonance converters are electrical circuits based on resonance at a specific resonance frequency. Usually, pulses are applied with a frequency close to this resonant frequency, thereby exciting the resonant circuit at the resonant frequency, which results in a periodically varying output voltage.
Implementation Method 2
For contactless igniting the arc necessary for the welding process between the electrode and the workpiece to be welded, a high voltage is beneficial.
Data Source
AI summary
The invention relates to a method for contactless ignition an arc (L) between an electrode (3) and a workpiece (4) which is to be welded, for carrying out a welding process, wherein a welding current (I) and a welding voltage (U) are provided at an output (2) of a welding current source (1), wherein the welding current source (1) contains a resonance converter (5) for generating a periodically varying, preferably substantially sawtooth-shaped, open circuit welding voltage (ULL) with voltage maxima (ULL,max) which recur periodically with a repetition rate (fw) and a welding current source (1) for carrying out the igniting process. In order to achieve reliable contactless ignition of the arc (L) without complicated circuitry, the resonance converter (5) is formed by a series-parallel resonant converter, and temporally synchronous high-frequency pulses (UI,HF) are superimposed on the open circuit welding voltage (ULL) in the region of at least some of the periodically recurring voltage maxima (ULL,max) of the open circuit welding voltage (ULL).