Superposition Circuit for AC Arc Re-ignition
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Solution Overview
Problem
In AC arc welding, the arc often extinguishes during polarity transitions, leading to inefficient welding processes as existing power sources lack sufficient voltage to re-ignite the arc quickly, especially in processes like TIG welding where the arc must be re-established from scratch.
Innovation Solution
A welding power source system incorporating a superposition circuit with a pre-charge capacitor and dedicated charging source provides an energy limited arc re-ignition voltage, allowing for rapid and reliable re-ignition of the arc during polarity transitions by applying a high voltage between the electrode and workpiece, even when the power source voltage is limited.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard welding power source with limited voltage output is used, then the power source design is simple and cost-effective, but the arc cannot re-ignite reliably during polarity transitions in AC welding
Solution Approach 1:
The superposition circuit pre-charges a capacitor to a high voltage level (e.g., 400V) before the polarity transition occurs. When the welding current crosses zero and the arc extinguishes, this pre-charged capacitor immediately provides the high voltage needed to re-ignite the arc in the opposite polarity direction, ensuring reliable arc re-ignition without requiring the main power source to have high voltage capability.
Solution Approach 2:
The superposition circuit acts as an intermediary between the limited-voltage welding power source and the high-voltage requirement for arc re-ignition. The dedicated charging source and pre-charge capacitor in the superposition circuit generate and store the necessary high voltage, which is then applied to the welding output only during the brief polarity transition period when arc re-ignition is needed, allowing the main power source to remain simple while achieving reliable arc re-ignition.
2Reliability
If the welding power source increases its maximum voltage output to enable arc re-ignition, then arc re-ignition becomes possible, but the power source design becomes more complex and expensive
Solution Approach 1:
The superposition circuit pre-charges a capacitor to a high voltage level (e.g., 400V) before the polarity transition occurs. When the welding current crosses zero and the arc extinguishes, this pre-charged capacitor immediately provides the high voltage needed to re-ignite the arc in the opposite polarity direction, ensuring reliable arc re-ignition without requiring the main power source to have high voltage capability.
Solution Approach 2:
The superposition circuit activates only during the brief periodic intervals when the welding current crosses zero and polarity transitions occur. The controller detects the zero-crossing point and triggers the superposition circuit to apply high voltage to the welding output only during these short windows when arc re-ignition is needed, rather than maintaining high voltage capability continuously.
3Reliability
If a high voltage is applied continuously to ensure arc re-ignition, then arc re-ignition is reliable, but energy consumption increases and the welding process becomes inefficient
Solution Approach 1:
The superposition circuit activates only during the brief periodic intervals when the welding current crosses zero and polarity transitions occur. The controller detects the zero-crossing point and triggers the superposition circuit to apply high voltage to the welding output only during these short windows when arc re-ignition is needed, rather than maintaining high voltage capability continuously.
Solution Approach 2:
The superposition circuit pre-charges a capacitor to a high voltage level (e.g., 400V) before the polarity transition occurs. When the welding current crosses zero and the arc extinguishes, this pre-charged capacitor immediately provides the high voltage needed to re-ignite the arc in the opposite polarity direction, ensuring reliable arc re-ignition without requiring the main power source to have high voltage capability.
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 solution ensures consistent and efficient arc re-ignition in both polarities, reducing the need for repeated arc establishment and improving the overall efficiency of AC arc welding processes by providing a sufficient voltage for arc re-ignition during polarity changes.
Implementation Method 1
A superposition circuit having a pre-charge capacitor and a dedicated charging source configured to directly or indirectly charge the pre-charge capacitor provides the voltage needed during current polarity transition to quickly and reliably re-ignite the arc
Implementation Method 2
an AC gas tungsten arc welding process (GTAW or TIG) or an AC gas metal arc welding process (GMAW or MIG), it is desirable for the arc between the electrode and the workpiece to quickly re-ignite
Data Source
AI summary
Systems and methods providing an energy limited arc re-ignition voltage for AC arc welding processes to re-ignite an arc during polarity transitions. In arc welding power source embodiments, configurations of bridge and superposition circuits allow for the directional switching of the welding output current through the welding output circuit path and provide a voltage between the electrode and the workpiece of the welding output circuit path that is sufficient to re-ignite the arc during polarity transition of the output current. The superposition circuit provides a capacitor for storing energy from a dedicated charging source which produces the voltage level for re-igniting the arc during the zero crossing of the output current in both polarities.