Polarity Switching Arc Welding Current Control
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Solution Overview
Problem
Existing polarity switching methods in short circuiting arc welding face challenges such as arc extinction and high surge voltages during polarity changes, requiring complex and expensive surge protection circuits, especially when switching between electrode positive and negative polarities during welding.
Innovation Solution
The method involves reducing the welding current during a predetermined short circuit initial period after polarity switching, allowing polarity change at a stable short circuiting stage, thereby eliminating arc extinction and reducing surge voltage, without the need for an arc re-striking circuit or high-capacity surge protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If polarity switching is made during the arcing stage, then welding quality can be improved for varying joints and thickness, but arc extinction occurs resulting in defective welding
Solution Approach 1:
The control circuit detects the arcing stage and initiates polarity switching in advance during the subsequent short circuiting stage, before the arc would naturally extinguish. This preliminary timing action prevents arc extinction while maintaining welding quality, as the polarity change occurs when the circuit is already in short circuiting mode rather than during active arcing.
2Reliability
If polarity switching is made during the short circuiting stage to prevent arc extinction, then welding reliability improves, but high surge voltage occurs requiring complex and expensive surge protection circuits
Solution Approach 1:
The control circuit initiates polarity switching during the short circuiting stage, which is the preliminary phase before potential surge voltage issues arise during arcing. By completing the polarity transition when current is naturally low during short circuiting, the system avoids the high surge voltages that would occur if switching happened during arcing, thereby eliminating the need for complex surge protection circuits.
Solution Approach 2:
The control circuit continuously monitors welding current and voltage to detect the short circuiting stage, and uses this feedback information to determine the optimal timing for polarity switching. This feedback mechanism ensures switching occurs at the precise moment when surge voltage is minimized, automatically adapting to varying welding conditions without requiring additional protective circuitry.
3Reliability
If polarity switching is made during the short circuiting stage, then arc extinction is prevented, but high welding current causes high surge voltage exceeding 500V
Solution Approach 1:
The control circuit detects the transition to short circuiting stage and initiates polarity switching at this preliminary moment when welding current is naturally low. By timing the switching action to occur during the initial phase of short circuiting rather than later when current builds up, the system prevents arc extinction while keeping surge voltage well below the problematic 500V threshold.
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 enhances welding quality by preventing arc extinction and reducing the cost of the welding power source by eliminating the need for expensive surge protection circuits and ensuring reliable polarity switching during welding.
Implementation Method 1
a short circuiting state and an arcing state appear repeatedly between the welding wire and the base metal
Implementation Method 2
a constant voltage power source is used
Data Source
AI summary
A method of performing polarity switching short circuiting arc welding is provided. In the arc welding, a welding wire is fed at a constant feeding rate, a short circuiting state and a arcing state appear repeatedly between the welding wire and a base metal, and the output polarity of a welding power source is switched in accordance with a polarity switching signal for performing electrode positive welding and electrode negative welding. In accordance with the method, the welding current is reduced during a predetermined short circuit initial period, when a first arc is formed after the polarity switching signal changes. Then, the output polarity of the welding power source is changed when the short circuit initial period has lapsed. Further, the welding current is increased for terminating the arc forming between the welding wire and the base metal.