Stud Welding Arc Voltage Measurement Using Pilot Current and Switched Inductance
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Solution Overview
Problem
Existing stud welding installations face inaccuracies in measuring arc voltage due to electrical resistance and inductance in the welding circuit, leading to measurement errors exceeding 50% when measured at the output terminals of the power supply device.
Innovation Solution
A method that determines electrical variables of the welding circuit by bridging the input circuit to ignore the inductance, allowing for accurate calculation of arc voltage without additional hardware complexity, using a pilot current to stabilize the arc and a switch to manage the inductance, enabling real-time determination of resistance and inductance during the welding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If arc voltage is measured at the output terminals of the power supply device, then measurement can be performed without additional hardware, but measurement accuracy deteriorates due to voltage drop across resistance and inductance
Solution Approach 1:
The patent extracts the welding circuit inductance from the measurement circuit by introducing a separate test current path. The test current flows through the welding circuit inductance without passing through the measurement circuit, thereby eliminating the inductance's interfering effect on voltage measurements while maintaining measurement simplicity
Solution Approach 2:
The patent introduces a test current as an intermediary element to separately measure the welding circuit inductance. This test current serves as a mediator that allows indirect determination of inductance effects without directly measuring through the main power circuit, thus resolving the contradiction between simple measurement and accurate results
2Measurement precision
If measurement lines are laid parallel to connecting lines from power supply device to welding head, then arc voltage measurement accuracy is improved, but device complexity and susceptibility to mechanical faults increase
Solution Approach 1:
The patent merges the measurement functions into the existing power supply device structure. The test current measurement and voltage measurements are integrated within the power supply device, eliminating the need for separate parallel measurement lines and reducing overall system complexity while maintaining measurement accuracy
Solution Approach 2:
The power supply device is given multiple functions: it simultaneously provides welding current and performs both voltage measurements and inductance measurements. This multi-functionality eliminates the need for dedicated separate measurement hardware, reducing device complexity while maintaining measurement precision
3Ease of manufacture
If resistance of welding circuit is measured by subtracting voltage drop across resistance from terminal voltage, then resistance measurement is simplified, but measurement accuracy deteriorates due to ignoring inductance voltage drop
Solution Approach 1:
The patent segments the measurement process into distinct phases: first measuring the welding circuit inductance using test current, then using this inductance value to compensate for inductive voltage drop during actual welding voltage measurements. This segmentation allows each measurement to be optimized independently, achieving both simplicity and accuracy
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 allows for precise and accurate measurement of arc voltage, reducing errors and enabling online control of the welding process, with the ability to identify changes in welding current and voltage, facilitating quick short-circuit detection and improved welding quality without additional hardware requirements.
Implementation Method 1
determination of a first electrical variable when the input circuit is not bridged, and determination of a second electrical variable when the input circuit is bridged
Implementation Method 2
A method that determines electrical variables of the welding circuit by bridging the input circuit to ignore the inductance, allowing for accurate calculation of arc voltage
Data Source
AI summary
A stud welding apparatus comprising a power supply including power electronics operable for supplying a variable welding voltage together with one of a pilot current and a welding current that is much larger than the pilot current; and a current measuring circuit operable for measuring the electrical current to the weld head; and an input circuit electrically connected between the power electronics and the power supply output, the input circuit including a first inductance, a first resistance, and a switch operable to bridge the first inductance and the first resistance; and a welding circuit electrically connected between the power supply output and the weld stud, the welding circuit having a welding circuit resistance and a welding circuit inductance, and the welding circuit inductance is much smaller than the first inductance of the input circuit; and a voltage measuring device is operable for measuring a voltage across the welding circuit.