TIG Arc Start Pulse Control for Lower EMI Footprint
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Solution Overview
Problem
High frequency arc starting in TIG welding systems generates a large electromagnetic interference (EMI) footprint, which is undesirable for nearby electronics.
Innovation Solution
The use of pseudo-random noise (PRN) generator control logic to generate a dithered pulse waveform through a hybrid combination of pulse width modulation (PWM) and pulse position modulation (PPM) techniques, reducing the average power spectral density and spreading the frequency spectrum, thereby minimizing EMI during arc starts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high frequency sinusoidal waveform is applied to start the arc, then arc initiation is achieved, but electromagnetic interference footprint increases
Solution Approach 1:
The patent applies periodic pulsed DC waveform instead of continuous high frequency sinusoidal waveform. The controller delivers a series of pulses with specific duty cycle and frequency, achieving arc initiation through repeated on-off cycles rather than continuous high frequency oscillation, thereby reducing EMI while maintaining reliability
Solution Approach 2:
The patent changes the waveform parameters from high frequency sinusoidal to pulsed DC with adjustable pulse width, frequency, and duty cycle. By optimizing these parameters, the system achieves arc start without requiring the high voltage high frequency waveform that causes EMI, thus resolving the contradiction between reliable arc initiation and EMI reduction
2Reliability
If high voltage high frequency waveform is used, then dielectric resistance breakdown occurs and conductive path forms, but large electromagnetic interference is generated
Solution Approach 1:
The controller uses periodic pulsed waveform to progressively break down the dielectric resistance of the shielding gas. The repeated pulses accumulate ionization effects over time, eventually forming a conductive path without requiring a single high voltage surge, thus reducing EMI while achieving the same result
Solution Approach 2:
The pulsed waveform applies preliminary ionization attempts in successive pulses, gradually preparing the gas path for conduction. Each pulse contributes to ionization accumulation, and the preliminary actions of multiple pulses collectively achieve the breakdown that would otherwise require a single high voltage impulse
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 maintains peak arc power while significantly reducing the EMI footprint, ensuring reliable arc initiation with minimal interference to nearby electronics.
Implementation Method 1
pseudo-random noise (PRN) generator control logic circuitry configured to generate a dithered pulse waveform with a pseudo-randomly selected data sequence of binary values based on one or more baselines, and to apply the dithered pulse waveform to an oscillator during arc starting
Implementation Method 2
hybrid combination of pulse width modulation (PWM) and pulse position modulation (PPM) techniques, reducing the average power spectral density and spreading the frequency spectrum
Implementation Method 3
HF waveform arc starts typically create a relatively large electromagnetic interference (EMI) footprint
Implementation Method 4
The high frequency electric field generated at the tip of the electrode breaks down the dielectric resistance of the path between the electrode tip and the work piece within the column of shielding gas
Implementation Method 5
breaks down the dielectric resistance of the path between the electrode tip and the work piece
Implementation Method 6
HF waveform arc starts typically create a relatively large electromagnetic interference (EMI) footprint
Implementation Method 7
welding power source electrically coupled to the welding torch via a weld cable configured to supply electrical energy to the welding torch
Data Source
AI summary
A system and methods for electrically starting an arc in a welding process are disclosed. The system and methods may reduce an electromagnetic interference (EMI) footprint during the arc start by reducing the average power spectral density output and broadening the frequency spectrum of the arc EMI footprint. In one embodiment, a welding system may include a welding torch and a welding power source electrically coupled to the welding torch via a weld cable configured to supply electrical energy to the welding torch. The welding power source may include pseudo-random noise (PRN) generator control logic circuitry configured to generate a dithered pulse waveform with a pseudo-randomly selected data sequence of binary values based on one or more baselines, and to apply the dithered pulse waveform to an oscillator during arc starting in a tungsten inert gas (TIG) welding process performed by the welding torch.