Three-Stage Arc Welding Power Source With Soft Switching
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Solution Overview
Problem
Existing electric arc welding power sources with a single regulated inverter stage suffer from high heat losses, lower efficiency, and increased component size due to the need for high-frequency switching, which results in higher costs and operational difficulties.
Innovation Solution
A three-stage power source is introduced, where the inverter is unregulated as a second stage, allowing for a third stage to provide actual regulation, optimizing switching frequency and using a fixed high duty cycle to minimize heat and enhance efficiency, with a first stage including an active soft switching circuit and a second stage featuring inherent soft switching capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single regulated inverter stage is used, then welding current regulation is achieved, but switching losses increase and efficiency decreases
Solution Approach 1:
The power source is divided into three independent stages: first stage (power factor correction), second stage (unregulated high-frequency inversion), and third stage (welding current regulation). This segmentation allows each stage to operate at its optimal frequency and duty cycle, with the second stage operating at high frequency with fixed high duty cycle to minimize switching losses while the third stage handles regulation, thereby resolving the contradiction between switching losses and welding efficiency.
2Temperature
If high-frequency switching is used in a regulated inverter, then welding current control is achieved, but heat losses increase
Solution Approach 1:
The regulation function is extracted from the high-frequency inverter stage and placed in a separate third stage. The second stage operates as an unregulated high-frequency inverter with fixed high duty cycle, eliminating the heat losses associated with regulated high-frequency switching, while the third stage provides welding current control, thus resolving the contradiction between heat losses and welding control.
3Volume of moving object
If a regulated inverter operates at high frequency, then component size is reduced, but operational difficulties increase
Solution Approach 1:
The system is segmented into three stages with the second stage operating at high frequency with fixed high duty cycle to minimize component size, while the third stage handles all regulation functions. This segmentation allows the high-frequency stage to use smaller components without facing the operational difficulties of regulated high-frequency switching, as the duty cycle is fixed and simplifies control.
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 configuration reduces switching losses, increases efficiency, and improves heat distribution in power switching components, leading to better welding performance and reduced component size and cost.
Implementation Method 1
the pulse width modulator converter of the first stage has zero voltage switching for the active converter switch and zero reverse recovery current for the output rectifier diode
Implementation Method 2
The turn on signal for the power switch is applied while the anti-parallel diode is conducting to provide a zero voltage switching of the modulating switch at turn on
Implementation Method 3
An anti-parallel diode of the pulse width modulator switch is thus forward biased. The turn on signal for the power switch is applied while the anti-parallel diode is conducting to provide a zero voltage switching of the modulating switch at turn on
Data Source
AI summary
A three stage power source for an electric arc welding process comprising an input stage having an AC input and a first DC output signal; a second stage in the form of an unregulated DC to DC converter having an input connected to the first DC output signal, a network of switches switched at a high frequency with a given duty cycle to convert the input into a first internal AC signal, an isolation transformer with a primary winding driven by the first internal high frequency AC signal and a secondary winding for creating a second internal high frequency AC signal and a rectifier to convert the second internal AC signal into a second DC output signal of the second stage, with a magnitude related to the duty cycle of the switches; and, a third stage to convert the second DC output signal to a welding output for welding wherein the input stage has a regulated DC to DC converter with a boost power switch having an active soft switching circuit.