Conference Paper

A two-stage power converter for welding applications with increased efficiency and reduced filtering

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

The power supply technology used in welding applications changed dramatically from manually tap-controlled 50 Hz bulky transformers which had large leakage inductance to provide stable arc burn to switch-mode fast controlled high-frequency power electronics. Nowadays, the typical converter configuration consist of a diode rectifier supplying via a large electrolytic capacitor a smooth DC-link voltage to a high switching frequency H-bridge inverter that steps down the voltage and provides isolation via a high frequency transformer whilst operating with adjustable duty-cycle to maintain the output current constant. This topology allows for important size reduction since the size of magnetics decreases rapidly with the increase of the frequency. This paper proposes a more complex two-stage configuration with a buck DC/DC converter operating at a reduced switching frequency to feed adjustable voltage to an H-bridge inverter, which is operating always with the required voltage at 50% duty-cycle, enabling in addition the minimization of the output filter size and of the switching losses.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

Article
This paper proposes a novel, reliable, efficient and cost-effective implementation of partial soft switching in a silicon carbide (SiC)-based variable-frequency phase-modulated resonant transition converter (PMRTC) used in manual metal arc welding (MMAW) applications at a peak power of 1.3 kW. The switching frequency (\(f_{sw}\)) of the converter is increased from 100 kHz at no load to around 150 kHz for a rated power of 1.0 kW. Such an approach is not found in the existing literature. At such frequencies, a significant proportion of the output filter inductance is contributed by the inherent self-inductance of the output “lead cables”. The switching losses in the semiconductor devices are reduced at no-load condition by reduction of the operating frequency. Load regulation is achieved at 150 kHz by implementing phase-shifted PWM technique. Implementation of partial soft switching without using additional components is another significant contribution of this work. The reduced size and weight of the filter inductor in turn reduces the overall size, weight and cost of the system but puts a restriction on the output lead cable length, which is another salient finding of this work. Since at high frequency the transformer model changes, design and finite-element method (FEM)-based simulation of the transformer are also presented in this paper. Loss calculations at 100 and 150 kHz are discussed. The entire converter is fabricated in the laboratory. Experimental and simulated results are found to be in excellent agreement.
Article
The high-current delivered by a dedicated power supply is the condicio sine qua non to obtain the strong magnetic field produced by superconducting magnets. The end goal of such power supply is to control the current, very precisely, across this distinctive kind of load. To this extent, the topology and a specific mode of operation that fit the requirements is analysed and presented in this paper. To obtain a contemporary power supply design, a design optimisation of the overall system with respect to efficiency and volume is carried out. Considering the modularity specification, the system is split into elementary building blocks and one optimally designed unit is practically implemented and verified against predictions from the design tool. In sum, this paper provides the comprehensive design process for a modern 2-quadrant high-current low-voltage DC/DC power supply.
Article
This paper presents the hybrid control of DC-DC resonant converter for DC micro-grid. The hybrid control is the simultaneous variation of frequency and duty ratio which can provide excellent voltage regulation and maintain zero voltage switching (ZVS) over wide load range. Hence excellent conversion efficiency is also maintained over wide load range using hybrid control. However, the conventional control methods for DC-DC resonant converter using either variable switching frequency or duty ratio have their own limitations. The frequency control requires wide variation in switching frequency for output voltage regulation which leads to higher switching losses at turn-off of switches and lower efficiency particularly at light load. The duty ratio control has a limitation of loosing of ZVS at light loads. The simulation and experimental results of hybrid control of resonant converter operating above 100 kHz with maximum duty ratio of 0.48 for 3kW are presented from full load to no load. The maximum efficiency of the resonant converter is found to be 98% which was achieved at 75% of full load.
Article
This paper suggests a high-efficiency portable welding machine based on full-bridge converter with input-series-output-parallel (ISOP)-connected single transformer. Link voltage balance problem is theoretically analyzed according to deviations of transformer leakage inductances and transformer turns-ratios and simple voltage-balancing circuit using flying capacitor is introduced to remove this problem. Also, active-snubbing method is also proposed to improve overall efficiency by recovering parasitic resonant energy and regulating the voltage stress of rectifiers to the level that schottky diodes are available. The feasibility of the proposed structure has been verified with 17.5-kW welding machine with 60-kHz switching frequency.
Article
This paper proposes a power-factor-corrected canonical switching cell (CSC) converter-based switched-mode power supply for arc-welding applications. In the proposed arc-welding power supply (AWPS), CSC converter operating in discontinuous inductor current mode (DICM) is used to attain inherent power factor correction. The DICM operation substantially reduces the complexity of the control and effectively regulates the dc-link voltage. At the back end, a pulsewidth-modulated (PWM) isolated full bridge dc-dc converter is used to provide a high-frequency isolation, which is mandatory for the arc-welding process. A dual-loop control scheme is utilized to incorporate overcurrent protection and to regulate dc voltage at the output making it suitable for arc-welding applications. Test results are presented to confirm the viability of the proposed AWPS. The performance of the proposed AWPS is evaluated on the basis of total harmonic distortion (THD) of the supply current, power factor, dynamic response, and voltage regulation to prove its effectiveness.
Article
In this study, a high-performance single-phase inverter arc welding machine is presented. Power control of the developed welding machine is realized with a high-frequency, phase-shifted full bridge (PSFB) pulse-width modulation (PWM) converter. The PSFB PWM converter operates with soft switching at no load and full load. There is no need to use a passive snubber in the converter. Welding machine control is implemented with a digital signal processor (DSP) and phase-shift PWM IC. By means of the DSP, advanced arc welding functions and protection features such as shortcircuit, over-current, and temperature protection are achieved. The current and voltage waveforms given are from an IGBT-based PSFB PWM arc welding machine operating at 75 kHz switching frequency and 160 A output current. The experimental results show that the proposed system has promising feasibility in industrial applications.
Article
This paper presents the analysis, design and implementation of a power factor corrected Arc Welding Power Supply (AWPS) with a boost converter at the front end and three full-bridge (FB) converters connected in parallel at the load end. The modular arrangement of the FB converters offers several meritorious features like usage of power devices with comparatively lower voltage and current ratings, ease of power expandability, easy maintenance, etc. The boost converter operates in continuous conduction mode minimizing the input current ripple and leading to the lowest RMS current thereby improving the input power quality. Individual control loops are designed for each power stage. A dual loop control scheme is employed to incorporate over-current limit on the proposed AWPS which ensures excellent weld bead quality. The proposed AWPS is implemented to validate its performance over a wide range of line/load variations. Test results confirm its fast parametrical response to load and source voltage variations and over-current protection leading to improved welding performance and weld bead quality. The system is found to perform extremely well with very low input current THD and unity power factor, adhering to international power quality norms.
Article
A broad range of energy-using products have been analyzed to shape the eco-design requirements for the European market under the Ecodesign Framework Directive 2009/125/EC in the last several years. Only recently, this approach also addressed production equipment, including ovens, furnaces, machine tools, and related machinery. Welding equipment has been subject to such an analysis as part of the study on machine tools. This article summarizes the individual steps of this technical, economic, and environmental analysis to facilitate the understanding of the policy intentions: The study followed a standardized methodology and identified, through this approach, a significant energy savings potential of 7.6 petajoules per year and suitable policy options. The article discusses these options, addressing in particular the challenges faced by industrial equipment. Some shortcomings of the methodology to be used have to be stated. These are time and resource constraints to develop policy measures with adequate resources, uncertain market evidence, and the challenge to forecast the effect of engineering options not yet implemented in a product. Under these conditions, the findings are a compromise between feasibility and scientific robustness.
Article
In this paper, a new technique for controlling dc-dc resonant converters is investigated. A variable inductance is used to control and regulate the dc output voltage maintaining constant switching frequency for the half-bridge transistors. The output voltage characteristics of the series resonant and parallel resonant converters under the proposed magnetic control are obtained and analyzed. In order to evaluate the proposed technique, a laboratory prototype for a 48 V-input 5 V/10 A-output 500 kHz parallel resonant converter is presented. A methodology for obtaining the converter dynamic response using a step response test is carried out. From the dynamic response, a compensator for operating the converter at closed loop is developed and tested in the laboratory. The results prove that the proposed technique is suitable for controling resonant inverters at constant frequency using a low-cost half-bridge inverter.
Article
Switched mode power supplies (SMPS) are commonly used in telecommunication towers and welding equipments. In medium capacity SMPS, power quality at the utility interface is a major concern. A new autoconnected transformer is presented for power quality improvement in 18-pulse AC-DC converter fed SMPS with least magnetic rating. Various autoconnected transformers are studied for 18-pulse AC-DC rectification and a new autoconnected transformer is selected to improve the power quality of the supply current. The effect of load variation on SMPS is studied to demonstrate the performance and effectiveness of the proposed 18-pulse AC-DC converter-based SMPS in the wide operating range of the power supply system. A set of power quality indices at input AC mains and magnetic rating of various autoconnected transformers are presented to compare their performance. Laboratory prototype of the proposed autoconnected transformer-based 18-pulse AC-DC converter is developed and test results are presented to validate the proposed design and developed model of the converter system.
Conference Paper
This paper proposes a new DC/AC power converter topology that is obtained by merging a buck type DC/DC converter and a DC/AC three-phase PWM voltage source inverter (VSI) without the need of the passive components (smoothing inductor and capacitance) between the two stages. The novel topology is characterized by less hard switchings needed to synthesize the desired output voltage states, mostly because the average voltage seen by the VSI is modulated in such a way that enables the elimination of its zero voltage state and allows for some zero voltage switchings, reducing the switching losses, that makes this topology more suitable for higher frequency operation, which would ultimately reduce the size of the converter in applications where a load side output filter needs to be fitted
Conference Paper
A three-phase welding inverter power supply (WIPS) with power factor correction (PFC) function is proposed to deal with the input current distortion problem that baffled WIPS application for several years. In this paper, a switch-rectifier is used and controlled by a digital signal processor (DSP) based on space vector modulation (SVM) to replace diode-rectifier of the conventional WIPS. The control strategy to realize PFC function in WIPS is studied. A new two-mode work scheme is proposed to overcome the problems brought by switch-rectifier when WIPS work in open-load period. A new WIPS device with PFC function is constructed and experimented to confirm the validity.
Conference Paper
Dynamic behavior is of great importance for a welding power supply, but has not been investigated adequately. In view of the large signal characteristics of the dynamic process of arc welding, a nonlinear model of the control system for the welding inverter has been put forward and computer simulation is conducted. From the comparison between the simulation and experiments, it is proved the model is correct and the method is a useful approach for analysis and design of an arc welding inverter
Conference Paper
According to the adoption of inverter circuit topology for welding machine area, the improvement of welding performance con be achieved. However conventional CO<sub>2</sub> inverter arc welding machine uses the constant voltage characteristics. So the metal transfer is performed under nonoptimum conditions in view of spatter generation. In this paper the new control algorithm is proposed for welding machine, which is the instantaneous output current control method using single chip microprocessor. But the optimum waveform of welding current is still uncertain, as a first step for figuring out the optimized waveforms, this study was performed, and as a result of performance test of the proposed system, it was demonstrated that all of the waveform variation parameters could be set individually and the generated spatter is reduced compared to conventional inverter arc welding machine
Conference Paper
The inverter circuit has been adopted to welding machines to improve welding performance. As the conventional inverter welding machine has a diode rectifier, there are many problems such as input current harmonics generation and low power factor, which can be solved by the high power factor inverter arc welding machine proposed. The characteristics of new type noise cut transformer is investigated, which could prevent switching devices from being destroyed by electrical noise generated from arc welding procedure. The experimental results are shown from the view point of welding performances and power factor. Through the experimental results the welding performances such as spatter and bead are greatly improved and the power factor is maintained roughly to unity
Conference Paper
The main objectives of using inverter welders instead of line frequency welders are portability, increased performance, the need to weld special materials such as aluminium or stainless steel, i.e. versatility, and also cost at higher power levels. This paper gives a brief introduction of inverter welders on the market worldwide, and also highlights the special requirements for inverter welders used in African conditions. The zero voltage switching partial series resonant converter, a new robust DC-DC converter having inherent higher overvoltage immunity is presented. It features the use of IGBTs at high switching frequencies, and provides outstanding welding characteristics for a number of different welding processes
Welding Process Handbook
  • K Weman
Welding-related Expenditures, Investments and Productivity Measurement in US Manufacturing, Construction and Mining Industries
  • American Welding Society
  • Edison Welding Institute
  • Us Bureau Of Export
  • Administration
Inverter Based Welding Power Supplies for Welding Aluminum, The Lincoln Electric Company
  • F G Armao