Alternating current welding using four quadrant switches

Welding metals such as aluminum and magnesium requires AC current. This work proposes a novel control strategy for a high-frequency rectifier built with four quadrant switches (4QSW) to transform high frequency AC current (125 kHz) into the welding arc bipolar current, controlled in amplitude, frequency and even DC offset. The rectifier is connected to the output of a resonant inverter to achieve positive and negative polarity discharges both voltage and current by operating in two quadrants, i.e. positive and negative. As long as the input power to the converter is supplied by a current source, the typical dead-time set to avoid short circuit conditions jeopardize the safe operation of the switches. A field-programmable gate array (FPGA) is selected to implement the digital control due to its high resolution for the purpose to adapt the 4QSW's drive signals without dead-time in the most accurate manner.This work was supported by FEDER and the Spanish Ministry of Science through the project CICYT-FEDER TEC2011-23612: “Power conversion with new digital control techniques and soft-saturation magnetic cores

Unfolded resonant converter with current doubler structure module for welding applications

A new multiphase resonant converter arrangement with series dual phase in the primary side and parallel dual current doubler in the secondary side, operating as a phase shift controlled current source is presented. Sharing the voltage and current stress among the active and passive components with a high DC input voltage and arc current motivates this structure, which also uses WBG devices to increase the efficiency at high switching frequency. The resulting module is intended to operate in continuous and pulsating mode and can be parallelized to extend the output arc current rate.This work was funded by the Spanish Ministry of Science and the EU through the project TEC2014-52316-R: ‘Estimation and Optimal Control for Energy Conversion with Digital Devices’ ECOTRENDD

Converter With Four Quadrant Switches for EDM Applications

This paper presents a high-frequency rectifier stage using four quadrant switches as synchronous rectifiers for an electrical discharge machining (EDM) power supply. The EDM impulse generator is a series–parallel resonant inverter operating in current-mode. The device specifications and drive requirements of the converter are studied with the objective of generating unipolar and bipolar current waveforms suitable for different types of EDM operations

Performance study of arc characterization for linear and non-linear loads in an electrical distribution system

Arc fault is part of faults due to electrical sources that can cause fire hazard, malfunction or damage of equipment and even loss of life and properties. Many studies revealed that conventional circuit breaker lack the ability to protect an arc fault, responding only to short circuits and overloads. Therefore the need to study the performance characteristic of an arc and its properties in order to ease future design of arc detectors. The objective of the study is to characterize and study the effect of an arc on voltage and current with different loads, simulate the effect of an arc and harmonic content with different load and compare the effect of linear and nonlinear load to arc in low voltage electrical distribution system. This project proposes a mathematical model which describes the behavior of the electric arc in power circuits. The arc is studied like a circuit component and simulation was done for a series arc only with the help of MATLAB software package. Results show that occurrence of an arc gives rise to the current and a drop in the voltage for both linear and nonlinear load, it lasts in ms for linear and in seconds for the latter. Effect of the arc with an increase in load for both linear and nonlinear load has led to a decrease in both current and voltage THD. With linear load, the current THD increases while the Voltage THD decreases in the case of nonlinear load