COMPUTERIZED SIMULATION AND EXPERIMENTAL RESEARCH ON SOFT-SWITCHING ARC WELDING INVERTER POWER SOURCE

Based on the existing component models in the Pspice software package, a combined model for Insulat- ed the Bipolar Transistor (IGBT) is established, in which a non - linear is introduced to represent the parasitic capacitance. Using this model, computerized simulation is conducted for the FB - ZVZCS - PWM soft - ewitching converter,the switching and energy-transferring characteristics of the components are analyzed.The simulation results are testified by experiments.It is proved that by abopting appropriate models,computerized simulation becomes an effective tool for investigation of arc welding inverter power source.

A novel arc welding inverter with unit power factor based on DSP control

A novel inverter power source is developed characterized with constant output current and unit power factor input. Digital signal processor （ DSP ） is used to realize power factor correction and control of back-stage inverter bridge of the arc welding inverter. The fore-stage adopts double closed loop proportion and integration （PI） rectifier technique and the back- stage adopts digital pulse width modulation （ PWM） technique. Simulated waves can be obtained in Matlab/Simulink and validated by experiments. Experiments of the prototype showed that the total harmonic distortion （THD） can be controlled within 10% and the power factor is approximate to 1.

SIMULATION AND EXPERIMENTATION OF THE ARC WELDING INVERTER USING THE SOFT SWITCHING TECHNIQUE

The FB-ZVZCS-PWM converter is realized by the way of subjoiningblock-capacitor into the FB-ZVS-PWM converter. At the freewheeling interval, the primary current isattenuated fast to zero and maintained. And then, power device of the static leg becomes azero-current-switch (ZCS), power device of the shifted leg becomes a zero-voltage-switch(ZVS). Thus,on one hand IGBT (Insulated gate bipolar transistor) with tail current can be easily used infull-bridge soft-switching converter; on the other hand additional circuiting energy is greatlyreduced. At the same time, less duty cycle loss, lower secondary parasitic resonance, widersoft-switching load range can be achieved. Based on the existing component models in the Pspicesoftware package, a combined model of IGBT is established, in which a non-linear capacitor isintroduced to replace the parasitic capacitor. Using this model, computerized simulation isconducted for the FB-ZVZCS-PWM soft-switching converter, the switching and energy-transferringcharacteristics of the power device are analyzed. Finally, based on the achievement above, a 10 kWarc welding inverter with FB-ZVZCS-PWM converter is developed. The simulation results are testifiedby experiments. It is proved that by adopting appropriate models, computerized simulation is aneffective and useful tool for the development of the arc welding inverter.

Reducing the minimum output power of soft-switching inverter arc welding power supplies

The full-bridge zero-voltage and zero-current switching inverter, which can adjust the output power by keeping the duty-cycle of lagging arm constant, changing the duty-cycle of leading arm, is a common circuit topology of soft-switching inverter arc welding power supplies. However, the output power still remains a certain value when the duty-cycle of leading arm decreases to zero. The working-mode of soft-switching inverter and the waveforms of major parameters with the condition of duty-cycle of leading arm being zero are studied in this paper. U-1 characteristic experiments prove that the minimum output power of soft-switching circuit, which depends on the charged voltage of capacitors in parallel with leading arm, can be decreased by reducing the duty-cycle of lagging arm. By switching working-modes between half-bridge and full-bridge, the output power can swing from zero to the power rating.

ZVS of arc welding inverter in light load

It is very difficult for arc welding inverter to realize Zero-Voltage-Switching （ZVS） because the load of arc welding inverter changes violently. An improved PS-FB-ZVS-PWM （ Phase-Shifted Full-Bridge Zero-Voltage-Switching Pulse-Width-Modulation） topology is proposed in this paper. A saturate resonant inductor is in series with the primary side of the transformer, while an auxiliary inductor is in parallel with the secondary side of the transformer to increase reactive current in light load or unload state, so the zero voltage switching of power devices is realized during switching course in light load or unload state.

Insulated gate bipolar transistor inverter for arc welding

This paper introduces the Insulated gate bipolar transistor(IGBT)in- verter for arc welding.The principle of the inverter,the structure and charac- teristics of IGBT and the current feedback system using LEM current transduc- er are discussed.By the measurement of its efficiency and power factor and the tests of welding processes,the developed 150A IGBT inverter proves to be a kind of energy-saving portable power supply for arc welding with broad prospects.

Digital control of pulsed gas metal arc welding inverter using TMS320LF2407A

A digital control of pulsed gas metal arc welding inverter was proposed. A control system consisting of analogue parts was replaced with a new digital control implemented in a TMS320LF2407A DSP chip. The design and constructional features of the whole digital control were presented. The resources of the DSP chip were efficiently utilized and the circuits are very concise, which can enhance the stability and reliability of welding inverter. Experimental results demonstrate that the developed digital control has the ability to accomplish the excellent pulsed gas metal arc welding process and the merits of the developed digital control are stable welding process, little spatter and perfect weld appearance.

INTELLIGENT CONTROL SYSTEM OF PULSED MAG WELDING INVERTER BASED ON DIGITAL SIGNAL PROCESSOR

A fuzzy logic intelligent control system of pulsed MAG welding inverter based on digital signal processor （DSP） is proposed to obtain the consistency of arc length in pulsed MAG welding. The proposed control system combines the merits of intelligent control with DSP digital control. The fuzzy logic intelligent control system designed is a typical two-input-single-output structure, and regards the error and the change in error of peak arc voltage as two inputs and the background time as single output. The fuzzy logic intelligent control system is realized in a look-up table （LUT） method by using MATLAB based fuzzy logic toolbox, and the implement of LUT method based on DSP is also discussed. The pulsed MAG welding experimental results demonstrate that the developed fuzzy logic intelligent control system based on DSP has strong arc length controlling ability to accomplish the stable pulsed MAG welding process and controls pulsed MAG welding inverter digitally and intelligently.

Digital close loop control system for current-programmed mode arc welding inverter

A small-signal model of current programmed mode pulse width modulation converter including the equivalent sampling effect is introduced and analyzed. In this model, an addition pole is brought out by the sampling effect in the current loop gain, and it affects dynamic bandwidth and stability of the inner current loop. By selecting the appropriate stability parameter which determines the additional pole and describes the degree of peaking in closed loop transfer function, a control model of current programmed full bridge arc welding inverter with maximum frequency bandwidth and stability can be obtained. Small and large amplitude pulse current outputs are employed in simulations and experiments and results validate the design method.

Principle and parameter design of arc welding inverter using soft switching technique

The soft switching are welding inverter reduces switching losses and improves operating environment of devices by using Zero-Voltage-Transition (ZVT) technique. Step-by-step analysis of each timing interval and the associating voltage and current waveforms are included for the Full-Bridge Zero-Voltage-Switched PWM converter. Numerous design equations supporting the phase-shifted soft switching technique are highlighted.

A research of arc welding inverter with high stable precision

This paper mainly introduces an output control method with high stable precision of a large power IGBT arc welding inverter. Experiments indicate that this kind of control mode can effectively improve the static and dynamic characteristics and stability of power supply system. And it can decrease the spatters in the welding process apparently. This power supply is especially suitable to automatic robot welding assembly line. It will be the developing direction of robot welding supply in the future.

EDGE PROCESS ON ARC WELDING INVERTER COMMUTATING

Half-bridge circuit is taken as example, the physical essential of current pulse front edge and back edge in PWM of PFM converter is analyzed. The appearance of varying current-source or transfor- mation from voltage-source into current-source in primary of converter is necessary condition for forming front and back edges. Through synchrenously varying of primary current and secondary current , and current shifting between two secondary windings in constant magnetic condition, transformation of basic Stages is realized.