Research Of Digitalized AC Square-Wave Submerged Arc Welding Power Source

The advance of digital technology, power electronics technology and control theory promotes arc welding power source developing from the analog stage to the digital stage. Digital inverter welding power source becomes the direction of welding because of its high reliability, high accuracy, and easy control of large-scale integration. According to the problems of too big body, complex control circuit and bad reliability, a dual-inverter main circuit of the machine and control systerm based on MCU+DSP is designed in this issue.This paper introduces the characteristic and application of Submerged Arc Welding in detail, expounds the history of digital inverter source in main circle and control system, describes the present situation of digital AC square Submerged Arc Welding both at home and abroad, designs the digital welding system with double-inverter circle and achieves the output of stabilized AC square.On the basis of characteristics of the arc and output, this paper employs double-inverter circle as the main circle, applies the improved phase-shifted soft-switch theory and uses half-bridge topology structure as the second inverter circle, researches the principles and control methods of the inverse processing and calculates the parameters. Depending on the demands of drive circle, PWM control chip UC3846 with current control mode and integrated chip EXB841 are chosen to control the open and close of IGBT and these can restrain magnetism inclined to one side and over current.The control system is realized on MCU+DSP. ATmega64L is chosen as the MCU to control the speed feedback of wire feeding and trolly, algorithm of closed loop PI, PWM control of motor and safekeeping circles to prevent over current, over voltage and over temperature. The DSP MC56F8323 controls the feedback of welding current, welding voltage and PI algorithm of them, welding sequence in time, so that the fine output of source is certified. The control case renders the welding parameters and conditions using buttons and whirling coder.The communication between control board and control case uses RS-485 protocol. Through the software design, PI adjustment of welding parameters is achived. In the paper, software and circuits of controlling system are analysed, and several methods are employed to solve the problem of Electro Magnetic Compatibility. This paper analyses the affects of the parameters of AC Square-Wave and the practical square of current and voltage systematically, and it proves that the Submerged Arc Welding designed can control the arc ignition, welding processes and arc blowout exactly. Using the control case, the welding parameters can be rendered and displayed exactly and the status of welding source can be detected in high speed.At last, the conclusion of control systerm and experimental work is made. Analyze the problem and deficiency of the system, and new research direction is presented.