If Arc Welding Generator Excitation Current Control Studies

As many Chinese electric welding machines have the disadvantages of complex control circuits, defective reliability and flexibility and insuffieient function, This article discussed a digital control method of excitation current based on intermediate frequency combustion arc welding generator.This method can make the arc welding generator has a No-load voltage of up to85V,and the arc welding generator will have excellent steep drop external characteristic. The welder also has a thrust current function which will act while the arc voltage is too low,in other words,the output current of the machine also has a constant current and voltage external thrust current,against the manual arc welding process, Arc welding generator excitation control circuit collect the welding current and arc voltage signals,the analog signals will be transformed into digital signals while they are collected,then a PWM pulse will be generated according to these digital signals.This PWM pulse will be used to control the conduction or shutdown of an IGBT, which is in series with the rotor windings as a DC chopper. To take this method mentioned above,we can control the excitation circuit through the pulse width of the PWM pulse.And this method can achieve a quick respond of the generator external characteristics of different load conditions.The paper first describes the machine's hardware system, including the principle of the synchronous generator and the advantages of the medium frequency synchronous generator., compared to ordinary generators。Then Author described in detail the first set of control solution using3525chip constitute the main control circuit, including the circuit design features and parameters selection and operating principle. The second control solution is to use STC89C52AD MCU as the main control chip, author describes in detail the hardware and software implementations of the control solution. Finally,through the experimental data,author briefly analysis the advantages and disadvantages of the two options, and raises improved methods.Experiments show that:the external characteristics of the arc welding generator responses fast, welding parameters can be adjusted continuously, the adjustment range can meet the actual demand, and the machine is able to meet the requirements of a variety of manual arc welding process, especially to meet the thrust current which is demanded by the downwad welding process requirements.