1. Due to technical innovation and the improvement of welding quality requirements of users, the welding machine has been improved many times.
2. The original welding machine is an AC welding machine, and its main component is a power frequency transformer, which is an isolated AC welding power supply used to reduce the voltage and generate low voltage and large current, and is used for welding basic metals.
3. In the later welding, it was found that a group of rectifiers was added at the output end of the transformer, and the welding effect after converting the arc into DC was better than that of AC arc in most cases, so the first generation of DC welding machine came into being.
4. On this basis, the designer improved the circuit according to the user's needs, so that the welding machine has the function of current regulation and adapts to the welding of various workpieces, and the SCR rectifier welding machine was born.
5. In the application of the above welding machine for many years, users have also raised the problems of heavy equipment, constant action and low efficiency. Our technicians introduced inverter technology into the design of welding machine, among which SCR inverter welding machine was in the leading position in the 1990s. (Note: SCR inverter welding machine adopts frequency conversion control, and the frequency is generally between several hundred Hz and several thousand Hz. )
6. Application principle of inverter technology in welding machine: firstly, AC power supply is changed into DC power supply through rectifier bridge, and then sent to power electronic switch. After switching, DC becomes low-voltage alternating current. This process is reversed. Finally, the low-voltage alternating current is output DC after rectification, and welding can be carried out. This process is represented by letters: AC-DC-AC-DC.
At the end of 7.90' s, a new type of PWM inverter welding machine began to enter the market gradually, among which the inverter welding machine with field effect transistor or IGBT as power electronic switch has spread to this day.
8. The working principle of inverter hand arc welding machine with IGBT as power electronic switch is mainly described.
See below.
Principle analysis: Three-phase electricity enters the equipment after passing through the air switch. It is rectified for the first time by a three-phase rectifier bridge, then sent to a filter to smooth the waveform, and then sent to an inverter circuit to generate alternating current of about 20KHz. After that, the output rectifier module carries out secondary rectification and filtering, and then outputs it to the welding terminal.
After sampling the current and voltage respectively at the output end, the sending operation control circuit calculates the given signal, outputs it to the pulse width modulator, and sends it to the electronic switch (IGBT module) after being amplified by the driving circuit. Finally, the whole circuit forms closed-loop control to obtain stable welding current for welding.
9. Hand arc welding machine is characterized by steep drop, that is, the welding output current is constant within the rated maximum output voltage range. When the welding voltage exceeds the maximum rated output voltage, the output current will gradually decrease. The relationship between welding voltage and current in constant current range is: u = 20+0.04 * i.
10, the CO2 welder is flat, that is, the welding output voltage is constant within the rated maximum output current range. The relationship between welding voltage and current in constant voltage range is: u =14+0.05 * i.
1 1, argon arc welding machine is characterized by steep drop, and the current-voltage relationship is: u =10+0.04 * i.