It can be divided into two categories, AC welders and DC welders.
a. AC welding machine
The AC that the AC welding machine refers to is the output voltage of the welding machine. The composition of the AC welding machine is a transformer, the iron core and the primary and secondary windings. The input voltage is divided into 220 and 380, and some are 220 and 380 Voltage, according to different winding taps, to adapt to different voltage levels. According to the number of turns of the adjustable winding, the current is adjusted.
The principle of an AC welding machine is a transformer, but this transformer is different from an ordinary transformer. After the output voltage of an ordinary transformer is connected to a load, the voltage drop is very small. When a short circuit occurs, the short circuit current will be terrible, so It is strictly forbidden to short circuit, because it will burn out in a very short time. The transformer of the AC welding machine, through the adjustment of the winding mode of the winding, can realize the steep drop characteristic of the voltage by adjusting the inductance of the magnetic flux and the series inductance, because it is basically in a short-circuit state (large load state) when it is connected. When a short circuit occurs, the voltage will drop rapidly and sharply, so the current can be limited, but if a short circuit occurs for a long time, it will still be burned. This is the basic characteristic of the transformer, the voltage drop characteristic. The electric welding machine uses this feature to realize welding.

b. DC welding machine
DC motors are divided into two forms
1) One is that the AC welder realizes DC output by adding a rectifier device at the output end. This is relatively simple and understandable. Anyone with a little knowledge of electronics should know its working principle.
2) The other is the more common electronic inverter DC welding machine, and the working principle of this welding machine is more complicated. First of all, the alternating current waits until the local pressure direct current voltage through the current, and then through the high frequency electronic switching circuit, realizes the inverter output high frequency and low alternating voltage, and then obtains the low voltage pulsating direct current voltage through the diode charge current.
problem analysis
1. If the welding machine is marked as 220V, it is strictly forbidden to connect the so-called 380V voltage of the two live wires, it will burn you without discussion.
2. If the welding machine can be connected to 380V, some can be connected to 220V, and some cannot. This is determined according to the internal working principle of the welding machine.
3. To be able to work with 220V and 380V dual voltage, there must be a switching circuit or switch.
4. This is very clear, not all electrical appliances can work normally with dual voltage input.
5. Be sure to pay attention to when we connect electrical equipment, we must pay attention to the voltage level and scope of application, otherwise it will burn you without discussion.