Please explain the principle of the electric welding machine

An electric welding machine is a special transformer. The difference is that the voltage drop is small when the transformer is connected to the load, and the voltage drop is large when the welding machine is connected to the load. This is mainly achieved by mediating the amount of inductance of the magnetic flux and the series inductor. Although the circuit is closed, it is precisely because.

The circuit is closed so that the current is equal everywhere in the entire closed circuit; However, the resistance is different everywhere, especially the resistance at the unfixed contact is the largest, and this resistance is called contact resistance in physics. According to the law of thermal effect of electric current (also called Joul's law) q=i rt, it can be seen that the current is equal, the greater the resistance, the higher the heat of the part, the contact resistance of the contact between the contact of the electrode and the metal body to be connected during welding is the largest, then the electric heat generated in this part is naturally the most, the welding rod is an alloy with a lower melting point, which is naturally easy to melt, and the melted alloy electrode core is cooled after being stained on the welded object, and the welding object is bonded together. At this time, because the above-mentioned gap is very small at the moment when the electrode is lifted, the voltage between the electrode and the weldment is higher (60-70V), coupled with the above-mentioned preheating, the end of the electrode and the weldment being welded are easy to emit electrons, and the air at the gap is broken down and conducted, and a dazzling spark is produced at the same time, which is the arc discharge.

The temperature at the arc discharge can reach more than 2000K, and the electrode and weldment are melted, so that the welding is realized.

The large-capacity step-down transformer provides tens of volts of low voltage, hundreds of amperes of high current, and then rectifies the AC if the DC one.

1. The principle of electric welding:

The principle of electric welding is that in a closed circuit, the current is discharged in a place with large resistance, and the high-temperature molten metal generated by the discharge forms a molten pool, and the molten metals penetrate each other to complete the melting welding.

In the actual welding, the workpiece and the electrode are connected to the power supply and connected to different electrodes, and the electrode and the workpiece are in instantaneous contact to ionize the air to produce an arc, and the temperature of the arc can reach about 5000-6000K, so that the surface of the workpiece is melted to form a molten pool, and the electrode metal is mixed and filled in the weld with the melted base metal after melting, so that the surface of the workpiece forms a metallurgical weld.

During the welding process, the coating of the outer layer of the electrode plays a very large role in protecting the weld metal.

2. Wiring of the output circuit of the electric welding machine:

The AC welding machine is used to output the secondary coil of welding current, which has a high current and low voltage. The output voltage is about 50-80V AC. The secondary winding finally leads out two terminals, these two terminals do not have a grounding wire, any terminal is called grounding.

As long as the welding wire forms a closed loop with the wire called grounding, electric welding can be performed. That's where that grounding wire comes in.

Electric welding, commonly known as arc welding, is the principle: a voltage is applied between the electrode and the workpiece, the arc is ignited by scratching or contact, and the energy of the arc is used to melt the electrode and heat the base metal. Arc:

Air breakdown, plasma conduction, generally electron rent or tung to the anode movement, so the general electrode is connected to the anode. The anode temperature can reach 20,000 degrees Celsius Power supply: AC, DC and silicon rectifier, inverter, etc

A transformer, but different from an ordinary transformer, must have an air gap, a different structure of transfer iron and moving coil two kinds of DC: a kind of generator, the country has banned production, the effect is good, but the energy consumption is high Rectifier: thyristor or diode rectification Inverter:

The most common is IGBT

The working principle of an ordinary electric welding machine is similar to that of a transformer, which is a step-down transformer. At both ends of the tooth and coil is the welded workpiece and the electrode, which ignites the arc and welds the gap of the workpiece and the electrode in the high temperature of the arc.

The welding transformer has its own characteristics, that is, the fast hole high has the characteristics of a sharp drop in voltage. The voltage drops after the electrode is ignited; When the electrode is adhered to a short circuit, the pressure per mu is also sharply reduced. The reason for this phenomenon is the characteristics of the core of the electric welding transformer.

The adjustment of the working voltage of the welding machine, in addition to a 220 380 voltage conversion, the secondary coil also has a tap conversion voltage, and at the same time, there is an iron core to adjust, how much the iron core can enter, the shunt magnetic circuit, the more entered, the lower the welding voltage.

The working schematic diagram is similar to that of a transformer, and it cannot be drawn here.

<> welding machine principle: when the welded object and the welded object come into contact with each other, the welding machine intervenes, and the slag collapse causes a short circuit in the circuit, resulting in an extremely high arc temperature, melting and fusing them. Attention to the model round item when the welding machine is operated:

1. The welding machine must be placed in a dry and ventilated position, and leakage will occur if placed in a wet position. 2. The welding machine must be designed with an independent opening beam before closing the box, and protective equipment should be worn during the work, and the switch should be locked after the operation is completed. 3. When working in a wet position, the welding machine should be put on the dry wooden board, and the staff should stand on the insulating board to work.

1. Principle: The high-temperature arc generated by the positive and negative electrodes in an instantaneous short circuit is used to melt the solder and the welded material on the electrode to achieve the purpose of combining them.

2. How to use: Before use, check and confirm that the wiring of the primary and secondary pole wires is correct, and the input voltage conforms to the nameplate regulations of the welding machine. After the power is turned on, it is strictly forbidden to touch the live part of the primary line.

3. When moving the welding machine, the power supply must be cut off, and the welding machine must not be moved by dragging the cable. When there is a sudden power failure during welding, the power supply should be cut off immediately. When you are welding, it is absolutely not allowed to use iron plate lap to replace the lap iron of the welding machine.

There is also the shell of the electric welding machine, which must have good zero or grounding protection, and the assembly and disassembly of its power supply should be carried out by an electrician. Between the primary and secondary windings of the welding machine, between the winding and the limb core, and between the winding, the lead wire and the shell, the insulation resistance is not less than the megaohm.

4. The length of the power cord of the primary ruler of the AC arc welding machine should not be more than 5 meters, and the length of the secondary wire cable of the electric welding machine should not be more than 30 meters. The welding tongs and the wire must be well insulated and firmly connected, and gloves should be worn when replacing the welding rod. Work in wet locations.

It should stand on an insulating plywood or wooden board. It is strictly forbidden to weld on vessels or pipelines with pressure, and the power supply must be cut off before welding live equipment.

The electric welding machine uses the high-temperature arc generated by the positive and negative electrodes in an instantaneous short circuit to melt the solder and the welded material on the electrode to achieve the purpose of combining them. The structure is very simple, it is a high-power transformer, and the welding machine can be divided into two types according to the type of output power supply, one is AC power supply; One is direct current.

The principle of inductance is used, the inductance will produce a huge voltage change when it is turned on and off, and the high-voltage arc generated by the positive and negative poles in the instantaneous short circuit is used to melt the solder on the electrode to achieve the purpose of combining them.

How to use the welding machine.

The operator places the electrode rod of the spot welder at the welding position and allows the two electrodes to be in contact with the welding element so that the electrode arms are parallel.

2.Set the current switching stage of the spot welding machine, the switching parameters of the spot welding machine are usually related to the material and shape of the welding components. After turning on the power of the spot welding machine, the operator adjusts the pressure nut by changing the electrode pressure to achieve its operation within the compression range.

3.Prepare for welding. The operator turns on the cooling water, and then starts welding, places the welding element in the two electrodes, presses down the foot pedal, gradually increases the pressure on the electrode, and turns on the power contact with the increase of the pressure of the foot pedal, and when the transformer works, the secondary circuit is turned on and begins to heat the weldment, wait for a period of time, the spring tension of the spot welding machine recovers, and the power supply can be cut off.

4.Welding assembly. Before welding the weldments made of steel, the staff should clean up the dirt, oxidation and rust on the surface of the weldments. Between the welding of hot-rolled steel, the operator should pickle and blast the weld.

If the operator welds without treatment, it will inevitably shorten the life of the electrode, reduce the welding quality and work efficiency. Only thinly coated mild steels are welded directly.

It is to use the high-temperature arc generated by the positive and negative electrodes in the instantaneous short circuit to melt the solder and the welded material on the electrode to achieve the purpose of combining them. The structure of the welding machine is very simple, to put it bluntly, it is a high-power transformer, which turns 220V AC into a low-voltage, high-current power supply, which can be DC or AC. Welding transformers have their own characteristics, that is, they have the characteristics of a sharp drop in voltage.

After the electrode ignites, the voltage drops, in. The adjustment of the working voltage of the welding machine, in addition to the one-time 220 380 voltage conversion, the secondary coil also has a tap conversion voltage, and at the same time, it is also adjusted with an iron core, which can be adjusted. The welding machine is generally a high-power transformer, which is made by using the principle of inductance, and the inductance will produce a huge voltage change when it is turned on and off, and the high-voltage arc generated by the positive and negative poles in the instantaneous short circuit is used to melt the solder on the welding electrode.

to achieve the purpose of bringing them together. A voltage is applied between the electrode and the workpiece, which ignites the arc by scratching or contacting, and uses the energy of the arc to melt the electrode and heat the base metal.

The current and voltage are stepped-down by the three-phase main transformer, rectified by the thyristor element, and the output current is controlled by changing the phase of the thyristor trigger angle. The current signal is taken from the shunt at the DC output end of the rectifier as a negative feedback signal of the current, and as the DC output current increases, the negative feedback also increases, the conduction angle of the thyristor decreases, and the output current and voltage decrease, so as to obtain the external characteristics of the decrease. The thrust circuit is when the output terminal voltage is lower than 15V, so that the output current increases, especially when the short circuit, the external characteristics of external drag are formed, so that the welding rod is not easy to stick.

The arc striking circuit is to increase the given voltage for a short time every time the arc starts, so that the arc current is larger and the arc is easy to start.

From the above description, it can be known that the circuit is in a short-circuit state when the arc of electric welding starts, the voltage drops sharply, and the current needs to be very large; After the arc starts, the arc should be stabilized, at this time, the solution of the welding rod and the tank is still in a short-circuit transition state, the voltage is still dropping, and the current is still large; After the transition is completed, it is in a normal welding state, the voltage rises and the current drops.

The arc starting current is the maximum current that the welding machine can output when the welding arc starts.

The thrust current is that when the molten iron is in the short circuit transition during the welding machine, the welding machine superimposes a current to make the molten iron transition stable and not easy to stick to the strip.

The welding current is the working current provided by the welding machine when it is welding normally.