Traditional welding machines with constant transformers of enormous size are gradually becoming a thing of the past. Instead, compact welding inverters have now appeared . They are convenient in work, even beginners can use them. In order to find out what kind of device it is, you need to consider the design and principle of operation of the welding inverter.
About design
The device differs from traditional and more familiar to every welder transformers.
In the inverter, the processes of converting the operating current occur differently. These processes proceed in stages using a small transformer, the dimensions of which are slightly larger than a pack of cigarettes. Another difference is the electronic control system. It allows you to facilitate the welding process. Thanks to the electronic system, high-quality seams are formed. This is how an inverter welding machine works. Reviews about this equipment are mostly positive. Many use it because of the compactness and quality of the seam.
General principle of work
Initially, input currents with a voltage of 220 volts with a variable frequency flow through the rectifier and then are converted to constant. Additionally, the current is smoothed using a filter. Often, a traditional circuit based on electrolytic capacitors is used as it. Further, a constant voltage and current pass through a semiconductor modulator, where they again turn into alternating, but with higher frequencies. In different models, this figure is different, but does not exceed 100 kHz. Then the current is rectified again and the voltage drops to the value necessary for welding metals. The principle of operation of the welding inverter is based on high-frequency converters. The presence of these nodes allows the use of small transformers, due to which the mass of the unit is significantly reduced. For example, in order for the inverter welding machine to be able to produce a current of 160 Amps, the transformer should weigh no more than 250 grams. To achieve the same result using a traditional apparatus, the transformer would have a minimum weight of 18 kilograms. It is very uncomfortable.
Control unit - the main advantage of inverter welding machines
A very important role in the operation of this equipment is played by electronics. Due to it, feedback is provided. This helps to fully control the electric arc, if necessary, adjust or keep its parameters at the desired level.
The slightest deviation of the arc characteristics is instantly read out using microprocessors. This principle of operation of the inverter of the welding machine and the presence of an electronic control unit guarantee an electric arc with the most stable characteristics. This ultimately increases the quality of welding.
Circuit diagram
In the rectifier, an alternating current with a frequency of 50 Hz and a voltage of 220 volts passes through a powerful diode bridge. The ripple of the current with a variable frequency is smoothed out due to the presence of electrolytic capacitors in the circuit. During operation, the diode bridge is subject to overheating, so radiators are installed on the diodes. In addition, the inverter is equipped with a thermal fuse. It works if the diodes are heated to 90 degrees. The thermal fuse protects the diodes reliably. Near the diode bridge, you can see quite dimensional powerful capacitors. Their capacity can vary from 140 to 800 microfarads. Also in the circuit there are necessarily filters that do not allow any interference during operation. We examined what the welding inverter has as a principle of operation.
The scheme also implies other elements. Consider them below.
Inverter: what it is
The inverter itself is built on two mosfets. These are powerful transistors. They tend to heat up very much, so they are equipped with a radiator. Such semiconductor elements solve the problem of switching currents passing through a pulse transformer. Operating frequencies here may exceed several thousand kHz. As a result of this, a variable high frequency current is generated. Transistors must be resistant to voltage surges. Manufacturers equip devices with special protective circuits. Often they are assembled based on a resistor and capacitor circuit. Next, the secondary winding on the step-down transformer comes into play. It has small voltages - up to 70 Volts. But the current strength can be 130-140 amperes.
Output rectifier
In order for DC and voltage to form at the output, reliable output rectifiers are used. This circuit is assembled on the basis of dual diodes, which have a common cathode. These elements are characterized by high speed, they instantly open and quickly close. The reaction time of such diodes is about 50 nanoseconds. This speed is very important.
Diodes have to work with high-frequency currents, ordinary semiconductor elements can not cope with this task. They simply would not have enough speed when switching. In case of repair, even knowing the device of the welding inverter, the principle of operation, these diodes are recommended to be replaced with elements with the same characteristics.
The device and operation of the electronic system
It receives power from voltage regulators rated at 15 volts. These elements are mounted on radiators. The supply voltage for the board comes from the main rectifier. When voltage is applied, capacitors are charged first. The tension is growing at this moment. To protect the diode assembly, a restrictive circuit with a powerful resistor is used. When the capacitors are fully charged, the welding machine will begin its work. The relay contacts are closed, and the resistor will no longer participate in the process.
Additional nodes and systems
The device and the principle of operation of the welding inverter imply the presence of other systems and components that provide the device with such high performance. So, you can highlight the control system, as well as drivers. The main element here is the PWM controller chip. It provides control over the action of powerful transistors. Also in the device there are various control and adjustment circuits. In this case, the main element is a transformer. It is needed to control the strength and other characteristics of the current after the output transformer.
The principle of operation of the welding inverter also implies the presence of a system to control the voltage and characteristics of the output currents in the supply network. This unit consists of an operational amplifier based on a microcircuit. The main purpose of the system is to start the emergency protection mode in case of urgent need. It is also designed to monitor the operation and serviceability of the electronic unit.
TIG Argon Welders
Welding metals in an inert gas environment is one of the most popular methods of manual welding today. Working with argon ensures high quality seams due to the complete isolation of the bath. Thus, it is possible to work with any metals, even aluminum, magnesium, titanium and their alloys. The principle of operation of a welding inverter with argon is no different from an ordinary inverter. The main difference is that not only the welding current source is used in the process, but also a special torch. TIG welding involves constant heating of the work area using an electric arc, which is created by means of a refractory tungsten electrode. Many are interested to know how this type of inverter welding machine works. Let's find out.
TIG welding machine design
The device for argon arc welding is a current source and a special torch.
The first is needed to generate an electric arc, as well as to maintain its value in normal parameters. A huge number of metals and alloys with which you can work in this way, involves many adjustments. Today, semiconductor inverter units are used for this. This is a TIG welding inverter. The principle of operation does not differ from a conventional inverter, but the output of such a device is combined. Direct current is used to work with stainless steels, copper alloys. The variable is suitable for magnesium, aluminum and other similar alloys. The operating mode, when intermittent currents are supplied, is used to weld thin parts. Also in the design there is a burner. What is she like?
This is a special device in which a tungsten electrode is installed. It has a nozzle through which argon is supplied. Unlike traditional
semiautomatic welding machines, the gas supply to the TIG welding torch begins before the arc is ignited. This avoids burnout of metals.
Conclusion
The affordable cost of such equipment allows you to seriously think about purchasing such a unit for the household. If you learn to use such a device with confidence, you can even make money. There is a great demand for argon welding today. You can purchase an inexpensive domestic welding inverter TIG-180 s. The principle of operation of this apparatus allows its use in manual welding mode. This is a universal solution. Its cost is from 13 to 15 thousand rubles. The cheapest Chinese models can be purchased at a price of 6 thousand rubles. Professional devices cost about 50 thousand rubles.