The principle of the welding inverter: description, circuit and device

Traditional welding machines with permanent transformers of huge sizes are gradually disappearing into the past. Instead they now have compact welding inverters. They are easy to use, even beginners can use them. In order to find out what kind of device it is, you need to consider the design and operation of the welding inverter.

About construction

The device is different from traditional and more familiar to each welder of transformers. In the inverter, the processes of transforming the operating current occur differently. These processes proceed step by step with the help of a small transformer, the size of which is slightly larger than a pack of cigarettes. Another difference is the electronic control system. It makes it easier to weld. Thanks to the electronic system, quality seams are formed. Here's how the 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 variable frequency flow through the rectifier and then converted to constants. In addition, the current is smoothed by means of a filter. Often used as a traditional circuit based on electrolytic capacitors. Further, the constant voltage and current pass through the semiconductor modulator, where they again become an alternating one, but with higher frequencies. In different models this indicator differs, but does not exceed 100 kHz. The current is then rectified again and the voltage is reduced to the value required for welding the metals. The principle of operation of a 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 has decreased to a considerable extent. For example, to make an inverter welding machine capable of delivering a current of 160 amperes, the transformer should weigh no more than 250 grams. To achieve the same result using a traditional apparatus, the transformer would have a minimum mass of 18 kilograms. It is very uncomfortable.

The control unit is the main advantage of inverter welding machines

Electronics plays a very important role in the work of this equipment. 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 characteristics of the arc is instantaneously read by means of microprocessors. This principle of operation of the welding machine inverter and the presence of an electronic control unit guarantee an electric arc with the most stable characteristics. This eventually increases the quality of welding work.

Schematic diagram

In the rectifier, alternating current with a frequency of 50 Hz and a voltage of 220 volts passes through a powerful diode bridge. Current ripple with variable frequency is smoothed by the presence of electrolytic capacitors in the circuit. During operation, the diode bridge is subject to overheating, so the 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 reliably protects the diodes. Near the diode bridge, you can see quite large capacitors. Their capacity can range from 140 to 800 μF. Also in the scheme there are necessarily filters that do not allow any interference during operation. We looked at the welding principle of the welding inverter. The scheme also implies other elements. Let us consider them below.

Inverter: what it is itself

Directly the inverter itself is built on two moppets. These are powerful transistors. They have the property of being very hot, so they are equipped with a radiator. Such semiconductor elements solve the problem of switching currents passing through a pulse transformer. Operating frequencies here can exceed several thousand kHz. As a result, a high variable frequency current is generated. Transistors must be resistant to voltage drops. Manufacturers equip the devices with special protective circuits. Often they are assembled on the basis of a circuit on resistors and capacitors. Further into the case comes the secondary winding on the step-down transformer. It has small voltages - up to 70 volts. But the current can be 130-140 Amps.

Output Rectifier

In order to produce a constant current and voltage at the output, reliable output rectifiers are used. This circuit is assembled on the basis of double diodes, which have a common cathode. These elements are characterized by high speed of operation, 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 with such a problem can not cope. They simply did not have enough speed when switching. In case of repair, even knowing the welding inverter device, the principle of operation, these diodes are recommended to be changed to elements with the same characteristics.

The device and operation of the electronic system

It is powered by voltage regulators rated at 15 volts. These elements are installed on radiators. The supply voltage for the board comes from the main rectifier. When the voltage is applied, capacitors are first charged. The tension at this moment is growing. To protect the diode assembly, a limiting circuit with a powerful resistor is used. When the capacitors are fully charged, the welding machine will begin its work. The relay contacts close, and the resistor will no longer participate in the process.

Additional nodes and systems

The device and operating principle of the welding inverter implies the existence of other systems and components that provide the device with such high performance. So, you can highlight the management system, as well as drivers. The main element here is the PWM controller chip. It provides control of the action of powerful transistors. Also in the device there are various control, as well as adjusting circuits. In this case, the main element is the transformer. It is needed to control the power and other characteristics of the current after the output transformer. The operating principle of the welding inverter also implies the presence of a system for monitoring the voltage and the characteristics of the currents at the output in the supply network. This unit consists of an operational amplifier based on a chip. 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 health of the electronic unit.

WELDING MACHINES FOR TIG WELDING

Welding of metals in inert gases is one of the most popular methods of manual welding for today. Work with the use of argon provides high quality joints due to the complete insulation of the bath. Thus it is possible to work with any metals, even with aluminum, magnesium, titanium and their alloys. The principle of operation of a welding inverter with argon is nothing special from an ordinary inverter. The main difference is that the process uses not only a welding current source, but also a special burner. TIG welding involves the constant heating of the working area by means of an electric arc, which is created by means of a refractory tungsten electrode. Many are interested in learning how an inverter welding machine of this type works. Let's find out.

The design of the TIG welding machine

The device for argon-arc welding is a current source and a special torch. The first is needed to generate an electric arc, and also to maintain its magnitude in normal parameters. A huge number of metals and alloys, with which you can work in this way, means a lot of adjustments. Today, semiconductor inverter units are used for this purpose. 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. Constant current is used for working with stainless steels, copper alloys. Variable also suitable for magnesium, aluminum and other similar alloys. The operating mode, when intermittent currents are applied, is used for welding thin parts. Also in the design there is a burner. What is it? This is a special device in which a tungsten electrode is mounted . It has a nozzle through which argon is fed. Unlike traditional semiautomatic welding machines, the gas supply to the TIG welding torch starts before the arc is kindled. This avoids the burnout of metals.

Conclusion

The affordable cost of such equipment makes it possible to seriously consider purchasing such an aggregate for the household. If you learn how to confidently use such a device, you can even earn money. Today, argon welding is in great demand. You can buy inexpensive domestic welding inverter TIG-180 s. The principle of operation of this unit allows you to use it in the manual welding mode. This is a universal solution. The cost of it 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.