The method of welding metals today has many methods and most of them are based on the use of electricity. Electric welding, in turn, is also divided into several types, including the inverter method.

The latter became popular relatively recently, and before small-sized and easy-to-carry devices appeared on store shelves, home welding was the lot of a few. After the mass introduction of welding inverters, it turned out that the principle of the device and operation of this device is quite simple and, if desired, you can assemble the same one yourself.

Description

An inverter is a device that converts direct current into alternating current, and a double conversion occurs in an inverter-type welding machine:

  1. Alternating current with a power not exceeding 5 amperes, with a voltage of 220/380 volts and a frequency of 50 Hz, is converted into direct current with the same values.
  2. The resulting direct current is converted into alternating current with a voltage of several tens of volts and a current of up to several hundred amperes.

Such a transformation is more beneficial, since the obtained characteristics of the welding current are highly stable and easily controlled, which makes it possible to set the optimal welding mode for various sizes of parts to be welded.

Welding inverters are monoblock devices, and their main advantage is ergonomics. Unlike welding transformers, including those delivering direct current, inverters can be carried by one person, and having low power, they weigh only a few kilograms and are easily hung on the shoulder.

The conversion takes place at the expense of a transformer and electronic circuits that require high-quality cooling, so a powerful fan is also placed in the case. Despite the apparent complexity, the welding inverter can be assembled with your own hands. Such a device will be able to provide welding no worse than its factory counterparts.


Principle of operation

The main element of the system is a power transformer with a rectifier. Its secondary winding is very hot, so when configuring the device, it is very important to place it in the path of the air flow coming from the fan.

The rectified current is passed through a filter of triodes with a high switching frequency, as a result, the frequency of the secondary alternating current can reach a value of 50 kHz. The inverse relationship between the frequency and dimensions of electrical equipment has long been known, which made it possible to give inverters such a modest size. The same principle is successfully used wherever space saving is needed, for example, in the on-board network of an aircraft or a submarine, the frequency of the electric current is also measured in thousands of hertz.

In the welding transformer, the electromotive force is converted, while the high-frequency currents are converted in the inverter, which made it possible to significantly reduce the weight of the transformer and reduce the consumption of material for its manufacture. For overload protection, a fuse is installed on the secondary side, which can be replaced from the front panel. The user can adjust the strength of the current supplied to the electrode using the regulator, the current value is displayed on a digital display.

Application area

It is difficult to imagine construction work in which welding would not be used. Welding inverters have significantly expanded the scope of its application, as they have a fairly large share of mobility, in contrast to bulky transformer devices. Today, inverter welding is used:

  • For welding parts made of ferrous metals.
  • For welding parts made of non-ferrous metals.
  • When it is necessary to weld in difficult places, for example, in underground pipeline tunnels.
  • For welding shaped parts in production.
  • For welding at home.

In industry, inverters with automatic and semi-automatic welding wire feed are used for welding, which makes it possible to unify the process and reduce the share of manual labor.

Advantages and disadvantages

The main advantage of inverter welding machines is their size, because before that, it was necessary to cook either at a stationary post, or else, move a heavy welding transformer using improvised means to the place of welding.

Thanks to double conversion, the welding current of the inverter does not depend on the mains and therefore always remains with constant values, which made it possible to avoid such unpleasant phenomena during welding as:

  • Electrode sticking.
  • Absence of an arc at low voltage in the network.
  • Overburning or underburning of metal.

The inverter is universal and suitable for welding cast iron or non-ferrous metals with appropriate electrodes, as well as for TIG welding with non-consumable electrodes. The operator has the ability to adjust the current over a wide range.

The disadvantage of inverters is a relatively high cost compared to transformers, but given the advantages, it is completely leveled. Like any electronics, the microchips of the device require careful handling, so it is recommended to periodically clean the interior of dust.

Also, electronics can fail in conditions of low temperatures or high humidity, so the environmental conditions must be consistent with the nameplate data of the device.


How to do it yourself?

Although inverter welding machines are commercially available in a modern design, they have become available relatively recently, they are not something new. In fact, only convenient digital control and more modern electronic components have been added.

The principle of operation, as well as the apparatus itself, were developed several decades ago, and even today, many assembly schemes are relevant. You can assemble an inverter yourself with old electrical parts, based on modern electronic components. Such a device will come out much cheaper than the factory counterpart.

Necessary materials and tools

To assemble the device you will need:

  • Ferrite core for power transformer.
  • Copper bus or wire for creating windings.
  • Fixing bracket for connecting halves of the core.
  • Heat resistant tape.
  • Computer fan.
  • Transistors.
  • Soldering iron, pliers, wire cutters.

Scheme

To date, all welding inverter circuits are unified and built on the basis of the use of a pulse transformer and powerful MOSFET type transistors.

Each of the manufacturers makes minor changes in the form of proprietary developments, however, in general, the functionality of the device does not undergo any significant changes.

The schematic diagram of Yuri Negulyaev, a scientist and developer of a domestic inverter-type welding machine, can also be taken as a basis.

Walkthrough

  1. To accommodate all the elements, you need to choose a case. It is recommended to use an old system computer unit, as ventilation holes are already provided there.
  2. It is necessary to increase the strength of the body, since the weight of the unit can reach up to ten kilograms. For this, metal corners on threaded fasteners are installed in the corners.
  3. The primary winding of the transformer - the wire is wound across the entire width of the frame, this contributes to the stable operation of the transformer during voltage drops. For winding, only copper wires are used, in the absence of a bus, several wires are connected into a bundle.
  4. The secondary winding of the transformer is wound in several layers; for this, several wires with a cross section of 2 mm are used, connected in a bundle.
  5. A reinforced layer of insulation is required between the windings to prevent mains voltage from entering the secondary winding.
  6. An air gap is provided between the transformer core and the windings to ensure air circulation.
  7. Separately, a current transformer is made on a ferrite core, which is fixed on the positive line during assembly and connected to the control panel.
  8. Transistors must be attached to the radiator, but always through a thermally conductive dielectric gasket. This will provide efficient heat dissipation and short circuit protection.
  9. The diodes of the rectifier circuit are attached in a similar way to an aluminum plate. The outputs of the diodes are connected by an uninsulated wire with a cross section of 4 mm.
  10. Power conductors inside the case are bred in such a way as to exclude a short circuit.
  11. The fan is installed on the rear wall, which will save space and allow several radiators to be blown at once.

 Wiring diagram of the welding inverter

Machine setup

After assembling the machine, additional settings are required to obtain the correct welding current and voltage values:

  1. Mains voltage is supplied to the board and the fan drive.
  2. It is necessary to wait until the power capacitors are fully charged, then check the operation of the relay, making sure that there is no voltage on the current-limiting resistor installed in the capacitor circuit, and then close it.
  3. Using an oscilloscope, the value of the current generated by the inverter is determined, for which the frequency of the pulses entering the transformer winding is measured.
  4. The welding mode is checked on the control unit, for which a voltmeter is connected to the output of the oscilloscope amplifier. In low-power inverters, the voltage value reaches about 15 volts.
  5. The operation of the output bridge is checked by applying a voltage of 16 volts from the power supply. It should be remembered that in idle mode, the consumption of the unit is about 100 mA and this must be taken into account when making measurements.
  6. Work with power capacitors is tested. The voltage is changed from 16 volts to 220. The oscilloscope is connected to the output transistors and the amplitude of the signal is controlled, it should be identical to that which was in the tests with reduced voltage.

Maintenance and repair

For assembly, maintenance and it is necessary to have a sufficient level of electrical knowledge. In the absence of such and the need for repair, the user can only perform routine maintenance:

  • Cleaning the device from dust is done with a vacuum cleaner with the case open. If the machine is constantly used in construction work, then regular cleaning is necessary.
  • Replacing the fuse - protects the circuitry of the device from damage due to overload and short circuits.
  • Repair of switching parts on welding cables.


Welding semi-automatic inverter

In technological processes, welding of template parts is required and the highest quality can be achieved using automatic and semi-automatic welding machines with wire feed for welding. You can get such a device from a home-made or industrial inverter only if you have the appropriate knowledge and the correct reconfiguration of the control unit.

The fact is that power sources for manual and semi-automatic welding are designed with different current-voltage characteristics, and an inverter to which only a wire feeder is added will eventually give an uneven seam with torn edges.

  1. It should be remembered that power capacitors and transistors in the inverter circuit require additional security measures, in particular, the mandatory presence of a current-limiting resistor. Applying current without it can lead to an explosion.
  2. Welding cables should not be extended, their length must not exceed 2.5 meters.

It is quite possible to make a welding inverter with your own hands, even without in-depth knowledge in electronics and electrical engineering, the main thing is to strictly adhere to the scheme and try to understand well how such a device works. If you make an inverter, the technical characteristics and efficiency of which will differ little from those of serial models, you can save a decent amount.

You should not think that a home-made device will not give you the opportunity to effectively carry out welding work. Such a device, even assembled according to a simple scheme, will allow you to weld with electrodes with a diameter of 3-5 mm and an arc length of 10 mm.

Characteristics of a homemade inverter and materials for its assembly

Having assembled a welding inverter with your own hands according to a fairly simple electrical circuit, you will receive an effective device with the following technical characteristics:

  • the value of the consumed voltage - 220 V;
  • the strength of the current supplied to the input of the device - 32 A;
  • the current generated at the output of the device is 250 A.

During operation, the diodes of such a bridge get very hot, so they must be mounted on radiators, which can be used as cooling elements from old computers. To mount the diode bridge, it is necessary to use two radiators: the upper part of the bridge is attached to one radiator through a mica gasket, the lower part through a layer of thermal paste to the second one.

The conclusions of the diodes from which the bridge is formed must be directed in the same direction as the conclusions of the transistors, with the help of which the direct current will be converted into high-frequency alternating current. The wires connecting these terminals should be no longer than 15 cm. Between the power supply and the inverter unit, which is based on transistors, there is a sheet of metal attached to the body of the device by welding.

Power block

The basis of the power unit of the welding inverter is a transformer, due to which the value of the high-frequency voltage decreases, and its strength increases. In order to make a transformer for such a block, it is necessary to select two cores Ш20х208 2000 nm. Newsprint can be used to provide a gap between them.

The windings of such a transformer are not made of wire, but of a copper strip 0.25 mm thick and 40 mm wide.

Each layer is wrapped with cash register tape to provide thermal insulation, which demonstrates good wear resistance. The secondary winding of the transformer is formed from three layers of copper strips, which are isolated from each other using a fluoroplastic tape. The characteristics of the transformer windings must comply with the following parameters: 12 turns x 4 turns, 10 kv. mm x 30 sq. mm.

Many people try to make step-down transformer windings from thick copper wire, but this is not the right solution. Such a transformer operates on high-frequency currents, which are forced out to the surface of the conductor without heating its interior. That is why, for the formation of windings, the best option is a conductor with a large surface area, that is, a wide copper strip.

Plain paper can also be used as a thermal insulation material, but it is less wear-resistant than cash register tape. From elevated temperature, such a tape will darken, but its wear resistance will not suffer from this.

The transformer of the power unit will become very hot during its operation, therefore, for its forced cooling, it is necessary to use a cooler, which can be used as a device previously used in the computer system unit.

inverter unit

Even a simple welding inverter must perform its main function - to convert the direct current generated by the rectifier of such an apparatus into high-frequency alternating current. To solve this problem, power transistors are used that open and close at a high frequency.

Schematic diagram of the inverter unit (click to enlarge)

The inverter unit of the apparatus, which is responsible for converting direct current to high-frequency alternating current, is best assembled on the basis of not one powerful transistor, but several less powerful ones. Such a constructive solution will allow to stabilize the current frequency, as well as to minimize noise effects during welding.

The electronic also contains capacitors connected in series. They are necessary to solve two main tasks:

  • minimization of resonant emissions of the transformer;
  • reducing losses in the transistor block that occur when it is turned off and due to the fact that the transistors open much faster than they close (at this moment, current losses may occur, accompanied by heating of the transistor block keys).

Cooling system

The power elements of the home-made welding inverter circuit become very hot during operation, which can lead to their failure. To prevent this from happening, in addition to the radiators on which the most heated blocks are mounted, it is necessary to use fans responsible for cooling.

If you have a powerful fan available, you can get by with one by directing the air flow from it to a step-down power transformer. If you are using low-power fans from older computers, you will need about six of them. At the same time, three such fans should be installed next to the power transformer, directing the air flow from them to it.

To prevent overheating of a homemade welding inverter, you should also use a temperature sensor by installing it on the hottest radiator. Such a sensor, if the radiator reaches a critical temperature, will turn off the flow of electric current to it.
In order for the inverter ventilation system to work effectively, properly executed air intakes must be present in its case. The grilles of such intakes, through which air flows will flow into the device, should not be blocked by anything.

Do-it-yourself inverter assembly

For a home-made inverter device, you need to choose a reliable case or make it yourself, using sheet metal with a thickness of at least 4 mm. As a base on which the welding inverter transformer will be mounted, you can use a sheet of getinax with a thickness of at least 0.5 cm. The transformer itself is mounted on such a base using brackets that you can make yourself from copper wire with a diameter of 3 mm.

To create electronic circuit boards of the device, you can use foil textolite with a thickness of 0.5–1 mm. When installing magnetic circuits that will heat up during operation, it is necessary to provide for gaps between them necessary for free air circulation.

For automatic control, you will need to purchase and install a PWM controller in it, which will be responsible for stabilizing the welding current and voltage. To make it convenient for you to work with your home-made device, it is necessary to mount controls in the front of its body. Such bodies include a toggle switch for turning on the device, a variable resistor knob with which the welding current is regulated, as well as cable clamps and signal LEDs.

Diagnostics of a homemade inverter and its preparation for work

Doing is half the battle. An equally important task is its preparation for work, during which the correct functioning of all elements is checked, as well as their settings.

The first thing to do when testing a homemade welding inverter is to apply 15 V to the PWM controller and one of the cooling fans. This will allow you to simultaneously check the performance of the controller and avoid its overheating during such a test.

After the capacitors of the device are charged, a relay is connected to the electrical supply, which is responsible for closing the resistor. If voltage is applied directly to the resistor, bypassing the relay, an explosion may occur. After the relay trips, which should happen within 2-10 seconds after the voltage is applied to the PWM controller, you need to check if the resistor has closed.

When the relays of the electronic circuit work, the PWM board should form rectangular pulses to the optocouplers. This can be checked using an oscilloscope. The correct assembly of the diode bridge of the device must also be checked; for this, a voltage of 15 V is applied to it (the current strength should not exceed 100 mA).

The transformer phases may have been connected incorrectly during the assembly of the device, which may lead to incorrect operation of the inverter and strong noise. To prevent this from happening, the correct connection of the phases must be checked; for this, a two-beam oscilloscope is used. One beam of the device is connected to the primary winding, the second - to the secondary. The phases of the pulses, if the windings are connected correctly, should be the same.

The correctness of the manufacture and connection of the transformer is checked using an oscilloscope and connecting electrical devices with various resistances to the diode bridge. Focusing on the noise of the transformer and the readings of the oscilloscope, they conclude that it is necessary to refine the electronic circuit of a home-made inverter apparatus.

To check how much you can continuously work on a homemade inverter, you need to start testing it from 10 seconds. If the radiators of the device do not heat up during operation of this duration, you can increase the period up to 20 seconds. If such a time period did not negatively affect the state of the inverter, you can increase the duration of the welding machine up to 1 minute.

Maintenance of a homemade welding inverter

In order for the inverter device to serve for a long time, it must be properly maintained.

In the event that your inverter has stopped working, you need to open its cover and blow out the insides with a vacuum cleaner. Those places where dust remains can be thoroughly cleaned with a brush and a dry cloth.

The first thing to do when diagnosing a welding inverter is to check the voltage supply to its input. If the voltage is not supplied, you should diagnose the performance of the power supply. The problem in this situation may also be that the fuses of the welding machine have blown. Another weak link of the inverter is the temperature sensor, which, in the event of a breakdown, must not be repaired, but replaced.

When performing diagnostics, it is necessary to pay attention to the quality of the connections of the electronic components of the device. Poorly made connections can be determined visually or using a tester. If such connections are identified, they must be corrected so as not to encounter further overheating and failure of the welding inverter.

Only if you pay due attention to the maintenance of the inverter device, you can count on the fact that it will serve you for a long time and will enable you to perform welding work as efficiently and efficiently as possible.

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Inverter welding quickly entered the workspace of mobile teams and individual specialists who fulfill orders on call. The presence of such a welding machine is also useful for every owner in a garage or a private house. The compact dimensions of the device, low weight and high seam quality indicators favorably distinguish it from the background of large transformers. Unfortunately, the store price does not allow everyone to become the owner of this equipment. But for those who know how to work with their own hands, there is a way out - this is a home-made welding inverter. What tools and materials will be needed to create it? How to assemble the main nodes? What is included in the maintenance and repair of a homemade device?

When deciding to create an apparatus from handy parts, affordable, and suitable for welding at home or on small orders, one should be aware of the reality of the result. A home-made inverter welding machine loses significantly in appearance in front of store counterparts. For a reputable private entrepreneur specializing in heating installations, installation of fences, metal doors and other services, such a unit will not look authoritative.

But a simple do-it-yourself welding inverter is perfect for personal needs in a private house, or working in a garage. Such a device will be able to consume 220V from the network, convert them to 30V, and increase the current strength to 200A. This is quite enough to work with electrodes with a diameter of 3 and 4 mm. The quality of the seam will be better than a bulky transformer, since the alternating current is converted to direct current, and then back to alternating current, but at a high frequency.

Such inverters are suitable for welding fences, gates, own heating, doors. It is convenient to carry it, and even cook with it, hanging it on your shoulder. If a beginner trains hard, watches videos and tries to put seams in practice, it will become possible to weld thin sheets of steel. Subsequently, you can improve the circuits of welding inverters by adding a wire feed mechanism, a drum mount and gas valves to them with your own hands to make a semi-automatic device. It can also be converted to argon welding.

Required parts and tools

To create an inverter welding machine with your own hands, you can not do without going to the store or to the market. It is impossible to collect it absolutely free of charge from items in the garage. But the final cost will be three times cheaper than buying finished products. In welders and their creation, the following are used:

  • Screwdriver Set;
  • pliers;
  • soldering iron, for the manufacture of an electrical board;
  • drill, for holes for switches and ventilation;
  • hacksaw;
  • sheet metal under the body;
  • bolts and screws;
  • devices and buttons on the panel;
  • capacitors, transistors and diodes;
  • copper bus for winding;
  • wires to connect all nodes;
  • elements for the core;
  • insulating paper and electrical tape;
  • power and working cables.

Before you start creating a do-it-yourself welding inverter, the circuit of which should already be printed on paper, you should watch a few videos from experts on step-by-step assembly. This will help you see clearly what you will have to face, and compare the result. The following is a step-by-step instruction on how to make a welding inverter with your own hands. Some deviations and variations are allowed, depending on what power the device needs at the output, and what materials at hand are available.

Transformer

The electrical component of the inverter starts with a transformer. He is responsible for lowering the voltage to a working level that is safe for life, and increasing the current strength to a value capable of melting metal. First of all, you need to choose the material for the core. These can be factory standard plates or a homemade sheet iron frame. The video on the net helps to see the main principle of this design, regardless of the options used.

It is better to wind welding transformers from a copper bus, since the optimal characteristics are a sufficient width and a small cross section. Such parameters will allow you to use all the physical resources of the material. But if there is no such bus, then you can use a wire of a different section. All this affects the degree of heating of the product during operation.

The transformer is wound manually and consists of two parts: primary and secondary windings. Suitable for a do-it-yourself inverter:

  • Ferrite 7 x 7. The primary winding is created from a 0.3 mm PEV wire, which is wound evenly, turn to turn, 100 turns.
  • The next layer is insulating paper. Cash register tape or fiberglass will do. The first darkens strongly when heated, but retains its properties.
  • The secondary winding is applied in several levels. The first is PEV 1.0 mm in 15 turns. Since there are few turns, they should be evenly distributed over the entire width. They are covered with varnish and a layer of paper.
  • The second layer consists of 0.2 mm HDPE in 15 turns, followed by insulation similar to the previous layers.
  • The final level is made of PEV 0.35 in 20 revolutions. You can also isolate the layers with PTFE tape.

Frame

When the main element of the inverter is created with your own hands, you can start manufacturing the case. You can focus on the width of the transformer so that it fits freely inside. From its dimensions, it is worth calculating another 70% of the required space for the rest of the details. The protective cover can be assembled from 0.5 - 1.0 mm steel sheet. The corners can be joined by welding, bolting, or making the sides solid on a bender (which will incur additional costs). You will need to provide a handle or a belt mount to carry the inverter.

When creating the case, it is worth providing for easy disassembly and access to the main elements in case of repair. It is necessary to make holes on the front side for:

  • current switches;
  • power button;
  • light diodes signaling the inclusion;
  • cable connectors.

Store-bought welding inverters are powder coated. In home production, ordinary paint is suitable. The traditional colors for welding machines are red, orange and blue.

Cooling

Enough holes must be drilled in the case for ventilation. It is desirable that they are in opposite directions opposite each other. You will also need a fan. It can be a cooler from an old computer. You need to install it by working on the exhaust of hot air. The influx of cold is made through the holes. Place the cooler as close as possible to the transformer, the hottest element of the device.

Current conversion

The welding inverter circuit necessarily includes a diode bridge. He is responsible for changing the voltage to constant. Diode soldering is carried out according to the "oblique bridge" scheme. These elements are also subject to heat, so they should be mounted on radiators that are available in old system units. To find them, you can contact the repair shops for computers.

Two radiators are placed along the edges of the diode bridge. Between them and the diodes, it is necessary to install gaskets made of thermoplastic or other insulator. The outputs are sent to the contact wires of the transistors, which are responsible for returning the current to alternating, but at an increased frequency. The wires connected together must be 150 mm long. It is recommended to separate the transformer and the diode bridge with an internal partition.

In the inverter circuit, the presence of capacitors is mandatory, with a serial connection. They are responsible for reducing transformer resonance and minimizing losses in transistors. The latter open quickly and close slowly. In this case, current losses appear, which the capacitors compensate.

Assembly and packaging

After creating all the components of the device, you can proceed to the assembly. A transformer, a diode bridge, an electronic control circuit are attached to the base. All wires are connected. On the outer panel are fixed:

  • resistor switches;
  • power button;
  • light indicators;
  • PWM controller;
  • cable connectors.

It is better to buy a holder and a mass clamp ready-made, because they are safer and more convenient. But it is possible to make a holder yourself, from steel wire with a diameter of 6 mm. When all the parts are installed and connected, you can start checking the device. The initial voltage is measured. At 15V, it should not show above 100A. The diode bridge is tested with an oscilloscope. After that, temporary suitability for work is tested by monitoring the heating of radiators.

DIY repair

For long and trouble-free operation, the inverter is important to properly maintain. To do this, blow out dust once every two months, after removing the casing. If the device has stopped working, you can repair it yourself by watching a video on the network of the main breakdowns and solutions.

What is checked first:

  • Input voltage. If it is missing or insufficient in size, then the device will not work.
  • Circuit breakers. When jumping, protective elements burn out or a shutdown is triggered automatically.
  • Temperature sensor. If damaged, blocks the operation of subsequent nodes.
  • Contact terminals and solder joints. Breaking the circuit stops the flow of current and work processes.

Having studied the circuits of conventional inverters, and having acquired the necessary parts, as well as watching training videos, you can assemble a high-quality welding machine that will be very useful to a good owner.

Currently, the most popular, functional and productive equipment for welding is the inverter welding machine.

For welding, an inverter is often used. It is compact and easy to use.

High-power field-effect transistors are used as power switches in such equipment. This allowed to significantly reduce the size and weight of the unit. There is a wide range of such equipment available on the market. All available models have almost the same principle of operation. The only drawback that can save you from the desire to buy such a unit is its rather high cost. However, you can make a little effort and assemble the inverter yourself.

Features of a homemade inverter welding machine

The inverter welding machine under consideration consists of the following main elements:

  • power supply;
  • power key drivers;
  • power part.

A homemade inverter welding machine will have the following characteristics:

  • the maximum value of the consumed current is 32 A;
  • welding current - no more than 250 A;
  • mains voltage - 220 V.

The inverter can weld such a welding machine without any problems using an electrode with a diameter of 3-5 mm and an arc length of up to 10 mm. The efficiency of a home-made unit is in no way inferior to ready-made store-bought welding devices.

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Preparing to assemble the welding machine

To assemble the unit you will need the following:

  • electrical steel;
  • cotton fabric;
  • copper wires;
  • fiberglass;
  • textolite.

To stabilize the voltage, the windings must be made across the entire width of the frame. In total, the design of the inverter welding machine under consideration will have 4 windings:

  • primary - consists of 100 turns, PEV 0.3 mm;
  • three secondary windings - one for 15 turns (PEV 1 mm), the other - also from 15 turns (PEV 0.2 mm), the third - from 20 turns (PEV 0.3 mm).

The board with the power supply is mounted separately. Between it and the power part there will be a sheet of metal. It must be electrically attached to the body of the inverter welding machine.

Conductors will be used to control the shutters. They should be soldered at a minimum distance from the transistors. They should be twisted in pairs with each other. The section doesn't really matter. The length of the conductors should be no more than 15 cm.

Before assembling the inverter welding machine, you need to carefully study and understand its circuit diagram.

The power supply of the unit in question is a traditional flyback. The primary winding of the block will need to be covered with a shielding winding. It is made from the same wire. The superimposed turns must completely cover the primary ones and have the same direction with them. Between the windings, insulation is arranged. It can be made from varnished cloth or masking tape.

When setting up the power supply of the welding machine, you need to choose such a resistance that the voltage supplied to the power supply of the relay is 20-25 V. Select reliable and powerful radiator elements for the input rectifiers. For this purpose, models that were used in old computers are excellent. They can be bought inexpensively on the radio market.

The control circuit includes only 1 thermal sensor. It will be placed inside the radiator housing. On the same radio market, you should buy a PWM controller for the control unit. Through its control channel, the current in the arc will be stabilized. With the help of a capacitor, the PWM voltage will be determined. The welding current depends on the voltage itself.

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Step-by-step instructions for assembling an inverter welding machine

Use winding wire to wind the inductor.

First of all, prepare all the parts indicated in the circuit diagram. To assemble such a welding inverter, you can use available materials that are sold in any radio and electronics store. Before using the parts, make sure they are working.

Pick up a ready-made choke or make it on a steel magnetic circuit. For the manufacture of the inductor winding, use the PEV-2 wire. You need to make 175 turns.

The most affordable capacitors that can be used to assemble such an inverter welding machine are K78 capacitors.

They were widely used in old television sets, so finding them is not difficult. The operating voltage of the capacitors must be at least 1000 V. If you cannot find a capacitor with the desired voltage, use several elements so that their total capacitance matches the required rating.

To assemble the inverter, you will need several transistors.

Buy a few low power KU221A transistors. You should not use one powerful transistor instead, because. because of this, the operating frequency will decrease, and an unpleasant loud sound will appear during welding. Yes, and improperly selected power can lead to the fact that very soon it will be necessary to carry out equipment repairs.

When assembling the welding inverter, maintain the required clearances between the windings and magnetic circuits. Lay textolite plates in the windings. This will increase the electrical safety of the welding machine and ensure its sufficient cooling.

Next, you need to attach the transformer to the base of the homemade welding inverter. Use 2-3 staples for this. Staples can be made of copper wire with a diameter of 3 mm. Boards are made of foil textolite. For this, a material with a thickness of about 0.5-1 mm is suitable. In each board, 4 narrow slots should be prepared, due to which the load on the diode leads will be reduced.

After you have brought the toggle switch handle and LEDs to the front side, you will practically get a ready-made reference device.

Install all assembled units of the unit on the base. It can be made from a getinax plate. A plate 0.5 cm thick will suffice. In its center, you need to make a round window for the fan. Be sure to protect the latter with a grill. There must be an air gap between the magnetic cores.

Bring out on the front side of the base the LEDs and the toggle switch handle, as well as the cable clamps and the variable resistor handle. As a result, you will get an almost finished welding machine. This design must be placed in a casing made of textolite or vinyl plastic. The walls of the casing must have a thickness of 4 mm. Place a button on the electrode holder. It and the cable connected to it must be securely insulated.

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Connecting a homemade welding machine

The finished welding inverter must be connected to the network or to the battery. Use clamps to connect to the battery. Be sure to observe the polarity. The black clip goes to "-", and the red clip goes to "+". If there is a connection between the battery and the on-board network of the unit, it can not be disconnected. At the moment of connecting the outputs of the welding inverter with the battery, a spark should appear.

Plug your devices into an outlet. The socket must have a fuse or an automatic switch-off function. If necessary, an extension cable up to 50 m can be used.

Turn on the implement button. If everything is normal, the green LED will light up. It will stay green until the battery voltage is out of range.

When connecting and using a homemade inverter, one more very important point must be taken into account. In the event that during the operation of the welding inverter on the load, the battery voltage drops to 10.5 W and continues to fall for more than 1 minute, the machine will automatically turn off. This will prevent the battery from completely discharging and eliminating the need to repair it. Shorter voltage drops will not harm the welding machine, the battery or the network.

Due to their mobility, inverter welding machines are widely used in everyday life and in production. They have huge advantages compared to welding transformer units for welding work. Everyone should know the principle of operation, the device and their typical malfunctions. Not everyone has the opportunity to purchase a welding inverter, so radio amateurs post their own welding inverter circuits on the Internet.

General information

Transformer welding machines are relatively inexpensive and easy to repair due to their simple design. However, they are heavy and sensitive to supply voltage (U). At low U, it is impossible to perform work, since significant drops in U occur, as a result of which household appliances may fail. In the private sector, there are often problems with power lines, since in the former CIS countries, most power lines require cable replacement.

An electrical cable consists of strands that often oxidize. As a result of this oxidation, there is an increase in the resistance (R) of this twist. With a significant load, they heat up, and this can lead to an overload of power lines and transformer substation. If you connect an old-style welding machine to an electricity meter, then at low U, protection will work (“knock out” machines). Some try to connect a welder to an electricity meter, breaking the law.

Such a violation is punishable by a fine: electricity consumption occurs illegally and in large quantities. In order to make work more comfortable - not to depend on U, not to lift weights, not to overload power lines and not to break the law - you need to use an inverter-type welding machine.

Device and principle of operation

The welding inverter is designed in such a way that it is suitable for both home use and enterprise work. It is capable of ensuring stable combustion of the welding arc with small dimensions and even using a welding current that is significantly higher than that of an ordinary welding machine. It uses high-frequency current to generate a welding arc and is an ordinary switching power supply (the same as a computer one, only with a higher current strength), which makes the welding machine circuit simple.

The basic principles of its operation are as follows: rectification of the input voltage; converting the rectified U into a high-frequency alternating current using transistor switches and further rectifying the alternating U into a high-frequency direct current (Figure 1).

Figure 1 - Schematic arrangement of an inverter type welder.

When using high-power key transistors, a direct current is converted, which is rectified using a diode bridge into a high-frequency current (30..90 kHz), which makes it possible to reduce the dimensions of the transformer. A diode rectifier only allows current to flow in one direction. There is a "cut-off" of the negative harmonics of the sinusoid.

But at the output of the rectifier, a constant U with a pulsating component is obtained. To convert it into an acceptable direct current in order to correctly operate key transistors operating only from direct current, a capacitor filter is used. A capacitor filter is one or more high-capacity capacitors that can noticeably smooth out ripples.

The diode bridge and filter make up the power supply for the inverter circuit. The input of the inverter circuit is made on key transistors that convert the constant U into a high-frequency variable (40..90 kHz). This conversion is needed to power a pulse transformer, at the output of which a low-U high-frequency current is obtained. A high-frequency rectifier is powered from the transformer outputs, and a high-frequency direct current is generated at the output.

The device is not very complicated, and any welding inverter can be repaired. In addition, there are many schemes by which you can make a homemade inverter for welding.

Homemade welding machine

It is easy to assemble an inverter for welding, as there are many circuits. It is possible to make welding from a computer power supply, knock down a box for it, but you get a low-power welder. Details on creating a simple inverter from a computer PSU for welding can be found on the Internet. The inverter for welding on a PWM controller such as UC3845 is very popular. The microcircuit is flashed using a programmer, which can only be purchased at a specialized store.

For firmware, you need to know the basics of the C ++ language, in addition, it is possible to download or order a ready-made program code. Before assembly, you need to decide on the main parameters of the welder: the maximum allowable supply current is no more than 35 A. With a welding current equal to 280 A, U of the supply network is 220 V. If we analyze the parameters, we can conclude that this model exceeds some factory models. To assemble the inverter, follow the block diagram in Figure 1.

The power supply circuit is simple, and it is quite simple to assemble it (diagram 1). Before assembling, you need to decide on the transformer and find a suitable case for the inverter. To make a power supply inverter, you need a transformer. .

This transformer is assembled on the basis of a SH7x7 or SH8x8 ferrite core with a primary winding of a wire with a diameter (d) of 0.25..0.35 mm, the number of turns is 100. Several secondary windings of the transformer must have the following parameters:

  1. 15 turns with d = 1..1.5 mm.
  2. 15 turns with d = 0.2..0.35 mm.
  3. 20 turns with d = 0.35..0.5 mm.
  4. 20 turns with d = 0.35..0.5 mm.

Before winding, you need to familiarize yourself with the basic rules for winding transformers.

Scheme 1 - Scheme of the inverter power supply

It is advisable not to connect the parts by hinged mounting, but to make a printed circuit board for this purpose. There are many ways to manufacture a printed circuit board, but we should focus on a simple option - laser ironing technology (LUT). The main stages of manufacturing a printed circuit board:

After the manufacture of the transformer and the printed circuit board, it is necessary to proceed with the installation of radio components according to the power supply circuit of the welding inverter. To assemble the PSU, you will need radio components:

After assembly, the PSU cannot be connected and checked, since it is designed specifically for the inverter circuit.

Inverter manufacturing

Before starting the manufacture of a high-frequency transformer for the inverter, it is necessary to make a getinax board, guided by scheme 2. The transformer is made on a magnetic circuit of the Sh20x28 2000 NM type with an operating frequency of 41 kHz. For its winding (I winding) it is necessary to use copper sheet with a thickness of 0.3..0.45 mm and a width of 35..45 mm (width depends on the frame). Need to do:

  1. 12 turns (cross-sectional area (S) about 10..12 sq. mm.).
  2. 4 turns for the secondary winding (S = 30 sq. mm.).

A high-frequency transformer cannot be wound with an ordinary wire due to the appearance of the skin effect. Skin effect - the ability of high-frequency currents to be forced out to the surface of the conductor, thereby heating it. The secondary windings should be separated with a PTFE film. In addition, the transformer must be properly cooled.

The inductor is made on a magnetic circuit of the type "Sh20 × 28" made of ferrite 2000 NM with S of at least 25 square meters. mm.

The current transformer is made on two rings of the "K30 × 18 × 7" type and is wound with a copper wire. Winding l is threaded through the annular part, and winding II consists of 85 turns (d = 0.5 mm).

Scheme 2 - Scheme of an inverter welding machine with your own hands (inverter).

After the successful manufacture of the high-frequency transformer, it is necessary to mount the radio elements on the printed circuit board. Before soldering, treat the copper tracks with tin, do not overheat the parts. List of inverter elements:

  • PWM controller: UC3845.
  • MOSFET transistor VT1: IRF120.
  • VD1: 1N4148.
  • VD2, VD3: 1N5819.
  • VD4: 1N4739A 9V.
  • VD5-VD7: 1N4007.
  • Two diode bridges VD8: KBPC3510.
  • C1: N. 22
  • C2, C4, C8: 0.1uF.
  • C3: 4.7 N and C5: 2.2 N, C15, C16, C17, C18: 6.8 N (only use K78-2 or CBB-81).
  • C6: 22 microns, C7: 200 microns, C9-C12: 3000 microns 400 V, C13, C21: 10 microns, C20, C22: 47 microns at 25 V.
  • R1, R2: 33k, R4: 510, R5: 1.3k, R7: 150, R8: 1 at 1W, R9: 2M, R10: 1.5k, R11: 25 at 40W, R12, R13 , R50, R54: 1k, R14, R15: 1.5k, R17, R51: 10, R24, R25: 30 at 20W, R26: 2.2k, R27, R28: 5 at 5W, R36, R46- R48, R52, R42-R44 - 5, R45, R53 - 1.5.
  • R3: 2.2k and 10k.
  • K1 for 12 V and 40A, K2 - RES-49 (1).
  • Q6-Q11: IRG4PC50W.
  • Six MOSFET transistors IRF5305.
  • D2 and D3: 1N5819.
  • VD17 and VD18: VS-HFA30PA60CPBF; VD19-VD22: VS-HFA30PA60CPBF.
  • Twelve zener diodes: 1N4744A.
  • Two optocouplers: HCPL-3120.
  • Inductor: 35 microns.

Before checking the circuit for operability, you must once again visually check all connections.

Before assembling, you need to carefully familiarize yourself with the inverter welding circuit and purchase everything you need for manufacturing: buy radio components in specialized radio stores, find suitable transformer frames, copper sheet and wire, think over the design of the case. Planning work greatly simplifies the assembly process and saves time. When soldering radio components, a soldering station (induction with a hairdryer) should be used to prevent possible overheating and failure of radio elements. You must also follow the safety rules when working with electricity.

Further customization

All power elements of the circuit must have high-quality cooling. Transistor keys must be "planted" on thermal paste and a radiator. It is advisable to use heatsinks from powerful microprocessors (Athlon). The presence of a fan for cooling in the case is required. The power supply circuit can be modified by placing a capacitor unit in front of the transformer. It is necessary to use K78-2 or SVV-81, since other options are not allowed.

After the preparatory work, you need to start setting up the welding inverter . For this you need:

There are also more advanced models of inverter-type welders, the power circuit of which includes thyristors. The Timvala inverter, which can be found on amateur radio forums, has also become widespread. It has a more complex scheme. More details can be found on the Internet.

Thus, knowing the device and principle of operation of an inverter-type welding machine, it is not an impossible task to assemble it with your own hands. The homemade version is practically not inferior to the factory one and even surpasses some of its characteristics.