Homemade welding inverter from available circuit parts. Homemade inverter welding machine from parts of old TVs

The inverter type is used in the workshop and mobile teams. Differs in small weight and dimensions, high quality of a welded seam. The home master also does not interfere with his own apparatus, which is often too expensive to buy. In this case, you can assemble a welding inverter with your own hands. Even the simplest scheme will allow you to work with electrodes with a diameter of 3–4 mm and use the device for personal needs. According to the description, it has enough power from a 220 V household network.

Figure 5 - Scheme of the inverter welding machine

Inside the inverter, the input voltage is rectified. Then the converted voltage is transformed into a high-frequency alternating current using transistor switches. Next, the AC is converted to DC.

The installation of high power key transistors and a diode bridge reduces the size of the transformer. The output is a high-frequency current of 30–90 kHz. A diode rectifier produces a constant voltage at the output. It is converted to direct current by a filter of several large capacitors, which is necessary to smooth out the ripple.

The diode bridge and filter represent the power supply of the inverter. At the input there are key transistors that provide power to the pulse transformer. Behind it, a high-frequency rectifier is connected, which produces high-frequency direct current.

The scheme is considered simple and accessible for self-implementation.

List of required materials and tools

Do-it-yourself inverter welding will consume 32 A, and after conversion it will give out a current of 250 A, which will provide a strong and high-quality seam. To complete the task, you will need the following components:

• transformer with a ferrite core for the power section;
• copper sheet for windings;
• PEV wire;
• steel sheets for the body or a finished box;
• insulating material;
• textolite;
• fans and radiators;
• capacitors, resistors, transistors and diodes;
• PWM controller;
• front panel buttons and switches;
• wires for connecting nodes;
• large power cables.

We recommend that you purchase a ground clamp and holder from a special tool store. Some craftsmen make a holder out of 6 mm steel wire. Before you start assembling your welding inverter, it is recommended to watch the training video, study the step-by-step instructions and print the diagram. From the tools you need to prepare a soldering iron, pliers, a knife, a set of screwdrivers and fasteners.

Simple Inverter Welding Circuits

The first step towards making a welding inverter is choosing a proven working circuit. There are several options that require detailed study.

The simplest welding machine:

Schematic diagram of the welding inverter:

Staged assembly process

The components of a home-made welding inverter are mounted on a base made of a 5 mm thick getinaks plate. A round hole is made in the center for the fan. Then it is fenced with bars. LEDs, toggle switches and resistor knobs are output to the front panel of the case. The wires should be arranged with an air gap. In the future, the case will need to be closed with a casing made of sheets of textolite or vinyl plastic with a thickness of at least 4 mm. A button is installed at the place where the electrode is attached. It and the connection cable are carefully insulated.

The rewound transformer is placed on the panel. For fastening, you will need brackets made of copper wire with a diameter of at least 3 mm. Under the boards, foil textolite 1 mm thick is used. Small cuts are made in each to reduce the load on the diode terminals. Fasten the boards towards the terminals of the transistors. The sequence and correctness of the assembly is checked against the scheme of a home-made inverter.

Capacitors are soldered onto the board, about 14 pieces in number. They will bring transformer surges into the power circuit. Built-in snubbers containing capacitors C15 and C16 will help neutralize resonant current surges from the transformer. Snubbers are chosen from good quality and proven manufacturers, because they have a very important role in the inverter. They should reduce resonant surges and IGBT losses at the moment of shutdown. The devices take on all the power, which reduces heat generation by several times. The models SVV-81 and K78-2 were recognized as the best.

For cooling and protection against overheating, heatsinks from Pentium 4 and Athlon 64 type computers are well suited.

Housing of the welding inverter

The case will be needed for compact placement of all components. The width of the transformer should be freely placed in it. Another 70% of the space is devoted to everything else. There must be jumpers to install boards.

The upper protective cover can be bent from a sheet of 0.5-1 mm, welded or made up of several plates. In the sheets covering the side walls, make ventilation holes. The case must have a handle for transportation.

The design should be easy to understand. On the front panel, grooves are made for installing the power button, current switches, PWM controller, indicator lights and connectors.

As a decorative coating, ordinary or hammer paint in red, blue and orange is suitable.

Where to get the power supply and how to connect it

The welding inverter power supply can be made from an uninterruptible power supply. All you need is a transformer and a UPS case with the rest of the stuffing removed. The input will be a winding with high resistance and a "native" socket at the end of the case. After applying a voltage of 220 V, you need to find a pair with a potential difference of 15 V. These wires will become the output from the PSU. Here you will also need to install a diode bridge, to which consumers will be connected. The output will be a voltage of about 15 V, which will sag under load. Then the voltage will have to be selected empirically.

Switching power supply allows you to reduce the size and weight of the transformer, save materials. Powerful DC transistors installed in the inverter circuit provide switching from 50 to 80 kHz. With the help of a group of powerful diodes (diode bridge), a constant pulsating voltage is obtained at the output. The capacitor filter produces a DC voltage of over 220 V after conversion. The filter and rectifier bridge module forms a power supply. The PSU powers the inverter circuit. The transistors are connected to a pulse-type step-down transformer with an operating frequency of 50–90 kHz. The power of the transformer is the same as that of the power welding machine. At the output of the transformer, the high-frequency current feeds the rectifier, which delivers high-frequency direct current.

You can make a transformer on E42 type cores from an old tube monitor. You will need 5 of these devices. One will go for the throttle. For the rest of the elements, cores of 2000 NM are needed. The open circuit voltage will be 36 V with an arc length of 4–5 mm. Output cables are recommended to be filled in ferrite tubes or rings.

Welding resonant inverter circuit:

Diode bridge

The diode "oblique bridge" is designed for transformation in the AC power supply to DC. Proper selection of resistors will maintain a voltage of 20-25 V between the transformer and the relay. During operation, the assembly will get very hot, so it is mounted on radiators from the computer. They will need 2 pieces for the top and bottom elements. The top one is placed on a mica gasket, and the bottom one is placed on thermal paste.

The output wires are left 15 cm long. During installation, the bridge is separated by a steel sheet attached to the body.

winding transformer

The transformer is the power part of the inverter, which is responsible for lowering the voltage to a working value and increasing the current strength to the level of metal melting. For its manufacture, standard plates of a suitable size are used or a frame is cut out of metal sheets. There are two windings in the design: primary and secondary.

The transformer is wound with a strip of copper sheet 4 cm wide and 0.3 mm thick, because width and a small cross section are important. Then the physical properties of the material are used optimally. The wire may not withstand increased heat. The core of a thick wire remains unused at high-frequency currents, which causes the transformer to overheat. Such a transformer will work for a maximum of 5 minutes. Here you need only a conductor of large cross section and minimum thickness. Its surface transmits current well and does not heat up.

The thermal layer will be replaced by cash register paper. Xerox is also suitable, but it is less durable and can be torn when winding. Ideally, the insulator should be a varnished cloth, which is laid in at least one layer. Good insulation is the key to high voltage. The length of the strip should be enough to cover the perimeter and enter 2–3 cm. To increase electrical safety, textolite plates are laid between the windings.

The secondary winding of the transformer is carried out by 3 copper strips, separated by a fluoroplastic plate. On top again there is a layer of thermal tape.

The cash register tape as insulation has one drawback - it darkens when heated. But it does not tear and retains its properties.

It is allowed to replace copper sheet with PEV wire. Its advantage is that it is multi-stranded. This solution is worse than using a copper strip, because the bundle of wires has air gaps and they have little contact with each other. The total cross-sectional area is lower and heat transfer slows down. In the design of the inverter with SEW, 4 windings are made. The primary consists of 100 turns of PEV wire with a diameter of not more than 0.7 mm. Three secondary ones have 15 + 15 + 20 turns, respectively.

Connecting the inverter unit

The manufacture of a resonant inverter is carried out on the basis of parts from an old monitor or TV. A computer power supply, its cooler and radiators are used.

Zener diodes KS-213 are used to protect transistors. Frequency-type power transistors should be near the transformer in order to dampen interference and interference.

Tracks on a textolite board with a thickness of 4–6 mm under the power bridge will have to be expanded, taking into account the fact that currents of the order of 30 A flow. The minimum cross section of the supply cable should be taken at least 3 mm². The power diodes at the output are protected by an RC circuit.

Design and connection of the cooling system

For good cooling of working units, a sufficient number of ventilation holes must be provided in the case. They are located on opposite walls. A 220 V cooler from an old computer at 0.15 A and above is used as a fan.

It is oriented to extract hot air. The inflow of cold air will provide holes.

The fan is placed as close as possible to the transformer. The second fan should blow the radiator with rectifier diodes. The operation of the welding inverter is associated with increased heat generation, so you need to use at least two fans.

It is advisable to install a temperature sensor on the most heated element. When overheated, it will work to turn off the power of the inverter itself.

Electrode sticking prevention mechanism

When working with electrodes, welders face problems during ignition of the arc and sticking of the electrodes. The electrodes heat up, they consume more power, the wires overheat from the load and knock out the machines. The transformer hums, the rods bend, and the coating crumbles, but the process does not go.

The automatic sticking prevention mechanism will help to solve the problem and save the welding inverter. The module assembled according to the scheme is built into the primary and secondary windings. The device will simplify the work, the arc will become easier to ignite, and there will be no network overload.

Main scheme

The principle of operation of the scheme is as follows. The secondary winding of the welding transformer is connected to an AC rectifier and a voltage stabilizer. The output is connected to a low-current relay RES-10 for closing. A ceramic capacitor C3 is connected in series. It is selected according to the power of the transformer, with a capacity of 2–10 microfarads and a voltage of over 400 V. It acts as a reactive resistor.

After power is applied to the capacitor, an alternating voltage appears in the secondary winding. Then relay P2 is activated, opening the power relay P1 with a voltage of 220 V. In parallel, capacitor C4 with a characteristic of 20–25 A is connected to the winding. Its contacts short-circuit C3, and the transformer turns on in normal mode.

With a stable arc on the secondary winding, the voltage is kept in the range of 35–45 V. This is enough for relay P2. In a short circuit, the alternating current disappears on the secondary winding. As a result, P2 is de-energized and turns off relay P1. In this case, the primary winding is fed only through the capacitor C3, on which the mains voltage closes. A small current of 150–200 mA is safe for the network. The electrodes do not stick, and if this happens, they are easily separated. After stabilization of the situation, the relay is activated and the transformer is switched on to the operating mode.

Everything is fine, but with a short circuit, clicks are heard. They get rid of such a nuisance by turning on the thyristors in the key mode according to the diagram below.

The capacitor successfully replaces a 100–300 W incandescent lamp. When short circuited, it will flare up.

Pre-launch diagnostics of the device

Diagnostics and preparation of the welding inverter for operation is no less important process than the assembly itself.

The inverter is powered by 15V and connected to the PWM board. In parallel, power is supplied to the convector, which will reduce the heating of the device and reduce noise.

After charging the capacitors, a relay is connected, which is necessary to close the resistor. This reduces power surges when the inverter is turned on.

Turning on the inverter to the 220 V network bypassing the resistor can cause an explosion.

Now you need to check the operation of the resistor closing relay after applying current to the PWM. Impulses are diagnosed on the board a few seconds after the relay is triggered. To check the serviceability and operability of the bridge, 15 V is supplied to it. Idling is set and the current strength is above 100 mA.

The correct installation of the transformer phases is controlled by an oscilloscope for 2 beams. The bridge is pre-powered by capacitors using a 200W 220V lamp. The PWM frequency is set to 55kHz. On the oscilloscope, you need to track that the voltage does not exceed 330 V.

The frequency of the assembled welding inverter is determined by a smooth decrease in the PWM frequency until a slight inversion appears on the lower IGBT key. The resulting indicator is divided by two, and the saturation frequency is added to the result. The resulting number will be the working frequency fluctuation of the transformer.

Bridge consumption must be within 150 mA. The light of the lamp is dim. Intense light indicates winding breakdown or bridge design errors. The transformer should not have sound and noise effects. If they appear, check the polarity. Test power to the bridge is connected using a household appliance, such as a kettle, at 2.2 W.

The conductors coming out of the PWM are made short, twisted and laid further from interference sources. The inverter current is gradually increased through the resistor. The bottom switch, according to the oscilloscope, should remain within 500 V. The standard figure is 340 V. The appearance of noise can damage the IGBT.

Trial welding starts from 10 s. After that check the radiators. If they are not cold, then they prolong welding up to 20 s. Then you can cook for 1 minute or longer.

The transformer overheats after using 2-4 electrodes. The fan needs 2 minutes to cool down, after which it continues to work.

The characteristics of most budget inverters cannot be called outstanding, at the same time, few will refuse the pleasure of using equipment with a significant margin of reliability. Meanwhile, there are many ways to improve an inexpensive welding inverter.

Typical scheme and principle of operation of the inverter

The more expensive the welding inverter, the more auxiliary units involved in the implementation of special functions in its circuit. But the power converter circuit itself remains practically unchanged even with expensive equipment. The stages of transformation of the mains electric current into welding current are quite easy to follow - at each of the main nodes of the circuit, a certain part of the overall process takes place.

From the mains cable through a protective switch, voltage is supplied to the rectifier diode bridge, coupled with high-capacity filters. On the diagram, this area is easy to notice, there are impressive “banks” of electrolytic capacitors here. The rectifier has one task - to “unfold” the negative part of the sinusoid symmetrically upwards, while the capacitors smooth out the ripples, bringing the direction of the current almost to a pure “constant”.

Scheme of operation of the welding inverter

Next in the diagram is the inverter itself. This part is also easily identifiable and houses the largest aluminum heatsink. The inverter is based on several high-frequency field-effect transistors or IGBT transistors. Quite often, several power elements are combined in a common housing. The inverter again converts direct current into alternating current, but at the same time its frequency is much higher - about 50 kHz. Such a chain of transformations allows the use of a high-frequency transformer, which is many times smaller and lighter than a conventional one.

The voltage is removed from the step-down transformer by the output rectifier, because we want to weld on direct current. Thanks to the output filter, the nature of the current changes from high-frequency pulsating to an almost straight line. Naturally, in the considered chain of transformations there are many intermediate links: sensors, control and control circuits, but their consideration goes far beyond the scope of amateur radio electronics.

The design of the welding inverter: 1 - filter capacitors; 2 - rectifier (diode assembly); 3 - IGBT transistors; 4 - fan; 5 - step-down transformer; 6 - control board; 7 - radiators; 8 - throttle

Units suitable for modernization

The most important parameter of any welding machine is the current-voltage characteristic (CVC), due to which stable arc burning is ensured at different arc lengths. The correct CVC is created by microprocessor control: the small “brain” of the inverter changes the operating mode of the power switches on the go and instantly adjusts the welding current parameters. Unfortunately, it is impossible to reprogram a budget inverter in any way - the control microcircuits in it are analog, and replacing it with digital electronics requires outstanding knowledge of circuitry.

However, the “skills” of the control circuit are quite enough to level the “curvature” of a novice welder who has not yet learned how to stably hold the arc. It is much more correct to focus on the elimination of some "childhood" diseases, the first of which is a strong overheating of electronic components, leading to degradation and destruction of power keys.

The second problem is the use of radio elements of dubious reliability. Eliminating this shortcoming greatly reduces the likelihood of breakdowns after 2-3 years of operation of the device. Finally, even a novice radio technician will be quite capable of realizing the indication of the actual welding current to be able to work with special brands of electrodes, as well as make a number of other minor improvements.

Improved heat dissipation

The first drawback that the vast majority of inexpensive inverter devices sin is a poor heat removal circuit from power switches and rectifier diodes. It is better to start refinement in this direction by increasing the intensity of forced airflow. As a rule, case fans powered by 12 V service circuits are installed in welding machines. In "compact" models, forced air cooling may be completely absent, which is certainly nonsense for electrical engineering of this class.

It is enough to simply increase the air flow by installing several of these fans in series. The problem is that the "native" cooler will most likely have to be removed. In order to work effectively in a series assembly, the fans must have an identical shape and number of blades, as well as rotational speed. It is extremely easy to assemble identical coolers into a “stack”, just tighten them with a pair of long bolts along diametrically opposite corner holes. Also, do not worry about the power of the service power supply, as a rule, it is enough to install 3-4 fans.

If there is not enough space inside the inverter housing to install fans, one high-performance "duct" can be attached outside. Its installation is easier for the reason that it does not require connection to internal circuits, the power is removed from the terminals of the power button. The fan, of course, must be installed opposite the ventilation louvres, some of which can be cut out to reduce aerodynamic drag. The optimal direction of air flow is to the hood from the housing.

The second way to improve heat dissipation is to replace standard aluminum radiators with more efficient ones. A new radiator should be chosen with the largest number of fins as thin as possible, that is, with the largest area of ​​contact with air. It is optimal for these purposes to use computer CPU cooling radiators. The process of replacing radiators is quite simple, just follow a few simple rules:

1. If the standard radiator is isolated from the flanges of the radio elements with mica or rubber gaskets, they must be retained when replacing.
2. To improve thermal contact, silicone thermal paste should be used.
3. If the heatsink needs to be cut to fit in the case, the cut fins must be carefully processed with a needle file to remove all burrs, otherwise dust will accumulate abundantly on them.
4. The heatsink must be tightly pressed against the microcircuits, so you must first mark and drill mounting holes on it, you may need to cut threads in the body of the aluminum sole.

In addition, we note that it makes no sense to change the piece heatsinks of separate keys, only the heat sinks of integrated circuits or several high-power transistors installed in a row are replaced.

Welding current display

Even if a digital current setting indicator is installed on the inverter, it does not show its real value, but some service value, scaled for visual display. The deviation from the actual current value can be up to 10%, which is unacceptable when using special brands of electrodes and working with thin parts. You can get the real value of the welding current by installing an ammeter.

Within 1 thousand rubles, a digital ammeter of the SM3D type will cost, it can even be carefully built into the inverter housing. The main problem is that a shunt connection is required to measure such high currents. Its cost is in the range of 500-700 rubles for currents of 200-300 A. Please note that the type of shunt must comply with the recommendations of the ammeter manufacturer, as a rule, these are 75 mV inserts with an intrinsic resistance of about 250 μΩ for a measurement limit of 300 A.

You can install the shunt either on the positive or on the negative terminal from inside the case. Usually, the dimensions of the connecting bus are sufficient to connect an insert with a length of about 12-14 cm. The shunt cannot be bent, therefore, if the length of the connecting bus is not enough, it must be replaced with a copper plate, a pigtail from a peeled single-wire cable or a piece of welding core.

The ammeter is connected by measuring outputs to the opposite terminals of the shunt. Also, for the operation of a digital device, it is required to supply a supply voltage in the range of 5-20 V. It can be removed from the wires for connecting fans or found on the board with potential points for powering control microcircuits. The ammeter's own consumption is negligible.

Increased duty cycle

On-duration in the context of welding inverters is more reasonably referred to as load duration. This is the part of the ten minute interval in which the inverter is actually doing work, the rest of the time it should be idling and cooling down.

For most inexpensive inverters, the actual duty cycle is 40-45% at 20°C. Replacing radiators and an intensive airflow device can increase this figure to 50-60%, but this is far from the ceiling. It is possible to achieve a PN of the order of 70-75% by replacing some radio elements:

1. The inverter key binding capacitors must be changed to elements of the same capacity and type, but designed for a higher voltage (600-700 V);
2. Diodes and resistors from the key binding should be replaced with elements with a higher power dissipation.
3. Rectifier diodes (valves), as well as MOSFET or IGBT transistors, can be replaced with similar, but more reliable ones.

The replacement of the power keys themselves should be discussed separately. First you need to rewrite the marking on the element body and find a detailed datasheet for a specific element. According to the passport data, choosing an element for replacement is quite simple, the key parameters are the limits of the frequency range, operating voltage, the presence of a built-in diode, case type and current limit at 100 ° C. It is better to calculate the latter with your own hands (for the high-voltage side, taking into account the losses on the transformer) and purchase radio elements with a current limit margin of about 20%. Of the manufacturers of this kind of electronics, International Rectifier (IR) or STMicroelectronics are considered the most reliable. Despite the rather high price, it is highly recommended to purchase parts from these brands.

Output choke winding

One of the simplest and at the same time most useful additions to a welding inverter will be the winding of an inductive coil, which smooths out the DC ripple that inevitably remains during the operation of a pulse transformer. The main specificity of such an undertaking is that the inductor is made individually for each individual device, and can also be adjusted over time as the electronic components degrade or when the power threshold changes.

To make a choke, you need nothing at all: an insulated copper conductor with a cross section of up to 20 mm 2 and a core, preferably made of ferrite. Either a ferrite ring or the core of an armored transformer is optimally suited as a magnetic circuit. If the magnetic circuit is made of sheet steel, it must be drilled in two places with an offset of about 20-25 mm and pulled together with rivets in order to be able to cut through the gap without any problems.

The throttle starts to work, starting from one full turn, however, the real result is visible, starting from 4-5 turns. When testing, turns should be added until the arc begins to noticeably stretch strongly, preventing separation. When it becomes difficult to cook with a margin, you need to throw off one turn from the coil and connect a 24 V incandescent lamp in parallel with the throttle.

Fine tuning of the throttle is performed using a plumbing screw clamp, which can reduce the gap in the core, or a wooden wedge, which can be used to increase this gap. It is necessary to ensure that the burning of the lamp during the ignition of the arc is as bright as possible. It is recommended to make several chokes for operation in the ranges up to 100 A, from 100 to 200 A and more than 200 A.

Conclusion

All "mounted" additions, such as a choke or ammeter, are best mounted with a separate attachment, which is included in the gap of any of the welding cores using a bayonet-type plug. Thus, enough space for ventilation will remain inside the inverter housing, and additional devices can be easily disconnected as unnecessary.

It must be remembered that it will not be possible to carry out a cardinal, deep modernization, in other words, RESANTA cannot be turned into KEMPPI by reasonable forces and means. However, making fixtures and fine-tuning equipment is a great way to better learn arc welding technology and get into the professional intricacies.

Household requires certain tools. Welding work is carried out using an inverter, which is widely in demand in everyday life. Making a welding inverter with your own hands will not be difficult and financial investments, it is enough to have a little knowledge of electricians, reading drawings. A high-quality inverter on the market costs a lot of money, and more affordable analogues may not meet the required parameters.

Characteristics of a homemade inverter and materials for its assembly

For efficient operation of the device, you need to use high-quality materials. Some parts can be used from old power supplies or found on disassembly of radio components. The main technical characteristics of the device:

• The consumed voltage is 220 volts.
• At the input, the current strength is not less than 32 amperes.
• The current produced by the device is 250 A.

The main circuit of the welding inverter consists of a power supply, chokes, power unit. To make the device, you will need tools and parts:

• Set of screwdrivers for dismantling and further assembly.
• A soldering iron is necessary for connecting electronic elements.
• Knife and blade for metal for the manufacture of the correct shape of the structure.
• A piece of metal 5-8 mm thick to form the case.
• Self-tapping screws or bolts with nuts for fastening.
• Boards for electronic circuits.
• Copper products in the form of wires are used to wind the transformer.
• Fiberglass or textolite.

Homemade do-it-yourself single-phase welding inverter is popular in household use .

Such an inverter is powered by a 220 V household network, there are times when it is necessary to manufacture a device powered by a 380 V three-phase network. Such devices are characterized by increased efficiency and power, and are used for mass work.

What you need to build an inverter

The main task of the welding inverter is to convert the current strength sufficient for household use. The work with the electrode is carried out at a distance of 1 cm to obtain a strong seam. The manufacture of a home-made welding inverter takes place according to the plan, in accordance with the scheme.

The power supply is initially made, for its components you will need:

• A transformer having a core made of ferritic material.
• Transformer winding with a minimum number of turns - 100 pieces, with a cross section of 0.3 mm.
• The secondary winding is made of three parts, the inner one consists of 15 turns with a wire cross section of 1 mm, the middle one with the same number of turns with a cross section of 0.2 mm, the outer layer of 20 curls with a diameter of at least 0.35 mm.

Homemade inverter must be manufactured in accordance with the required characteristics. For stable, voltage-resistant operation, windings are used across the full width of the frame. Aluminum wires are not able to provide sufficient arc throughput, they have an unstable heat sink. A high-quality device is made with a copper bus.

Manufacturing of transformer and inductor

The main task of the transformer is to convert the high-frequency current voltage with its sufficient strength. Cores can be used models Ш20×208, in the amount of two pieces. The gap between the parts can be provided with your own hands using plain paper. The winding is done by hand, with a copper strip 40 mm wide, the thickness must be at least 0.2 mm. Thermal insulation is achieved using cash register thermal tape, it shows good wear resistance and strength.

The use of copper wire when winding the core is unacceptable, because. it displaces current to the surface of the device. To remove excess heat, a fan or cooler from a computer power supply, as well as a radiator, is used.

The inverter unit is responsible for the throughput of the electric arc through the use of transistors and chokes.

Due to this, the output current is stabilized, during the do-it-yourself inverter welding process, the device makes less noise.

Capacitors connected in series are responsible for several functions:

• Resonance spikes are minimized.
• Loss of amps due to the design of transistors, which open much faster than they close.

Transformers get very hot due to the large amount of current passing. Heatsinks and fans are used to control the temperature. Each element is mounted on a radiator made of heat-removing material, if it is possible to install one powerful cooler, this will reduce assembly time and simplify the design.

The design of the welding machine

The basis for the device is the case, it is possible to use a system unit from an ATX computer, it is recommended to look for older models at dismantling, since the metal was used thicker and better. A metal canister is also suitable, in which case it is necessary to cut holes for ventilation, install additional fasteners.

Ferrite material is used to wind the power supply transformer with your own hands. The winding of the wire on the core is carried out over the entire width, this will make it possible to improve the performance of the device, eliminate voltage drops. Copper wire is used in a home-made welding inverter, brand PEV-2, the primary winding is insulated with fiberglass.

The function of the power block is to reduce the current strength.

Transformers are installed with a gap, newsprint is laid between them. The coils are wound with their own hands in several layers of the primary winding, then the secondary winding is superimposed in three layers. To protect against short circuits, a gasket that does not pass current is used.

To prevent a short circuit, power conductors are diverted in different directions, and a fan is used for cooling.

How to set up inverter operation

Assembling a welding inverter does not require much effort if you have the necessary tools and materials. The cost of a product made by hand is minimal due to the use of inexpensive products.

Setting up the device for proper operation often requires the help of specialists, but it can be done by yourself if the requirements are met.

1. Voltage is applied to the inverter board, cooling fan first. This approach will eliminate overheating of the system and early failure.
2. A little time is allotted for charging the power capacitors, after which the resistor is closed in the circuit. The relay is checked at the output of the resistor, the voltage must correspond to zero. The current-limiting resistor is necessary for the safe use of the inverter, without using it, the machine may catch fire.
3. The oscilloscope measures the incoming current pulses to the transformer, the ratio should be 66 to 44 percent.
4. The welding process with a do-it-yourself inverter is checked by a voltmeter connected to an optocoupler at the output of its amplifier.
5. A voltage of 16 volts is applied to the output bridge, for this a suitable power supply is used. When idling, the current consumption is about 100 mA.

The test is carried out with short-term welding processes. When welding up to 10 seconds, it is necessary to control the temperature of the inverter, if the transformers are not very hot, it is possible to gradually increase the operating mode.

The use of a do-it-yourself welding inverter implies the failure of the device. For diagnostics, you need to open the case of the device with your own hands, check the voltage at the input. A common problem is the failure of the power supply, due to insufficient cooling or low-quality materials used for prolonged operation. You should also visually inspect the connections and check them with a multimeter. In cases of failure of the temperature sensor or fuses, it is necessary to replace them with new ones.

Advantages and disadvantages

A self-made device can be used both in the household and in small industries. At first glance, the design consists of many elements, the scheme seems difficult to do with your own hands. By following a sequence of steps, using quality materials, it is possible to achieve long-term performance at low cost. A simple welding inverter is quite expensive on the market and is not of high quality.

The disadvantages are the short time of a long service life of a homemade inverter. For large volumes, it is recommended to make a three-phase inverter device with your own hands, but it is difficult to find a power source of this type.

In this material, you can see a diagram by which you can assemble a welding inverter with your own hands. The value of the maximum current consumption is 32 A, the supply voltage is 220 V. The approximate value of the welding current is 250 A, this makes it possible to carry out welding using a 5-ki electrode. The arc has a length of 10 mm. The power supply in terms of efficiency is not inferior to store appliances, and sometimes even surpasses them (we are talking about inverter ones).

General view (it remains only to insert into the body)

Figure 1 shows the diagram according to which the power supply is built in an inverter-type welding machine.

Rice. 1 Do-it-yourself welding inverter, power supply device

Inverter PCB

Driver circuit board

The winding of the transformer is carried out according to the memo below:

The secondary winding consists of the same wire and is wound in 18 turns. The power supply has a total weight of approximately 350 g.

PCB arc length limiter

Rice. 2 Welding inverter, circuit diagram

Figure 2 shows a schematic diagram of a welding inverter.

The primary winding of the current transformer is the output of the primary of the output transformer, threaded through the hole in the board, and at the same time through the core of the current transformer.

The printed circuit board has been tested, everything works fine on it.

Do-it-yourself welding inverter - 2 working and proven schemes:

While it's winter, I don't want to go outside. Up to -25 degrees however. But it's sunny every day. Cool. The house is warm and the sun shines through the window. Slowly began to collect welding inverter. Collect do-it-yourself welding inverter I was going for a long time, but there was no time. In winter, there is more free time and therefore more freedom for creativity. The prices for welding inverters in city stores are very decent. I need a simple device for rare summer jobs. There is an option to buy the cheapest Chinese device, but it will be much worse than a home-made inverter for the same money. Yes, I love making things with my own hands. At first I wanted to make a transformer welder, but I didn’t come across a free magnetic circuit for making a transformer, but I don’t want to buy it at all because it’s not a small price, but for what, in fact, to assemble a shitty welder. No, that won't work.

I took a closer look at modern welding inverters, and what actually is not so difficult. The weight of the structure is easier overall to get. Yes, and the load of inverters on the already “sagging” country power grid is lower. I took as a basis the scheme of a welding inverter such as the resonant bridge of Mr.

Two of his books "The welding inverter is simple" And "The welding inverter is just Part 2" in PDF format can be easily downloaded from the Internet. Enter the query in the search engine: “The welding inverter is just Negulyaev” or something like that.

Click on the diagram to view it in full size.

I will not write here the same thing that you can already read in the books mentioned above. Therefore, for the details in the book. On the Internet, many specialists hayat Negulyaev and his invention. Basically it all comes down to what can be done cooler. And I don't need more. Like, for example, it is better to use special modern drivers for IGBT. I don't want to pay extra money for them. Then this inverter itself is not resonant, but quasi-resonant, or maybe it is still resonant? The scheme works anyway. Reliable enough. Allows you to shoot 200 - 250 amps.

Started collecting. Made a parts list and went shopping. It turned out that not everything is so simple, and even the shops of radio components in St. Petersburg do not have most of the necessary parts. IGBT IRG4PC50UD there were no transistors for the bridge in Micronics. There is in Simitron, but sale only to legal entities. Megaelectronics is also bad and, at best, only on order. In Chip and Dip there is, but as always in the best traditions of the store at a triple price. The same story with the output power diodes 150EBU04 and especially with ferrite.

Long searched for components in stores. From the Chinese (order via the Internet with free delivery) In addition to the availability of everything you need, there I am pleased with the price. Even when ordering from sellers with paid delivery, you still get much cheaper than we have on the Internet or in a real store. I thought why I would produce components on order. Wait two weeks for these orders. Then go pick them up at different places. Overpay. In China, I will get everything much cheaper (at least what I wanted) and the parcel will almost come into my hands (the post office is a three-minute walk from my house).

The parcel arrived pretty quickly. Everything was very well packaged and arrived safe and sound. While I was waiting for this package, I soldered a generator from my old stocks. Here is the part of the diagram.

It only remained to stick the UC3825N chip into the crib. Here's what happened.

Then he wound the choke Dr.3. for a voltage multiplier 15 turns of mounting wire, preferably 1 sq. mm. on ferrite ring 28x16x9 2000HM1. Motal self-made of two ball screws 0.5 sq. mm. the factory insulation is removed and they are twisted together. Then PVC insulation was restored with electrical tape. After winding, the winding is varnished.

The manufacture of transformer Tr.3 took longer, since the winding refused to fit. It seems that the wire took a smaller diameter than the author of the book already mentioned more than once.

It was possible to wind 26 turns on a ferrite ring 28x16x9 2000HM1, which in principle is enough (25-30 turns are needed). I used what was at hand, namely a 6-wire CQR, removing the general insulation.

Conveniently, each winding is obtained in its own color. I still recommend using MGTF, it has more reliable insulation.

The resonant capacitor was assembled from six domestic capacitors K78-2 0.15 uF / 1000V. with a total capacity of 0.225 uF / 2000 V.

This is a responsible knot and it cannot be sculpted from anything. The photo of the composite capacitor shows one 150 KiloOhm resistor, another one of the same was later added. (Each in parallel with its line of capacitors.)

The input capacitor for 5 uF 450V, especially for alternating current, will not be small in size.
It has a convenient bolt-on mount.

Ferrite rings (although it is not mentioned in the book) are recommended to be put on the leads connected to the output diodes D3 and D5 150EBU04 of the output transformer Tr.

Also in parallel with them (D3 and D5 150EBU04) it does not hurt to put transyls (protective diode) of type 1.5KE350CA.

If it suddenly happens that your fuckers burn, do not rush to throw them away. The fact is that 150ebu04 is a composite diode and consists of two parallel crystals of 75 amperes each.

It often happens that only one of them burns out. It is necessary to saw through the middle of the terminal on which there are teeth for soldering. Sawing is necessary until you go deep into the component body itself by a millimeter. As a result, if you are lucky, you will get a fairly powerful 75 amp diode.

The welding inverter bridge itself on four IGBT transistors IRG4PC50UD turned out like this.

The transistors are located on the other side of the board, a heatsink with cooler cooling (fan) will be attached to them. The tracks are additionally reinforced with a millimeter-section copper conductor.

For the manufacture of power transformer Tr.1 and resonant inductor Dr.1, I use Epcos ferrite core E65 No. 87 (approximate domestic analogue of 20 × 28 2200HMC). One core per transformer and one per inductor. At the output of the welding inverter, 160 Amperes will pull.

In such a package, as in the photo, came to me in a parcel.

I stumbled upon a thermal relay by accident when I went to a gas equipment store. In which they traded all sorts of gas boilers and simple columns. They also sold spare parts for this very gas equipment. I look lies on the display case of the thermostat KSD301, just 90 degrees as I wanted. The current margin is much more than I need. If I'm not mistaken, it cost 30 rubles apiece, but definitely no more.

Bought two. I will put one on a radiator with IGBT transistors IRG4PC50UD, and the other on a radiator with output power diodes 150EBU04. The thermal relays themselves can be connected to a break in the wire through which the control signal goes to the input relay 12V 30A.

I already had a 30A 12V input relay in stock. For those who do not have it, I advise you to purchase it in stores for domestic cars to save money. There, a relay with such characteristics will cost an order of magnitude cheaper than in a radio components store. For example, recently I was in a car shop for GAZ cars and saw a suitable Russian-made relay for only 50 rubles.