How to make a welding transformer with your own hands. How to calculate winding
Nowadays, it is difficult to imagine any work with metal without using a welding machine. With this device you can easily join or cut iron of various thicknesses and dimensions. Naturally, to perform high-quality work, you will need certain skills in this matter, but first of all you need the welder himself. Nowadays, you can naturally buy it, as, in principle, and hire a welder, but this article will focus on how to make a welding machine with your own hands. Moreover, with all the wealth of various models, reliable ones are quite expensive, and cheap ones do not shine with quality and durability. But even if you decide to buy a welder in a store, familiarity with this article will help you choose the required device, since you will know the basics of their circuitry. Welders are of several types: DC, AC, three-phase and inverter. In order to determine which option you need, consider the design and device of the first two types, which can be assembled with your own hands at home without specific skills.
AC
This type of welding machine is one of the most common options, both in industry and in private households. It is easy to use, compared to the rest, it can be made quite easily at home, which is confirmed by the photo below. To do this, you need to have a wire for the primary and secondary windings, as well as a transformer steel core for winding the welder. In simple words, an AC welding machine is a high power step-down transformer.
The optimum voltage for a home-assembled welding machine is 60V. The optimal current is 120-160A. Now it is easy to calculate what cross-section the wire should have in order to make the primary winding of the transformer (the one that will be connected to the 220 V network). The minimum cross-sectional area of a copper wire should be 3-4 square meters. mm, the optimal one is 7 sq. mm, because it is necessary to take into account the possible additional load, as well as the necessary margin of safety. We get that the optimal diameter of the copper core for the primary winding of the step-down transformer should be 3 mm. If you decide to take an aluminum wire in order to make a do-it-yourself welding machine, then the cross-section for the copper wire must be multiplied by a factor of 1.6.
It is important that the wires are in a rag sheath, you cannot use conductors in PVC insulation - it will melt and occur when the wires are heated. If you do not have a wire of the required diameter, then you can use thinner strands, winding them in parallel. But then it should be borne in mind that the thickness of the winding will increase, and, accordingly, the dimensions of the device itself. It should be borne in mind that the limiting factor may be a free window in the core and the wire may simply not fit there. For the secondary winding, you can use a thick stranded copper wire - the same as the core on the holder. Its cross section should be selected based on the current in the secondary winding (recall that we are focusing on 120 - 160A) and the length of the wires.
The first step is to make the transformer core of a homemade welding machine. The best option would be a rod-type core as shown in Figure 1:
This core must be made from transformer steel plates. The thickness of the plates should be between 0.35 mm and 0.55 mm. This is necessary to reduce. Before assembling the core, you need to calculate its dimensions, this is done as follows:
- First, the window size is calculated. Those. dimensions c and d in Figure 1 must be selected to accommodate all transformer windings.
- Secondly, the roll area, which is calculated by the formula: Scroll = a * b, must be at least 35 sq. see If the S-roll is greater - then the transformer will heat up less and, accordingly, work longer, and you will not need to interrupt frequently in order for it to cool down. It is better that the Skren be equal to 50 square meters. cm.
Next, we start assembling the plates of a homemade welding machine. It is necessary to take the L-shaped plates and fold them, as shown in Figure 2, until you can make the core of the required thickness. Then we fasten it with bolts in the corners. At the end, it is necessary to process the surface of the plates with a file and insulate them by wrapping them with rag insulation in order to additionally protect the transformer from breakdown onto the case. 
Next, we proceed to winding the welding machine from a step-down transformer. First, we wind the primary winding, which will consist of 215 turns, as shown in Figure 3. 
It is advisable to branch off from turns 165 and 190. We attach a thick textolite plate on top of the transformer. We fix the ends of the windings on it using a bolted connection, noting that the first bolt is a common wire, the second is a branch from 165 turns, the third is a branch from 190 turns and the 4th is from 215. This will make it possible to subsequently adjust the welding current by switching between different terminals of your welding device. This is a very important feature, and the more taps you make, the more precise your adjustment will be.
Then we start winding 70 turns of the secondary winding, as shown in Figure 4. 
Fewer turns are wound on the other side of the core - where the primary winding is wound. The ratio of turns should be about 60% to 40%. This contributes to the fact that after you catch the arc and start welding, eddy currents will partially cut off the operation of the winding with a large number of turns, which will lead to a decrease in the welding current, and accordingly improve the quality of the seam. Thus, the arc will be easy to catch, but too much current will not interfere with high-quality cooking. We will also fix the ends of the winding with bolts on the textolite plate. You can not attach them, but lead the wires directly to the electrode holder and the crocodile to ground, this will remove the connections, where there can be potential for voltage drop and heating. For better cooling, it is highly desirable to install a fan for blowing, for example, from a refrigerator or microwave.
Now your homemade welding machine is ready. Having connected the holder and ground to the secondary winding, it is necessary to connect the network to the common wire and the wire extending from the 215th turn of the primary winding. If you need to increase the amperage, then you can make fewer turns of the primary winding by switching the second wire to a contact with fewer turns. The current can be reduced by using a resistance made of a piece of transformer steel bent in the form of a spring, connected to the holder. It is always necessary to ensure that the welding machine does not overheat by regularly checking the temperature of the core and windings. For these purposes, you can even install an electronic thermometer.
This is how you can make a welding machine from a step-down transformer with your own hands. As you can see, the instructions are not too complicated and even an inexperienced electrician can assemble the device on his own.
DC
Some types of welding require a DC welder. This tool can be used to cook cast iron and stainless steel. You can make a do-it-yourself DC welding machine in no more than 15 minutes by reworking a homemade AC machine. To do this, a rectifier assembled on diodes must be connected to the secondary winding. As for the diodes, they must be able to withstand 200 A and have good cooling. D161 diodes are suitable for this.
Capacitors C1 and C2 with the following characteristics will help us to equalize the current: capacity 15000 uF and voltage 50V. Next, we collect the circuit, which is indicated in the drawing below. Choke L1 is required to regulate the current. Contacts x4 is a plus for connecting the holder, and x5 is a minus for supplying current to the part to be welded.
Three-phase welding machines are used for welding in industrial conditions, they are equipped with two-electrode holders, so we will not consider them in this article, and inverters are made on the basis of printed circuit boards and complex circuits with a large number of expensive radio components and a complex setup process using special equipment. However, we still recommend that you familiarize yourself with the inverter design in the video below.
Visual master classes
So, if you decide to make a welding machine at home, we recommend watching the video tutorials provided below, which will clearly show how to assemble a simple welder yourself from scrap materials, and also explain to you some details and nuances of work:
Now you know the basic principles of the construction of welders and you can make a welding machine with your own hands, both on direct and alternating current, using the instructions from our article.
Also read:
At the moment, there are several modifications of various welding machines. DIY welding transformers can be made quite easily if you have certain skills.
The most popular are transformer welding, designed for contact and arc welding of metal structures. The popularity of this type of transformer for welding is due to several reasons:
- simplicity and reliability of the device;
- the presence of a wide range of use of this type of equipment;
- the presence of high mobility.
In addition to the listed advantages, the use of this type of apparatus has a number of disadvantages, the main among them are the following:
- low efficiency of the transformer apparatus;
- high dependence of the quality of the seam on the availability of skills to work as a welder.
For installation, you can make a transformer with your own hands. The device is a unit that increases the current strength while simultaneously lowering its voltage.
Manufacturing technology of a transformer for a welding machine
A variety of welding transformer circuits have been developed. The most popular is the unit equipped with the U-shaped configuration of the magnetic core. In the presence of a U-shaped magnetic core, the wire winding of the primary and secondary windings is quite simple. U-shaped devices are easily disassembled when repairs are required. To create a welding machine, you need to know the principle of operation of a welding transformer.
In order to operate the device for domestic needs, it is required to put such coils on the core, which would allow welding metal blanks with electrodes having a diameter of 3-4 mm. When creating the unit, it is required to calculate the welding transformer. When making an assembly for a welding device, you need to collect a magnetic core. When assembling the core, remember that the cross section must be at least 25-35 cm². The calculation of the welding transformer, in particular, the required cross-sectional area, is carried out according to the formula S = a * b, cm².
After the calculation and manufacture of the core, a wire is selected for the manufacture of windings. When choosing an electrical conductor, special attention is paid to its cross-section and overall length. For the manufacture of the primary winding coil, it is best to use a special heat-resistant winding wire made of copper, covered with cotton or fiberglass insulating material. It is desirable that the copper wire has a square or rectangular cross-section.
If you have a wire of the required cross-section and there is no required insulating material, you can make it yourself. For this purpose, several narrow strips of cotton or fiberglass are prepared. The width of the strip should be 2 cm. After the strips of insulating material are made, they wind the copper wire. The wrapped wire is impregnated with electrical varnish.
In order for the welding machine to weld metal workpieces well, it is necessary to provide a normal level of AC voltage without load. At idle speed, this parameter should be equal to 60-65 V. When welding, the voltage should be within 18-24 V, depending on the diameter of the electrode.
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Features of calculating the parameters of a transformer for a welding device
The manufacture of a homemade welding transformer is required to begin with the calculation of all technical parameters.
In preparation for the manufacture of a transformer, it is required to calculate several technical parameters of the equipment, on which the normal operation of the welding installation completely depends. The main parameters requiring calculations are as follows:
- cross-sectional area of the core;
- cross-sectional area of the primary winding wire;
- the cross-sectional area of the secondary wire.
When making calculations, it is imperative to take into account the maximum power that the welding unit will have. For example, with a power consumption of 5 kW, the cross-sectional area of the primary wire should be about 5 mm². When making a winding, the best option would be if the cross-sectional area is 6-7 mm². With the specified parameters of the power consumption of the primary winding and its cross-section, the secondary winding must have a cross-section of 30 mm² (excluding the insulating material).
Before winding the coils on the core, it is required to calculate not only the number of turns, but also the length of the wire. The primary winding must have a voltage that is lower than that of a household network. In order to lower the voltage by an appropriate value, it is required to calculate the number of turns per volt of voltage for this purpose. The formula used is n = 48 / Sм, where Sм is the cross-sectional area of the core, expressed in square centimeters.
With a good, high-quality magnetic circuit, n = 0.9-1. Based on this, the total number of turns of the coil is determined in accordance with the formula W1 = U1 / n, therefore, with optimal performance of the magnetic circuit, about 200-300 turns are obtained, depending on the cross-section of the magnetic circuit. Depending on the number of turns, the length of the copper wire is selected. The secondary winding is calculated in the same way.
According to experts, making a welding machine with your own hands is not difficult.
However, in order to do it, you need to clearly understand for what, for what work it will be used.
A homemade device is completed and assembled from available units and parts. A plasma mechanism can also be considered as an option for craftsmen.
Practice shows that with an accurate selection of components, the device will serve for a long time and reliably.
It is important that the electrical circuit is as simple as possible. Sometimes they even use a microwave transformer.
The device must operate on a 220 V AC household.
If you choose 380 V as the operating voltage, then the circuit and design of the device will become noticeably more complicated.
Block diagram of the welding machine
For the production of welding, devices operating on alternating and direct current are used.
The diagram of any device includes a transformer (it is possible to use a microwave transformer), a rectifier, a choke, a holder, an electrode. It is in this sequence that an electric current flows through a closed circuit.
The circuit is closed when an electric arc occurs between the electrode and the metal workpieces to be connected.
In order for the quality of the welded joint to be high, it is necessary to ensure stable burning of this arc.
And to set the required combustion mode, a current regulator is used.
DC machines are used for welding thin sheet metal elements. With this welding method, you can use any electrodes and electrode wire without ceramic coating.
The electrode holder is connected to the rectifier through a choke. This is done in order to smooth out the voltage ripple.
An inductor is a coil of copper wires that is wound on any core. The rectifier, in turn, is connected to the secondary winding of the transformer.
The transformer is connected to the household power supply. The connection sequence is simple and intuitive.
AC voltage conversion is performed using a step-down transformer.
According to Ohm's law, the voltage that is induced on the secondary winding of the transformer decreases, and the current increases from 4 amperes to 40 or more.
Approximately this value is required for welding. In principle, this device can be called the simplest welding machine.
And with the help of wires, connect the electrode holder to it. But it is impossible to use the holder for practical purposes, since the diagram does not contain other necessary elements.
And most importantly, there is no current regulator in it. As well as a rectifier and other elements.
The transformer is considered the main element of the welding machine. It can be purchased or adapted from a used one.
Many craftsmen use a transformer from a microwave that has served its life. In terms of its dimensions and weight, a micropulse element always takes up a lot of space in the structure.
If we consider the welding unit as a whole, then we can distinguish three main blocks, which it includes:
- power unit;
- rectifier unit;
- inverter unit.
A homemade inverter device can be configured in such a way that it has a minimum size and weight.
Such devices, designed for use in the household, are now sold in stores.
The advantages of an inverter device over traditional units are obvious. First of all, it should be noted the compactness of the device, ease of use, reliability.
Only one component in the parameters of this device is of concern - its high cost.
The most general calculations confirm that making such a device with your own hands is easier and more profitable.
The main elements, practically, can always be found among the electrical machines and devices that have ended up in the storerooms. Or in a junkyard.
The simplest current regulator can be made from a piece of a heating coil, which is used in household electric stoves. The choke is made of a piece of copper wire.
Radio amateurs have come up with the simplest pulse welding method according to the scheme. It is used to attach wires to a metal board.
No complicated gadgets - just a choke and a couple of wires. The current regulator is also not needed. Instead, a fuse is included in the circuit.
One electrode is connected to the board through a choke.
As the second, a crocodile clip is used. The plug with wires is connected to a household outlet.
The clamp with the wire is sharply applied to the board in the place where it needs to be welded. A welding arc occurs and at this moment the fuses in the electrical panel may blow out.
This does not happen, because the fuse-link burns out faster. And the wire remains securely welded to the board.
Product complete set
Self-made is going in order to carry out small tasks in the household.
All elements, electronic devices, wires and metal structures must be assembled in a specific place. Where the product will be assembled.
The choke can be used from fluorescent lamp fittings. The number of wires, preferably copper, of different cross-sections, you need to stock up more.
If it was not possible to find a ready-made choke, then it must be made independently.
This will require a steel magnetic circuit from the old starter and several meters of copper wires with a cross section of 0.9 squares.
Power Supply
The main element of the power supply in the inverter is the transformer.
It can be converted from a laboratory autotransformer or used to convert a transformer from a microwave oven that has already served its life.
It is very important not to damage the primary winding when removing the transformer from the microwave oven.
The secondary winding is removed and reworked. The number of turns and the diameter of the copper wires are calculated depending on the preselected power of the welding machine.
The spot welding method is well implemented with an apparatus made on a microwave transformer.
The rectifier is used to convert AC voltage to DC voltage. The main elements of this device are diodes.
They are commutated into specific circuits, most often bridge circuits. An alternating current is supplied to the input of such a circuit, and a constant current is removed from the output terminals.
Diodes are selected of such power to withstand the initially specified loads. For their cooling, special radiators made of aluminum alloys are used.
When marking the installation board, it is advisable to provide a place for a choke, which is designed to smooth out impulses. The rectifier is assembled on a separate board, from getinax or PCB.
Inverter unit
The inverter converts the direct current from the rectifier into alternating current, which has a high oscillation frequency.
The conversion is carried out using electronic circuits based on thyristors or power transistors.
If a voltage of 220 volts with a frequency of 50 Hz is applied to the input terminals of the transformer, then a constant current of up to 150 Amperes and a voltage of 40 volts is recorded at the output terminals of the inverter.
These current parameters allow welding of metal parts from different alloys.
The electronic regulator allows you to select the mode corresponding to a specific operation.
Practice shows that a home-made welding machine, in terms of its characteristics, is not inferior to factory products.
Some time ago, welding mini-inverters appeared in the trading network. It took manufacturing companies years to achieve this miniaturization.
While craftsmen have long been able to make a plasma welding machine made by their own hands.
Local conditions pushed them to this step - the cramped workshop and the significant weight of the factory inverters. Plasma apparatus is an excellent way out of this situation.
And the fact that instead of copper wires, the secondary winding of the transformer is made of copper tin is also known for a long time.
Welding machine assembly sequence
When placing elements on a metal or textolite base, you need to follow a certain order. The rectifier should be close to the transformer.
The choke is on the same board as the rectifier. The current regulator should be located on the control panel. The body of the device can be made of sheet steel or aluminum.
Or adapt the chassis from an old oscilloscope and even a computer system unit. It is very important not to "sculpt" the elements as close to each other as possible.
It is imperative to make holes in the walls for the installation of cooling fans and a constant flow of air.
The board with thyristors and other elements is placed as far as possible from the transformer, which gets very hot during operation. Just like a rectifier.
Quite often, in the practice of any owner, it becomes necessary to connect metal parts. One such connection method is welding. But what if there is no welding machine? Of course, you can buy it, but you can also make the simplest device yourself, and in almost half an hour.
Prologue
The simplest prototype of a welding machine - an electric arc projector - was used in the middle of the twentieth century in film studios during the filming of films.
At home, it is possible to make a simple rare home-made welding machine from a 200 W autotransformer. (An approximate diagram of the autotransformer is shown in the figure). The output voltage is regulated by rearranging the TV plug in the sockets.
On the secondary winding of the transformer, it is necessary to find two terminals on which the voltage will be about 40 V. It remains to connect the graphite electrodes to these terminals and the welding machine is ready! True, it should be borne in mind that when using such an autotransformer for welding purposes, it is desirable to know well the basics of electrical safety, since galvanic isolation from the mains is not ensured.
The scope of such a homemade welding machine is quite wide: from welding metal products to hardening the working surfaces of the tool.
Application examples of the Voltaic arc
In the practice of radio amateurs, at times there is a need for welding or very strong heating of small parts. In such cases, there is no need to use a serious welding machine, because it is not necessary to have special equipment to create high-temperature plasma.
Let's consider several examples of the practical application of the Voltaic arc.
Welding of the magnetron filament with the supply rails
In this case, welding is simply necessary, although many, when faced with such difficulty, replace the magnetron. But most often there are only two malfunctions: the heating is cut off at the point (item 1) and the pass-through capacitors (item 2) fail due to breakdown.
The picture shows a magnetron from a Kenwood microwave oven, which has been in operation after repair for more than twenty years.
Of course, making a thermocouple is a completely hopeless business, but it happens that it needs to be repaired in the event of a "ball" breaking. Typically, these thermocouples are found in multimeters that have a temperature measurement mode.
If it is necessary to change the shape of the spring or to make a hole, take into account that the hardened spring is too hard for drilling and too fragile for punching a hole with a punch.
And in the case of hardening a steel tool (made of tool steel), it is enough to heat the working surface to a crimson color and cool it in a bath with machine oil. The illustration shows the hardened tip of a screwdriver after machining the working edge.
Small welding work can be performed using a transformer with a power of 200 watts and an output voltage in the range of 30 to 50 volts. In this case, the welding current should be 10-12 Amperes. There is no need to worry about overheating of the transformer as the arc burns for a short time.
A conventional laboratory autotransformer LATR with a current strength of 9 Amps or more is also suitable. However, the full degree of danger must be taken into account due to the fact that there is no galvanic isolation from the mains.
In order to prevent damage to the graphite roller of the LATR current collector, it is advisable to introduce restrictions on the input current by using a fuse (fuse). Then an accidental short circuit in the electrode circuit is no longer scary.
The electrodes can be any graphite rods of simple pencils (preferably soft).
The metal part of the wiring terminal block is used as a holder for the lead.
This figure shows an example of a holder using a terminal block, with one hole used for attaching the handle and the other for clamping the lead in the terminal.
In order to prevent the disposable syringe (item 3) from melting when the terminal block (item 1) is heated, fiberglass washers (item 2) are used. And for a standard connection to the cable, you can use the standard socket from the device (item 4).
So, the connection diagram is quite simple: one terminal of the secondary winding is connected to the holder, and the second terminal is connected to the part to be welded.
There is another option for attaching the electrode holder using an electrical terminal. The second holder is needed in the case of welding metal products with the same melting point or, if necessary, to heat the metal product (hardening, changing the shape).
Wiring diagram for connecting two graphite electrodes to the secondary winding of the transformer.
To save the eyes from corneal burns and sparks, it will not be enough to use dark glasses due to the low density of light filters. You can make the following device: as a shield can be a frame of binocular glasses with removed lenses; the filter is secured with a clerical clip. Or you can use the goggles used in SMD technology.
In the case of welding copper with nichrome or steel, you will need a flux. When a small amount of water is added to sodium tetraborate (borax) or boric acid, a slurry is obtained, which lubricates the welding places.
Flux preparation materials can usually be found at a hardware store. You can also use the borax insect control agent containing boric acid.
Diagram of connecting an analog CCTV camera to a TV, computer
It is no secret that a do-it-yourself welding machine for a person familiar with electrical engineering is not so difficult to make. This especially makes sense if it is intended for use in a personal household, where it is used only from time to time. In this case, a home-made welding machine, the cost of which is much lower than the factory one, is quite capable of replacing it. Parts for its construction can be freely removed from various electrical household devices that are out of order or, if necessary, made and assembled by yourself. The schemes of such devices can be different. The decisive factor here is usually the availability of parts and materials.
Choosing a suitable welding machine diagram
All electric arc welding machines are divided into inverter and transformer. It should be noted right away that the question of how to make a welding machine on your own largely depends on the ability to get parts from certain household appliances. If all parts are purchased at market prices, then, as a result, the cost price will approach the price of a branded device, yielding to it in efficiency. That is why you need to have some knowledge in the field of electrical engineering and know where which part is installed and where it can be removed for free or for a small price.
The number of turns on the primary winding should be about 240. At the same time, to ensure the possibility of adjusting the welding current with a step of 20 to 25 turns, several taps are made. The secondary winding is wound with copper wire with a cross section of 30 to 35 mm in an amount of 65 to 70 turns. To adjust the welding current, bends must also be made on it. The insulation of the secondary winding must be particularly reliable and heat-resistant, so it should be given special attention. Each of the layers must be fitted with additional cotton insulation.
The transformer welding machine can operate with alternating or direct current. The first one is the simplest in design, but more difficult to use. For direct current, it is quite easy to modify it by installing a diode bridge. Such a device is reliable, durable and unpretentious to use, but it has a significant weight and is sensitive to voltage drops in the mains. If it falls below 200 V, it becomes very difficult to strike and hold the arc.
In contrast to the transformer inverter welding machine, thanks to the use of modern electronic parts, it has a relatively low weight. It may well be worn on the shoulder by one person. Such a device has a current stabilization device, which greatly facilitates the work when welding. Lowering the voltage for him practically does not create interference, and he can work from a household power supply. However, the inverter device is very sensitive to overheating and requires great care in its operation, otherwise it easily breaks down.
Assembling the transformer welding machine
The main part of such an apparatus is a transformer. Its main characteristic should be the ability to stably hold the operating current, and this is based on such an indicator as the external current-voltage characteristic of the power supply. In other words, the welding current should not differ significantly from the current produced by the short circuit.
To do this, the current must be limited by one of such methods as increasing the magnetic leakage of the transformer, ballast resistance or installing a choke. The transformer itself can be removed from a burnt out high-frequency microwave oven. If there is no access to it, then you can make a welding transformer with your own hands.
To make the core, you need to purchase transformer iron plates. Ideally, the core area should be from 40 to 55 cm², with such indicators, the winding will not overheat unnecessarily. Primary windings for self-made welding transformers should consist of a thick heat-resistant copper wire with a cross section of at least 5 mm, or better, more, enclosed in fiberglass or cotton insulation. It is not recommended to use plastic or rubber insulation for such purposes, since it is less resistant to overheating and is easier to break through, which causes a short circuit on the primary winding.
It must be remembered that the secondary winding of the welding transformer must be wound on both sides of the core. It can be connected either in series or in anti-parallel. It should be remembered that the winding must be done on both sides in the same direction. After that, the transformer is placed in a metal case. Holes are cut from its end to cool the device, and an exhaust fan removed from the power supply unit of an outdated or broken computer is installed. Several dozen holes are drilled on the opposite side of the case for air circulation. The cables and electrode holder can then be connected.
How to assemble a homemade inverter welding machine?
An inverter welding machine can be completely assembled from parts from old TVs. This requires not only some general electrical engineering knowledge, but also some knowledge of electronics. Its scheme is rather complicated. The inverter is a pulsed DC source, and several ferrite cores, which are on the line transformers in old TVs, are suitable for its manufacture. They are folded in three, and already a winding of copper or aluminum wire is wound around them.
Since the primary winding is most susceptible to overheating, small gaps should be left between the turns to facilitate cooling. It is worth remembering that an aluminum wire must be taken of a larger cross section than a copper one, since its thermal conductivity is lower. To fix the inverter windings, a wire band of 10 mm copper wire is used, superimposed on fiberglass insulation.
Capacitors can also be removed from the TV, but it is only worth remembering that it is not recommended to take paper capacitors from low-frequency circuits, since they will not be able to work for a long time under such loads. It is better to take SCRs that are fairly low-power and connect them in parallel than to take one powerful one, since a large thermal load falls on them and it is easier to cool them. SCRs are mounted on a metal plate with a thickness of at least 3 mm, which facilitates the removal of excess heat. Diodes for assembling a diode bridge can also be easily recruited from several old TVs. The bridge itself is also mounted on a heat sink plate.
Some parts for the inverter device are missing in TVs, and they have to be made by ourselves. First of all, it is a choke. It is not difficult to make it without a frame made of copper wire with a cross section of at least 4 mm, wound with 11 turns at intervals of at least 1 mm. Since the main thermal load will fall on the throttle, an additional air cooling system must be installed. In this capacity, it is quite possible to use an ordinary household fan, mounted in the body of the welding machine so that the air stream falls directly on the choke.
All elements of the electronic circuit are assembled on a printed circuit board made of fiberglass with a thickness of at least 1.5 mm. A heatsink is attached to the board itself, making it easier to cool the entire system. A round hole is cut out in the center of the board for installing a fan, since the device will not work for a long time without forced air cooling. The welding inverter has the main advantage of being able to do mini-welding works by welding thin metal sheets. The welding seam itself comes out more accurate than that of a transformer device. This is critical when doing a DIY car repair job.
A do-it-yourself welder includes parts obtained for free or at a bargain price, but does its job well.
