How to assemble a welding machine with your own hands? We assemble a simple welding machine at home How to make a welding machine yourself

It's no secret that a do-it-yourself welding machine for a person familiar with electrical engineering is not so difficult to make. This makes sense especially 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 design can be freely removed from various electrical household devices that have failed or, if necessary, manufactured and assembled by yourself. Schemes of such devices can be different. The decisive factor here is usually the availability of parts and materials.

Choosing the Right Welding Machine

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 depends largely on the ability to get parts from certain household appliances. If all parts are purchased at market prices, then as a result, the cost will approach the price of a branded device, yielding to it in efficiency. That is why you need to have certain knowledge in the field of electrical engineering and know where which part is placed 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 adjustment welding current with a step of 20 to 25 turns, several taps are made. The secondary winding is wound copper wire section from 30 to 35 mm in the amount of 65 to 70 turns. To adjust the welding current on it, you also need to make taps. The insulation of the secondary winding must be especially reliable and heat-resistant, so it should be given Special attention. Each of the layers must be laid with additional insulation made of cotton fabric.

The transformer welding machine can use alternating or direct current for operation. The first of them is the simplest in terms of device, 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 in use, but it has a significant weight and is sensitive to voltage drops in the mains. If it drops below 200V, it becomes very difficult to ignite and hold electric arc.

Unlike a transformer inverter welding machine, due to the use of modern electronic parts, it has a relatively small weight. It can be worn on the shoulder by one person. Such a device has a current stabilization device, which greatly facilitates the work during welding. Reducing the voltage for it practically does not create interference, and it can operate from a household power outlet. However, the inverter apparatus is very sensitive to overheating and requires great care in operation, otherwise it easily fails.

Assembly of the transformer welding machine

The main part of such an apparatus is a transformer. Its main characteristic should be the ability to stably keep 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 in one of such ways as increasing the magnetic leakage of the transformer, ballast resistance or installing a choke. The transformer itself can be removed from the burnt 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. The core area should ideally 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 thick heat-resistant copper wire with a cross section of at least 5 mm, and preferably more, enclosed in fiberglass or cotton insulation. Plastic or rubber insulation is not recommended for such purposes, since it is less resistant to overheating and breaks through more easily, which causes a short circuit in 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 must be remembered that the winding must be carried out 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 apparatus, and placed exhaust fan taken from the power supply of an obsolete or broken computer. On the opposite side of the case, several dozen holes are drilled for air circulation. The cables and the 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 knowledge, but also some knowledge of electronics. Its scheme is rather complicated. The inverter is a pulsed DC source, and for its manufacture, several ferrite cores are suitable, which are on horizontal transformers in old TVs. They are stacked in threes, and a winding of copper or aluminum wire is already wound on them.

Since the primary winding is most susceptible to overheating, small gaps must be left between the turns to facilitate the cooling process. It is worth remembering that aluminum wire must be taken with a larger cross section than copper, since its thermal conductivity is lower. To fix the inverter windings, a wire bandage made of 10 mm wide copper wire, superimposed on fiberglass insulation, is used.

Capacitors can also be removed from the TV, but just remember 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. SCRs are better to take rather low-power ones 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 dialed from several old TVs. The bridge itself is also mounted on a heat sink plate.

Some parts for the inverter apparatus are not available on TVs, and they have to be made independently. First of all, it's a throttle. It is easy to make it without a frame 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, you need to put additional system air cooling. In this capacity, it is quite possible to use an ordinary household fan mounted in the body of the welding machine in such a way that the air stream hits the throttle directly.

All elements of the electronic circuit are assembled on a fiberglass printed circuit board with a thickness of at least 1.5 mm. A heat sink is attached to the board itself, which facilitates cooling of the entire system. cut out in the center of the board round hole to install a fan, because without forced air cooling the device will not work for a long time. The main advantage of the welding inverter is the ability to do mini-welding, welding thin metal sheets. The welding seam itself comes out more accurate than that of a transformer apparatus. This is crucial for such a type of work as do-it-yourself car repair.

Welding machine, made by yourself, includes parts received for free or at a bargain price, but does its job well.

In construction, installation and repair work welding machine is used. Usually the design is purchased in ready-made but you can do it yourself. In this case, significant savings Money. Moreover, this process can captivate those who like to engage in the manufacture of something new.

Connections, electrodes and windings

In order to assemble the welding machine with your own hands, you need to decide on the scheme on the basis of which the work will be carried out. Even before the start of the main work, it is worth considering how the unit will be powered. If the voltage is higher, then the use of the device may harm human health.

Typically used to power equipment single-phase network in 220 V. In this case, it is necessary to use an additional winding (special ballast), with the help of which the periodically changing electric current is regulated during the welding period.

Before Assembly welding inverter with your own hands you need to purchase:

Transformer magnetic circuit.
Remote capacitor devices.
Welding mode switch.
Several types of windings (primary, secondary, additional).
Regulatory devices that help to establish the optimal welding mode.
Special heat sensors.
A device that notifies you with sounds optimal mode work.

Why Use Concrete

Before you make an inverter welding machine with your own hands, you need to make a case. It is made of specially prepared concrete, characterized by a high degree of plasticity. This material is able to quickly harden and become the desired shape.

The hull is made from fine-grained sand and cement in certain proportions. You should take 75 percent sand, 20 percent cement. In addition to these components, it is necessary to add an equal amount of PVA glue and glass wool. Sometimes the glue is replaced with a water-soluble latex material.

Novice craftsmen believe that the unit is quite easy to assemble with their own hands, in comparison with the creation of its body. With sequential work, the structure is assembled quite quickly.

The body must be at least 1 cm thick. The welding machine is cleaned, followed by drying, after which the body is started to be made. After waiting for the concrete to harden, spend external processing aggregate using an organic monomer.

To cope with this task, experts recommend using styrene or methyl methacrylate. They help to heat treat the surface of the device. In this situation, a temperature above 70 degrees Celsius should be applied.

As a result of monomer polymerization, a waterproof layer is formed on the surface of the unit body. It is he who protects the surface of the structure from environmental influences.

Simple design

For the layout of the welding machine, you can use a faulty household appliances. For example, you can use a failed microwave oven. Together with it, you should take electrical wiring, clamps, wooden details and tips.

Taking all these components, it is possible in a short time, even with minimal knowledge in the field of technology, to produce the design of an apparatus for spot welding.

Parts inside the unit are fixed with self-tapping screws, washers or brackets of appropriate sizes. It is optimal to use a serviceable transformer of a broken microwave oven, from which equipment is made by hand.

Assembly process

They begin work by removing the secondary winding from the transformer. This operation requires accuracy. It is carried out with an angle grinder.

Next, the lamellar core is removed from the surface of the secondary winding. After carrying out the operation on the transformer, parts cut off on both sides can be found. With their help, the work will be better. Ideally, it is necessary to ensure that the insulating layer on the core is free of any defects.

Then the magnetic shunt is attached. During its normal functioning, the work of a do-it-yourself welding machine is carried out. Then the transformer is rewound using a thick wire made of copper material. If the core is damaged, it needs to be repaired. If the defect is minimal, then the site is isolated.

At the next stage, it is necessary to wooden block seat the transformer, securing the top and bottom of the workstation with brackets. If the electrodes are attached qualitatively, then the unit will work better. If there are defects in the contacts, it will be difficult to weld the elements.

The fixation of the electrodes on the upper and lower parts of the bar is carried out with self-tapping screws. Then winding wires are connected to them. It is necessary to properly fix the copper terminals using pliers, which is usually very difficult for beginners. The structure is ready. Then it is necessary to check whether something can be welded using the unit, while it is important to follow the safety regulations.

Usually, it is not difficult to assemble a welding machine even for those people who have minimal technical knowledge. For this you can use step by step instructions with photos at all stages that exist a large number of on the Internet.

DIY welding machine photo

A good welding machine greatly facilitates all metal work. It allows you to connect and cut various details iron, which differ in their thickness and density of steel.

Modern technologies offer a huge selection of models that differ in power and size. Reliable designs have a fairly high cost. Budget options usually have a short lifespan.

Our material presents detailed instructions how to make a welding machine with your own hands. Before starting the workflow, it is recommended that you familiarize yourself with the variety welding equipment.

Types of welding machine

Devices of this technique differ in several types. Each mechanism has some features that are displayed on the work performed.

Modern welding machines are divided into:

DC models;
with alternating current
three-phase
invector.

The AC model is considered the most simple mechanism which you can easily do yourself.

A simple welding machine allows you to perform complex work with iron and thin steel. To assemble such a structure, you must have a certain set of materials.

These include:

winding wire;
core made of transformer steel. It is necessary for winding the welder.

All these parts can be purchased at specialized stores. Detailed consultation of experts helps to make the right choice.

AC design

Experienced welders call this design a step-down transformer.

How to make a welding machine with your own hands?

The first thing to do is to properly make the main core. For this model, it is recommended to choose the rod type of the part.

For its manufacture, you will need plates made of transformer steel. Their thickness is 0.56 mm. Before proceeding with the assembly of the core, it is necessary to observe its dimensions.

How to correctly calculate the parameters of the part?

Everything is quite simple. The dimensions of the central hole (window) must accommodate the entire winding of the transformer. The photo of the welding machine shows detailed diagram mechanism assembly.

The next step is to assemble the core. To do this, take thin transformer plates, which are interconnected up to required thickness details.

Next, we wind a step-down transformer, consisting of turns of thin wire. To do this, make 210 turns of thin wire. On the other hand, a winding of 160 turns is made. The third and fourth primary winding should contain 190 turns. After that, a thick platinum is attached to the surface.

The ends of the wound wire are fixed with a bolt. I mark its surface with the number 1. The following ends of the wire are fixed in a similar way with the application of appropriate markings.

Note!

The finished design should have 4 bolts with a different number of turns.

In the finished structure, the winding ratio will be 60% to 40%. This result ensures the normal operation of the apparatus and good quality welding fixture.

Control the feed electrical energy can be done by switching the wires to required amount windings. During operation, it is not recommended to overheat the welding mechanism.

DC apparatus

These models allow you to perform complex work on thick steel sheets and cast iron. The main advantage of this mechanism lies in the simple assembly, which does not take much time.

The welding invector is a design of the secondary winding with an additional rectifier.

Note!

It will be made of diodes. In turn, they must endure electricity at 210 A. For this, elements marked D 160-162 are suitable. Such models are often used to work on an industrial scale.

The main welding invector is made of printed circuit board. Such semi-automatic welding withstands power surges during long-term operation.

Repair of the welding machine will not be difficult. Here it is enough to replace the damaged area of the mechanism. In the event of a serious breakdown, it is necessary to re-carry out the primary and secondary windings.

DIY welding machine photo

Note!

When performing simple and small-scale welding work at home, everyone can assemble.

For assembly, you do not have to spend a lot of money, effort and time. Also, you do not need to purchase unreasonably expensive models of such equipment.

To make a mini welding machine with your own hands from improvised means, without much financial cost and effort, you need to understand how the equipment functions, after which you can start producing it at home.

First of all, it is necessary to determine the required power supply current homemade equipment for welding. The connection of parts of a massive structure requires a greater current intensity, and welding work with thin metal surfaces requires a minimum.

The current value is related to the selected electrodes to be used in the process. When welding products up to 5 mm, it is necessary to use rods up to 4 mm, and in a design with 2 mm thickness, the rods should be 1.5 mm.

When using electrodes of 4 millimeters, the current strength is regulated up to 200 amperes, in 3 millimeters up to 140 amperes, in 2 millimeters - up to 70 amperes and for the smallest up to 1.5 millimeters - up to 40 amperes.

You can form an arc for the welding process yourself, using the mains voltage, which is obtained due to the operation of the transformer.

This equipment includes:

magnetic core;
winding - primary and secondary.

Also, the transformer can be made independently. For the magnetic circuit, plates made of steel or other durable material are used. Windings are necessary to directly perform welding work and be able to connect the welding unit to a 220 volt network.

Transformer for welding.

Specialized equipment has additional devices that improve the quality and power of the arc, which makes it possible to independently adjust the current values.

You should not go deep enough into this topic, since one of the easiest ways to assemble a do-it-yourself welding machine is.

Its feature is work with alternating current, which ensures the performance of a high-quality seam when welding. metal surfaces. Such equipment can cope with any household work where it is necessary to weld metal or steel structures.

To make it you need to prepare:

Several meters of cable with a large thickness.
Material for the core, which will be located in the transformer.
The material itself must have increased permeability with magnetization.

The best option is when the core in the form of a rod has the letter "P". In some cases, it is allowed to use this part in a more modified form, for example, a round stator made from a damaged electric motor.

Scheme of the device of the welding transformer.

However, it is worth paying attention that it is more difficult to wind the windings on this form. Best of all, when the core cross-section for classic do-it-yourself welding equipment used for domestic purposes had an area of \u200b\u200babout 50 cm2.

In order for the equipment to have an affordable weight, it is not necessary to increase the cross section in volume, however, the technical effect will not be highest level. If the cross-sectional area does not suit you, then you can calculate it yourself using special schemes and formulas.

The primary winding must be made of copper wire, which will have enhanced characteristics: thermal resistance, since during the operation of the structure this part heats up very much.

Such a part must have cotton or fiberglass insulation. On extreme case, it is possible to use insulated rubber wire or rubber cloth, but beware of PVC wrapping.

The insulation is also made by hand, using cotton or fiberglass, or rather, its parts are 2 cm wide. Thanks to these pieces, it will be possible to wrap the wire, and then impregnate it with any varnish with an electrical purpose. Such insulation will not overheat after regular operation.

Similarly to the above calculations, it will be possible to calculate which cross-sectional area of \u200b\u200bthe winding - primary and secondary - will be the most optimal. Often the secondary winding has an area of about 30 mm2, and the primary winding up to 7 mm2, using a rod 4 mm in diameter.

Besides in a simple way you need to determine how much a piece of copper wire will stretch and how many turns it will take to wind two windings. After that, the coils are wound, and the frame is made using the geometric parameters of the magnetic circuit.

The main thing is to make sure that there are no difficulties when putting on the magnetic circuit. First of all, you need to choose the right core size. It is best made using electrical cardboard or textolite.

Using the same analogy, it will be possible to make a structure for welding small parts. For the home, you can use a small “mini” welding machine.

Welding Machine Manufacturing

Today it is almost impossible and rather difficult to weld metal or process it in the proper way without using welding equipment. After you make a welding machine with your own hands, you can do any work with metal products.

Scheme of a transformer with a separate choke.

To make a high-quality unit, you need to have the knowledge and skills that will help you understand the circuit of a DC or AC welding machine, which are two options for assembling equipment.

With the aim of home use it is best to learn how to do mini welding.

It is more convenient to call a wizard or purchase a ready-made unit, but sometimes it can be too costly, since it is quite difficult to determine the number of volts per welding machine when choosing a model for various parameters, such as the weight for the welding machine.

There are several types of welding machines: working on alternating current, direct, having three phases or inverter. To choose one of the options and start the assembly, it is necessary to consider each scheme of the first 2 types. During the preparatory process, you need to pay attention to the voltage stabilizer.

On alternating current

To make home-made welding machines, you need to select a voltage indicator, the best is 60 volts, the current is best regulated from 120 to 160 amperes.

You can independently determine the cross-sectional value of the required wire for the manufacture of the primary winding of the transformer, which must be connected to a 220-volt network.

The cross section according to the area parameters should not be more than 7 mm2, since it is worth noting the possible voltage drop and possible additional load.

Based on the calculations, optimal size the diameter of the copper core under the primary winding, which reduces the action of the mechanism, is 3 millimeters. When choosing aluminum for the wire, the cross section is multiplied by a value of 1.6.

It is worth noting that the wires must be wrapped with a rag, as they must be insulated. The fact is that as the temperature rises, the wire can melt and a short circuit will occur.

In the absence of the necessary wire, it is possible to replace it with a slightly thinner residential wire, winding it in pairs. However, it must be remembered that the winding thickness will increase, due to which the dimensions of the welding equipment will be large. Under the secondary winding, a thick wire with a large number of strands of copper is used.

DC

Electrical circuit of a DC welder.

Some welding machines work with direct current. Thanks to this unit, it is possible to weld cast iron products and stainless steel structures.

It may take no more than half an hour to create a DC welding machine with your own hands. In order to convert homemade products with alternating current, it is necessary that the secondary winding be connected, which is assembled on a diode.

In turn, the diode must withstand a current of 200 amperes and have good cooling. To trim the current value, you can use capacitors that have certain characteristics and voltage features. After that, the unit is assembled sequentially according to the scheme.

Chokes are used to regulate the current, and contacts to attach the holder. Additional parts are used in the transmission of current from an external carrier to the welding site.

In order to operate the welding machine for its intended purpose, it is necessary, first of all, to kindle an electric arc. This process is easy and is performed by the following steps: the tip of the electrode at a certain inclination from the side metal coating bring and strike on the surface of the structure.

If the action is performed correctly and successfully, a flash occurs. small sizes, and the material is melted, after which the necessary elements can be welded.

When making a mini welding machine with your own hands, you must be guided by the recommendations for working with it. To weld elements, you need to hold the rod in such a position that it is at a certain distance from each other of the parts to be welded. This distance can be equal to the cross section of the selected electrode.

Often a metal such as carbon steel is connected with a direct polar current. However, some alloys can only be welded with reverse current polarity. In addition, it is necessary to carefully control the quality of the seam and how the structure is melted.

Scheme of a simple welding machine.

It is worth emphasizing that the alternating current, located, can be regulated efficiently and smoothly. Often, no difficulties arise with setting the unit to the required parameters.

With a small current strength indicator, the seam will come out of poor quality, but you should not set an increased value, as there is a risk of burning the surface.

If it is necessary to weld surfaces of small thickness, then the rods will fit with a size of 1 to 3 millimeters, while the current strength should vary with marks of 20-60 A. Using large-section electrodes, you can weld hardware up to 5 millimeters, however, in this case, the current should be 100 A.

Upon completion of the welding process, using a homemade product, it is necessary to carefully remove the scale with light movements that appears on the seam, after which it is cleaned with a special brush.

Thanks to this action, you will be able to maintain a pleasant aesthetic appearance of your device. Do not worry if the cleaning of the equipment does not work out very well in the first couple. This skill is gained by experience and subject to the implementation of all recommendations for competent operation designs.

Outcome

Summing up, it is worth noting that DC welding machines are much easier to assemble and they are also easy to use, due to their low power.

If you have the necessary plumbing and electrical installation tools (we will talk about them in detail below), and you have the appropriate professional skills, then you can easily make do-it-yourself welding transformer.

Of course, you will have expenses, but incomparably less compared to the cost of purchasing a factory-made gadget. But how much fun you will get in the process of your favorite homemade work. And the delight, at the moment of the successful start of electric welding, in general, cannot be compared with anything!

We will give you a lot in the article useful tips selection, calculation and production welding transformer (hereinafter - ST), which will help to optimize costs and save the budget.

A properly made do-it-yourself device is no worse than a factory one.

The article will talk about two types of welding transformers. For welds:

arc;
contact.

Do-it-yourself welding transformer: what we need

The range of tools and equipment for the manufacture and assembly of both types of ST is identical. We will need the following:

indicator electrical voltage . To control the absence of the latter on electrical contacts, and ensuring, thereby, safety in the performance of electrical work;
angle grinder(it is also a “grinder”, “zipper-machine”, etc.) with a set of discs (cutting, grinding, etc.);
electric drill with a set of drills for metal and a core;
tester or voltmeter alternating current with a measurement limit of 400 V;
any " scriber". It is used for marking on metal;
locksmith clamps. For fixing parts when marking "in place";
electric tool set. The specific composition of the kit depends on the materials that will be used in the manufacture of ST. IN general case he is like this:
- complete electric soldering iron. We will perform soldering with solder POS-40;
- screwdrivers ( different size with straight and cross slots);
- keys:
  - wrench;
  - cap;
  - end;
- pliers, side cutters, etc. with insulated handles;
file set.

All work is more convenient to perform on locksmith workbench with an electrically insulating coating, equipped with a bench vise.

For the manufacture of ST, components and materials are required that differ depending on the type of transformer. In general, you need the following:

protective cover . Must provide:
- protection against electric shock;
- exclude the possibility of any objects getting inside the gadget;
magnetic circuit. Provides a powerful electromagnetic flux, which induces an electromotive force (hereinafter referred to as EMF) in the windings;
wire and wire. Necessary for the installation of windings;
coil frames. Windings are wound on them;
contact pads. Powerful terminal block with clamps for welding wires, small blocks - for wiring the circuit;
switches (switches). Carry out switching sections of the windings when selecting the value of the welding current;
interturn insulation material. Reduces the possibility of electrical breakdown of the winding insulation;
fasteners (bolts, screws, nuts, washers, etc.). They are necessary for mounting the gadget during assembly work;
insulating tape(type Х/Б).

Important: PVC insulating tape cannot be used, because it is destroyed when heated.

Homemade welding transformer for arc welding

Before proceeding with further work on the manufacture of ST, you should decide what exactly you will create. You need:

choose the design and electrical circuit diagram future device;
make an electrical and, if necessary, constructive calculation of its parameters.

Only after that, you should select the necessary equipment, materials and prepare, if necessary, a special tool.

How to calculate a welding transformer. Scheme

The question of how to calculate a home-made welding transformer is very specific, since it does not correspond typical schemes and generally accepted rules. The fact is that in the manufacture of homemade products, the parameters of their components are “adjusted” to the components already available (mainly to the magnetic circuit). Moreover, it often happens that:

transformers are not assembled from the best transformer iron;
windings are not wound with the most suitable wire and many other negative factors.

As a result, homemade products heat up and “buzz” (the core plates vibrate at the mains frequency: 50 Hz), but, at the same time, they “do their job” - they weld metal.

According to the shape of the cores, transformers of the following main types are distinguished:

rod;
armored.

Explanations for the figure:

a - armored;
b - rod.

transformers pivotal type, compared to transformers armored type, allow high current densities in the windings. Due to this, they have a higher efficiency, but the laboriousness of their manufacture is much higher. However, they are used more often.

On the rod core, the winding schemes shown in the figure are used.

Explanations for the figure:

a - network winding on two sides of the core;
b - the corresponding secondary (welding) winding, connected in anti-parallel;
c - network winding on one side of the core;
g - the secondary winding corresponding to it, connected in series.

For example, let's perform the calculation of ST assembled according to the scheme "c" - "g". Its secondary winding consists of two equal parts (halves). They are located on opposite arms of the magnetic circuit, and are connected to each other in series. The calculations consist in determining the theoretical and choosing the actual dimensions of the magnetic circuit.

We determine the power of the ST (according to the magnitude of the current in the secondary winding) from the following considerations. For electric welding in everyday life, coated electrodes are most often used Ø, mm: 2, 3, 4. We choose the “golden mean” for the most popular ones - 120 ... 130 A. The power of the ST is determined by the formula:

P = Uх.х. × Ist. × cos(φ) / η, where:

Ux.x. - voltage idle move;
Ist. - welding current;
φ is the phase angle between voltage and current. Accept: cos(φ) = 0.8;
η - efficiency. For homemade ST: efficiency = 0.7.

If we calculate the magnetic circuit according to the reference book, then its cross section for the selected current is 28 sq.cm. In practice, the cross section of the magnetic circuit for the same power can vary within: 25 ... 60 sq.cm.

For each section, it is necessary to determine (according to the reference book) the number of turns of the primary winding to provide a given power at the output. We only note that the larger the cross-sectional area of the magnetic circuit (S), the less turns of both coils will be needed. This is an essential point, since a large number of turns may not fit into the "window" of the magnetic circuit.

It is possible to use the magnetic circuit of an old transformer (for example, from a microwave oven, of course, after some reconstruction - replacement of the secondary winding).

If you do not have an old transformer, then you should purchase transformer iron, from which you will make the CT core.

Explanations for the figure:

a - L-shaped plates;
b - U-shaped plates;
c - plates from strips of transformer steel;
c and d are the dimensions of the "window", cm;
S \u003d a x b - cross-sectional area of \u200b\u200bthe core (yoke), sq. cm.

The calculation of the number of turns of the primary windings at a mains supply voltage of 220 ... 240 V, the welding currents selected by us and the parameters of the magnetic circuit can be made using the following formulas:
N1 = 7440 × U1/(Sout × I2). For windings on one arm (half of the windings on top of each other, connected in series);
N1 = 4960 × U1/(Sout × I2). The windings are spaced on different shoulders.

Conventions in both formulas:

U1 – power supply voltage;
N1 is the number of turns of the primary winding;
Siz - cross section of the magnetic circuit (sq.cm);
I2 - given welding current of the secondary winding (A).

The output voltage of the secondary winding of the ST in idle mode for self-made welding transformers is, as a rule, in the range of 45 ... 50V. Using the following formula, you can determine its number of turns:
U1/U2 = N1/N2.

For the convenience of selecting the strength of the welding current, taps are made on the windings.

Welding transformer winding and installation

For the primary winding of the transformer, a special heat-resistant copper wire is used, which has cotton or fiberglass insulation.

Taking into account the power selected above, the electric current in the primary winding can reach 25 A. Based on these considerations, the primary winding of the ST should be wound with a wire having a cross section of ≥ 5 ... 6 sq. mm. This, among other things, will significantly increase the reliability of the ST.

The secondary winding is carried out with copper wire, the cross section of which is: 30 ... 35 sq. Mm. Particular attention should be paid to the choice of insulation of the secondary winding wire, since a large welding current flows through it. It must be very reliable - special attention should be paid to heat resistance.

When installing windings, pay attention to the following:

winding is done in one direction;
between the rows of windings an insulating layer of additional insulation is laid (we recommend - cotton).

The assembled CT should be placed in a protective casing with holes for ventilation.

Video

See how the task of assembling the device was implemented:

Do-it-yourself contact welding from a welding transformer

Contact welding creates a welded joint of parts due to the following simultaneous effects on them:

heating the area of their contact with an electric current passing through it;
a compressive force is applied to the joint area.

There are three types contact welding:

point;
butt;
suture.

We will talk about homemade ST for the most popular: resistance spot welding (the other two require very sophisticated equipment).

Explanations for the figure:
1 - electrodes supplying welding current to the workpiece to be welded;
2 - welded products with lap joint;
3 - welding transformer.

For resistance welding, depending on the thickness and thermal conductivity of the materials of the parts to be welded, the following values its main parameters:

electric voltage in the power (welding circuit), V: 1…10;
the value of the welding current (amplitude of the welding pulse), A: ≥ 1000;
heating time (passage of the welding current pulse), sec: 0.01…3.0;

In addition, the following must be provided:

insignificant melting zone;
significant compressive force applied to the weld.

Scheme and calculation

Calculation of ST of resistance welding is performed according to the same algorithm as for arc welding (see above). When selecting data from the directory (current strength and voltage of the secondary winding for spot welding of the selected metal grade of a given thickness), it should be borne in mind that the current strength of the secondary winding for such transformers is of the order of 1000 ... 5000 A. The secondary winding is usually designed for units of volts and is only a few turns (sometimes one) thick wire. Therefore, to adjust the welding current, the following circuit of the primary winding of the transformer is recommended.

Very often, during the operation of homemade products, it turns out that there is not enough power of the ST. In this case, it is possible to connect a second transformer in accordance with the proposed scheme.

Winding and installation

These operations are performed according to the same basic rules and in compliance with the requirements as for ST arc welding. With special care, the turns of the secondary winding should be fixed. To do this, you can use its conclusions by passing them in a heat-resistant insulator.

Copper rods are used as electrodes.

Should be considered that the larger the diameter of the electrode, the better. Under no circumstances should the electrode diameter be smaller than the wire diameter. For low-power CTs, it is possible to use tips from powerful soldering irons.

During operation, monitor the condition Supplies: the electrodes must be sharpened periodically - otherwise they lose their shape. Over time, they wear down completely and need to be replaced.