Learning to weld metal: from the basics of welding to learning welding techniques. The basics of welding metal with an inverter for beginners How to make a homemade welding machine

In view of the fact that in everyday life ordinary people often need to work with metal, many use welding machines. But not everyone can afford the purchase of expensive equipment, which raises the question of how to assemble a welding machine with your own hands. The manufacturing process will differ depending on the type and design features of the welding device.

Types of welding machines

The modern market is filled with a fairly large variety of welding machines, but it is far from advisable to assemble everything with your own hands.

Depending on the operating parameters of the devices, the following types of devices are distinguished:

  • on alternating current - giving out alternating voltage from the power transformer directly to the welding electrodes;
  • at direct current - giving out a constant voltage at the output of the welding transformer;
  • three-phase - connected to a three-phase network;
  • inverter devices - issuing a pulsed current into the working area.

The first version of the welding unit is the simplest, for the second one you need to modify the classic transformer device with a rectifier unit and a smoothing filter. Three-phase welding machines are used in industry, so we will not consider the manufacture of such devices for domestic needs. An inverter or pulse transformer is a rather complicated device, so in order to assemble a homemade inverter, you must be able to read circuits and have basic electronic board assembly skills. Since the basis for the creation of welding equipment is a step-down transformer, we will consider the manufacturing procedure from the simplest to the more complex.

On alternating current

Classical welding machines work according to this principle: the voltage from the primary winding of 220 V is reduced to 50 - 60 V on the secondary and is fed to the welding electrode with the workpiece.

Before you start manufacturing, select all the necessary elements:

  • Magnetic core- stacked cores with a sheet thickness of 0.35 - 0.5 mm are considered more profitable, since they provide the smallest losses in the gland of the welding machine. It is better to use a ready-made core made of transformer steel, since the density of the plates fit plays a fundamental role in the operation of the magnetic circuit.
  • Coil winding wire- the cross section of the wires is selected depending on the magnitude of the currents flowing in them.
  • Insulating materials- the main requirement, both for sheet dielectrics and for the native coating of wires, is resistance to high temperatures. Otherwise, the insulation of the semi-automatic welding machine or transformer will melt and a short circuit will occur, which will lead to a breakdown of the machine.

The most profitable option is to assemble the unit from a factory transformer, in which both the magnetic circuit and the primary winding are suitable for you. But, if there is no suitable device at hand, you will have to make it yourself. You can familiarize yourself with the principle of manufacturing, determining the cross section and other parameters of a home-made transformer in the corresponding article:.

In this example, we will consider the option of manufacturing a welding machine from a microwave power supply. It should be noted that transformer welding must have sufficient power; for our purposes, a welding machine of at least 4–5 kW is suitable. And since one microwave transformer has only 1 - 1.2 kW, we will use two transformers to create the apparatus.

To do this, you will need to perform the following sequence of actions:


 Rice. 2: remove the high voltage winding

leaving only low-voltage, in this case, winding the primary coil is no longer necessary, since you are using the factory one.

  • Remove the current shunts from the coil circuit on each transformer, this will increase the power of each winding.
    Rice. 3: remove current shunts
  • For the secondary coil, take a copper bus with a section of 10 mm 2 and wind it on a pre-made frame from any materials at hand. The main thing is that the shape of the frame repeats the dimensions of the core.
    Rice. 4: wind the secondary winding on the frame
  • Make a dielectric gasket for the primary winding, any non-combustible material will do. In length, it should be enough for both halves after connecting the magnetic circuit.
    Rice. 5: make a dielectric pad
  • Place the power coil in the magnetic core. To fix both halves of the core, you can use glue or pull them together with any dielectric material.
    Rice. 6: put the coil into the magnetic core
  • Connect the outputs of the primary to the power cord, and the secondary to the welding cables.
    Rice. 7: connect the power cord and cables

Install a holder and an electrode with a diameter of 4 - 5 mm on the cable. The diameter of the electrodes is selected depending on the strength of the electric current in the secondary winding of the welding machine, in our example it is 140 - 200A. With other operating parameters, the characteristics of the electrodes change accordingly.

In the secondary winding, 54 turns were obtained, in order to be able to adjust the voltage at the output of the device, make two taps from 40 and 47 turns. This will allow you to adjust the current in the secondary by reducing or increasing the number of turns. The same function can be performed by a resistor, but only to the lower side of the nominal value.

DC

Such an apparatus differs from the previous one in more stable characteristics of the electric arc, since it is obtained not directly from the secondary winding of the transformer, but from a semiconductor converter with a smoothing element.


 Rice. 8: Rectification circuit diagram for welding transformer

As you can see, it is not required to wind the transformer for this, it is enough to modify the circuit of the existing device. Thanks to this, he will be able to produce a more even seam, cook stainless steel and cast iron. For manufacturing, you will need four powerful diodes or thyristors, approximately 200 A each, two capacitors with a capacity of 15,000 microfarads and a choke. The connection diagram of the smoothing device is shown in the figure below:


 Rice. 9: connection diagram of the smoothing device

The process of finalizing the electrical circuit consists of the following steps:


Due to the overheating of the transformer during operation, the diodes can quickly fail, so they need forced heat dissipation.


For connection, it is better to use tinned clamps, as they will not lose their original conductivity from high currents and constant vibration.


 Rice. 12: use tinned clips

The thickness of the wire is selected in accordance with the operating current of the secondary winding.


When welding metals with such an apparatus, it is always necessary to control the heating of not only the transformer, but also the rectifier. And when the critical temperature is reached, pause for the elements to cool, otherwise the do-it-yourself welding unit will quickly fail.

inverter apparatus

It is a rather complicated device for beginner radio amateurs. No less difficult process is the selection of the necessary elements. The advantage of such a welding machine is significantly smaller dimensions and lower power, in comparison with classical devices, the ability to implement, etc.


 Rice. 14: circuit diagram of the pulse unit

In operation, such a circuit converts the alternating voltage from the network to a constant one, then, using a pulse unit, it outputs a high-amplitude current to the welding area. This achieves relative savings in the power of the apparatus in relation to its performance.

Structurally, the inverter circuit of the welding machine includes the following elements:

  • diode rectifier with capacity magazine, ballast resistor and soft start system;
  • control system based on a driver and two transistors;
  • power part of the control transistor and output transformer;
  • output part of diodes and inductor;
  • cooler cooling system;
  • current feedback system to control the parameter at the output of the welding machine.

For you, you will need to wind a power transformer yourself, a current transformer based on a ferrite ring. For the bridge, it is better to use a ready-made assembly of high-speed semiconductor elements.

Unfortunately, most of the other items are unlikely to be at hand in the garage or at home, so they will have to be ordered or purchased from specialized stores. Because of this, assembling an inverter unit with your own hands will cost no less than the factory version, but taking into account the time spent, it will also be more expensive. Therefore, for inverter welding, it is better to purchase a ready-made machine with the specified operating parameters.

Video instructions



If you have a need to perform some simple welding work for domestic needs, it is not at all necessary to purchase an expensive factory unit. After all, if you know some of the subtleties, you can easily assemble a welding machine with your own hands, which will be discussed below.

Welding machines: classification

All welding machines are either electric or gas. It should be said right away that home-made welding machines should not be gas. Since they include explosive gas cylinders, it is not worth keeping such an installation at home.

Therefore, in the context of self-assembly of structures, we will talk about exclusively about electrical options. Such units are also divided into varieties:

  1. Generator sets - equipped with their own current generator. A distinctive feature - the big weight and dimensions. For home needs, this option is not suitable, and it will be difficult to assemble it yourself.
  2. Transformers - such installations, especially of the semi-automatic type, are very common among those who make welding equipment on their own. They are powered by a network of 220 or 380 V.
  3. Inverters - such installations are easy to use and ideal for the home, the design is compact and lightweight, but the electronic circuit is quite complex.
  4. Rectifiers - these devices are easy to assemble and use for their intended purpose. With their help, even a beginner can perform high-quality welds.

To assemble an inverter at home, you will need a circuit that will allow you to comply with the necessary parameters. It is recommended to take parts from old Soviet devices:

The options for the device are as follows:

  • It must work with electrodes whose diameter does not exceed 5 mm.
  • The maximum operating current is 250 A.
  • Voltage source - household network for 220 V.
  • Adjustment of welding current varies from 30 to 220 A.

The tool includes the following components:

  • power unit;
  • rectifier;
  • inverter.

Begin from transformer winding and act in the following order:

  1. Take the ferrite core.
  2. Perform the first winding (100 turns with a 0.3 mm PEV wire).
  3. The second winding is 15 turns, with a wire with a cross section of 1 mm).
  4. The third winding is 15 turns with a PEV wire of 0.2 mm.
  5. The fourth and fifth - respectively, 20 turns each with wires with a cross section of 0.35 mm.
  6. To cool the transformer, take a fan from the computer.

In order for transistor switches to work continuously, voltage should be applied to them after the rectifier and capacitors. Assemble the rectifier unit according to the diagram on the board, and fix all the components of the device in the case. Can be used old radio housing, but you can do it yourself.

Installed from the front of the case led indicator, which indicates that the device is connected to the network. Here you can put an additional switch, as well as a protective fuse. You can also install it on the back wall and even in the case itself.

It all depends on its size and design features. Variable resistance is installed on the front of the case, with its help you can adjust the operating current. When you have collected all the electrical circuits, check the device with a special device or tester and you can test it.

The assembly of the transformer version will be somewhat different from the previous one. This unit runs on alternating current, but for DC welding, you need to assemble a simple attachment to it.

To work you will need transformer iron for the core, as well as several tens of meters of thick wire or thick copper bus. All this can be found at the metal collection point. The core is best made U-shaped, toroidal or round. Many also take the stator from an old electric motor.

The assembly instruction for the U-shaped core looks like this:

  • Take transformer iron with a cross section of 30 to 55 s m 2. If the indicator is higher, the device will turn out to be too heavy. And if the cross section is less than 30, the device will not be able to work correctly.
  • Take a copper winding wire with a cross section of about 5 mm 2, equipped with heat-resistant fiberglass or cotton insulation. Insulation is important because the winding can heat up to 100 degrees or more during operation. The winding wire has a square or rectangular cross section. However, such an option is difficult to find. An ordinary one with a similar cross section is also suitable, but only you will need to remove the insulation from it, wrap it with fiberglass and carefully impregnate it with electrical varnish, and then dry it. The primary winding has 200 turns.
  • The secondary winding will require about 50 turns. The wire does not need to be cut. Connect the primary winding to the network, and on the secondary wires, find a place where the voltage is about 60 V. To find such a point, unwind or wind additional turns. The wire can be aluminum, but the cross section must be 1.7 times larger than for the primary winding.
  • Install the finished transformer into the housing.
  • To bring the secondary winding, copper terminals are required. Take a tube with a diameter of 10 mm and a length of about 4 cm. Rivet its end and drill a hole with a diameter of 10 mm, and insert the end of the wire, previously stripped of insulation, into the other end. Next, crimp it with light hammer blows. To strengthen the contact of the wire with the tube-terminal, apply notches on it with a core. Screw homemade terminals to the body with nuts and bolts. Details are best used copper. When winding the secondary winding, it is desirable to make taps every 5-10 turns, they will allow you to change the voltage on the electrode in steps;
  • To make an electric holder, take a pipe with a diameter of about 20 mm and a length of about 20 cm. At the ends, about 4 cm from the end, cut notches to half the diameter. Insert the electrode into the recess and press it with a spring based on a welded steel wire bush with a diameter of 5 mm. Attach the same wire that was used for the secondary winding to the second horse with a nut and screw. Slide a rubber tube with a suitable inner diameter onto the holder.

It is best to connect the finished device to the network using wires with a cross section of 1.5 s m 2 or more, as well as a knife switch. The current in the primary winding usually does not exceed 25 A, and in the secondary it ranges from 6-120 A. When working with electrodes with a diameter of 3 mm, every 10-15 make stops to let the transformer cool down. If the electrodes are thinner, this is not necessary. More frequent breaks are needed if you are working in cutting mode.

DIY mini welding

To assemble a miniature welding machine yourself, you only need a few hours and the following materials:

Gently at first disassemble the old battery and remove the graphite rod from it. At the end, sharpen it with sandpaper and wipe it with a dry cloth. Peel off the insulation from the end of a piece of thick wire 4-5 cm from the end and bend the loop using pliers or side cutters. Insert a carbon electrode into it.

Remove the secondary winding from the transformer and replace it wrap thick wire for 12-16 turns. Now all this is inserted into a suitable case - and the device is ready.

Its wires are connected to the terminals of the secondary winding, carbon the rod is inserted into the loop and crimps well. Connect the positive terminal to the electrode holder, and the negative terminal to the twisting of the working parts. The handle holder can be adapted for the electrode.

You can use a soldering iron or something similar. Plug the appliance into the household network and carry out connecting parts with graphite. A flame should appear, and a spherical weld will form at the end of the parts.

For a home workshop, the presence of a welding machine is very important. Such devices have different designs and modifications. Both beginners and experienced craftsmen often prefer not factory-made, but home-made devices that can be modified in their own way.

Reading time: 8 minutes

Technological advances have transformed welding machines into compact and intuitive devices from bulky and difficult to master. And if earlier a welding machine could only be found in a person who deals with this business professionally, now every summer resident and home craftsman has simple inverters. Now you can find an inverter for up to $ 50, and these are mere pennies in comparison with the devices of the previous generation.

But, despite the large assortment of modern welding machines, sometimes it is easier for a master to assemble his own device than to buy it in a store. And there are several reasons for this decision. In this article, we will tell you in detail why to make a home-made welding machine and how to make an inverter, semi-automatic and contact welding machine. As practice shows, it is these types of welding machines that are most often assembled by hand.

Homemade DC welding machines have many advantages over factory machines. We will list the main ones so that you understand the feasibility of assembling a homemade inverter, semiautomatic device or contact device.

Price

The first advantage is the price of a homemade device. The cost of a do-it-yourself welder rarely exceeds $ 100 and this is very profitable. Yes, there are cheap inverters for sale for $100 and even less, but are you sure that you will be able to fully use it for many years? We are not sure. Cheap factory-made welding machines are rarely durable and functional. But you need a full-fledged assistant in everyday life, and not a parody of a welding machine.

Still do not believe that a cheap device simply by definition cannot be of high quality? Think for yourself. For the production of the apparatus, it is not enough to have only parts. We also need personnel, workers, equipment, plus payment of taxes, salaries, etc. This is an increasing share of the costs, and in order to somehow reduce the price of the final product, manufacturers simply use low-quality components in the manufacture.

You can do otherwise. To assemble a DC welding machine for your needs, you need to immediately buy more or less high-quality parts. The cost price of the apparatus assembled by you will be the same as the price of the budget factory apparatus. But at the same time, your homemade welder will be much more reliable, durable and will be able to work in difficult conditions.

maintainability

Another advantage of a device assembled at home is your complete confidence in it. You know exactly what it is made of, what can fail, how to fix such a device and how much it will cost. In the case of a factory device, it is almost impossible to predict the outcome. In addition, now the range is so large that old-school welders simply do not want to spend time and effort on studying all types of devices. It is easier for them to assemble their own high-quality inverter or the same semi-automatic device.

Self-development

And the last one is not obvious, but still a plus - homemade products develop you and your skills in assembling electrical appliances. If you have long wanted to start assembling power tools or modernizing household appliances, then a home-made welder can be the first step. This is a very entertaining and interesting process that you will enjoy and can become a full-fledged hobby or even a side job. Well, if self-assembly of the device does not interest you, then At least you can do minor home repairs.

How to make an inverter?

To assemble an inverter welding machine with your own hands, you will need a minimum set of tools, parts and basic knowledge of electrical engineering. All the "stuffing" of a home-made inverter can be placed in a case from a desktop computer. Watch the video below, where the author talks about his homemade device.

Such a homemade inverter has a very simple device. There is a power section, a DC welding transformer and a choke. Additionally, you need to add a power supply. The device shown in the video is equipped with a current regulator and a power button. If you use a computer case, then add a few holes for hot air to exit and cold air to take in.

Here we will not list all the parts needed for assembly, because in the video the author explains everything in detail and quickly. You just need to watch one video and you can already assemble your inverter. All the necessary parts can be obtained either on the radio market or on online bulletin boards. If you have a garage, then look for parts there. Many craftsmen have an old transformer lying around somewhere from a household appliance like a microwave.

Such a home-made inverter is quite reliable and durable, while it is not as whimsical for storage as factory devices. Well, the assembly diagram of the welding inverter is in the public domain, it can be easily found on the Internet.

How to make a semi-automatic?

To assemble a semi-automatic, you will need an inverter as a "donor". It is not necessary to buy a new inverter in the store, you can literally take a used device from your hands for a penny. The wire feeder can be assembled literally from improvised parts. We do not recommend making any parts yourself, it is much easier and faster to buy them on the Internet. For example, you should not make a welding sleeve yourself. It is better to order it in the online store and do not bother.

Watch another video below, only about assembling a semi-automatic. In the video, the author tells in detail how he assembled a full-fledged semi-automatic device based on a conventional inverter for RDS welding.

Also read our detailed material on assembling a semi-automatic. There is also a diagram of a semi-automatic DC welding machine.

How to make contact welding?

Homemade contact welding is an extremely necessary thing. Such a device consumes little electricity, while allowing you to quickly weld thin sheet metal without coated electrodes, welding wire, gas and other consumables. There are many videos on the Internet with the manufacture of contact welding, but we will tell you our detailed instructions.

The first thing you need is a working transformer. You can get it from unnecessary household appliances like a microwave. If you want to assemble a powerful resistance welding machine, then use two transformers at once to increase the power.

Additionally, remove the copper wire. It must be thick, or tie several thin wires together. Make or buy levers to clamp metal between two metal electrodes. Do not forget about the base for the device. It can be a sheet of metal, weighing at least a couple of kg. If desired, it can mount the device directly on the welding table. You will also need clamps, a screwdriver, winding material (for example, electrical tape) and copper. You can make them yourself from copper parts.

Do-it-yourself contact welding can be assembled from any transformer, but it’s better to take a part from the same microwave. Since such a transformer is great for a homemade welding machine. For assembly, you will not need the entire transformer as a whole, but its magnetic circuit and primary winding. Remove the secondary winding from the transformer, do it carefully. Additionally dismantle the shunts. They are located on both sides of the secondary winding.

Now it's time to make a new winding. For it, we need a wire of at least 10 mm in diameter. Wind 2-3 turns, this will be enough for the transformer to work smoothly. If the wire you have chosen has too thick insulation, remove it and wrap the wire with electrical tape.

The base is ready. It remains to put together all the details. Put them in the case. You can make it yourself, or you can just take a casing from an inoperative electrical appliance that is suitable in size and configuration. Connect copper wires, necessary power buttons, etc. Everything is ready!

Instead of a conclusion

As you can see, to assemble a homemade DC welding machine with your own hands, you will need a minimum set of parts and basic knowledge in the field of electrical engineering. This is already enough to assemble an inverter, a semi-automatic device or a resistance welding machine. There are a wide variety of schemes for these devices on the Internet, you can choose the most suitable ones and use them. Improving a homemade apparatus is also possible. This is basically one of the benefits. A homemade welder can be remade and modified without fear of voiding the warranty and breaking the device.

Welding is the most reliable connection of one-piece parts. In everyday life, it is widely used in the manufacture of hedges using chain-link mesh, greenhouse frames, stoves for baths and garages, or various containers needed in summer cottages. A person who knows the skills of welding is able to create real masterpieces of openwork fences, roof sheds and other things necessary in everyday life on his personal plot.

What justifies the reliability of welding: the basics of welding

In terms of the strength of creating permanent joints, welding occupies a leading position. This is ensured by heating alloys of various metals using an electric arc, which leads to plastic deformation of the materials used. In this case, the mutual penetration of the elementary particles of the electrode into the structure of the materials being joined occurs. As a result, molecular bonds with ultrahigh strength appear.

Thanks to modern innovative technologies, it is now possible to use laser and electron beams, ultrasound and a gas burner flame for welding. But for welding in domestic conditions, electric arc welding remains the most optimal, a source of energy, to create an electric arc of which various types of welding machines, including inverters, are used.

Welding methods

There are the following welding methods:

  • gas press, using an oxyacetyl flame. The advantages of this type of welding are high productivity. Therefore, it is widely used in the oil and gas industry, in particular in the construction of highways for transporting oil and gas, as well as in mechanical engineering.
  • Contact carried out by an electric current having a relatively low voltage at a sufficiently high current strength. This method includes the following varieties: butt welding, seam and spot welding.

In addition, in some cases, roller and electroslag welding, friction and thermite, as well as a number of other varieties are used.

Choosing the right equipment

If you decide to master the technique of welding, then you will need welding equipment. It can be rented or bought. Currently, outlets offer welding machines equipped with a device that allows you to increase or decrease the current strength. Those who like to do everything with their own hands can make a welding machine from improvised means. In any case, you will need one of the following electrical energy converters:

  1. Transformer for converting the alternating current of a household electrical network into the current necessary for welding. When choosing a unit of this type, it must be borne in mind that cheap models will not be able to provide the necessary stability of the electric arc. They are characterized by "sagging" voltage. Plus, they're too heavy.
  2. Rectifier. This is a device that converts alternating electric current supplied to consumer networks into direct current. Unlike transformers, these units provide sufficient stability of the electric arc, which, in turn, improves the quality of the weld.
  3. inverter. It converts the alternating current of the household power supply into the required direct current, with the voltage necessary for high-quality welding. This apparatus is characterized by compactness and light weight, easy ignition, fast action and high performance.

** Recommendation. The most efficient of these devices is considered to be an inverter, which is characterized by efficiency and high performance.

How to choose the right electrodes for welding

The most common, arc welding, requires electrodes that are designed to supply current to the weld. In most cases, this is a wire consisting of a special melting powder. But for those who are faced with welding for the first time, it is better to use electrodes in the form of solid rods coated with a melting compound. They allow even a beginner to make an even seam. The optimal diameter of the electrode rod for this category of welders is 3 mm. Smaller diameter electrodes are used to connect thin sheets of metal, and to use

Larger diameter electrodes require higher power equipment.

Welding safety (welder equipment)

Welding work is accompanied by bright light radiation and a lot of splashes of hot metal. Therefore, the welder must take care to protect the skin of his face and eyes from burns. For these purposes, you will need a special shield and mask. But not only the face and eyes need protection. The skin of the hands is more susceptible to burns from flying splashes of melting metal. Therefore, tarpaulin or suede gloves are a necessary means of ensuring safety. The ideal option is the presence of a dressing gown or overalls made of thick canvas or rubberized fabric.

In order to ensure fire safety, in places where welding work is carried out, there must be a container with water or other means that protect against fire when an accidental spark enters.

Step-by-step instructions for performing welding work

  1. The surface to be welded must be carefully protected. It should be free of dirt and rust.
  2. Before starting welding work, it is necessary to insert the electrode into the holder of the welding machine and create an electric arc. To do this, it is necessary to cause the movement of current in the welding zone. This process can be carried out by striking the electrode rod on the metal or by touching the surface of the workpiece in the form of tapping.
  3. As soon as an electric arc appears, it is necessary to create a gap between it and the surface to be joined. This gap should have a constant value and be in the range from 3 to 5 mm.

** Recommendation. To obtain a smooth seam, without defects, it is necessary that the gap remains constant throughout the entire time of welding. Otherwise, the arc will be interrupted and the quality of the weld will deteriorate.

  1. The angle of inclination of the rod should be 70?. But it can be changed, in order to ensure the comfort of welding.
  2. Equally important is the stability of the supply of electric current. It must be borne in mind that too much of its force will cause the metal to melt, and at a low one, the arc is extinguished.

After you have mastered the technique of making a weld in the form of a roller, you can proceed directly to making permanent joints. Work begins with the creation of an arc. Then the welder proceeds to the direct connection of the parts. At the same time, his hand must make oscillatory movements from one element to another. The weld (trajectory of movement) can be made in the form of a herringbone, loop, zigzag, etc. At the end of the work, it is necessary to clean the seam from the formed slags.

Once you have mastered the basic skills of welding, you can move on to more complex operations, making butt and tee joints, as well as overlap and corner, moving in different directions. As soon as the hand gains confidence, you can start making more complex products.

Video - manual arc welding for beginners

Inverter welding is a modern device that is widely popular due to the low weight of the device and its dimensions. The inverter mechanism is based on the use of field effect transistors and power switches. To become the owner of a welding machine, you can visit any tool store and acquire such a useful thing. But there is a much more economical way, which is due to the creation of do-it-yourself inverter welding. It is the second method that we will pay attention to in this material and consider how to do welding at home, what is needed for this and what the circuits look like.

Features of the operation of the inverter

An inverter-type welding machine is nothing more than a power supply, the one that is now used in modern computers. What is the basis of the work of the inverter? In the inverter, the following picture of the conversion of electrical energy is observed:

2) The current with a constant sinusoid is converted into an alternating current with a high frequency.

3) The voltage value decreases.

4) The current is rectified while maintaining the required frequency.

A list of such transformations of the electrical circuit is necessary in order to be able to reduce the weight of the apparatus and its overall dimensions. After all, as you know, old welding machines, the principle of which is based on a decrease in the magnitude of the voltage and an increase in the current strength on the secondary winding of the transformer. As a result, due to the high value of the current strength, the possibility of arc welding of metals is observed. In order for the current to increase and the voltage to decrease, the number of turns on the secondary winding decreases, but the cross section of the conductor increases. As a result, it can be seen that the transformer-type welding machine not only has significant dimensions, but also a decent weight.

To solve the problem, a variant of the implementation of the welding machine by means of an inverter circuit was proposed. The principle of the inverter is based on increasing the current frequency to 60 or even 80 kHz, thereby reducing the weight and dimensions of the device itself. All that was required to implement an inverter welding machine was to increase the frequency by a thousand times, which was made possible thanks to the use of field-effect transistors.

Transistors provide communication between themselves with a frequency of about 60-80 kHz. A constant current value comes to the power circuit of the transistors, which is ensured by the use of a rectifier. A diode bridge is used as a rectifier, and capacitors provide voltage equalization.

Alternating current, which is transmitted after passing through the transistors to the step-down transformer. But at the same time, a hundreds of times smaller coil is used as a transformer. Why a coil is used, because the frequency of the current that is fed to the transformer is already increased 1000 times thanks to field effect transistors. As a result, we obtain similar data as in the case of transformer welding, only with a big difference in weight and dimensions.

What you need to build an inverter

To assemble inverter welding on your own, you need to know that the circuit is designed, first of all, for a consuming voltage of 220 volts and a current of 32 amperes. Already after the conversion of energy at the output, the current will be increased by almost 8 times and will reach 250 amperes. This current is enough to create a strong seam with an electrode at a distance of up to 1 cm. To implement an inverter-type power supply, you will need to use the following components:

1) A transformer consisting of a ferrite core.

2) Winding of the primary transformer with 100 turns of wire with a diameter of 0.3 mm.

3) Three secondary windings:

- internal: 15 turns and a wire diameter of 1 mm;

- medium: 15 turns and a diameter of 0.2 mm;

- outer: 20 turns and a diameter of 0.35 mm.

In addition, to assemble the transformer, you will need the following items:

- copper wires;

- fiberglass;

- textolite;

- electrical steel;

- cotton material.

What does an inverter welding circuit look like?

In order to understand what an inverter welding machine is in general, it is necessary to consider the diagram below.

Electrical diagram of inverter welding

All these components must be combined and thereby obtain a welding machine, which will be an indispensable assistant in the performance of plumbing work. Below is a schematic diagram of inverter welding.

Inverter welding power supply circuit

The board, on which the device's power supply is located, is mounted separately from the power unit. The separator between the power unit and the power supply is a metal sheet, electrically connected to the body of the unit.

To control the gates, conductors are used, which must be soldered near the transistors. These conductors are interconnected in pairs, and the cross section of these conductors does not play a special role. The only important thing to consider is the length of the conductors, which should not exceed 15 cm.

For a person who is not familiar with the basics of electronics, reading this kind of circuit is problematic, not to mention the purpose of each element. Therefore, if you do not have skills in working with electronics, then it is better to ask a familiar master to help you figure it out. Here, for example, below is a diagram of the power section of an inverter welding machine.

Scheme of the power part of inverter welding

How to assemble inverter welding: a step-by-step description + (Video)

To assemble the inverter welding machine, you must perform the following work steps:

1) Frame. As a body for welding, it is recommended to use an old system unit from a computer. It fits best, as it has the required number of holes for ventilation. You can use an old 10-liter canister that you can cut holes in and place the cooler. To increase the structural strength of the system housing, it is necessary to place metal corners, which are fixed with bolted connections.

2) Assembly of the power supply. An important element of the power supply is the transformer. It is recommended to use 7x7 or 8x8 ferrite as the basis of the transformer. For the primary winding of the transformer, it is necessary to wind the wire across the entire width of the core. Such an important feature entails an improvement in the operation of the device when voltage drops occur. As a wire, it is imperative to use copper wires of the PEV-2 brand, and in the absence of a bus, the wires are connected into one bundle. Fiberglass is used to insulate the primary winding. From above, after a layer of fiberglass, it is necessary to wind the turns of shielding wires.

Transformer with primary and secondary windings to create inverter welding

3) Power part. The step-down transformer acts as a power unit. Two types of cores are used as a core for a step-down transformer: W20x208 2000 nm. It is important to provide a gap between both elements, which is solved by placing newsprint. The secondary winding of the transformer is characterized by winding turns in several layers. Three layers of wires must be laid on the secondary winding of the transformer, and PTFE gaskets are installed between them. Between the windings, it is important to place a reinforced insulating layer, which will avoid voltage breakdown to the secondary winding. It is necessary to install a capacitor with a voltage of at least 1000 volts.

Transformers for the secondary winding from old TVs

To ensure air circulation between the windings, an air gap must be left. A current transformer is assembled on the ferrite core, which is connected to the positive line in the circuit. The core must be wrapped with thermal paper, so it is best to use a cash register tape as this paper. The rectifier diodes are attached to the aluminum heatsink plate. The outputs of these diodes should be connected with bare wires, the cross section of which is 4 mm.

3) inverter unit. The main purpose of the inverter system is the conversion of direct current into alternating current with a high frequency. To ensure the increase in frequency, special field-effect transistors are used. After all, it is transistors that work to open and close at a high frequency.

It is recommended to use more than one powerful transistor, but it is best to implement the circuit based on 2 less powerful ones. This is necessary in order to be able to stabilize the frequency of the current. The circuit cannot do without capacitors, which are connected in series and make it possible to solve such problems:

Inverter on aluminum plate

4) Cooling system. Cooling fans should be installed on the case wall, and for this you can use computer coolers. They are necessary in order to ensure the cooling of the working elements. The more fans you use, the better. In particular, it is mandatory to install two fans to blow the secondary transformer. One cooler will blow over the radiator, thereby preventing overheating of working elements - rectifier diodes. Diodes are mounted on the radiator as follows, as shown in the photo below.

Rectifier bridge on the cooling radiator

Photo of thermostat

It is recommended to install it on the heating element itself. This sensor will be triggered when the critical heating temperature of the working element is reached. When it is triggered, the power to the inverter device will be turned off.

Powerful fan for cooling the inverter device

During operation, inverter welding heats up very quickly, so the presence of two powerful coolers is a prerequisite. These coolers or fans are located on the body of the device so that they work to extract air.

Fresh air will enter the system through the holes in the device case. The system unit already has these holes, and if you use any other material, then do not forget to provide fresh air.

5) Board soldering is a key factor, since the entire circuit is based on the board. It is important to install diodes and transistors on the board in the opposite direction to each other. The board is mounted directly between the cooling radiators, with the help of which the entire circuit of electrical appliances is connected. The supply circuit is designed for a voltage of 300 V. The additional location of 0.15 μF capacitors makes it possible to dump excess power back into the circuit. At the output of the transformer, capacitors and snubbers are located, with the help of which overvoltages are damped at the output of the secondary winding.

6) Setting up and debugging work. After the inverter welding is assembled, it will be necessary to carry out a few more procedures, in particular, to set up the functioning of the unit. To do this, connect a voltage of 15 volts to the PWM (pulse width modulator) and power the cooler. Additionally included in the relay circuit through the resistor R11. The relay is included in the circuit in order to avoid power surges in the 220 V network. It is imperative to control the switching on of the relay, and then apply power to the PWM. As a result, a picture should be observed in which rectangular sections on the PWM diagram should disappear.

Homemade inverter device with a description of the elements

You can judge the correct connection of the circuit if, during setup, the relay outputs 150 mA. In the case when a weak signal is observed, this indicates an incorrect connection of the board. It is possible that there is a breakdown in one of the windings, therefore, to eliminate interference, it will be necessary to shorten all the supply wires.

Inverter welding in the case of the system unit from the computer

Device health check

After carrying out all the assembly and debugging work, it remains only to check the performance of the resulting welding machine. To do this, the device is powered from the mains 220 V, then high current strength is set and the readings are verified using the oscilloscope. In the lower loop, the voltage should be in the range of 500 V, but not more than 550 V. If everything is done correctly with a strict selection of electronics, then the voltage indicator will not exceed 350 V.

So, now you can check the welding in action, for which we use the necessary electrodes and cut the seam until the electrode burns out completely. After that, it is important to control the temperature of the transformer. If the transformer simply boils, then the circuit has its drawbacks and it is better not to continue the workflow.

After cutting 2-3 seams, the radiators will heat up to a high temperature, so after that it is important to allow them to cool down. For this, a 2-3 minute pause is enough, as a result of which the temperature will drop to the optimum value.

Checking the welding machine

How to use a homemade device

After the home-made device is included in the circuit, the controller will automatically set a certain current strength. If the wire voltage is less than 100 volts, then this indicates a malfunction of the device. You will have to disassemble the device and again re-check the correctness of the assembly.

Using this type of welding machine, it is possible to solder not only ferrous, but also non-ferrous metals. In order to assemble a welding machine, you will need not only knowledge of the basics of electrical engineering, but also free time to implement the idea.

Inverter welding is an indispensable thing in the garage of any owner, so if you have not yet acquired such a tool, then you can make it yourself.

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