Transformer from Latra 9a. A simple welding machine - a baby from Latra

When designing or repairing appliances and household equipment, a problem often arises: how to weld certain parts. Buying a welding machine is not entirely easy, but making it yourself...

In this article you can get acquainted with a simple homemade welding machine made according to an original design.

Welding machine operates from a 220 V network and has high electrical characteristics. Thanks to the application new form magnetic circuit, the weight of the device is only 9 kg with overall dimensions 125 x 150 mm. This is achieved by using transformer strip iron rolled into a torus-shaped roll, instead of the traditional package of W-shaped plates. The electrical characteristics of a transformer on a brake magnetic circuit are approximately 5 times higher than those of a W-shaped transformer, and electrical losses are minimal.

To get rid of the search for scarce transformer iron, you can purchase a ready-made 9 A LATR or use a brake magnetic circuit from a burnt-out laboratory transformer. To do this, remove the fence, fittings and remove the burnt winding. The freed magnetic circuit must be insulated from future winding layers with electrical cardboard or two layers of varnished cloth.

The welding transformer has two independent windings. The primary one uses PEV-2 1.2 mm wire, 170 m long. For ease of operation, you can use a shuttle ( wooden slats 50 x 50 mm with slots at the ends), on which the entire wire is pre-wound. A layer of insulation is placed between the windings. Secondary winding - copper wire in cotton or glass insulation - has 45 turns over the primary. Inside the wire is placed turn to turn, and with outside with a small gap - for uniform placement and better cooling.

It is more convenient to do the work together: one carefully, without touching the adjacent turns, so as not to damage the insulation, stretches and lays the wire, and an assistant holds the free end, protecting it from twisting. A welding transformer made in this way will produce a current of 50 - 185 A.

If you purchased a 9 A Latr and upon inspection it turns out that its winding is intact, then the matter becomes much simpler. Using the finished winding as the primary, you can assemble a welding transformer in 1 hour, giving a current of 70 - 150 A. To do this, you need to remove the fence, current collection slider and mounting hardware. Then identify and mark the 220 V terminals, and the remaining ends, securely insulated, are temporarily pressed to the magnetic circuit so as not to damage them when working with the secondary winding. Installation of the latter is carried out in the same way as in the previous version, using copper wire of the same cross-section and length.

The assembled transformer is placed on an insulated platform in the same casing, having previously drilled holes in it for ventilation. The wires of the primary winding are connected to a 220 V network using a ShRPS or VRP cable. A disconnecting circuit breaker must be provided in the circuit.

The leads of the secondary winding are connected to flexible insulated wires of the PRG, the electrode holder is attached to one of them, and the part to be welded is attached to the other. The same wire is grounded for the safety of the welder.

Current regulation is provided for by connecting in series the wire circuit of the ballast electrode holder - nichrome or constantan wire with a diameter of 3 mm and a length of 5 m, coiled like a snake, which is attached to asbestos cement sheet. All connections of wires and ballast are made using M10 bolts. Using the selection method, moving the wire connection point along the snake, the required current is set. It is possible to regulate the current using electrodes of different diameters. Electrodes with a diameter of 1 - 3 mm are used for welding.

All necessary materials For welding transformer can be purchased at the retail chain. And for a person familiar with electrical engineering, making such a device is not difficult.

When working, to avoid burns, it is necessary to use a fiber protective shield equipped with an E-1, E-2 light filter. A hat, overalls and mittens are also required. The welding machine should be protected from dampness and not allowed to overheat. Approximate operating mode with an electrode with a diameter of 3 mm: for a transformer with a current of 50 - 185 A - 10 electrodes, and with a current of 70 - 150 A - 3 electrodes, after which the device must be disconnected from the network for at least 5 minutes.

Nowadays, it is difficult to imagine any work with metal without the use of a welding machine. Using this device, you can easily connect or cut iron of various thicknesses and dimensions. Naturally for execution quality work You will need certain skills in this matter, but first of all you need the welder itself. Nowadays, of course, you can buy it, as well as, in principle, hire a welder, but in this article we will talk about how to make a welding machine with your own hands. Moreover, with all the wealth 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, reading this article will help you choose the necessary device, since you will know the basics of their circuitry. There are several types of welders: direct current, alternating, three-phase and inverter. In order to determine which option you need, we will consider the design and device of the first two types, which you can assemble with your own hands at home without any 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 and, compared to others, can be made quite easily at home, as evidenced 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 welding machine alternating current- This is a high-power step-down transformer.

The optimal voltage when operating a welding machine assembled at home is 60V. The optimal current is 120-160A. Now it’s 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 ​​the copper wire should be 3-4 square meters. mm, the optimal 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 optimal diameter The copper core for the primary winding of the step-down transformer should be 3 mm. If you decide to take an aluminum wire to make a welding machine with your own hands, then the cross-section for the copper wire must be multiplied by a factor of 1.6.

It is important that the wires are covered in rag braiding; you cannot use conductors in PVC insulation - when the wires heat up, it will melt and this will happen. If you do not have a wire of the required diameter, you can use thinner wires, winding them in parallel. But then it should be taken into account that the thickness of the winding will increase, and, accordingly, the dimensions of the device itself. It must 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 (remember that we are focusing on 120 - 160A) and the length of the wires.

The first step is to make a transformer core for a homemade welding machine. The best option there will 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 from 0.35 mm to 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 chosen such as to accommodate all the windings of the transformer.
• Secondly, the roll area, which is calculated by the formula: Roll = a*b, must be at least 35 square meters. cm. If there is more Skren, then the transformer will heat up less and, accordingly, work longer, and you will not need to interrupt often in order for it to cool down. It is better that the Skrena is equal to 50 square meters. cm.

Next, we proceed to 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 a core required thickness. Then we fasten it with bolts at the corners. Finally, 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 further protect the transformer from breakdown to the housing.

Next, we proceed to winding the welding machine from the step-down transformer. First, we wind the primary winding, which will consist of 215 turns, as shown in Figure 3.

It is advisable to make a branch from 165 and 190 turns. We attach a thick textolite plate to the top of the transformer. The ends of the windings are secured to it using bolted connection noting that the first bolt is a common wire, the second is a branch from the 165th turn, the 3rd is a branch from the 190th turn and the 4th is from the 215th. This will make it possible to subsequently regulate the current during welding by switching between different terminals of your welding device. This is a very important function, and the more branches you make, the more precise your adjustment will be.

Then we proceed to winding 70 turns of the secondary winding, as shown in Figure 4.

A smaller number of turns are wound on the other side of the core - where the primary winding is wound. The ratio of turns should be approximately 60% to 40%. This ensures that after you catch the arc and start welding, the eddy currents will partially turn 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. This way the arc will be easy to catch, but too much current will not interfere with quality welding. We will also secure the ends of the winding with bolts to the textolite plate. You can not attach them, but run the wires directly to the electrode holder and the crocodile to ground; this will remove connections where there could potentially be a voltage drop and heating. For better cooling, it is highly advisable 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 common wire and the wire extending from the 215th turn of the primary winding. If you need to increase the current, 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 using a resistance made from a piece of transformer steel bent into a spring and connected to a holder. It is always necessary to ensure that the welding machine does not overheat; to do this, regularly check 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 their own.

DC

Some types of welding require a DC welder. With this tool you can cook cast iron and stainless steel. You can make a DC welding machine with your own hands in no more than 15 minutes by remaking a homemade product using alternating current. To do this, you need to connect a rectifier assembled with diodes to the secondary winding. As for the diodes, they must withstand a current of 200 A and have good cooling. D161 diodes are suitable for this.

Capacitors C1 and C2 with the following characteristics will help us equalize the current: capacitance 15000 μF and voltage 50V. Next, we assemble the circuit shown in the drawing below. Inductor L1 is needed to regulate the current. Contacts x4 are plus for connecting the holder, and x5 are minus for supplying current to the part to be welded.

Three-phase welding machines are used for welding in industrial conditions, they have two-electrode holders installed, 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 lessons provided below, which will clearly show how to assemble a simple welder yourself from scrap materials, and will also explain to you some of the details and nuances of the work:

Now you know the basic principles of the design 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:

When designing, assembling or repairing something, you often have to connect parts. The types and methods of connections are different. For example, when connecting metal products, a threaded connection (screw or bolt with a nut), riveting, gluing, soldering and welding are used.

And if for the first three you only need mechanical tools, then soldering irons are needed for soldering, and for welding, some craftsmen make homemade DC and AC welding machines. Many of these units have been operating without failures for decades.

Homemade AC devices

When assembling, repairing or designing household appliances or any equipment, it becomes necessary to weld several parts together. AC welding machines are expensive and not easy to buy. But it is perfectly acceptable to make them yourself. The circuits of such devices are very different.

One of original designs made on the basis of the LATR transformer (laboratory autotransformer). This device operates from a regular network using alternating current. Its electrical characteristics are very high due to the special design of the magnetic circuit.

It is made of transformer strip iron (rolled) and has the shape of a ring or torus, although a conventional AC welding machine is assembled from plates similar to the letter “W”. The characteristics of a toroidal product are 4.7 times higher, and losses are almost minimal compared to an W-shaped core.

But such transformer strip iron is now in short supply, so it is easier to get a ready-made 9-amp laboratory autotransformer (LATR) or a toroidal magnetic circuit from a burnt product. It needs to be rewound - remove the old or burnt secondary winding and wind a new one with a thicker wire. Using all this, you will assemble a 75-155 Amp AC unit in about 1-2 hours.

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Rewind LATR

To replace the windings proceed as follows:

1. Remove the casing (if there is one).
2. Reinforcement made of non-magnetic material (plastic, aluminum) is removed along with the mechanical part.
3. Get rid of old or burnt windings:

• if the windings are not damaged, then the secondary is simply wound onto a special shuttle for use in other developments and designs. A shuttle measuring 4-5x10-20 cm can be cut from plywood;
• if the windings are burned out, then the wire is removed by any method: cut off, torn off.

1. The core is electrically insulated from the future winding by wrapping the iron in two layers of varnished cloth or making overlays from special electrical cardboard.
2. New windings are wound, isolating them from each other;
3. Assembly is carried out.

Devices made on the basis of the LATR transformer are wound with only two windings.

If the transformer burns out completely, you have to wind both windings.

The primary is performed with a 1.2 mm wire of the PEV-2 type. The approximate length of this piece is 170 m. A shuttle is used for winding. The wire is wound completely around it.

And then, having secured the end, they begin to perform forward movements hand inside the toroid, wrapping the wire around the insulated core. Winding is done turn to turn. After winding, the primary winding is covered with insulation (the same varnished fabric).

For more reliable insulation and efficient cooling of the device, you can use the air gap method between the windings. In this case, the primary winding does not need to be insulated from above - its own coating will suffice.

The method is:

• two rings are made of thick (3-5 mm) PCB with an external gauge 3-5 mm (on each side) larger than the diameter of the core with a wound “primary”;
• the edges are chamfered (they are rounded) to avoid damage to the insulation;
• the rings are secured at the top and bottom of the core with double-sided tape;
• the secondary winding is wound.

The secondary one - 45 turns - is performed with several wires twisted together, or a busbar, which must be in glassy or CB insulation. The cross section is calculated depending on the required welding current and is 5-7 A per 1 sq. mm. For a current of 170 A you will need a busbar or twist with a cross section of 35 mm or larger. The secondary winding (for cooling) is distributed over the toroid with a gap, trying to distribute it evenly.

If you have a working autotransformer or have purchased a new one, then the work comes down to only rewinding one (secondary) winding, since the primary is already wound with wire of the required cross-section and length.

It moves in the following sequence:

• First, unscrew the metal or plastic casing (if there is one);
• remove the slider with the graphite current collector;
• remove reinforcement from non-magnetic material (plastic, aluminum);
• identify (call the tester) and mark all network outputs;
• the remaining wires are wrapped with insulation or PVC tubes are put on them and laid on the side of the LATR perpendicular to the windings;
• then the secondary winding is mounted; the turns, diameter and brand of copper wires are similar to the option described above (completely burnt).

Welding machines, or rather their transformers, are recommended to be installed by two people. The first person pulls the wire and lays it down, trying not to spoil the insulation and maintain a distance between the turns. The second holds the end of the wire, preventing it from twisting.

If the insulation is broken and the ends of at least one turn touch, an interturn short circuit will occur, the transformer will overheat and the device will fail.

Welding machines with such a transformer operate at currents of 55-180 A.

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Wiring diagram

Any design that operates from the network has its own circuit. The welding machine described above also has it.

The rewound transformer is covered with an old casing (if it fits), a new one is prepared or dispensed with without a fence. It's not that dangerous. After all, the device has an output potential of no more than 50 V. And it is much easier to cool a transformer without a casing.

The terminals of the transformer windings are connected to your device as follows:

1. Primary (I) - connected to 220 V with a 2-4 mm flexible copper wire (VRP or ShRPS). An automatic switch (Q1) is required - an automatic switch like those found in houses.
2. Carefully insulated, but also flexible PRG wires of the appropriate cross-section are attached to the secondary (multi-ampere) one.

One end is attached to the workpiece and grounded (for electrical safety). On the other, a ballast resistor is mounted (to regulate the output current) and a homemade or standard electrode holder for the device.

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Current regulators

The regulator is a 3 mm caliber coiled wire made of constantan or nichrome wire approximately 5 m long. This is a kind of ballast connected in series to the electrical holder circuit.

The spiral is fixed separately on a sheet of asbestos cement. The welding current of the machine can be changed in three ways:

1. Selection method. A crocodile clip is attached to the regulating end big size. The current is changed by moving the clamp in a spiral. If you strengthen the spiral only at the ends (or straighten), the adjustment will be smooth.
2. Switching method. Take the switch. Its common terminal is connected to the control wire. The remaining terminals are connected to spiral turns. The current is controlled by discrete movement of the slider.
3. Replacement method. The current is changed by selecting electrodes (thick and thin, long and short). Regulation occurs within small limits. This method is almost never used.

These machines change the welding current by adjusting the secondary winding. A large current is removed from it, so changing the current electronically is unprofitable. It is necessary to install powerful parts, huge radiators and appropriate cooling.

A good welding machine makes all metal work much easier. It allows you to connect and cut various iron parts, which differ in their thickness and steel density.

Modern technologies offer huge selection models differing in power and size. Reliable designs have enough high cost. Budget options, as a rule, have a short service life.

Our material presents detailed instructions how to make a welding machine with your own hands. Before starting the work process, it is recommended to familiarize yourself with the type of welding equipment.

Types of welding machine

The devices of this technology come in several types. Each mechanism has some features that are reflected in the work performed.

Modern welding machines are divided into:

• DC models;
• with alternating current
• three-phase
• vector

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 collect similar design, you must have a certain set of materials.

These include:

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

All these parts can be purchased in specialized stores. Detailed consultation with specialists helps you 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 you need to do is to correctly manufacture the main core. For this model, it is recommended to choose a rod type of part.

To make it you will need plates made of transformer steel. Their thickness is 0.56 mm. Before you begin assembling the core, you must observe its dimensions.

How to correctly calculate the parameters of a 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 connected to each other to the required thickness of the part.

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 side, a winding of 160 turns is made. The third and fourth primary windings should contain 190 turns. After this, a thick platinum is attached to the surface.

The ends of the wound wire are secured with a bolt. I mark its surface with the number 1. The following ends of the wire are secured in a similar way with the corresponding markings applied.

Note!

IN finished design There should be 4 bolts with different numbers of turns.

In the finished design, the winding ratio will be 60% to 40%. This result ensures normal work apparatus and good quality welding fastening.

Control the supply electrical energy possible by switching wires to required amount windings It is not recommended to overheat the welding mechanism during operation.

DC apparatus

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

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

Note!

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

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

Repairing a welding machine is not 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-install the primary and secondary windings.

Photo of a do-it-yourself welding machine

Note!

The homemade welding machine from LATR 2 built on the basis of a nine-amp LATR 2 (laboratory adjustable autotransformer) and its design provides for adjustment of the welding current. The presence of a diode bridge in the design of the welding machine allows welding with direct current.

Current regulator circuit for a welding machine

The operating mode of the welding machine is adjustable variable resistor R5. Thyristors VS1 and VS2 each open in their own half-cycle alternately for a certain period of time thanks to a phase-shifting circuit built on elements R5, C1 and C2.

As a result, it becomes possible to change the input voltage on the primary winding of the transformer from 20 to 215 volts. As a result of the transformation, a undervoltage, allowing you to easily ignite the welding arc at terminals X1 and X2 when welding with alternating current and at terminals X3 and X4 when welding with direct current.

The welding machine is connected to the electrical network using an ordinary plug. A paired 25A circuit breaker can be used as switch SA1.

Conversion of LATR 2 into a homemade welding machine

First, remove from the autotransformer protective cover, electrical removable contact and fastening. Next, good electrical insulation is wound onto the existing 250-volt winding, for example, fiberglass, on top of which 70 turns of the secondary winding are laid. For the secondary winding, it is advisable to choose a copper wire with a cross-sectional area of ​​about 20 square meters. mm.

If there is no wire of a suitable cross-section, you can make a winding of several wires with with total area section 20 sq. mm. The modified LATR2 is mounted in a suitable homemade housing with ventilation holes. There you also need to install a regulator board, a packet switch, as well as terminals for X1, X2 and X3, X4.

In the absence of LATR 2, the transformer can be made homemade by winding the primary and secondary windings on a transformer steel core. The core cross-section should be approximately 50 square meters. cm. The primary winding is wound with PEV2 wire with a diameter of 1.5 mm and contains 250 turns, the secondary winding is the same as that wound on LATR 2.

At the output of the secondary winding, a diode bridge made of powerful rectifier diodes. Instead of the diodes indicated in the diagram, you can use D122-32-1 diodes or 4 VL200 diodes (electric locomotive). Diodes for cooling must be installed on homemade radiators with an area of ​​at least 30 square meters. cm.

Another important point is the choice of cable for the welding machine. For this welder, it is necessary to use a copper stranded cable in rubber insulation with a cross-section of at least 20 sq. mm. You need two pieces of cable 2 meters long. Each must be tightly crimped with terminal lugs to connect to the welding machine.

Portable USB oscilloscope, 2 channels, 40 MHz....

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