Homemade welding machine from latra. Homemade welding machine-transformer from latra Transformer from latra 9a

The homemade welding machine from LATR 2 It is built on the basis of a nine-ampere LATR 2 (laboratory adjustable autotransformer) and its design provides for welding current adjustment. 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 controlled by a variable resistor R5. Thyristors VS1 and VS2 open each in their own half-cycle alternately for a certain period of time due to the phase-shifting circuit built on the 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 reduced voltage appears on the secondary winding, which makes it easy to 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 mains with an ordinary plug. In the role of the switch SA1, you can use a paired machine for 25A.

Alteration of LATR 2 for a homemade welding machine

First, the protective cover, electrically removable contact and mount are removed from the autotransformer. Next, a good electrical insulation is wound on 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 desirable to choose a copper wire with a cross-sectional area of ​​\u200b\u200babout 20 square meters. mm.

If there is no wire of a suitable cross section, it is possible to make a winding of several wires with a total cross-sectional area of ​​20 sq. mm. The modified LATR2 is mounted in a suitable home-made case with ventilation holes. It is also necessary to install the regulator board, a package switch, as well as terminals for X1, X2 and X3, X4.

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

At the output of the secondary winding, a diode bridge of powerful rectifier diodes is connected. 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 essential point is the choice of cable for the welding machine. For this welder, it is necessary to use a copper multi-core 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 well crimped with terminal lugs for connection to the welding machine.

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

A common material for the manufacture of home-made welding transformers has long been burnt LATRs (laboratory autotransformers). Inside the LATR case there is a toroidal autotransformer made on a magnetic circuit of a significant cross section. It is this magnetic circuit that will be needed from LATR for the manufacture of a welding transformer. A transformer usually requires two identical magnetic rings from large LATRs.

LATRs are produced in different types, with maximum currents from 2 to 10A, not all of them are suitable for the manufacture of transformers for welding, only those whose magnetic core sizes allow you to lay the required number of turns. The most common among them is probably the autotransformer of the LATR-1M type. Depending on the winding wire, it is designed for currents of 6.7-9A, although the dimensions of the autotransformer itself do not change from this. The LATR-1M magnetic circuit has the following dimensions: outer diameter D=127 mm, inner diameter d=70 mm, ring height h=95 mm, section S=27 cm2, weight about 6 kg. A good welding transformer can be made from two rings from LATR-1M, however, due to the small internal volume of the window, you cannot use too thick wires and you will have to save every millimeter of window space. A significant disadvantage of the transformer from LATRs, in comparison with the scheme of the U-shaped transformer, is also that it is impossible to manufacture coils separately from the magnetic circuit. This means that you have to wind, pulling each turn through the window of the magnetic circuit, which of course greatly complicates the manufacturing process.

There are LATRs with more voluminous magnetic rings. They are much better suited for making welding transformers, but are less common. For other autotransformers similar in parameters to LATR-1M, for example, AOSN-8-220, the magnetic core has different dimensions: the outer diameter of the ring is larger, but the height and diameter of the window d = 65 mm are smaller. In this case, the window diameter must be expanded to 70 mm.

The ring of the magnetic core consists of pieces of iron tape wound on top of each other, fastened at the edges by spot welding. In order to increase the inner diameter of the window, it is necessary to disconnect the end of the tape from the inside and unwind its required amount. But don't try to rewind everything at once. It is better to unwind one turn, each time cutting off the excess. Sometimes the windows of larger LATRs are also expanded in this way, although this inevitably reduces the cross-sectional area of ​​the magnetic circuit.

In principle, a cross-sectional area and one ring would suffice for a welding transformer. But the problem is that smaller area magnetic cores inevitably require more turns, which increases coil volume and requires more window space.

Split-arm transformer

At the beginning of the manufacture of the transformer, it is necessary to insulate both rings. In this case, special attention should be paid to the corners of the edges of the rings - they are sharp, they can easily cut the superimposed insulation, and then close the winding wire. It is better to first smooth the corners with a file, and then apply some strong and elastic tape along the length, for example, a dense keeper or a cambric tube cut along. From above, the rings, each separately, are wrapped with a thin layer of fabric insulation.

Next, the isolated rings are connected together. The rings are tightly pulled together with a strong tape, and on the sides they are fixed with wooden pegs, also then tied with a tape - the core of the magnetic circuit for the transformer is ready.

The next step is the most important - laying the primary winding. The windings of this welding transformer are wound according to the scheme: primary in the middle, two sections of the secondary on the side arms.

The primary winding takes about 70-80 m of wire, which will have to be pulled through both windows of the magnetic circuit with each turn. In this case, you can not do without a simple device.

First, the wire is wound on a wooden reel and, in this form, is pulled through the windows of the rings without any problems.

The primary winding wire may have a diameter of 1.6-2.2 mm. For magnetic circuits made up of rings with a window diameter of 70 mm, a wire with a diameter of not more than 2 mm can be used, otherwise there will be little space for the secondary winding. The primary winding contains, as a rule, 180-200 turns at normal mains voltage, which is sufficient for efficient operation of a 3 mm electrode.

A cambric is put on the end of the wire, which is attracted by the HB tape to the beginning of the first layer. The surface of the magnetic circuit has a rounded shape, so the first layers will contain fewer turns than subsequent ones - to level the surface.

The wire lies coil to coil, in no case allowing the wire to overlap the wire. The wire layers must be insulated from each other. Again, to save space, the winding should be placed as compactly as possible. On a magnetic core of medium-sized rings, the interlayer insulation should be used thinner. One should not strive to wind the primary winding quickly. This process is slow, and after laying hard wires, fingers begin to hurt. It is better to do this in 2-3 approaches - after all, quality is more important than speed.

If the primary winding is made, most of the work is done, the secondary remains. But first you need to determine the number of turns of the secondary winding for a given voltage. To get started, turn on the ready-made primary network. The no-load current of this version of the transformer is small - only 70-150 mA, the rumble of the transformer should be barely audible. We wind 10 turns of any wire on one of the side arms and measure the output voltage on them. Each of the side arms accounts for half of the magnetic flux created on the central arm, so here for each turn of the secondary winding there is 0.6-0.7V. Based on the result obtained, the number of turns of the secondary winding is calculated, focusing on a voltage of 50V (about 75-80 turns).

The choice of material for the secondary winding is limited by the remaining space of the windows of the magnetic circuit. Moreover, each turn of a thick wire will have to be pulled along the entire length into a narrow window. The easiest way is to wind the usual stranded wire 16 mm 2 in synthetic insulation - it is soft, flexible, well insulated, it will only heat up slightly during operation. It is possible to make a secondary winding from several strands of copper wire.

Half of the turns of the secondary winding is wound on one shoulder, half on the other. If there are no wires of sufficient length, you can connect them from pieces - it's okay. Having wound the windings on both arms, it is necessary to measure the voltage on each of them, it may differ by 2-3V - the slightly different properties of the magnetic circuits of different LATRs affect, which does not particularly affect the properties of the arc during welding. Then the windings on the shoulders are connected in series, but care must be taken that they are not in antiphase, otherwise the output will be a voltage close to zero (see the article Winding a welding transformer). With a mains voltage of 220-230V, a welding transformer of this design should develop a current of 100-130A in arc mode. Current in case of short circuit of the secondary circuit - up to 180A.

It may turn out that it was not possible to fit all the calculated turns of the secondary winding into the windows, and the output voltage turned out to be lower than desired. The operating current will decrease from this not much. To a greater extent, lowering the open circuit voltage affects the process of arc ignition. The arc ignites easily at voltages close to 50V and above. Although the arc can be ignited without any problems at lower voltages. So if the manufactured transformer has an output of about 40V, then it can be used for work. Another thing is if you come across electrodes designed for high voltages - some brands of electrodes work from 70-80V.

toroidal transformer

On rings from LATRs, it is also possible to make a welding transformer according to a different - toroidal scheme. This also requires two rings, preferably from large LATRs. The rings are connected and insulated: one ring-magnetic circuit with a significant cross-sectional area is obtained.

The primary winding contains the same number of turns as in the previous circuit, but is wound along the entire length of the ring and, as a rule, lies in two layers. The problem of the shortage of the internal space of the magnetic circuit window of such a transformer circuit is even more acute than for the previous design. Therefore, it is necessary to isolate here with as thin layers and materials as possible. It is impossible to use thick winding wires here. Although in some installations LATRs of especially large sizes are used, a toroidal welding transformer can be made on only one ring of this type.

An advantageous difference between a toroidal circuit for a welding transformer is a higher efficiency. Each turn of the secondary winding will now have more than one volt of voltage, therefore, the "secondary" will have fewer turns, and the output power will be higher than in the previous circuit. However, the length of the turn on the toroidal magnetic circuit will be longer, and it is unlikely that it will be possible to save on the wire here. The disadvantages of this scheme include: the complexity of winding, the limited volume of the window, the impossibility of using a wire of large cross section, as well as the high intensity of heating. If in the previous version all the windings were separate and at least partially had contact with air, now the primary winding is completely under the secondary, and their heating is mutually enhanced.

It is difficult to use hard wires for the secondary winding. It is easier to wind it with soft stranded or multi-core wire. If you correctly select all the wires and carefully lay them, then the required number of turns of the secondary winding will fit into the space of the magnetic circuit window and the desired voltage will be obtained at the output of the transformer.

Sometimes a toroidal welding transformer is made from several rings of LATRs in a different way, they are not put on top of each other, but the iron strips of the tape are rewound from one to the other. To do this, first, the inner turns of the strips are selected from one ring in order to expand the window. The rings of other LATRs are completely unfolded into strips of tape, which are then wound as tightly as possible on the outer diameter of the first ring. After that, the assembled single magnetic core is wrapped very tightly with insulating tape. Thus, a ring-magnetic circuit is obtained with a more voluminous internal space than all the previous ones. In this it will be possible to accommodate a wire of considerable cross section. The required number of turns is calculated from the cross-sectional area of ​​the assembled ring.

The disadvantages of this design include the complexity of the manufacture of the magnetic circuit. Moreover, no matter how hard you try, you still won’t be able to manually wind the iron strips on top of each other as tightly as before. As a result, the magnetic circuit turns out to be flimsy. When working in the welding mode, the iron in it vibrates strongly, emitting a powerful hum.

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Nowadays it is difficult to imagine any work with metal without the use of a welding machine. With this device, you can easily connect or cut iron of various thicknesses and dimensions. Naturally, to perform high-quality work, you will need certain skills in this matter, but first of all, you need the welder himself. Nowadays, you can naturally buy it, as in principle, 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 of various models, reliable ones are quite expensive, and cheap ones do not shine with quality and durability. But even if you decide to buy a welder in a store, familiarity with this article will help you choose the necessary device, since you will know the basics of their circuitry. There are several types of welders: DC, AC, three-phase and inverter. In order to determine which option you need, consider the design and device of the first two types, which can be assembled without specific skills with your own hands at home.

On alternating current

This type of welding machine is one of the most common options, both in industry and in private households. It is easy to operate, compared to the rest it is quite easy to make at home, which confirms the photo below. To do this, you need to have a wire for the primary and secondary windings, as well as a core of transformer steel for winding the welder. In simple terms, an AC welding machine is a high power step-down transformer.

The optimal voltage during operation of a welding machine assembled at home is 60V. Optimum current 120-160A. Now it is easy to calculate what 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 one is 7 sq. mm, because it is necessary to take into account the possible additional load, as well as the necessary margin of safety. We get that the optimal diameter of the copper core for the primary winding of the step-down transformer should be 3 mm. If you decide to take an aluminum wire in order to make a 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 in a rag braid; conductors in PVC insulation cannot be used - when the wires are heated, it will melt and occur. If you do not have a wire of the required diameter, then you can use thinner cores by winding them in parallel. But then it should be borne in mind that the thickness of the winding will increase, and, accordingly, the dimensions of the apparatus 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 chosen based on the current in the secondary winding (recall that we focus on 120 - 160A) and the length of the wires.

The first step is to make the transformer core of a homemade welding machine. The best option would be a rod-type core as shown in Figure 1:

This core must be made from transformer steel plates. The thickness of the plates should be 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 size of the window is calculated. Those. dimensions c and d in figure 1 must be chosen to accommodate all the windings of the transformer.
• Secondly, the roll area, which is calculated by the formula: Sroll \u003d a * b, must be at least 35 square meters. see If there is more Sk, then the transformer will heat up less and, accordingly, work longer, and you will not need to be interrupted often in order for it to cool down. It is better that the screen is equal to 50 square meters. cm.

Next, we proceed to the assembly of the plates of a home-made welding machine. It is necessary to take the L-shaped plates and fold them, as shown in Figure 2, until you can make the core of the required thickness. Then we fasten it with bolts in the corners. At the end, it is necessary to process the surface of the plates with a file and insulate them by wrapping them with rag insulation in order to additionally protect the transformer from breakdown to the housing.

Next, we proceed to winding the welding machine from a step-down transformer. At the beginning, 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 on top of the transformer. We fix the ends of the windings on it using a bolted connection, marking 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 adjust the current strength during welding by switching between different outputs of your welding device. This is a very important function, and the more branches you make, the more accurate your adjustment will be.

After we start 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 made approximately 60% to 40%. This contributes to the fact that after you catch the arc and start welding, 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. Thus, the arc will be easy to catch, but too much current will not interfere with high-quality cooking. We also fix the ends of the winding with bolts on 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 heat. For better cooling, it is highly desirable to install a fan for blowing, for example, from a refrigerator or microwave.

Now your homemade welding machine is ready. Having connected the holder and the mass to the secondary winding, it is necessary to connect the network to the common wire and the wire extending from the 215th turn of the primary winding. If you need to increase the current, then you can make fewer turns of the primary winding by switching the second wire to a contact with fewer turns. You can reduce the current with the help of a resistance made of a piece of transformer steel bent in the form of a spring connected to the holder. It is always necessary to ensure that the welding machine does not overheat, for 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 will be able to assemble the device on their own.

DC

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

Capacitors C1 and C2 will help us equalize the current with the following characteristics: capacitance 15,000 microfarads and voltage 50V. Next, we assemble the circuit, which is indicated in the drawing below. Choke L1 is needed to regulate the current. Contacts x4 - plus for connecting the holder, and x5 - minus for supplying current to the part to be welded.

Three-phase welding machines are used for welding in production conditions, they are equipped with two-electrode holders, so we will not consider them in this article, and inverters are made on the basis of printed circuit boards and complex circuits with a large number of expensive radio components and a complex tuning 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 that you watch the video tutorials provided below, which will clearly show how to assemble a simple welder from improvised materials yourself, and also explain to you some 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:

1.1. General information.

Depending on the type of current used for welding, there are DC and AC welding machines. Welding machines using low direct currents are used for welding sheet metal, in particular, roofing and automotive steel. The welding arc in this case is more stable and, at the same time, welding can occur both on direct and reverse polarity of the supplied DC voltage.

At direct current, you can cook with electrode wire without coating and electrodes that are designed for welding metals at direct or alternating current. To give the arc burning at low currents, it is desirable to have an increased open-circuit voltage U xx up to 70 ...

Fig.1 Schematic diagram of the bridge rectifier of the welding machine, indicating the polarity when welding thin sheet metal

To smooth out voltage ripples, one of the CA leads is connected to the electrode holder through a T-shaped filter, consisting of a choke L1 and a capacitor C1. Inductor L1 is a coil of 50 ... 70 turns of a copper bus with a tap from the middle with a cross section of S = 50 mm 2 wound on a core, for example, from an OSO-12 step-down transformer, or more powerful. The larger the iron section of the smoothing inductor, the less likely it is that its magnetic system will enter saturation. When the magnetic system enters saturation at high currents (for example, when cutting), the inductance of the inductor decreases abruptly and, accordingly, current smoothing will not occur. The arc will then burn unsteadily. Capacitor C1 is a battery of capacitors such as MBM, MBG or the like with a capacity of 350-400 microfarads for a voltage of at least 200 V

Characteristics of powerful diodes and their imported counterparts can be. Or by clicking on the link you can download a guide to diodes from the series "Helping a radio amateur No. 110"

For rectification and smooth regulation of the welding current, circuits based on powerful controlled thyristors are used, which allow you to change the voltage from 0.1 xx to 0.9U xx. In addition to welding, these regulators can be used to charge batteries, power electric heating elements and other purposes.

In AC welding machines, electrodes with a diameter of more than 2 mm are used, which makes it possible to weld products with a thickness of more than 1.5 mm. During welding, the current reaches tens of amperes and the arc burns quite steadily. In such welding machines, special electrodes are used, which are intended only for welding on alternating current.

For the normal operation of the welding machine, a number of conditions must be met. The output voltage must be sufficient for reliable ignition of the arc. For an amateur welding machine U xx \u003d 60 ... 65V. For the safety of work, a higher no-load output voltage is not recommended; for industrial welding machines, for comparison, U xx can be 70..75 V..

Welding voltage value I St. must ensure stable arc burning, depending on the diameter of the electrode. The value of the welding voltage U sv can be 18 ... 24 V.

The rated welding current must be:

I St \u003d KK 1 * d e, where

I St- the value of the welding current, A;

K1 =30...40- coefficient depending on the type and size of the electrode d e, mm.

The short circuit current must not exceed the rated welding current by more than 30...35%.

It has been noted that stable arcing is possible if the welding machine has a falling external characteristic, which determines the relationship between current and voltage in the welding circuit. (fig.2)

Fig.2 Falling external characteristic of the welding machine:

At home, as practice shows, it is quite difficult to assemble a universal welding machine for currents of 15 ... 20 to 150 ... 180 A. In this regard, when designing a welding machine, one should not strive to completely cover the range of welding currents. It is advisable at the first stage to assemble a welding machine for working with electrodes with a diameter of 2 ... 4 mm, and at the second stage, if it is necessary to work at low welding currents, supplement it with a separate rectifier device with smooth regulation of the welding current.

An analysis of the designs of amateur welding machines at home allows us to formulate a number of requirements that must be met in their manufacture:

• Small dimensions and weight
• Mains supply 220 V
• The duration of work should be at least 5 ... 7 electrodes d e \u003d 3 ... 4 mm

The weight and dimensions of the device directly depend on the power of the device and can be reduced by reducing its power. The duration of the welding machine depends on the material of the core and the heat resistance of the insulation of the winding wires. To increase the welding time, it is necessary to use steel with high magnetic permeability for the core.

1. 2. Choice of core type.

For the manufacture of welding machines, mainly rod-type magnetic cores are used, since they are more technologically advanced in design. The core of the welding machine can be assembled from plates of electrical steel of any configuration with a thickness of 0.35 ... 0.55 mm and pulled together with studs isolated from the core (Fig. 3).

Fig.3 Rod-type magnetic circuit:

When selecting the core, it is necessary to take into account the dimensions of the "window" in order to fit the windings of the welding machine, and the area of ​​\u200b\u200bthe transverse core (yoke) S=a*b, cm 2 .

As practice shows, the minimum values ​​S=25..35 cm 2 should not be chosen, since the welding machine will not have the required power reserve and it will be difficult to obtain high-quality welding. And hence, as a consequence, the possibility of overheating of the device after a short operation. To avoid this, the cross section of the core of the welding machine should be S = 45..55 cm 2. Although the welding machine will be somewhat heavier, it will work reliably!

It should be noted that amateur welding machines on toroidal type cores have electrical characteristics 4 ... 5 times higher than those of a rod type, and hence small electrical losses. It is more difficult to manufacture a welding machine using a toroidal type core than with a rod type core. This is mainly due to the placement of the windings on the torus and the complexity of the winding itself. However, with the right approach, they give good results. The cores are made from strip transformer iron rolled into a roll in the shape of a torus.

Rice. 4 Toroidal type magnetic core:

To increase the inner diameter of the torus ("window"), a part of the steel tape is unwound from the inside and wound on the outer side of the core (Fig. 4). After rewinding the torus, the effective cross section of the magnetic circuit will decrease, therefore, it will be necessary to partially wind the torus with iron from another autotransformer until the cross section S is at least 55 cm 2.

The electromagnetic parameters of such iron are most often unknown, so they can be determined experimentally with sufficient accuracy.

1. 3. Choice of winding wire.

For the primary (network) windings of the welding machine, it is better to use a special heat-resistant copper winding wire in cotton or fiberglass insulation. Satisfactory heat resistance is also possessed by wires in rubber or rubber-fabric insulation. It is not recommended to use wires in polyvinyl chloride (PVC) insulation for operation at elevated temperatures due to its possible melting, leakage from the windings and short circuit of the turns. Therefore, PVC insulation from the wires must either be removed and wrapped around the wires along the entire length with cotton insulating tape, or not removed at all, but wrapped over the wire over the insulation.

When selecting the section of the winding wires, taking into account the periodic operation of the welding machine, a current density of 5 A/mm2 is allowed. The power of the secondary winding can be calculated by the formula P 2 \u003d I sv * U sv. If welding is carried out with an electrode de = 4 mm, at a current of 130 ... 160 A, then the power of the secondary winding will be: P 2 \u003d 160 * 24 \u003d 3.5 ... 4 kW, and the power of the primary winding, taking into account losses, will be about 5...5.5 kW. Based on this, the maximum current in the primary winding can reach 25 A. Therefore, the cross-sectional area of ​​the wire of the primary winding S 1 must be at least 5..6 mm 2.

In practice, it is desirable to take a slightly larger cross-sectional area of ​​\u200b\u200bthe wire, 6 ... 7 mm 2. For winding, a rectangular bus or a copper winding wire with a diameter of 2.6 ... 3 mm is taken, excluding insulation. The cross-sectional area S of the winding wire in mm2 is calculated by the formula: S \u003d (3.14 * D 2) / 4 or S \u003d 3.14 * R 2; D is the bare copper wire diameter, measured in mm. In the absence of a wire of the required diameter, the winding can be carried out in two wires of a suitable section. When using aluminum wire, its cross section must be increased by 1.6..1.7 times.

The number of turns of the primary winding W1 is determined from the formula:

W 1 \u003d (k 2 * S) / U 1, where

k 2 - constant coefficient;

S- cross-sectional area of ​​\u200b\u200bthe yoke in cm 2

You can simplify the calculation by using a special program for the calculation Welding Calculator

With W1 = 240 turns, taps are made from 165, 190 and 215 turns, i.e. every 25 turns. More taps of the network winding, as practice shows, is not practical.

This is due to the fact that by reducing the number of turns of the primary winding, both the power of the welding machine and U xx increase, which leads to an increase in the arcing voltage and a deterioration in the quality of welding. By changing only the number of turns of the primary winding, it is not possible to achieve overlapping of the range of welding currents without deteriorating the quality of welding. In this case, it is necessary to provide for switching turns of the secondary (welding) winding W 2 .

The secondary winding W 2 must contain 65 ... 70 turns of an insulated copper bus with a cross section of at least 25 mm2 (preferably a cross section of 35 mm2). A flexible stranded wire, such as a welding wire, and a three-phase power stranded cable are also suitable for winding the secondary winding. The main thing is that the cross section of the power winding is not less than required, and the wire insulation is heat-resistant and reliable. If the wire section is insufficient, winding in two or even three wires is possible. When using aluminum wire, its cross section must be increased by 1.6 ... 1.7 times. The welding winding leads are usually led through copper lugs under terminal bolts with a diameter of 8 ... 10 mm (Fig. 5).

1.4. Features of winding windings.

There are the following rules for winding the windings of the welding machine:

• Winding must be carried out on an insulated yoke and always in the same direction (for example, clockwise).
• Each winding layer is insulated with a layer of cotton insulation (fiberglass, electric cardboard, tracing paper), preferably impregnated with bakelite varnish.
• The winding leads are tinned, marked, fixed with cotton tape, and cotton cambric is additionally put on the network winding leads.
• With poor-quality wire insulation, winding can be done in two wires, one of which is a cotton cord or cotton thread for fishing. After winding one layer, the winding with cotton thread is fixed with glue (or varnish) and only after it has dried, the next row is wound.

The network winding on a rod-type magnetic circuit can be arranged in two main ways. The first method allows you to get a more "hard" welding mode. The network winding in this case consists of two identical windings W1, W2, located on different sides of the core, connected in series and having the same wire cross section. To adjust the output current, taps are made on each of the windings, which are closed in pairs ( Rice. 6 a, b)

Rice. 6. Ways of winding CA windings on a core of a rod type:

The second method of winding the primary (network) winding is winding the wire on one side of the core ( rice. 6 c, d). In this case, the welding machine has a steeply falling characteristic, welds "softly", the arc length has less effect on the magnitude of the welding current, and therefore on the quality of welding.

After winding the primary winding of the welding machine, it is necessary to check for the presence of short-circuited turns and the correctness of the selected number of turns. The welding transformer is connected to the network through a fuse (4 ... 6 A) and if there is an alternating current ammeter. If the fuse burns out or gets very hot, this is a clear sign of a shorted coil. In this case, the primary winding must be rewound, paying special attention to the quality of the insulation.

If the welding machine is very buzzing, and the current consumption exceeds 2 ... 3 A, then this means that the number of turns of the primary winding is underestimated and it is necessary to rewind a certain number of turns. A working welding machine should consume no more than 1..1.5 A at idle, not get warm and not buzz strongly.

The secondary winding of the welding machine is always wound on two sides of the core. According to the first method of winding, the secondary winding consists of two identical halves, connected in anti-parallel to increase the stability of the arc (Fig. 6 b). In this case, the wire cross section can be taken somewhat less, that is, 15..20 mm 2. When winding the secondary winding according to the second method, at first 60 ... 65% of the total number of its turns is wound on the side of the core free from windings.

This winding is used mainly to start the arc, and during welding, due to a sharp increase in the dispersion of the magnetic flux, the voltage across it drops by 80 ... 90%. The remaining number of turns of the secondary winding in the form of an additional welding winding W 2 is wound over the primary. Being power, it maintains the welding voltage within the required limits, and, consequently, the welding current. The voltage on it drops in the welding mode by 20 ... 25% relative to the open circuit voltage.

The winding of the windings of the welding machine on a toroidal type core can also be done in several ways ( Rice. 7).

Ways of winding the windings of the welding machine on a toroidal core.

Switching windings in welding machines is easier to do with copper lugs and terminals. Copper tips at home can be made from copper tubes of a suitable diameter 25 ... 30 mm long, fixing the wires in them by crimping or soldering. When welding in various conditions (strong or low-current network, long or short supply cable, its cross section, etc.), by switching the windings, the welding machine is set to the optimal welding mode, and then the switch can be set to the neutral position.

1.5. Setting up the welding machine.

Having made a welding machine, a home electrician must set it up and check the quality of welding with electrodes of various diameters. The setup process is as follows. To measure the welding current and voltage, you need: an AC voltmeter for 70 ... 80 V and an AC ammeter for 180 ... 200 A. The connection diagram of the measuring instruments is shown in ( Rice. eight)

Rice. eight Schematic diagram of connecting measuring instruments when setting up a welding machine

When welding with different electrodes, the values ​​of the welding current - I sv and the welding voltage U sv are taken, which should be within the required limits. If the welding current is small, which happens most often (the electrode sticks, the arc is unstable), then in this case, by switching the primary and secondary windings, the required values ​​\u200b\u200bare set, or the number of turns of the secondary winding is redistributed (without increasing them) in the direction of increasing the number of turns wound over the network windings.

After welding, it is necessary to control the quality of welding: the depth of penetration and the thickness of the deposited metal layer. For this purpose, the edges of the products to be welded are broken or sawn. According to the measurement results, it is desirable to compile a table. Analyzing the data obtained, the optimal welding modes are selected for electrodes of various diameters, remembering that when welding with electrodes, for example, with a diameter of 3 mm, electrodes with a diameter of 2 mm can be cut, because cutting current is 30...25% more than welding current.

The connection of the welding machine to the network should be made with a wire with a cross section of 6 ... 7 mm through an automatic machine for a current of 25 ... 50 A, for example, AP-50.

The electrode diameter, depending on the thickness of the metal to be welded, can be selected based on the following relationship: de=(1...1.5)*V, where B is the thickness of the metal to be welded, mm. The length of the arc is selected depending on the diameter of the electrode and is on average equal to (0.5...1.1)de. It is recommended to perform welding with a short arc of 2...3 mm, the voltage of which is 18...24 V. An increase in the length of the arc leads to a violation of the stability of its combustion, an increase in waste losses and spatter, and a decrease in the depth of penetration of the base metal. The longer the arc, the higher the welding voltage. The welding speed is chosen by the welder depending on the grade and thickness of the metal.

When welding in direct polarity, the plus (anode) is connected to the workpiece and the minus (cathode) to the electrode. If it is necessary that less heat is generated on the parts, for example, when welding thin-sheet structures, then reverse polarity welding is used. In this case, the minus (cathode) is attached to the workpiece to be welded, and the plus (anode) is attached to the electrode. This not only ensures less heating of the welded part, but also accelerates the process of melting the electrode metal due to the higher temperature of the anode zone and the greater heat supply.

Welding wires are connected to the welding machine through copper lugs under the terminal bolts on the outside of the body of the welding machine. Bad contact connections reduce the power characteristics of the welding machine, worsen the quality of welding and can cause them to overheat and even ignite the wires.

With a short length of welding wires (4..6 m), their cross-sectional area must be at least 25 mm 2.

During welding, fire safety rules must be observed, and when setting up the device and electrical safety - during measurements with electrical appliances. Welding must be carried out in a special mask with protective glass grade C5 (for currents up to 150 ... 160 A) and gloves. All switching in the welding machine must be done only after disconnecting the welding machine from the mains.

2. Portable welding machine based on "Latra".

2.1. Design feature.

The welding machine is powered by a 220 V AC mains. Rice. nine).

For the magnetic circuit of the transformer, tape transformer iron is used, rolled into a roll in the shape of a torus. As you know, in traditional designs of transformers, the magnetic circuit is recruited from W-shaped plates. The electrical characteristics of the welding machine, due to the use of a torus-shaped transformer core, are 5 times higher than those of machines with W-shaped plates, and the losses are minimal.

2.2. Improvements "Latra".

For the transformer core, you can use ready-made "LATR" type M2.

Note. All latras have a six-pin block and voltage: at the input 0-127-220, and at the output 0-150 - 250. There are two types: large and small, and are called LATR 1M and 2M. Which one I don't remember. But, for welding, it is precisely a large LATR with rewound iron that is needed, or, if they are serviceable, then the secondary windings are wound with a bus and after that the primary windings are connected in parallel, and the secondary windings are connected in series. In this case, it is necessary to take into account the coincidence of the directions of currents in the secondary winding. Then it turns out something similar to a welding machine, although it cooks, like all toroidal ones, a little harsh.

You can use a magnetic circuit in the form of a torus from a burned-out laboratory transformer. In the latter case, the fence and fittings are first removed from the Latra and the burnt winding is removed. If necessary, the cleaned magnetic core is rewound (see above), insulated with electric cardboard or two layers of varnished cloth, and the transformer windings are wound. The welding transformer has only two windings. For winding the primary winding, a piece of PEV-2 wire 170 m long and 1.2 mm in diameter is used ( Rice. ten)

Rice. ten Winding of the windings of the welding machine:

1 - primary winding;	3 - wire coil;
2 - secondary winding;	4 - yoke

For the convenience of winding, the wire is pre-wound on a shuttle in the form of a wooden lath 50x50 mm with slots. However, for greater convenience, you can make a simple device for winding toroidal power transformers

Having wound the primary winding, it is covered with a layer of insulation, and then the secondary winding of the transformer is wound. The secondary winding contains 45 turns and is wound with copper wire in cotton or vitreous insulation. Inside the core, the wire is coil to coil, and outside - with a small gap, which is necessary for better cooling. A welding machine manufactured according to the above method is capable of delivering a current of 80 ... 185 A. The circuit diagram of the welding machine is shown on rice. eleven.

Rice. eleven Schematic diagram of the welding machine.

The work will be somewhat simplified if it is possible to purchase a working "Latr" for 9 A. Then they remove the fence, the current-collecting slider and the mounting fittings from it. Next, the terminals of the primary winding for 220 V are determined and marked, and the remaining terminals are securely isolated and temporarily pressed against the magnetic circuit so that they are not damaged when winding a new (secondary) winding. The new winding contains the same number of turns of the same brand and the same wire diameter as in the variant considered above. The transformer in this case gives a current of 70 ... 150 A.
The manufactured transformer is placed on an insulated platform in the old casing, having previously drilled ventilation holes in it (Fig. 12))

Rice. 12 Variants of the casing of the welding machine based on "LATRA".

The outputs of the primary winding are connected to the 220 V network with a SHRPS or VRP cable, while an AP-25 disconnecting machine should be installed in this circuit. Each output of the secondary winding is connected to a flexible insulated wire PRG. The free end of one of these wires is attached to the electrode holder, and the free end of the other is attached to the workpiece. The same end of the wire must be grounded for the safety of the welder. The adjustment of the current of the welding machine is carried out by connecting in series to the wire circuit of the electrode holder pieces of nichrome or constantan wire d = 3 mm and 5 m long, rolled up with a “snake”. "Snake" is attached to a sheet of asbestos. All connections of wires and ballast are made with M10 bolts. Moving along the "snake" the point of attachment of the wire, set the required current. The current can be adjusted using electrodes of various diameters. For welding with such a device, electrodes of the type E-5RAUONII-13 / 55-2.0-UD1 dd \u003d 1 ... 3 mm are used.

When carrying out welding work, to prevent burns, it is necessary to use a fiber protective shield equipped with a light filter E-1, E-2. Headgear, overalls and gloves are obligatory. The welding machine should be protected from moisture and not allowed to overheat. Approximate modes of operation with an electrode d = 3 mm: for transformers with a current of 80 ... 185 A - 10 electrodes, and with a current of 70 ... 150 A - 3 electrodes. after using the specified number of electrodes, the device is disconnected from the mains for at least 5 minutes (and preferably about 20).

3. Welding machine from a three-phase transformer.

The welding machine, in the absence of "LATRA", can also be made on the basis of a three-phase step-down transformer 380/36 V, with a power of 1..2 kW, which is designed to power low-voltage power tools or lighting (Fig. 13).

Rice. thirteen General view of the welding machine and its core.

Even an instance with one blown winding is suitable here. Such a welding machine operates from an alternating current network with a voltage of 220 V or 380 V and with electrodes up to 4 mm in diameter allows welding metal with a thickness of 1 ... 20 mm.

3.1. Details.

Terminals for the conclusions of the secondary winding can be made from a copper tube d 10 ... 12 mm and a length of 30 ... 40 mm (Fig. 14).

Rice. fourteen The design of the terminal of the secondary winding of the welding machine.

On the one hand, it should be riveted and a hole d 10 mm drilled in the resulting plate. Carefully stripped wires are inserted into the terminal tube and crimped with light hammer blows. To improve contact on the surface of the terminal tube, notches can be made with a core. On the panel located at the top of the transformer, the standard screws with M6 nuts are replaced with two screws with M10 nuts. It is desirable to use copper screws and nuts for new screws and nuts. They are connected to the terminals of the secondary winding.

For the conclusions of the primary winding, an additional board is made of sheet textolite 3 mm thick ( fig.15).

Rice. fifteen General view of the scarf for the conclusions of the primary winding of the welding machine.

10 ... 11 holes d = 6mm are drilled in the board and M6 screws with two nuts and washers are inserted into them. After that, the board is attached to the top of the transformer.

Rice. sixteen Schematic diagram of the connection of the primary windings of the transformer for voltage: a) 220 V; b) 380 V (secondary winding not specified)

When the apparatus is powered from a 220 V network, its two extreme primary windings are connected in parallel, and the middle winding is connected to them in series ( fig.16).

4. Electrode holder.

4.1. Holder for electrodes made of d¾" pipe.

The simplest is the design of the electric holder, made of a pipe d¾ "and 250 mm long ( fig.17).

On both sides of the pipe at a distance of 40 and 30 mm from its ends, cuts are cut with a hacksaw to a depth of half the diameter of the pipe ( fig.18)

Rice. eighteen Drawing of the body of the holder of the electrodes from the pipe d¾"

A piece of steel wire d = 6 mm is welded to the pipe above a large recess. On the opposite side of the holder, a hole d = 8.2 mm is drilled, into which an M8 screw is inserted. A terminal is attached to the screw from the cable going to the welding machine, which is clamped with a nut. A piece of rubber or nylon hose with a suitable inner diameter is put on top of the pipe.

4.2. The holder of electrodes from steel corners.

A convenient and easy-to-design electrode holder can be made from two steel corners 25x25x4 mm ( rice. nineteen)

They take two such corners about 270 mm long and connect them with small corners and bolts with M4 nuts. The result is a box with a section of 25x29 mm. In the resulting case, a window for the latch is cut out and a hole is drilled for installing the axis of the latch and electrodes. The latch consists of a lever and a small key made of 4 mm thick steel sheet. This part can also be made from a corner of 25x25x4 mm. To ensure reliable contact of the latch with the electrode, a spring is put on the latch axis, and the lever is connected to the body with a contact wire.

The handle of the resulting holder is covered with an insulating material, which is used as a piece of rubber hose. The electric cable from the welding machine is connected to the housing terminal and fixed with a bolt.

5. Electronic current regulator for welding transformer.

An important design feature of any welding machine is the ability to adjust the operating current. there are such ways of adjusting the current in welding transformers: shunting with the help of various types of chokes, changing the magnetic flux due to the mobility of the windings or magnetic shunting, the use of stores of active ballast resistances and rheostats. All of these methods have both their advantages and disadvantages. For example, the disadvantage of the latter method is the complexity of the design, the bulkiness of the resistances, their strong heating during operation, and inconvenience when switching.

The most optimal method is the stepwise adjustment of the current, by changing the number of turns, for example, by connecting to the taps made when winding the secondary winding of the transformer. However, this method does not allow wide adjustment of the current, so it is usually used to adjust the current. Among other things, adjusting the current in the secondary circuit of the welding transformer is associated with certain problems. In this case, significant currents pass through the control device, which is the reason for the increase in its dimensions. For the secondary circuit, it is practically impossible to find powerful standard switches that would withstand currents up to 260 A.

If we compare the currents in the primary and secondary windings, it turns out that the current in the circuit of the primary winding is five times less than in the secondary winding. This suggests the idea of ​​placing the welding current regulator in the primary winding of the transformer, using thyristors for this purpose. On fig. 20 shows a diagram of the thyristor welding current controller. With the utmost simplicity and availability of the element base, this regulator is easy to manage and does not require configuration.

Power regulation occurs when the primary winding of the welding transformer is periodically switched off for a fixed period of time at each half-cycle of current. In this case, the average value of the current decreases. The main elements of the regulator (thyristors) are connected opposite and parallel to each other. They are alternately opened by current pulses generated by transistors VT1, VT2.

When the regulator is connected to the network, both thyristors are closed, capacitors C1 and C2 begin to charge through the variable resistor R7. As soon as the voltage on one of the capacitors reaches the avalanche breakdown voltage of the transistor, the latter opens, and the discharge current of the capacitor connected to it flows through it. Following the transistor, the corresponding thyristor opens, which connects the load to the network.

By changing the resistance of the resistor R7, you can control the moment the thyristors are turned on from the beginning to the end of the half-cycle, which in turn leads to a change in the total current in the primary winding of the welding transformer T1. To increase or decrease the adjustment range, you can change the resistance of the variable resistor R7 up or down, respectively.

Transistors VT1, VT2, operating in avalanche mode, and resistors R5, R6 included in their base circuits, can be replaced with dinistors (Fig. 21)

Rice. 21 Schematic diagram of replacing a transistor with a resistor with a dinistor, in the current regulator circuit of a welding transformer.

the anodes of the dinistors should be connected to the extreme terminals of the resistor R7, and the cathodes should be connected to the resistors R3 and R4. If the regulator is assembled on dinistors, then it is better to use devices such as KN102A.

As VT1, VT2, old-style transistors such as P416, GT308 have proven themselves well, however, these transistors, if desired, can be replaced with modern low-power high-frequency transistors with similar parameters. Variable resistor type SP-2, and fixed resistors type MLT. Capacitors of the MBM or K73-17 type for an operating voltage of at least 400 V.

All parts of the device are assembled on a textolite plate with a thickness of 1 ... 1.5 mm using surface mounting. The device has a galvanic connection with the network, so all elements, including thyristor heat sinks, must be isolated from the case.

A properly assembled welding current regulator does not require special adjustment, you just need to make sure that the transistors are stable in avalanche mode or, when using dinistors, that they are turned on.

A description of other designs can be found on the site http://irls.narod.ru/sv.htm, but I want to warn you right away that many of them have at least controversial points.

Also on this topic you can see:

http://valvolodin.narod.ru/index.html - many GOSTs, diagrams of both home-made devices and factory ones

http://www.y-u-r.narod.ru/Svark/svark.htm the same website of a welding enthusiast

When writing the article, some of the materials from the book by Pestrikov V. M. "Home electrician and not only ..." were used.

All the best, write to © 2005

The welding machine is powered by 220 V and has high electrical characteristics. Thanks to the use of a new form of magnetic core, the weight of the device is only 9 kg with overall dimensions of 125x150 mm. This is achieved by the use of torus-shaped ribbon transformer iron, instead of the traditional W-shaped plate pack.

The electrical characteristics of a transformer on a torus-magnetic circuit are approximately 5 times higher than those of an Ш-shaped one, and the electrical losses are minimal.

To get rid of the search for scarce transformer iron, you can buy a ready-made "Latr" for 9 A in the store or use a torus magnetic circuit from a burned-out laboratory transformer. To do this, remove the fence, fittings and remove the burnt winding. The released magnetic circuit must be isolated from future winding layers with electric cardboard or two layers of varnished cloth.

The welding transformer has two independent windings. In the primary, a PEV-2 wire with a diameter of 1.2 mm and a length of 170 m was used. For convenience, you can use a shuttle (a wooden lath 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.

The secondary winding - copper wire in cotton or vitreous insulation - has 45 turns over the primary. Inside the wire have a turn to turn, and from the outside; with a small gap - for uniform arrangement and better cooling.

Fig.1. Welding machine-baby.

Fig.2. Welding machine transformer: 1 - primary winding, 2 - secondary winding, 3 - wire coil, 4 - yoke.

Fig.3. Electric circuit of the welding machine.

It is more convenient to do the work together: one carefully, without touching the adjacent turns, so as not to damage the insulation, pulls and lays the wire, and the assistant holds the free end, preventing it from twisting. A welding transformer made in this way will give a current of 80-185 A.

If you purchased a "Latr" for 9 A and upon examination it turned out that its winding was intact, then the matter is greatly simplified. Using the finished winding as the primary one, it is possible to assemble a welding transformer in 1 hour, giving a current of 70-150 A. To do this, it is necessary to remove the fence, current-collecting slider and mounting hardware.

Then identify and mark the leads for 220 V, and securely insulate the remaining ends, temporarily press them against the magnetic circuit so as not to damage them during operation with the secondary winding. The installation of the latter is carried out in the same way as in the previous version, while using a copper wire of the same cross section and length.

The assembled transformer is placed on an insulated platform in the former casing, having previously drilled ventilation holes in it. The wires of the primary winding are connected to the 220 V network with a SHRPS or VRP cable; in the circuit, it is necessary to provide an AP-25 disconnecting machine.

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

Current regulation is provided by the inclusion in series of the ballast electrode holder wire circuit - nichrome or constantan wire with a diameter of 3 mm and a length of 5 m, folded with a "snake", which is attached to an asbestos-cement sheet. All wire and ballast connections are made with M10 bolts.

Using the selection method, moving the point of attachment of the wire along the "snake", set the required current. It is possible to adjust the current using electrodes of different diameters. Electrodes of the type E-5RA UONII-13/55 - 2.0-UD1 with a diameter of 1-3 mm are used for welding.

All necessary materials for the welding transformer can be purchased from the distribution network. And for a person familiar with electrical engineering, making such an apparatus is not difficult.

When working, in order to avoid burns, it is necessary to use a fiber protective shield equipped with a light filter E-1, E-2. Headgear, overalls and gloves are also required. The welding machine should be protected from moisture and not allowed to overheat.

Approximate mode of operation with an electrode with a diameter of 3 mm: for a transformer with a current of 80-185 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.

B. SOKOLOV, engineer, winner of TsV NTTM-87. Model designer 1987 No. 11.