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, to perform high-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 hire a welder, but in this article we will talk about how to make welding machine with your own hands. Moreover, with all the wealth of different 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 current, 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 An AC welding machine 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 find that the optimal diameter of the copper core for the primary winding of a 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. We fix the ends of the windings on it using a bolted connection, noting that the first bolt is a common wire, the second is a branch from 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 conclusions 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 the 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. This tool can be used to weld 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 complex process settings 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:

Operating modes are set using a potentiometer. Together with capacitors C2 and C3, it forms phase-shifting chains, each of which, when triggered during its half-cycle, opens the corresponding thyristor for a certain period of time. As a result, an adjustable 20-215 V appears on the primary winding of the welding T1. Transforming in the secondary winding, the required -Usv make it easy to ignite the arc for welding on alternating (terminals X2, X3) or rectified (X4, X5) current.

Fig.1. Homemade welding machine based on LATR.

Welding transformer based on the widely used LATR2 (a), its connection to the circuit diagram of a homemade adjustable welding machine for alternating or direct current (b) and a voltage diagram explaining the operation transistor regulator arc combustion mode.

Resistors R2 and R3 bypass the control circuits of thyristors VS1 and VS2. Capacitors C1, C2 are reduced to permissible level radio interference accompanying an arc discharge. A neon light bulb with a current-limiting resistor R1 is used as a light indicator HL1, signaling that the device is connected to the household power supply.

To connect the “welder” to the apartment electrical wiring, a regular X1 plug is used. But it is better to use a more powerful electrical connector, which is commonly called a “Euro plug-Euro socket”. And as a switch SB1, a “packet” VP25, designed for a current of 25 A and allowing you to open both wires at once, is suitable.

As practice shows, it makes no sense to install any kind of fuses (anti-overload circuit breakers) on the welding machine. Here you have to deal with such currents, if exceeded, the protection at the network input to the apartment will definitely work.

To manufacture the secondary winding, the casing-guard, current-collecting slider and mounting hardware are removed from the base LATR2. Then, a 250 V winding is applied to the existing winding (the 127 and 220 V taps remain unclaimed) reliable insulation(for example, made of varnished fabric), on top of which a secondary (step-down) winding is placed. And this is 70 turns of an insulated copper or aluminum busbar with a diameter of 25 mm2. It is acceptable to make the secondary winding from several parallel wires with the same general cross-section.

It is more convenient to carry out winding together. While one, trying not to damage the insulation of adjacent turns, carefully pulls and lays the wire, the other holds the free end of the future winding, protecting it from twisting.
The upgraded LATR2 is placed in a protective metal casing with ventilation holes, on which there is a mounting plate made of 10-mm getinax or fiberglass with a packet switch SB1, a thyristor voltage regulator (with resistor R6), a light indicator HL1 for connecting the device to the network and output terminals for welding on AC (X2, X3) or direct (X4, X5) current.

In the absence of a basic LATR2, it can be replaced with a homemade “welder” with a magnetic core made of transformer steel (core cross-section 45-50 cm2). Its primary winding should contain 250 turns of PEV2 wire with a diameter of 1.5 mm. The secondary one is no different from the one used in the modernized LATR2.

At the output of the low-voltage winding, a rectifier block with power diodes VD3-VD10 is installed for DC welding. In addition to these valves, more powerful analogs are also quite acceptable, for example, D122-32-1 (rectified current - up to 32 A).
Power diodes and thyristors are installed on heat sinks, the area of ​​each of which is at least 25 cm2. The axis of the adjusting resistor R6 is brought out from the casing. A scale with divisions corresponding to specific values ​​of direct and alternating voltage is placed under the handle. And next to it is a table of the dependence of the welding current on the voltage on the secondary winding of the transformer and on the diameter of the welding electrode (0.8-1.5 mm).

Of course, homemade electrodes made from carbon steel “wire rod” with a diameter of 0.5-1.2 mm are also acceptable. Blanks 250-350 mm long are covered with liquid glass - a mixture of silicate glue and crushed chalk, leaving the 40 mm ends necessary for connection to the welding machine unprotected. The coating must be thoroughly dried, otherwise it will start to “shoot” during welding.

Although both alternating (terminals X2, X3) and direct (X4, X5) current can be used for welding, the second option, according to reviews from welders, is preferable to the first. Moreover, polarity plays a very important role. In particular, when applying “plus” to “ground” (the object being welded) and, accordingly, connecting the electrode to the terminal with the “minus” sign, the so-called direct polarity occurs. It is characterized by the release of more heat than with reverse polarity, when the electrode is connected to the positive terminal of the rectifier, and the “ground” is connected to the negative terminal. Reverse polarity is used when it is necessary to reduce heat generation, for example, when welding thin sheets of metal. Almost all the energy released by the electric arc goes to the formation of a weld, and therefore the depth of penetration is 40-50 percent greater than with a current of the same magnitude, but of straight polarity.

And a few more very significant features. An increase in the arc current at a constant welding speed leads to an increase in the depth of penetration. Moreover, if the work is carried out on alternating current, then the last of these parameters becomes 15-20 percent less than when using direct current of reverse polarity. The welding voltage has little effect on the penetration depth. But the width of the seam depends on Ust: it increases with increasing voltage.

Hence an important conclusion for those involved in, say, welding work during body repairs passenger car from thin sheet steel: the best results will be obtained by welding with direct current of reverse polarity at a minimum (but sufficient for stable arc burning) voltage.

The arc must be kept as short as possible, then the electrode is consumed evenly, and the depth of penetration of the metal being welded is maximum. The seam itself is clean and durable, practically free of slag inclusions. And you can protect yourself from rare splashes of the melt, which are difficult to remove after the product has cooled, by rubbing the heat-affected surface with chalk (the drops will roll off without sticking to the metal).

The arc is excited (after applying the corresponding -Us to the electrode and the ground) in two ways. The essence of the first is to lightly touch the electrode to the parts being welded and then move it 2-4 mm to the side. The second method is reminiscent of striking a match on a box: sliding the electrode along the surface to be welded, it is immediately withdrawn a short distance. In any case, you need to catch the moment the arc occurs and only then, smoothly moving the electrode over the seam that forms immediately, maintain its quiet combustion.

Depending on the type and thickness of the metal being welded, one or another electrode is selected. If, for example, there is a standard assortment for a St3 sheet with a thickness of 1 mm, electrodes with a diameter of 0.8-1 mm are suitable (this is what the design in question is mainly designed for). For welding work on 2-mm rolled steel, it is advisable to have both a more powerful “welder” and a thicker electrode (2-3 mm).
For welding jewelry made of gold, silver, cupronickel, it is better to use a refractory electrode (for example, tungsten). You can also weld metals that are less resistant to oxidation using carbon dioxide protection.

In any case, the work can be performed either with a vertically positioned electrode or tilted forward or backward. But experienced professionals claim: when welding with a forward angle (meaning an acute angle between the electrode and the finished seam), more complete penetration and a smaller width of the seam itself are ensured. Backward angle welding is recommended only for lap joints, especially when you have to deal with rolled profiles (angles, I-beams and channels).

An important thing is the welding cable. For the device in question, stranded copper (total cross-section about 20 mm2) in rubber insulation is ideal. The required quantity is two one and a half meter sections, each of which should be equipped with a carefully crimped and soldered terminal lug for connection to the “welder”. For direct connection to ground, a powerful alligator clip is used, and with the electrode, a holder resembling a three-pronged fork is used. You can also use a car cigarette lighter.

It is also necessary to take care of personal safety. When electric arc welding, try to protect yourself from sparks, and even more so from splashes of molten metal. It is recommended to wear loose-fitting canvas clothing, protective gloves and a mask to protect your eyes from the harsh radiation of the electric arc (sunglasses are not suitable here).
Of course, we must not forget about the “Safety Rules when performing work on electrical equipment in networks with voltages up to 1 kV.” Electricity does not forgive carelessness!

Do-it-yourself welding in this case does not mean welding technology, but homemade equipment for electric welding. Working skills are acquired industrial practice. Of course, before going to the workshop, you need to master the theoretical course. But you can put it into practice only if you have something to work with. This is the first argument in favor of, when mastering welding on your own, first taking care of the availability of appropriate equipment.

Second, a purchased welding machine is expensive. Rent is also not cheap, because... the probability of its failure due to unskilled use is high. Finally, in the outback, getting to the nearest point where you can rent a welder can be simply long and difficult. All in all, It is better to start your first steps in metal welding by making a welding installation with your own hands. And then - let it sit in a barn or garage until the opportunity arises. It’s never too late to spend money on branded welding if things work out.

What are we going to talk about?

This article discusses how to make equipment at home for:

• Electric arc welding with alternating current of industrial frequency 50/60 Hz and direct current up to 200 A. This is enough to weld metal structures up to approximately a corrugated fence on a frame made of corrugated pipe or a welded garage.
• Micro-arc welding of twisted wires is very simple and useful when laying or repairing electrical wiring.
• Spot pulse contact welding– can be very useful when assembling products from thin steel sheets.

What we won't talk about

First, let's skip gas welding. The equipment for it costs pennies compared to consumables, you can’t make gas cylinders at home, and a homemade gas generator is a serious risk to life, plus carbide is expensive now, where it is still on sale.

The second is inverter electric arc welding. Really, welding inverter-semi-automatic allows the novice amateur to cook quite important designs. It is light and compact and can be carried by hand. But purchasing at retail the components of an inverter that allows for consistent high-quality welding will cost more than a finished machine. And an experienced welder will try to work with simplified homemade products, and refuse - “Give me a normal machine!” Plus, or rather minus - in order to make a more or less decent welding inverter, you need to have fairly solid experience and knowledge in electrical engineering and electronics.

The third is argon-arc welding. With whose light hand the assertion that it is a hybrid of gas and arc began to circulate in RuNet is unknown. In fact, this is a type of arc welding: inert gas argon does not participate in the welding process, but creates around working area a cocoon that insulates it from the air. As a result, the welding seam is chemically pure, free from impurities of metal compounds with oxygen and nitrogen. Therefore, non-ferrous metals can be cooked under argon, incl. heterogeneous. In addition, it is possible to reduce the welding current and arc temperature without compromising its stability and weld with a non-consumable electrode.

It is quite possible to make equipment for argon-arc welding at home, but gas is very expensive. Cook as usual economic activity aluminum, stainless steel or bronze are unlikely to be needed. And if you really need it, it’s easier to rent argon welding - compared to how much (in money) gas will go back into the atmosphere, it’s pennies.

Transformer

The basis of all “our” types of welding is a welding transformer. The procedure for its calculation and design features differ significantly from those of power supply (power) and signal (sound) transformers. The welding transformer operates in intermittent mode. If you design it for maximum current like transformers continuous action, it will turn out to be prohibitively large, heavy and expensive. Ignorance of the features of electrical transformers for arc welding is the main reason for the failures of amateur designers. Therefore, let’s take a walk through welding transformers in the following order:

1. a little theory - on the fingers, without formulas and brilliance;
2. features of magnetic cores of welding transformers with recommendations for choosing from random ones;
3. testing of available used equipment;
4. calculation of a transformer for a welding machine;
5. preparation of components and winding of windings;
6. trial assembly and fine-tuning;
7. commissioning.

Theory

An electrical transformer can be likened to storage tank water supply This is a pretty deep analogy: a transformer operates due to its energy reserve magnetic field in its magnetic circuit (core), which can be many times greater than that instantly transmitted from the power supply network to the consumer. And the formal description of losses due to eddy currents in steel is similar to that for water losses due to infiltration. Electricity losses in copper windings are formally similar to pressure losses in pipes due to viscous friction in the liquid.

Note: the difference is in losses due to evaporation and, accordingly, magnetic field scattering. The latter in the transformer are partially reversible, but smooth out the peaks of energy consumption in the secondary circuit.

An important factor in our case is the external current-voltage characteristic (VVC) of the transformer, or simply its external characteristic (VC) - the dependence of the voltage on the secondary winding (secondary) on the load current, with a constant voltage on the primary winding (primary). For power transformers, the VX is rigid (curve 1 in the figure); they are like a shallow, vast pool. If it is properly insulated and covered with a roof, then water losses are minimal and the pressure is quite stable, no matter how consumers turn the taps. But if there is gurgling in the drain - sushi oars, the water is drained. In relation to transformers, the power source must keep the output voltage as stable as possible to a certain threshold less than the maximum instantaneous power consumption, be economical, small and light. For this:

• The steel grade for the core is selected with a more rectangular hysteresis loop.
• Design measures (core configuration, calculation method, configuration and arrangement of windings) reduce dissipation losses, losses in steel and copper in every possible way.
• The magnetic field induction in the core is taken to be less than the maximum permissible current form for transmission, because its distortion reduces efficiency.

Note: transformer steel with “angular” hysteresis is often called magnetically hard. This is not true. Magnetically hard materials retain strong residual magnetization; they are made by permanent magnets. And any transformer iron is soft magnetic.

You cannot cook from a transformer with a hard VX: the seam is torn, burned, and the metal splatters. The arc is inelastic: I moved the electrode slightly wrong and it goes out. Therefore, the welding transformer is made to look like a regular water tank. Its CV is soft (normal dissipation, curve 2): as the load current increases, the secondary voltage gradually drops. The normal scattering curve is approximated by a straight line incident at an angle of 45 degrees. This allows, due to a decrease in efficiency, to briefly extract several times more power from the same hardware, or resp. reduce the weight, size and cost of the transformer. In this case, the induction in the core can reach a saturation value, and for a short time even exceed it: the transformer will not go into a short circuit with zero power transfer, like a “silovik”, but will begin to heat up. Quite long: the thermal time constant of welding transformers is 20-40 minutes. If you then let it cool down and there is no unacceptable overheating, you can continue working. The relative drop in the secondary voltage ΔU2 (corresponding to the range of the arrows in the figure) of normal dissipation gradually increases with increasing range of fluctuations of the welding current Iw, which makes it easy to hold the arc during any type of work. The following properties are provided:

1. The steel of the magnetic circuit is taken with hysteresis, more “oval”.
2. Reversible scattering losses are normalized. By analogy: the pressure has dropped - consumers will not pour out much and quickly. And the water utility operator will have time to turn on the pumping.
3. The induction is chosen close to the overheating limit; this allows, by reducing cosφ (a parameter equivalent to efficiency) at a current significantly different from the sinusoidal one, to take more power from the same steel.

Note: reversible scattering loss means that part of the power lines penetrates the secondary through the air, bypassing the magnetic circuit. The name is not entirely apt, just like “useful scattering”, because “reversible” losses for the efficiency of a transformer are no more useful than irreversible ones, but they soften the I/O.

As you can see, the conditions are completely different. So, should you definitely look for iron from a welder? Not necessary, for currents up to 200 A and peak power up to 7 kVA, but this is enough for the farm. Using design and design measures, as well as with the help of simple additional devices (see below), we will obtain on any hardware a VX curve 2a that is somewhat more rigid than normal. The efficiency of welding energy consumption is unlikely to exceed 60%, but for occasional work this is not a problem. But on delicate work and low currents, holding the arc and welding current will not be difficult, without much experience (ΔU2.2 and Iw1), at high currents Iw2 we will get acceptable weld quality, and it will be possible to cut metal up to 3-4 mm.

There are also welding transformers with a steeply falling VX, curve 3. This is more like a booster pump: either the output flow is at nominal level, regardless of the feed height, or there is none at all. They are even more compact and lightweight, but in order to withstand the welding mode at a steeply falling VX, it is necessary to respond to fluctuations ΔU2.1 of the order of a volt within a time of about 1 ms. Electronics can do this, which is why transformers with a “steep” VX are often used in semi-automatic welding machines. If you cook from such a transformer manually, then the seam will be sluggish, undercooked, the arc will again be inelastic, and when you try to light it again, the electrode will stick every now and then.

Magnetic cores

The types of magnetic cores suitable for the manufacture of welding transformers are shown in Fig. Their names begin with the letter combination respectively. standard size. L means tape. For a welding transformer L or without L, there is no significant difference. If the prefix contains M (SHLM, PLM, ShM, PM) - ignore without discussion. This is iron of reduced height, unsuitable for a welder despite all its other outstanding advantages.

After the letters of the nominal value there are numbers indicating a, b and h in Fig. For example, for W20x40x90, the cross-sectional dimensions of the core (central rod) are 20x40 mm (a*b), and the window height h is 90 mm. Core cross-sectional area Sc = a*b; window area Sok = c*h is needed for accurate calculation of transformers. We will not use it: for an accurate calculation, we need to know the dependence of losses in steel and copper on the value of induction in a core of a given standard size, and for them, the grade of steel. Where will we get it if we run it on random hardware? We will calculate using a simplified method (see below), and then finalize it during testing. It will take more work, but we will get welding that you can actually work on.

Note: if the iron is rusty on the surface, then nothing, the properties of the transformer will not suffer from this. But if there are spots of tarnish on it, this is a defect. Once upon a time, this transformer overheated very much and the magnetic properties of its iron were irreversibly deteriorated.

Another important parameter magnetic circuit - its mass, weight. Because the specific gravity steel is unchanged, it determines the volume of the core, and, accordingly, the power that can be taken from it. Magnetic cores with the following weight are suitable for the manufacture of welding transformers:

• O, OL – from 10 kg.
• P, PL – from 12 kg.
• W, SHL – from 16 kg.

Why Sh and ShL are needed heavier is clear: they have an “extra” side rod with “shoulders”. OL may be lighter because it does not have corners that require excess iron, and the bends of the magnetic force lines are smoother and for some other reasons, which will be discussed later. section.

Oh OL

The cost of toroid transformers is high due to the complexity of their winding. Therefore, the use of toroidal cores is limited. A torus suitable for welding can, firstly, be removed from the LATR - a laboratory autotransformer. Laboratory, which means it should not be afraid of overloads, and the hardware of LATRs provides a VH close to normal. But…

LATR is a very useful thing, first of all. If the core is still alive, it is better to restore the LATR. Suddenly you don’t need it, you can sell it, and the proceeds will be enough for welding suitable for your needs. Therefore, “bare” LATR cores are difficult to find.

Secondly, LATRs with a power of up to 500 VA are weak for welding. From the LATR-500 iron you can achieve welding with a 2.5 electrode in the mode: cook for 5 minutes - it cools down for 20 minutes, and we heat up. As in Arkady Raikin’s satire: mortar bar, brick yok. Brick bar, mortar yok. LATRs 750 and 1000 are very rare and useful.

Another torus suitable for all properties is the stator of an electric motor; Welding from it will turn out to be good enough for an exhibition. But it is no easier to find than LATR iron, and it is much more difficult to wind on it. In general, a welding transformer from an electric motor stator is a separate topic, there are so many complexities and nuances. First of all, with a thick wire wound around the donut. Having no winding experience toroidal transformers, the probability of ruining an expensive wire and not getting welded is close to 100%. Therefore, alas, you will have to wait a little longer with the cooking apparatus on a triode transformer.

Sh, ShL

Armor cores are structurally designed for minimal dissipation, and it is almost impossible to standardize it. Welding on a regular Sh or ShL will turn out to be too tough. In addition, the cooling conditions for the windings on Ш and ШЛ are the worst. The only armored cores suitable for a welding transformer are those of increased height with spaced biscuits windings (see below), on the left in Fig. The windings are separated by dielectric non-magnetic heat-resistant and mechanically strong gaskets (see below) with a thickness of 1/6-1/8 of the core height.

For welding, the core Ш is welded (assembled from plates) necessarily across the roof, i.e. yoke-plate pairs are alternately oriented back and forth relative to each other. The method of normalizing dissipation by a non-magnetic gap is unsuitable for a welding transformer, because the losses are irreversible.

If you come across a laminated Sh without a yoke, but with a cut in the plates between the core and the lintel (in the center), you are in luck. The plates of the signal transformers are laminated, and the steel on them, to reduce signal distortion, is used to initially give normal VX. But the likelihood of such luck is very low: signal transformers with kilowatt power are a rare curiosity.

Note: do not try to assemble a high Ш or ШЛ from a pair of ordinary ones, as on the right in Fig. A continuous straight gap, albeit a very thin one, means irreversible scattering and a steeply falling CV. Here, dissipation losses are almost similar to water losses due to evaporation.

PL, PLM

Rod cores are most suitable for welding. Of these, those laminated in pairs of identical L-shaped plates, see Fig., their irreversible scattering is the smallest. Secondly, the P and PL windings are wound in exactly the same halves, with half turns for each. The slightest magnetic or current asymmetry - the transformer hums, heats up, but there is no current. The third thing that may not seem obvious to those who have not forgotten the school gimlet rule is that the windings are wound onto the rods in one direction. Does something seem wrong? Does the magnetic flux in the core have to be closed? And you twist the gimlets according to the current, and not according to the turns. The directions of the currents in the half-windings are opposite, and magnetic fluxes are shown there. You can also check if the wiring protection is reliable: apply the network to 1 and 2’, and close 2 and 1’. If the machine does not immediately knock out, the transformer will howl and shake. However, who knows what's going on with your wiring. Better not.

Note: You can also find recommendations - to wind the windings of the welding P or PL on different rods. Like, VH is softening up. That’s how it is, but for this you need a special core, with rods of different sections (the secondary is smaller) and recesses that release power lines into the air in the desired direction, see fig. on right. Without this, we will get a noisy, shaking and gluttonous, but not cooking transformer.

If there is a transformer

A 6.3 A circuit breaker and an AC ammeter will also help determine the suitability of an old welder lying around God knows where and God knows how. You need either a non-contact induction ammeter (current clamp) or a 3 A pointer electromagnetic ammeter. A multimeter with alternating current limits will not lie, because the shape of the current in the circuit will be far from sinusoidal. Also, a long-neck liquid household thermometer, or, better yet, a digital multimeter with the ability to measure temperature and a probe for this. The step-by-step procedure for testing and preparing for further operation of an old welding transformer is as follows:

Calculation of a welding transformer

In RuNet you can find different methods for calculating welding transformers. Despite the apparent inconsistency, most of them are correct, but with full knowledge of the properties of steel and/or for a specific range of standard values ​​of magnetic cores. The proposed methodology developed in Soviet times, when instead of choice there was a shortage of everything. For a transformer calculated using it, the VX drops a little steeply, somewhere between curves 2 and 3 in Fig. at first. This is suitable for cutting, but for thinner work the transformer is supplemented external devices(see below), stretching the VC along the current axis to curve 2a.

The basis of calculation is usual: the arc burns stably under a voltage Ud of 18-24 V, and its ignition requires an instantaneous current 4-5 times greater than the rated welding current. Corresponding, minimum voltage idle move Uxxx of the secondary will be 55 V, but for cutting, since everything possible is squeezed out of the core, we take not the standard 60 V, but 75 V. There is no other way: it’s unacceptable according to TB, and the iron won’t pull it out. Another feature, for the same reasons, is the dynamic properties of the transformer, i.e. its ability to quickly transition from short-circuit mode (say, when shorted by drops of metal) to working mode is maintained without additional measures. True, such a transformer is prone to overheating, but since it is our own and in front of our eyes, and not in the far corner of a workshop or site, we will consider this acceptable. So:

• According to the formula from paragraph 2 previous. list we find the overall power;
• We find the maximum possible welding current Isv = Pg/Ud. 200 A is guaranteed if 3.6-4.8 kW can be removed from the iron. True, in the first case the arc will be sluggish, and it will be possible to cook only with a deuce or 2.5;
• We calculate the operating current of the primary at the maximum permissible network voltage for welding I1рmax = 1.1Pg(VA)/235 V. In fact, the norm for the network is 185-245 V, but for a homemade welder at the limit this is too much. We take 195-235 V;
• Based on the found value, we determine the tripping current of the circuit breaker as 1.2I1рmax;
• We assume the current density of the primary J1 = 5 A/sq. mm and, using I1рmax, we find the diameter of its copper wire d = (4S/3.1415)^0.5. Its total diameter with self-insulation is D = 0.25 + d, and if the wire is ready - tabular. To operate in the “brick bar, mortar yoke” mode, you can take J1 = 6-7 A/sq. mm, but only if the required wire is not available and is not expected;
• We find the number of turns per volt of the primary: w = k2/Sс, where k2 = 50 for Sh and P, k2 = 40 for PL, ShL and k2 = 35 for O, OL;
• We find the total number of its turns W = 195k3w, where k3 = 1.03. k3 takes into account the energy loss of the winding due to leakage and in copper, which is formally expressed by the somewhat abstract parameter of the winding’s own voltage drop;
• We set the laying coefficient Kу = 0.8, add 3-5 mm to a and b of the magnetic circuit, calculate the number of winding layers, average length coil and meter of wire
• We calculate the secondary similarly at J1 = 6 A/sq. mm, k3 = 1.05 and Ku = 0.85 for voltages of 50, 55, 60, 65, 70 and 75 V, in these places there will be taps for rough adjustment of the welding mode and compensation for fluctuations in the supply voltage.

Winding and finishing

The diameters of the wires in the calculation of windings are usually greater than 3 mm, and varnished winding wires with d>2.4 mm are rarely widely sold. In addition, the welder windings experience strong mechanical loads from electromagnetic forces, so finished wires are needed with an additional textile winding: PELSH, PELSHO, PB, PBD. They are even more difficult to find, and they are very expensive. The meterage of the wire for the welder is such that it is possible to insulate cheaper bare wires yourself. An additional advantage is that you can twist several times to the desired S stranded wires, we get a flexible wire, which is much easier to wind. Anyone who has tried to manually lay a tire of at least 10 square meters on a frame will appreciate it.

Isolation

Let's say there is a 2.5 sq.m. wire available. mm in PVC insulation, and for the secondary you need 20 m by 25 squares. We prepare 10 coils or coils of 25 m each. We unwind about 1 m of wire from each and remove the standard insulation, it is thick and not heat-resistant. We twist the exposed wires with a pair of pliers into an even, tight braid, and wrap it in order of increasing insulation cost:

1. Using masking tape with an overlap of 75-80% turns, i.e. in 4-5 layers.
2. Calico braid with an overlap of 2/3-3/4 turns, i.e. 3-4 layers.
3. Cotton electrical tape with an overlap of 50-67%, in 2-3 layers.

Note: the wire for the secondary winding is prepared and wound after winding and testing the primary, see below.

Winding

A thin-walled homemade frame will not withstand the pressure of turns of thick wire, vibrations and jerks during operation. Therefore, the windings of welding transformers are made of frameless biscuits, and they are secured to the core with wedges made of textolite, fiberglass or, in extreme cases, bakelite plywood impregnated with liquid varnish (see above). The instructions for winding the windings of a welding transformer are as follows:

• We prepare a wooden boss with a height equal to the height of the winding and with dimensions in diameter 3-4 mm larger than a and b of the magnetic circuit;
• We nail or screw temporary plywood cheeks to it;
• We wrap the temporary frame in 3-4 layers of thin polyethylene film, going over the cheeks and turning them over outside so that the wire does not stick to the wood;
• We wind the pre-insulated winding;
• Along the winding, we impregnate it twice with liquid varnish until it drips through;
• Once the impregnation has dried, carefully remove the cheeks, squeeze out the boss and peel off the film;
• We tightly tie the winding in 8-10 places evenly around the circumference with thin cord or propylene twine - it is ready for testing.

Finishing and finishing

We mix the core into a biscuit and tighten it with bolts, as expected. Winding tests are carried out in exactly the same way as tests of a questionable finished transformer, see above. It is better to use LATR; Iхх at an input voltage of 235 V should not exceed 0.45 A per 1 kVA overall power transformer. If it’s more, the primary is wound up. Winding wire connections are made with bolts (!), insulated with heat-shrinkable tube (HERE) in 2 layers or with cotton electrical tape in 4-5 layers.

Based on the test results, the number of turns of the secondary is adjusted. For example, the calculation gave 210 turns, but in reality Ixx fit into the norm at 216. Then we multiply the calculated turns of the secondary sections by 216/210 = 1.03 approx. Do not neglect decimal places, the quality of the transformer largely depends on them!

After finishing, we disassemble the core; We wrap the biscuit tightly with the same masking tape, calico or “rag” tape in 5-6, 4-5 or 2-3 layers, respectively. Wind across the turns, not along them! Now saturate it with liquid varnish again; when it dries - twice undiluted. This galette is ready, you can make a secondary one. When both are on the core, we test the transformer again now at Ixx (suddenly it curled somewhere), fix the biscuits and impregnate the entire transformer with normal varnish. Phew, the most dreary part of the work is over.

Pull VX

But he’s still too cool for us, remember? Needs to be softened. The simplest way– a resistor in the secondary circuit is not suitable for us. Everything is very simple: at a resistance of only 0.1 Ohm at a current of 200, 4 kW of heat will be dissipated. If we have a welder with a capacity of 10 kVA or more, and we need to weld thin metal, we need a resistor. Whatever current is set by the regulator, its emissions when the arc is ignited are inevitable. Without active ballast, they will burn the seam in places, and the resistor will extinguish them. But for us, weaklings, it will be of no use.

The reactive ballast (inductor, choke) will not take away excess power: it will absorb current surges, and then smoothly release them to the arc, this will stretch the VX as it should. But then you need a throttle with dispersion adjustment. And for it, the core is almost the same as that of a transformer, and the mechanics are quite complex, see fig.

We will go the other way: we will use active-reactive ballast, colloquially called gut by old welders, see fig. on right. Material – steel wire rod 6 mm. The diameter of the turns is 15-20 cm. How many of them are shown in Fig. Apparently, for power up to 7 kVA this gut is correct. The air gaps between the turns are 4-6 cm. The active-reactive choke is connected to the transformer with an additional piece of welding cable (hose, simply), and the electrode holder is attached to it with a clothespin clamp. By selecting the connection point, it is possible, coupled with switching to secondary taps, to fine-tune the operating mode of the arc.

Note: An active-reactive choke can become red-hot during operation, so it requires a fireproof, heat-resistant, dielectric, non-magnetic lining. In theory, a special ceramic cradle. It is acceptable to replace it with dry sand cushion, or already formally with a violation, but not grossly, the welding gut is laid on bricks.

But other?

This means, first of all, an electrode holder and a connecting device for the return hose (clamp, clothespin). Since our transformer is at its limit, we need to buy them ready-made, but those like those in Fig. right, no need. For a 400-600 A welding machine, the quality of contact in the holder is hardly noticeable, and it will also withstand simply winding up the return hose. And our homemade one, working with effort, can go haywire, seemingly for some unknown reason.

Next, the body of the device. It must be made of plywood; preferably bakelite impregnated, as described above. The bottom is 16 mm thick, the panel with the terminal block is 12 mm thick, and the walls and cover are 6 mm thick, so that they do not come off during transportation. Why not sheet steel? It is ferromagnetic and in the stray field of a transformer can disrupt its operation, because we get everything we can out of him.

As for the terminal blocks, the terminals themselves are made from M10 bolts. The base is the same textolite or fiberglass. Getinax, bakelite and carbolite are not suitable; pretty soon they will crumble, crack and delaminate.

Let's try a permanent one

Welding with direct current has a number of advantages, but the input voltage of any welding transformer becomes more severe at constant current. And ours, designed for the minimum possible power reserve, will become unacceptably stiff. The choke-intestine will no longer help here, even if it worked on direct current. In addition, it is necessary to protect expensive rectifier diodes 200 A against current and voltage surges. We need a reciprocal-absorbing infra-low frequency filter, FINCH. Although it looks reflective, you need to take into account the strong magnetic coupling between the halves of the coil.

The circuit of such a filter, known for many years, is shown in Fig. But immediately after its implementation by amateurs, it became clear that the operating voltage of capacitor C is low: voltage surges during arc ignition can reach 6-7 values ​​of its Uхх, i.e. 450-500 V. Further, capacitors are needed that can withstand the circulation of high reactive power, only and only oil-paper ones (MBGCH, MBGO, KBG-MN). The following gives an idea of ​​the weight and dimensions of single “cans” of these types (by the way, not cheap ones). Fig., and a battery will need 100-200 of them.

With a coil magnetic circuit it is simpler, although not entirely. Suitable for it are 2 PL power transformers TS-270 from old tube “coffin” TVs (the data is in reference books and in RuNet), or similar ones, or SLs with similar or larger a, b, c and h. From 2 submarines, an SL is assembled with a gap, see figure, of 15-20 mm. It is fixed with textolite or plywood spacers. Winding - insulated wire from 20 sq. mm, how much will fit in the window; 16-20 turns. Wind it into 2 wires. The end of one is connected to the beginning of the other, this will be the middle point.

The filter is adjusted in an arc at the minimum and maximum values ​​of Uхх. If the arc is sluggish at minimum, the electrode sticks, the gap is reduced. If the metal burns at maximum, increase it or, which will be more effective, cut off part of the side rods symmetrically. To prevent the core from crumbling, it is impregnated with liquid and then normal varnish. Finding the optimum inductance is quite difficult, but then welding works flawlessly on alternating current.

Microarc

The purpose of microarc welding is discussed at the beginning. The “equipment” for it is extremely simple: a step-down transformer 220/6.3 V 3-5 A. In tube times, radio amateurs connected to the filament winding of a standard power transformer. One electrode – the twisting of the wires itself (copper-aluminum, copper-steel is possible); the other is a graphite rod like a 2M pencil lead.

Nowadays, for micro-arc welding, they use more computer power supplies, or, for pulsed micro-arc welding, capacitor banks, see the video below. On direct current, the quality of work, of course, improves.

Video: homemade machine for welding twists

Video: DIY welding machine from capacitors

Contact! There is contact!

Resistance welding in industry is mainly used in spot, seam and butt welding. At home, primarily in terms of energy consumption, pulsed point is feasible. It is suitable for welding and welding thin, from 0.1 to 3-4 mm, steel sheet parts. Arc welding it will burn through a thin wall, and if the part is the size of a coin or less, then the softest arc will burn it entirely.

The principle of operation of resistance spot welding is illustrated in the figure: copper electrodes forcefully compress the parts, a current pulse in the steel-to-steel ohmic resistance zone heats the metal until electrodiffusion occurs; metal does not melt. The current needed for this is approx. 1000 A per 1 mm of thickness of the parts being welded. Yes, a current of 800 A will grab sheets of 1 and even 1.5 mm. But if this is not a craft for fun, but, say, a galvanized corrugated fence, then the very first strong gust of wind will remind you: “Man, the current was rather weak!”

However, resistance spot welding is much more economical than arc welding: the no-load voltage of the welding transformer for it is 2 V. It consists of 2-contact steel-copper potential differences and the ohmic resistance of the penetration zone. The transformer for resistance welding is calculated in the same way as for arc welding, but the current density in the secondary winding is 30-50 or more A/sq. mm. The secondary of the contact-welding transformer contains 2-4 turns, is well cooled, and its utilization factor (the ratio of welding time to idling and cooling time) is many times lower.

There are many descriptions on the RuNet of homemade pulse-spot welders made from unusable microwave ovens. They are, in general, correct, but repetition, as written in “1001 Nights,” is of no use. And old microwaves don’t lie in heaps in trash heaps. Therefore, we will deal with designs that are less known, but, by the way, more practical.

In Fig. – construction of a simple apparatus for pulsed spot welding. They can weld sheets up to 0.5 mm; It is perfect for small crafts, and magnetic cores of this and larger sizes are relatively affordable. Its advantage, in addition to its simplicity, is the clamping of the running rod of the welding pliers with a load. To work with a contact welding pulser, a third hand would not hurt, and if one has to forcefully squeeze the pliers, then it is generally inconvenient. Disadvantages – increased risk of accidents and injuries. If you accidentally give a pulse when the electrodes are brought together without the parts being welded, then the plasma will shoot out from the tongs, metal splashes will fly, the wiring protection will be knocked out, and the electrodes will fuse tightly.

The secondary winding is made of a 16x2 copper busbar. It can be made from strips of thin sheet copper (it will be flexible) or made from a piece of flattened coolant supply tube household air conditioner. The bus is isolated manually as described above.

Here in Fig. – drawings of a pulse spot welding machine are more powerful, for welding sheets up to 3 mm, and more reliable. Thanks to a fairly powerful return spring (from the armored mesh of the bed), accidental convergence of the pliers is excluded, and the eccentric clamp provides strong, stable compression of the pliers, on which the quality of the welded joint significantly depends. If something happens, the clamp can be instantly released with one blow on the eccentric lever. The disadvantage is the insulating pincer units, there are too many of them and they are complex. Another one is aluminum pincer rods. Firstly, they are not as strong as steel ones, and secondly, they are 2 unnecessary contact differences. Although the heat dissipation of aluminum is certainly excellent.

About electrodes

In amateur conditions, it is more advisable to insulate the electrodes at the installation site, as shown in Fig. on right. There is no conveyor at home; you can always let the device cool down so that the insulating bushings do not overheat. This design will allow you to make rods from durable and cheap steel corrugated pipe, and also lengthen the wires (up to 2.5 m is permissible) and use a contact welding gun or external pliers, see fig. below.

In Fig. On the right, another feature of electrodes for resistance spot welding is visible: a spherical contact surface (heel). Flat heels are more durable, so electrodes with them are widely used in industry. But the diameter of the flat heel of the electrode must be equal to 3 times the thickness of the adjacent material being welded, otherwise the weld spot will be burned either in the center (wide heel) or along the edges (narrow heel), and corrosion will occur from the welded joint even on stainless steel.

The last point about electrodes is their material and size. Red copper burns out quickly, so commercial electrodes for resistance welding are made of copper with a chromium additive. These should be used; at current copper prices it is more than justified. The diameter of the electrode is taken depending on the mode of its use, based on a current density of 100-200 A/sq. mm. According to heat transfer conditions, the length of the electrode is at least 3 of its diameters from the heel to the root (the beginning of the shank).

How to give impetus

In the simplest homemade devices In pulsed contact welding, the current pulse is given manually: simply turn on the welding transformer. This, of course, does not benefit him, and welding is either insufficient or burnt out. However, automating the supply and standardization of welding pulses is not so difficult.

A diagram of a simple but reliable welding pulse generator, proven by long practice, is shown in Fig. Auxiliary transformer T1 is a regular 25-40 W power transformer. The voltage of winding II is indicated by the backlight. You can replace it with 2 LEDs connected back-to-back with a quenching resistor (usual, 0.5 W) 120-150 Ohm, then the voltage II will be 6 V.

Voltage III - 12-15 V. 24 is possible, then capacitor C1 (regular electrolytic) is needed for a voltage of 40 V. Diodes V1-V4 and V5-V8 - any rectifier bridges for 1 and from 12 A, respectively. Thyristor V9 - 12 or more A 400 V. Optothyristors from computer power supplies or TO-12.5, TO-25 are suitable. Resistor R1 is a wire-wound resistor; it is used to regulate the pulse duration. Transformer T2 – welding.

A common material for the manufacture of homemade welding transformers has long been burnt LATRs (laboratory autotransformers). Inside the LATR housing there is a toroidal autotransformer made on a magnetic core of large 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 core rings from large LATRs.

LATRs are produced 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 the required number of turns to be laid. The most common among them is probably the LATR-1M autotransformer. Depending on the winding wire, it is designed for currents of 6.7-9A, although this does not change the dimensions of the autotransformer itself. The LATR-1M magnetic core has the following dimensions: outer diameter D=127 mm, inner diameter d=70 mm, ring height h=95 mm, cross-section S=27 cm 2, weight about 6 kg. From two rings from LATR-1M you can make a good welding transformer, 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 a transformer made from LATRs, compared to the U-shaped transformer circuit, is also that it is impossible to manufacture the coils separately from the magnetic circuit. This means that you will 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 larger magnetic conductor 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 circuit 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 magnetic circuit ring consists of pieces of iron tape wound on each other, fastened at the edges 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 the required amount. But don’t try to rewind everything at once. It is better to unwind one turn at a time, cutting off the excess each time. Sometimes the windows of larger LATRs are expanded in this way, although this inevitably reduces the cross-sectional area of ​​the magnetic circuit.

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

Transformer with spaced arms

At the beginning of transformer manufacturing, it is necessary to insulate both rings. Special attention In this case, you should pay attention to the corners of the edges of the rings - they are sharp, they can easily cut the applied insulation, and then short-circuit the winding wire. It is better to first smooth out the corners somewhat with a file, and then apply some kind of strong and elastic tape along it, for example, a thick keeper tape or a cambric tube cut lengthwise. On top of the rings, each separately, is wrapped with a thin layer of fabric insulation.

Next, the isolated rings are connected together. The rings are pulled tight strong tape, and are fixed on the sides with wooden pegs, also then tied with tape - the magnetic core 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 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, there is no way to 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 can have a diameter of 1.6-2.2 mm. For magnetic cores made up of rings with a window diameter of 70 mm, you can use a wire with a diameter of no more than 2 mm, otherwise there will be little space left for the secondary winding. The primary winding contains, as a rule, 180-200 turns at normal mains voltage, which is sufficient for efficient work 3 mm electrode.

A cambric is put on the end of the wire, which is attracted by cotton 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 layers to level the surface.

The wire is laid turn to turn, in no case allowing wire to overlap wire. The layers of wire must be insulated from each other. Again, to save space, the winding should be placed as compactly as possible. On a magnetic circuit made of small rings, the interlayer insulation should be used thinner. You should not try to wind the primary winding quickly. This process is slow, and after laying the hard wires, your fingers begin to hurt. It’s 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, leaving the secondary. But first you need to determine the number of turns of the secondary winding for a given voltage. To begin, connect the ready-made primary to the network. The no-load current of this version of the transformer is small - only 70-150 mA, the hum of the transformer should be barely audible. We wind 10 turns of any wire onto 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 there is 0.6-0.7V for each turn of the secondary winding. 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 secondary winding material is limited by the remaining space of the magnetic circuit windows. Moreover, each turn of a thick wire will have to be pulled along its entire length into a narrow window. The easiest way is to wind it with ordinary stranded wire 16 mm 2 in synthetic insulation - it is soft, flexible, well insulated, and will only heat up slightly during operation. You can make a secondary winding from several strands of copper wire.

Half of the turns of the secondary winding are wound on one arm, half on the other. If there are no wires of sufficient length, you can connect them from pieces - no problem. Having wound the windings on both arms, you need to measure the voltage on each of them, it can differ by 2-3V - the slightly different properties of the magnetic cores of different LATRs affect it, which does not particularly affect the properties of the arc during welding. Then the windings on the arms are connected in series, but care must be taken that they are not out of phase, otherwise the output voltage will be close to zero (see the article Winding of a welding transformer). With a network voltage of 220-230V, a welding transformer of this design should develop a current of 100-130A in arc mode. Current at short circuit 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. This will not decrease the operating current much. To a greater extent, a decrease in open circuit voltage affects the arc ignition process. The arc ignites easily at voltages close to 50V and higher. 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. It’s another matter if you come across electrodes designed for high voltage, - some brands of electrodes operate from 70-80V.

Toroidal transformer

Using rings from LATRs, you can also make a welding transformer using a different - toroidal scheme. For this you also need two rings, preferably from large LATRs. The rings are connected and insulated: one ring-magnetic core 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 length of the entire ring and, as a rule, lies in two layers. The problem of the lack of internal space in the magnetic circuit window of such a transformer circuit is even more acute than for the previous design. Therefore, you need to isolate here as much as possible thin layers and materials. Thick winding wires cannot be used here. Although some installations use LATRs of especially large sizes, only one ring of this type can produce a toroidal welding transformer.

The advantageous difference between the toroidal circuit for a welding transformer is its 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 a toroidal magnetic circuit will be longer, and it is unlikely that it will be possible to save on wire here. The disadvantages of this scheme include: the complexity of winding, the limited volume of the window, the inability to use large-section wire, and also the high heating intensity. If in the previous version all windings were located separately and at least partially had contact with air, now the primary winding is completely under the secondary, and their heating is mutually reinforcing.

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

Sometimes a toroidal welding transformer is made from several rings of LATRs in a different way, they are not placed on top of each other, but the iron strips of the tape are rewinded from one to another. To do this, first the inner turns of strips are selected from one ring to widen the window. The rings of other LATRs unravel completely into strips of tape, which are then wound as tightly as possible onto outside diameter first ring. After this, the assembled single magnetic circuit is wrapped very tightly with insulating tape. Thus, a ring-magnetic core is obtained with a more voluminous internal space than all previous ones. This one can accommodate a wire of significant cross-section. The required number of turns is calculated based on the cross-sectional area of ​​the assembled ring.

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

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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 a huge selection of models that differ in power and size. Reliable designs have a fairly 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 assemble such a structure, 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 a detailed diagram of the assembly of the mechanism.

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 operation of the device and good quality welding fastening.

You can control the supply of electrical energy by switching wires to the required amount of winding. 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 an electric current of 210 A. For this, elements marked D 160-162 are suitable. Such models are quite often used for work on an industrial scale.

The main welding injector is made from a printed circuit board. This semi-automatic welding machine can withstand 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!