What to make a welding machine with your own hands. How to assemble a simple welding machine at home: drawings of inverter models and step-by-step assembly instructions

It is no secret that a do-it-yourself welding machine for a person familiar with electrical engineering is not so difficult to make. This especially makes sense if it is intended for use in a personal household, where it is used only from time to time. In this case, a home-made welding machine, the cost of which is much lower than the factory one, is quite capable of replacing it. Parts for its construction can be freely removed from various electrical household devices that are out of order or, if necessary, made and assembled by yourself. The schemes of such devices can be different. The decisive factor here is usually the availability of parts and materials.

Choosing a suitable welding machine diagram

All electric arc welding machines are divided into inverter and transformer. It should be noted right away that the question of how to make a welding machine on your own largely depends on the ability to get parts from certain household appliances. If all parts are purchased at market prices, then, as a result, the cost price will approach the price of a branded device, yielding to it in efficiency. That is why you need to have some knowledge in the field of electrical engineering and know where which part is installed and where it can be removed for free or for a small price.

The number of turns on the primary winding should be about 240. At the same time, to ensure the possibility of adjusting the welding current with a step of 20 to 25 turns, several taps are made. The secondary winding is wound with copper wire with a cross section of 30 to 35 mm in an amount of 65 to 70 turns. To adjust the welding current, bends must also be made on it. The insulation of the secondary winding must be particularly reliable and heat-resistant, so it should be given special attention. Each of the layers must be fitted with additional cotton insulation.

The transformer welding machine can operate with alternating or direct current. The first one is the simplest in design, but more difficult to use. For direct current, it is quite easy to modify it by installing a diode bridge. Such a device is reliable, durable and unpretentious to use, but it has a significant weight and is sensitive to voltage drops in the mains. If it falls below 200 V, it becomes very difficult to strike and hold the arc.

In contrast to the transformer inverter welding machine, thanks to the use of modern electronic parts, it has a relatively low weight. It may well be worn on the shoulder by one person. Such a device has a current stabilization device, which greatly facilitates the work when welding. Lowering the voltage for him practically does not create interference, and he can work from a household power supply. However, the inverter device is very sensitive to overheating and requires great care in its operation, otherwise it easily breaks down.

Assembling the transformer welding machine

The main part of such an apparatus is a transformer. Its main characteristic should be the ability to stably hold the operating current, and this is based on such an indicator as the external current-voltage characteristic of the power supply. In other words, the welding current should not differ significantly from the current produced by the short circuit.

To do this, the current must be limited by one of such methods as increasing the magnetic leakage of the transformer, ballast resistance or installing a choke. The transformer itself can be removed from a burnt out high-frequency microwave oven. If there is no access to it, then you can make a welding transformer with your own hands.

To make the core, you need to purchase transformer iron plates. Ideally, the core area should be from 40 to 55 cm², with such indicators, the winding will not overheat unnecessarily. Primary windings for self-made welding transformers should consist of a thick heat-resistant copper wire with a cross section of at least 5 mm, or better, more, enclosed in fiberglass or cotton insulation. It is not recommended to use plastic or rubber insulation for such purposes, since it is less resistant to overheating and is easier to break through, which causes a short circuit on the primary winding.

It must be remembered that the secondary winding of the welding transformer must be wound on both sides of the core. It can be connected either in series or in anti-parallel. It should be remembered that the winding must be done on both sides in the same direction. After that, the transformer is placed in a metal case. Holes are cut from its end to cool the device, and an exhaust fan removed from the power supply unit of an outdated or broken computer is installed. Several dozen holes are drilled on the opposite side of the case for air circulation. The cables and electrode holder can then be connected.

How to assemble a homemade inverter welding machine?

An inverter welding machine can be completely assembled from parts from old TVs. This requires not only some general electrical engineering knowledge, but also some knowledge of electronics. Its scheme is rather complicated. The inverter is a pulsed DC source, and several ferrite cores, which are on the line transformers in old TVs, are suitable for its manufacture. They are folded in three, and already a winding of copper or aluminum wire is wound around them.

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

Capacitors can also be removed from the TV, but it is only worth remembering that it is not recommended to take paper capacitors from low-frequency circuits, since they will not be able to work for a long time under such loads. It is better to take SCRs that are fairly low-power and connect them in parallel than to take one powerful one, since a large thermal load falls on them and it is easier to cool them. SCRs are mounted on a metal plate with a thickness of at least 3 mm, which facilitates the removal of excess heat. Diodes for assembling a diode bridge can also be easily recruited from several old TVs. The bridge itself is also mounted on a heat sink plate.

Some parts for the inverter device are missing in TVs, and they have to be made by ourselves. First of all, it is a choke. It is not difficult to make it without a frame made of copper wire with a cross section of at least 4 mm, wound with 11 turns at intervals of at least 1 mm. Since the main thermal load will fall on the throttle, an additional air cooling system must be installed. In this capacity, it is quite possible to use an ordinary household fan, mounted in the body of the welding machine so that the air stream falls directly on the choke.

All elements of the electronic circuit are assembled on a printed circuit board made of fiberglass with a thickness of at least 1.5 mm. A heatsink is attached to the board itself, making it easier to cool the entire system. A round hole is cut out in the center of the board for installing a fan, since the device will not work for a long time without forced air cooling. The welding inverter has the main advantage of being able to do mini-welding works by welding thin metal sheets. The welding seam itself comes out more accurate than that of a transformer device. This is critical when doing a DIY car repair job.

A do-it-yourself welder includes parts obtained for free or at a bargain price, but does its job well.

Figure 1. Diagram of a bridge rectifier for a welding machine.

Welding machines are available in DC and AC.

S.A. direct current are used when welding at low currents of thin sheet metal (roofing steel, automobile, etc.). DC arc is more stable, direct and reverse polarity can be welded. On direct current, you can weld with electrode wire without coating and with electrodes intended for welding, both on direct current and on alternating current. To give stability to arc burning at low currents, it is desirable to have an increased open-circuit voltage Uxx of the welding winding (up to 70 - 75 V). For rectifying alternating current, the simplest "bridge" rectifiers on powerful diodes with cooling radiators are used (Fig. 1).

To smooth out voltage ripples, one of S.A. And they are connected to the electrode holder through a choke L1, which is a coil of 10-15 turns of a copper bus with a cross section of S = 35 mm 2 wound on any core, for example, from. For rectification and smooth regulation of the welding current, more complex circuits are used with the use of powerful controlled thyristors. One of the possible circuits on thyristors of the T161 (T160) type is given in the article by A. Chernov "Both will charge and weld" (Modelist-constructor, 1994, No. 9). The advantages of DC regulators are their versatility. The range of voltage variation by them is 0.1-0.9 Uxx, which makes it possible to use them not only for smooth adjustment of the welding current, but also for charging batteries, powering electric heating elements and other purposes.

Figure 2. Diagram of the falling external characteristics of the welding machine.

Rice. 1. Bridge rectifier for the welding machine. Connection of S.A. is shown. for welding thin sheet metal on "reverse" polarity - "+" on the electrode, "-" on the workpiece to be welded U2: - output alternating voltage of the welding machine

AC welding machines are used for welding with electrodes, the diameter of which is more than 1.6 - 2 mm, and the thickness of the products to be welded is more than 1.5 mm. In this case, the welding current is significant (tens of amperes) and the arc burns quite steadily. The electrodes used are intended for welding only on alternating current. For normal operation of the welding machine, you must:

1. Provide output voltage for reliable arc ignition. For amateur S.A. Uxx = 60 - 65v. A higher open-circuit output voltage is not recommended, which is mainly associated with ensuring the safety of work (Uxx industrial welding machines - up to 70 - 75 V).
2. Provide welding voltage Uw, required for stable arc burning. Depending on the diameter of the electrode - Uw = 18 - 24v.
3. Provide a rated welding current Iw = (30 - 40) de, where Iw is the value of the welding current, A; 30 - 40 - coefficient depending on the type and diameter of the electrode; de - electrode diameter, mm.
4. Limit the short-circuit current Isc, the value of which should not exceed the rated welding current by more than 30 - 35%.

Stable arc burning is possible if the welding machine has a falling external characteristic, which determines the relationship between the current and voltage in the welding circuit (Fig. 2).

S.A. shows that for a rough (stepwise) overlap of the range of welding currents, it is necessary to switch both the primary windings and the secondary (which is structurally more complicated due to the large current flowing in it). In addition, mechanical devices for moving the windings are used to smoothly change the welding current within the selected range. When removing the welding winding relative to the mains, magnetic leakage fluxes increase, which leads to a decrease in the welding current.

Figure 3. Diagram of a rod-type magnetic circuit.

When designing an amateur SA, 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, to supplement it with a separate rectifier device with smooth regulation of the welding current. Amateur welding machines must meet a number of requirements, the main of which are the following: relative compactness and low weight; sufficient duration of operation (at least 5 - 7 electrodes de = 3 - 4 mm) from the 220V network.

The weight and dimensions of the apparatus can be reduced due to a decrease in its power, and an increase in the duration of operation - due to the use of steel with high magnetic permeability and heat-resistant insulation of the winding wires. These requirements are easy to fulfill, knowing the basics of designing welding machines and adhering to the proposed technology for their manufacture.

Rice. 2. Falling external characteristic of the welding machine: 1 - a family of characteristics for different ranges of welding; Isv2, Isvz, Isv4 - ranges of welding currents for electrodes with a diameter of 2, 3 and 4 mm, respectively; Uxx- open circuit voltage CA. Ikz - short-circuit current; Ucv - welding voltage range (18 - 24 V).

Rice. 3. Rod-type magnetic circuit: a - L-shaped plates; b - U-shaped plates; c - plates made of strips of transformer steel; S = axb- cross-sectional area of ​​the core (core), cm 2 s, d- window dimensions, see.

So, the choice of the type of core. For the manufacture of welding machines, mainly rod-type magnetic cores are used, since they are more technologically advanced in design. The core is collected from plates of electrical steel of any configuration with a thickness of 0.35-0.55 mm, tightened with pins isolated from the core (Fig. 3). When selecting a core, it is necessary to take into account the dimensions of the "window" to accommodate the windings of the welding machine, and the cross-sectional area of ​​the core (core) S = axb, cm 2. As practice shows, one should not choose the minimum values ​​of S = 25 - 35 cm, since the welding machine will not have the required power reserve and it will be difficult to obtain high-quality welding. And overheating of the welding machine after a short time is also inevitable.

Figure 4. Diagram of a toroidal type magnetic circuit.

The section of the core should be S = 45 - 55 cm 2. The welding machine will be a little heavier, but it won't let you down! Amateur welding machines with toroidal cores, which have higher electrical characteristics, are about 4 - 5 times higher than that of a rod one, are becoming more widespread, and electrical losses are small. Labor costs for their manufacture are more significant and are primarily associated with 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 of tape transformer iron, rolled into a torus-shaped roll. An example is a core made of an autotransformer "Latr" for 9 A. To increase the inner diameter of the torus ("window"), a part of the steel tape is unwound from the inside and wound onto the outer side of the core. But, as practice shows, "Latra" alone is not enough to produce high-quality SA. (small cross section S). Even after working with 1 - 2 electrodes with a diameter of 3 mm, it overheats. It is possible to use two similar cores according to the scheme described in B. Sokolov's article "Welding baby" (Sam, 1993, No. 1), or to manufacture one core by rewinding two (Fig. 4).

Rice. 4. Toroidal magnetic circuit: 1.2 - autotransformer core before and after rewinding; 3 design by S.A. based on two toroidal cores; W1 1 W1 2 - mains windings connected in parallel; W 2 - welding winding; S = axb- cross-sectional area of ​​the core, cm 2, s, d- inner and outer diameters of the torus, cm; 4 - electrical circuit S.A. based on two joined toroidal cores.

Special attention should be paid to amateur SA made on the basis of stators of asynchronous three-phase electric motors of high power (more than 10 kW). The choice of the core is determined by the cross-sectional area of ​​the stator S. The stamped stator plates do not fully correspond to the parameters of electrical transformer steel, therefore, it is inappropriate to reduce the cross-section S to less than 40 - 45 cm.

Figure 5. Scheme of fastening the conclusions of the CA windings.

The stator is freed from the housing, the stator windings are removed from the inner grooves, the groove bridges are cut with a chisel, the inner surface is protected with a file or an abrasive wheel, the sharp edges of the core are rounded off and wrapped tightly, overlapping with cotton insulating tape. The core is ready for winding the windings.

Selection of windings. For primary (network) windings, it is better to use a special copper winding wire in h.b. (fiberglass) insulation. Wires in rubber or rubber-fabric insulation also have satisfactory heat resistance. Unsuitable for work at elevated temperatures (and this is already incorporated into the design of an amateur SA) wires in polyvinyl chloride (PVC) insulation due to its possible melting, leakage from the windings and their short circuit. Therefore, PVC insulation from the wires must either be removed and the wires wrapped along the entire length of the h.b. with insulating tape, or do not remove, but wrap the wire over the insulation. Another method of winding that has been tested in practice is also possible. But more on that below.

When selecting the cross-section of the winding wires, taking into account the specifics of the work of S.A. (periodic) we assume a current density of 5 A / mm 2. With a welding current of 130 - 160 A (electrode de = 4 mm), the power of the secondary winding will be P 2 = Iw x 160x24 = 3.5 - 4 kW, the power of the primary winding, taking into account losses, will be about 5 - 5.5 kW, and therefore the maximum current of the primary winding can reach 25 A. Therefore, the cross-section of the wire of the primary winding S 1 must be at least 5 - 6 mm. In practice, it is advisable to use a wire with a cross section of 6 - 7 mm 2. Either it is a rectangular bus, or a copper winding wire with a diameter (without insulation) 2.6 - 3 mm. (Calculation according to the well-known formula S = piR 2, where S is the area of ​​the circle, mm 2 pi = 3.1428; R is the radius of the circle, mm.) If the section of one wire is insufficient, winding in two is possible. When using an aluminum wire, its cross-section must be increased by 1.6 - 1.7 times. Is it possible to reduce the cross-section of the mains winding wire? Yes, you can. But at the same time S.A. will lose the required power reserve, it will heat up faster, and the recommended core section S = 45 - 55 cm in this case will be unjustifiably large. The number of turns of the primary winding W 1 is determined from the following ratio: W 1 = [(30 - 50): S] x U 1 where 30-50 is a constant coefficient; S - core section, cm 2, W 1 = 240 turns with taps from 165, 190 and 215 turns, i.e. every 25 turns.

Figure 6. Diagram of ways of winding CA windings on a rod-type core.

A larger number of network winding taps, as practice shows, is impractical. And that's why. By reducing the number of turns of the primary winding, both the power of the SA and Uxx increase, which leads to an increase in the arc voltage and a deterioration in the quality of welding. Consequently, it is impossible to achieve overlapping of the range of welding currents only by changing the number of turns of the primary winding without deteriorating the quality of welding. To do this, it is necessary to provide for switching the 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 mm (preferably a cross section of 35 mm). Flexible stranded wire (for example, welding wire) and three-phase power stranded cable are also quite suitable. The main thing is that the cross-section of the power winding should not be less than the required one, and the insulation should be heat-resistant and reliable. With insufficient wire cross-section, winding in two or even three wires is possible. When using an aluminum wire, its cross-section must be increased by 1.6 - 1.7 times.

Rice. 5. Fastening of the CA winding leads: 1 - CA case; 2 - washers; 3 - terminal bolt; 4 - nut; 5 - copper tip with a wire.

The difficulty of acquiring switches for high currents, and practice shows that it is most simple to lead the leads of the welding winding through copper lugs under terminal bolts with a diameter of 8-10 mm (Fig. 5). Copper lugs are made from copper tubes of a suitable diameter 25-30 mm long and fixed to the wires by crimping and preferably soldering. Let's pay special attention to the order of winding winding. General rules:

1. Winding should be done on an insulated core and always in one direction (eg clockwise).
2. Each layer of the winding is insulated with a layer of h.b. insulation (fiberglass, electrical cardboard, tracing paper), preferably impregnated with bakelite varnish.
3. The conclusions of the windings are tinned, marked, fixed with h.b. braid, on the conclusions of the network winding, they additionally put on h.b. cambric.
4. In case of doubts about the quality of insulation, winding can be carried out using a cotton cord, as it were, in two wires (the author used a cotton thread for fishing). After winding one layer, the winding with h.b. thread is fixed with glue, varnish, etc. and after drying, the next row is wound.

Figure 7. Diagram of ways of winding CA windings on a toroidal core.

Consider the order of arrangement of the windings on a rod-type magnetic circuit. The mains winding can be positioned in two main ways. The first method allows you to obtain a more "hard" welding mode. The mains winding in this case consists of two identical windings W 1 W 2 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 (Fig. 6a, c).

The second method involves winding the primary (network) winding on one of the sides of the core (Fig. 6 c, d). In this case, the CA has a steeply dipping characteristic, it cooks "softly", the arc length has less effect on the value of the welding current, and, consequently, on the quality of welding. After winding the primary winding of the CA, 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 - 6A) and preferably an alternating current ammeter. If the fuse burns out or gets very hot, then this is a clear sign of a short-circuited loop. Consequently, the primary winding will have to be rewound, paying particular attention to the quality of the insulation.

Rice. 6. Methods of winding CA windings on a rod-type core: a - mains winding on both sides of the core; b - the corresponding secondary (welding) winding, connected in counter-parallel; c - mains winding on one side of the core; d - the corresponding secondary winding, connected in series.

If the welding machine hums strongly, and the current consumption exceeds 2 - 3 A, then this means that the number of the primary winding is underestimated and it is necessary to wind up some more turns. A serviceable AC consumes no more than 1 - 1.5 A no-load current, does not heat up and does not buzz much. The secondary winding CA is always wound on both sides of the core. For the first method of winding, the secondary winding also consists of two identical halves, included to increase the stability of the arc burning (Fig. 6) counter-parallel, and the wire cross-section can be taken slightly less - 15 - 20 mm 2.

Figure 8. Wiring diagram for measuring devices.

For the second method of winding, the main welding winding W 2 1 is wound on the side of the core free of windings and makes up 60 - 65% of the total number of turns of the secondary winding. It serves mainly to ignite the arc, and during welding, due to a sharp increase in the magnetic leakage flux, the voltage across it drops by 80 - 90%. An additional welding winding W 2 2 is wound over the primary. Being power, it maintains the welding voltage, and therefore the welding current, within the required limits. The voltage across it drops in welding mode by 20 - 25% relative to the open circuit voltage. After the manufacture of S.A, it is necessary to adjust it and check the quality of welding with electrodes of various diameters. The setup process is as follows. To measure welding current and voltage, it is necessary to purchase two electrical measuring devices - an alternating current ammeter for 180-200 A and an alternating current voltmeter for 70-80 V.

Rice. 7. Methods of winding CA windings on a toroidal core: 1.2 - uniform and sectional winding of windings, respectively: a - network b - power.

Their connection diagram is shown in Fig. 8. When welding with different electrodes, the values ​​of the welding current - Iw and the welding voltage Uw, which must be within the required limits, are removed. If the welding current is small, which happens most often (the electrode sticks, the arc is unstable), then in this case, either by switching the primary and secondary windings, the required values ​​are 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 network winding. After welding, you can make a break or sawing of the edges of the welded products, and immediately the quality of the welding becomes clear: the penetration depth and the thickness of the deposited metal layer. It is useful to draw up a table based on the measurement results.

Figure 9. Diagram of welding voltage and current meters and current transformer design.

Based on the data in the table, the optimal welding modes are selected for electrodes of various diameters, keeping in mind that when welding with electrodes, for example, 3 mm in diameter, electrodes with a diameter of 2 mm can be cut, because cutting current is 30 -25% higher than welding current. The difficulty of purchasing the measuring devices recommended above forced the author to start making a measuring circuit (Fig. 9) based on the most common DC milliammeter at 1-10 mA. It consists of voltage and current meters assembled in a bridge circuit.

Rice. 9. Schematic diagram of welding voltage and current meters and current transformer design.

The voltage meter is connected to the output (welding) winding of S.A. Adjustment is carried out using any tester that monitors the output voltage of the welding. With the help of variable resistance R.3, the arrow of the device is set to the final division of the scale at the maximum value of Uxx The scale of the voltage meter is quite linear. For greater accuracy, you can remove two or three control points and calibrate the measuring device to measure voltages.

It is more difficult to set up a current meter as it connects to a self-made current transformer. The latter is a toroidal core with two windings. The dimensions of the core (outer diameter 35-40 mm) are not of fundamental importance, the main thing is that the windings fit. The core material is transformer steel, permalloy or ferrite. The secondary winding consists of 600 - 700 turns of PEL, PEV insulated copper wire, better than PELSHO with a diameter of 0.2 - 0.25 mm and is connected to a current meter. The primary winding is the power wire that runs inside the ring and connects to the terminal bolt (Figure 9). Setting up a current meter is as follows. To the power (welding) winding S.A. connect a calibrated resistance from a thick nichrome wire for 1 - 2 seconds (it gets very hot) and measure the voltage at the output of S.A. By determining the current flowing in the welding winding. For example, when connecting Rн = 0.2 ohm, Uout = 30v.

Mark a point on the scale of the instrument. Three to four measurements with different R H are enough to calibrate the current meter. After calibration, the devices are installed on the S.A case, using generally accepted recommendations. When welding in various conditions (strong or low-current network, long or short supply cable, its cross-section, etc.), S.A. is tuned by switching the windings. to the optimal welding mode, and then the switch can be set to the neutral position. A few words about contact spot welding. To the design of S.A. this type has a number of specific requirements:

1. The power delivered at the time of welding should be maximum, but not more than 5-5.5 kW. In this case, the current consumed from the network will not exceed 25 A.
2. The welding mode must be "hard", and, consequently, the winding of the windings of S.А. should be carried out according to the first option.
3. The currents flowing in the welding winding reach values ​​of 1500-2000 A and higher. Therefore, the welding voltage should be no more than 2-2.5v, and the open circuit voltage should be 6-10v.
4. The cross-section of the wires of the primary winding is at least 6-7 mm, and the cross-section of the secondary winding is at least 200 mm. Achieve this cross-section of wires by winding 4-6 windings and their subsequent parallel connection.
5. It is impractical to make additional taps from the primary and secondary windings.
6. The number of turns of the primary winding can be taken as the minimum calculated due to the short duration of S.A.
7. It is not recommended to take a section of the core (core) less than 45-50 cm.
8. Welding lugs and submarine cables to them must be copper and carry appropriate currents (lug diameter 12-14 mm).

A special class of amateur S.A. represent devices made on the basis of industrial lighting and other transformers (2-3 phase) for an output voltage of 36V and a power of at least 2.5-3 kW. But before taking on the alteration, it is necessary to measure the core section, which should be at least 25 cm, and the diameters of the primary and secondary windings. It will immediately become clear to you what can be expected from the alteration of this transformer.

And in conclusion, a few technology tips.

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 diameter of the electrode, depending on the thickness of the welded metal, can be selected based on the following ratio: da = (1-1.5) L, where L is the thickness of the welded metal, mm.

The length of the arc is selected depending on the diameter of the electrode and is on average 0.5-1.1 d3. 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 losses for waste 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 on straight polarity, the plus (anode) is connected to the part and the minus (cathode) is connected to the electrode. If it is necessary that a smaller amount of heat is generated on the part, for example, when welding thin-sheet structures, welding is used in reverse polarity (Fig. 1). 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 provides less heating of the workpiece to be welded, but also accelerates the process of melting the electrode metal due to the higher temperature of the anode zone and greater heat supply.

Welding wires are connected to the CA through copper lugs for terminal bolts on the outside of the welding machine body. Poor contact connections reduce the power characteristics of the CA, deteriorate the quality of welding and can cause them to overheat and even fire the wires. With a small length of welding wires (4-6 m), their cross-section should be at least 25 mm. When performing welding work, it is necessary to observe the rules of fire and electrical safety when working with electrical appliances.

Welding work should be carried out in a special mask with C5 protective glass (for currents up to 150-160 A) and gloves. All switching of the CA should be performed only after disconnecting the welding machine from the mains.

20 years ago, at the request of a friend, I assembled a reliable welder for him to work from a 220 volt network. Before that, he had problems with neighbors due to a voltage drop: an economy mode with current regulation was required.

After studying the topic in reference books and discussing the issue with colleagues, I prepared an electrical control circuit based on thyristors, mounted it.

In this article, based on personal experience, I tell you how I assembled and set up a DC welding machine with my own hands on the basis of a homemade toroidal transformer. It came out in the form of a small instruction.

I still have the schematic and working sketches, but I cannot give photographs: there were no digital devices then, and my friend moved.

Versatile features and tasks

A friend needed an apparatus for welding and cutting pipes, corners, sheets of various thicknesses with the ability to work with electrodes of 3 ÷ 5 mm. At that time they did not know about welding inverters.

We settled on a direct current design as a more versatile one that provides high-quality seams.

Thyristors removed the negative half-wave, creating a pulsating current, but they did not begin to smooth the peaks to an ideal state.

The welding output current control circuit allows you to adjust its value from small values ​​for welding up to 160-200 amperes required when cutting with electrodes. She:

• made on a board made of thick getinax;
• closed with a dielectric casing;
• mounted on the body with the output of the knob of the adjusting potentiometer.

The weight and dimensions of the welding machine are smaller compared to the factory model. Placed it on a small cart with wheels. To change jobs, one person rolled it freely without much effort.

The power cable was connected through an extension cord to the connector of the input electrical panel, and the welding hoses were simply wound onto the body.

Simple design of DC welding machine

According to the installation principle, the following parts can be distinguished:

• homemade transformer for welding;
• its power supply circuit from the 220 network;
• output welding hoses;
• power unit of a thyristor current regulator with an electronic control circuit from a pulse winding.

Pulse winding III is located in the power zone II and is connected through a capacitor C. The amplitude and duration of the pulses depend on the ratio of the number of turns in the capacitor.

How to make the most convenient transformer for welding: practical tips

In theory, any model of transformer can be used to power the welding machine. The main requirements for it:

• ensure the voltage of the arc ignition at idle;
• reliably withstand the load current during welding without overheating the insulation from long-term operation;
• meet electrical safety requirements.

In practice, I have come across different designs of homemade or factory transformers. However, they all require an electrical calculation.

For a long time I have been using a simplified technique that allows you to create fairly reliable designs of a medium-accuracy transformer. This is quite enough for household purposes and power supplies for radio amateur devices.

It is described on my website in the article This is an average technology. It does not require specification of the grades and characteristics of electrical steel. We usually do not know them and cannot take them into account.

Core manufacturing features

Craftsmen make magnetic wires from electrical steel of all kinds of profiles: rectangular, toroidal, double rectangular. They even wind turns of wire around the stators of burnt out powerful asynchronous electric motors.

We had the opportunity to use decommissioned high-voltage equipment with dismantled current and voltage transformers. We took from them strips of electrical steel, made two rings of them - a donut. The cross-sectional area of ​​each was calculated to be 47.3 cm 2.

They were insulated with varnished cloth, fastened with cotton tape, forming a figure of a reclining figure of eight.

A wire was wound on top of the reinforced insulating layer.

Secrets of the power winding device

The wire for any circuit must have good, strong insulation, designed to last when heated. Otherwise, it will simply burn out during welding. We proceeded from what was at hand.

We got a wire with varnish insulation, closed on top with a fabric sheath. Its diameter - 1.71 mm is too small, but the metal is copper.

Since there was simply no other wire, they began to make the power winding out of it with two parallel lines: W1 and W'1 with the same number of turns - 210.

The core bagels were mounted tightly: so they have smaller dimensions and weight. However, the cross-section for the winding wire is also limited. Installation is difficult. Therefore, each half-winding of the power supply was smashed to its own rings of the magnetic circuit.

In this way we:

• doubled the cross-section of the power winding wire;
• saved space inside bagels for placing the power winding.

Wire alignment

You can get tight winding only from a well-aligned core. When we removed the wire from the old transformer, it turned out to be bent.

We figured out the required length in our minds. Of course she was not enough. Each winding had to be made of two parts and spliced ​​with a screw clamp directly on the donut.

The wire was stretched on the street along its entire length. We picked up the pliers. They pinched the opposite ends with them and pulled them with force in different directions. The vein turned out to be well aligned. They twisted it into a ring with a diameter of about a meter.

Wire winding technology on torus

For winding the power supply, we used the method of winding with a rim or wheel, when a ring of large diameter is made from the wire and is wound inside the torus by rotating one turn at a time.

The same principle is used when putting on a winding ring, for example, on a key or trinket. After the wheel is wound inside the donut, they begin to spin it gradually, laying and fixing the wire.

This process was well demonstrated by Alexey Molodetsky in his video "Winding a torus on a rim".

This work is difficult, painstaking, requires perseverance and attention. The wire must be tightly laid, count, control the process of filling the inner cavity, keep a record of the number of coils wound.

How to wind a power winding

For her, we found a copper wire of a suitable cross section - 21 mm 2. We figured out the length. It affects the number of turns, and the open circuit voltage required for good ignition of the electric arc depends on them.

We made 48 turns with an average output. In total, we got three ends on the donut:

• medium - for direct connection of "plus" to the welding electrode;
• extreme - to thyristors and after them to ground.

Since the bagels are fastened and the power windings are already mounted on them along the edges of the rings, the winding of the power circuit was carried out by the "shuttle" method. The aligned wire was folded in a snake and pushed through the bagel holes for each loop.

The mid-point soldering was performed with a screw connection with its insulation with varnished cloth.

Reliable welding current control circuit

Three blocks are involved in the work:

1. stabilized voltage;
2. the formation of high-frequency pulses;
3. separation of pulses on the circuit of the control electrodes of thyristors.

Voltage stabilization

An additional transformer with an output voltage of about 30 V is connected from the power winding of the 220 volt transformer. It is rectified by a diode bridge based on D226D and stabilized by two D814V zener diodes.

In principle, any power supply unit with similar electrical characteristics of current and voltage at the output can work here.

Pulse block

The stabilized voltage is smoothed by a capacitor C1 and fed to a pulse transformer through two bipolar transistors of forward and reverse polarity KT315 and KT203A.

Transistors generate pulses to the primary winding Tr2. This is a toroidal type pulse transformer. It is made on permalloy, although a ferrite ring can also be used.

The winding of three windings was carried out simultaneously with three pieces of wire with a diameter of 0.2 mm. Made in 50 turns. The polarity of their inclusion matters. It is shown by dots on the diagram. The voltage on each output circuit is about 4 volts.

Windings II and III are included in the control circuit of power thyristors VS1, VS2. Their current is limited by resistors R7 and R8, and part of the harmonic is cut off by diodes VD7, VD8. We checked the appearance of the pulses with an oscilloscope.

In this chain, the resistors must be selected for the voltage of the pulse generator so that its current reliably controls the operation of each thyristor.

The firing current is 200 mA, and the firing voltage is 3.5 volts.

Do-it-yourself welding in this case does not mean welding technology, but home-made equipment for electric welding. Working skills are acquired through practical training. Of course, before going to the workshop, you need to master the theoretical course. But you can only put it into practice if you have something to work on. This is the first argument in favor of the fact that, independently mastering the welding business, take care of the availability of the appropriate equipment first.

Second, a purchased welding machine is expensive. Renting is also not cheap, because the probability of its failure with unskilled use is great. Finally, in the hinterland, getting to the nearest location where you can rent a welder can simply be long and difficult. All in all, it is better to start the first steps in welding metals with making a welding machine with your own hands. And then - let him stand in the barn or garage until the occasion. It is never too late to spend money on branded welding, if it goes well.

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 approximately to the fence from corrugated board on a frame from a professional pipe or welded garage.
• Microarc welding of wire twists is very simple and useful when laying or repairing electrical wiring.
• Spot impulse resistance welding - can be very useful when assembling products from a thin steel sheet.

What we will not talk about

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

The second is inverter arc welding. Indeed, the semiautomatic welding inverter allows the novice amateur to cook quite critical designs. It is lightweight and compact and can be carried by hand. But the retail purchase of inverter components, which allows you to consistently maintain a high-quality seam, will cost more than the finished device. An experienced welder will try to work with simplified homemade products and refuse - "Give me a normal machine!" Plus, or rather a minus - to make a more or less decent welding inverter, you need to have quite solid experience and knowledge in electrical engineering and electronics.

The third is argon-arc welding. From whose light hand the statement that it is a hybrid of gas and arc went to walk in Runet is unknown. In fact, this is a kind of arc welding: the inert gas argon does not participate in the welding process, but creates a cocoon around the working area, isolating it from the air. As a result, the weld is chemically clean, free from impurities of metal compounds with oxygen and nitrogen. Therefore, it is possible to cook under argon non-ferrous metals, incl. dissimilar. In addition, it is possible to reduce the welding current and arc temperature without compromising its stability and to weld with a non-consumable electrode.

It is quite possible to make equipment for argon-arc welding at home, but gas is very expensive. It is unlikely that you will need to cook aluminum, stainless steel or bronze as part of routine economic activities. And if you really need to, then it is easier to rent argon welding - compared to how much (in money) gas will go back into the atmosphere, this is a penny.

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 works in intermittent mode. If designed for maximum current as continuous transformers, it will turn out to be prohibitively large, heavy and expensive. Ignorance of the features of electric arc welding transformers is the main reason for the failure of amateur designers. Therefore, we will walk through the welding transformers in the following order:

1. a little theory - on the fingers, without formulas and zaum;
2. features of the magnetic cores of welding transformers with recommendations for choosing from accidentally turned up;
3. tests of the second-hand available;
4. calculation of the transformer for the welding machine;
5. preparation of components and winding of windings;
6. trial assembly and debugging;
7. commissioning.

Theory

An electrical transformer can be likened to a storage tank for a water supply. This is a rather deep analogy: a transformer operates due to the reserve of magnetic field energy in its magnetic circuit (core), which can many times exceed 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 the same for water losses due to infiltration. Power losses in the copper of the windings are formally similar to the pressure losses in pipes due to viscous friction in the liquid.

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

An important factor in our case is the external current-voltage characteristic (VVAC) of the transformer, or simply its external characteristic (VX) - 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, VX is rigid (curve 1 in the figure); they are like a shallow vast basin. If it is properly insulated and covered with a roof, then the water loss is minimal and the pressure is quite stable, no matter how the consumers turn the taps. But if there is a gurgle in the drain - sushi oars, the water is drained. With regard to transformers, the power engineer 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 chosen with a more rectangular hysteresis loop.
• Structural measures (core configuration, calculation method, configuration and arrangement of windings) in every possible way reduce dissipation losses, losses in steel and copper.
• The induction of the magnetic field in the core is taken less than the maximum allowable for the transmission of the current form, because its distortion reduces efficiency.

Note: transformer steel with "angular" hysteresis is often called magnetic hardness. This is not true. Hard magnetic materials retain strong residual magnetization, they are made by permanent magnets. And any transformer iron is soft magnetic.

It is impossible to cook from a transformer with a rigid VX: the seam is torn, burnt, the metal is splashed. The arc is inelastic: I almost moved it with the electrode, it goes out. Therefore, the welding transformer is already made similar to a conventional water tank. Its IQ is soft (normal dissipation, curve 2): as the load current increases, the secondary voltage decreases smoothly. The normal scatter curve is approximated by a straight line falling at an angle of 45 degrees. This allows, due to a decrease in efficiency, to briefly remove several times more power from the same iron, or, respectively. to reduce the weight and dimensions and the cost of the transformer. In this case, the induction in the core can reach the saturation value, and even exceed it for a short time: the transformer will not go into a short circuit with zero power transfer, like a "silovik", but will start to heat up. Quite long: the thermal time constant of the welding transformers is 20-40 minutes. If you then let it cool down and there was no unacceptable overheating, you can continue to work. The relative drop of the secondary voltage ΔU2 (corresponding to it, the swing of the arrows in the figure) of normal dispersion increases smoothly with an increase in the amplitude of oscillations of the welding current Iw, which makes it easy to keep the arc in any type of work. The following properties are provided:

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

Note: reversible leakage losses means that some of the lines of force penetrate the secondary through the air bypassing the magnetic circuit. The name is not quite apt, as well as "useful scattering", since "Reversible" losses for the efficiency of a transformer are no more useful than irreversible ones, but they soften the VC.

As you can see, the conditions are completely different. So, by all means look for iron from a welder? Optional, for currents up to 200 A and peak power up to 7 kVA, but this will be enough on the farm. By design and design measures, as well as with the help of simple additional devices (see below), we will obtain curve 2a on any BX gland, somewhat more rigid than normal. In this case, the efficiency of energy consumption in welding is unlikely to exceed 60%, but for occasional work it is not scary for oneself. But on fine work and low currents, it will be easy to keep the arc and welding current, without much experience (ΔU2.2 and Ib1), at high currents Ib2 we will get an acceptable weld quality, and it will be possible to cut metal up to 3-4 mm.

There are also welding transformers with steeply dipping VX, curve 3. This is more like a pumping pump: either the output flow is in nominal regardless of the feed height, or it is not at all. They are even more compact and lightweight, but in order to withstand the welding mode on a steeply dipping VX, it is necessary to respond to fluctuations ΔU2.1 of the order of a volt in a time of the order of 1 ms. Electronics can do this, so transformers with "cool" VX are often used in semi-automatic welding machines. If from such a transformer you cook by hand, then the seam will go sluggish, undercooked, the arc is again inelastic, and when you try to ignite it again, the electrode now and then sticks.

Magnetic cores

The types of magnetic cores suitable for the manufacture of welding transformers are shown in Fig. Their names begin with a letter combination acc. 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 iron of reduced height, unsuitable for the welder, with all other outstanding advantages.

The letters of the type are followed by the numbers denoting a, b and h in Fig. For example, for Ш20х40х90 the dimensions of the core cross-section (central rod) are 20x40 mm (a * b), and the window height h is 90 mm. Core cross-sectional area Sс = a * b; window area Sok = c * h is needed for accurate calculation of transformers. We will not use it: for an accurate calculation, you need to know the dependence of losses in steel and copper on the value of induction in the core of a given standard size, and for them - the steel grade. Where can we get it if we wind it on random hardware? We will calculate using a simplified method (see below), and then we will bring it to the test. It will take more work, but we will get welding on which you can actually work.

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

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

• Oh, OL - from 10 kg.
• P, PL - from 12 kg.
• Ш, ШЛ - from 16 kg.

Why Sh and ShL are needed more heavily is understandable: they have an "extra" lateral rod with "shoulders". The OL can be easier, because there are no angles in it for which an excess of iron is needed, and the bends of the magnetic field lines are smoother and for some other reasons, which are already in the next. section.

Oh OL

The prime cost of transformers on tori 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, so it should not be afraid of overloads, and the LATR iron provides a VC close to normal. But…

LATR is a very useful thing, first. If the core is still alive, it is better to restore the LATR. Suddenly it is not needed, you can sell it, and the proceeds will be enough for welding suitable for your needs. Therefore, it is difficult to find "bare" LATR cores.

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

Another torus suitable for all its properties is the stator of an electric motor; welding from it will turn out even for an exhibition. But finding it is no easier 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 difficulties and nuances there. First of all - with the winding of a thick wire on the "donut". Without experience in winding toroidal transformers, the probability of spoiling an expensive wire and not getting welding is close to 100%. Therefore, alas, with a cooking apparatus on a troidal transformer, you will have to wait.

Ш, ШЛ

Armor cores are structurally designed for minimal dispersion, and it is practically impossible to normalize it. Welding on a conventional W or SL will turn out to be too tough. In addition, the conditions for cooling the windings on Ш and ШЛ are the worst. The only armored cores suitable for a welding transformer are of increased height with spaced wafer 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.

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

If you turn up a lined Ш without a yoke, but with a notch of the plates between the core and the bulkhead (in the center), you are in luck. Signal transformer plates are loaded, and steel on them, to reduce signal distortion, goes to give normal VX initially. But the likelihood of such luck is very small: signal transformers for kilowatt powers are a rare wonder.

Note: do not try to collect a high Ш or ШЛ from a pair of ordinary ones, as on the right in fig. A solid straight gap, albeit very thin, is irreversible scattering and a steeply dipping VX. Here, the dissipation losses are almost the same as the evaporation losses of water.

PL, PLM

Rod cores are most suitable for welding. Of these, those charged in pairs of identical L-shaped plates, see Fig., Their irreversible scattering is the smallest. Second, the P and PLov windings are wound in exactly the same halves, half turns for each. The slightest magnetic or current asymmetry - the transformer hums, heats up, but there is no current. The third, which may seem unobvious, for those who have not forgotten the school rule of the gimbal - the windings are wound on the rods in one direction... Is there something wrong? Does the magnetic flux in the core have to be closed? And you twist the gimbals along the current, not along the turns. The directions of the currents in the semi-windings are opposite, and the magnetic fluxes are shown there. You can also check if the protection of the wiring is reliable: supply the network to 1 and 2 ', and close 2 and 1'. If the machine gun does not immediately knock out, then the transformer will howl and shake. However, who knows what you have with the wiring. Better not.

Note: you can also find recommendations - winding the windings of the welding P or PL on different rods. Like, VX is softening. That is how it is, but a special core is needed for this, with rods of different cross-sections (secondary housing on the smaller one) and recesses that release the lines of force into the air in the desired direction, see Fig. on right. Without this, we will get a loud, shaking and gluttonous, but not a boiling 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 the devil knows how. An ammeter is needed either a non-contact induction (current clamp) or an electromagnetic switch for 3 A. A multimeter with alternating current limits will be unacceptable to lie, because the shape of the current in the circuit will be far from sinusoidal. Another - a liquid household thermometer with a long neck, or, better, a digital multimeter with the ability to measure temperature and a probe for this. A step-by-step procedure for testing and preparing for further operation of the old welding transformer is as follows:

Calculation of the 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 series of standard types of magnetic cores. The proposed methodology was developed in Soviet times, when instead of a choice there was a deficit of everything. For the transformer calculated according to it, VX falls a little steeply, somewhere between curves 2 and 3 in Fig. at the beginning. This is suitable for cutting, and for thinner work, the transformer is supplemented with external devices (see below) that stretch the VX along the current axis to curve 2a.

The basis of the calculation is the usual: the arc burns stably under a voltage of Ud 18-24 V, and its ignition requires an instantaneous current 4-5 times higher than the nominal welding current. Accordingly, the minimum no-load voltage Uхх 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 is unacceptable for TB, and the iron will not pull out. Another feature, for the same reasons, is the dynamic properties of the transformer, i.e. its ability to quickly switch from the short circuit mode (say, when closed by drops of metal) into the working one, is maintained without additional measures. True, such a transformer is prone to overheating, but since it is its own and in front of our eyes, and not in the far corner of the workshop or site, we will consider it permissible. So:

• According to the formula from clause 2 before. the list we find the overall power;
• We find the maximum possible welding current Iw = Pg / Ud. 200 A are provided if 3.6-4.8 kW can be removed from iron. True, in the 1st case, the arc will be sluggish, and it will be possible to cook only with a two or 2.5;
• We calculate the operating current of the primary at the maximum allowable mains voltage for welding I1рmax = 1.1Pg (VA) / 235 V. In fact, the norm for the network is 185-245 V, but for a home-made 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 accept the current density of the primary J1 = 5 A / sq. mm and, using I1рmax, we find the diameter of its wire in copper d = (4S / 3.1415) ^ 0.5. Its full diameter with self-isolation is D = 0.25 + d, and if the wire is ready - tabular. To work in the "brick bar, yok solution" 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 Ш and П, k2 = 40 for ПЛ, ШЛ and k2 = 35 for О, ОЛ;
• We find the total number of its turns W = 195k3w, where k3 = 1.03. k3 takes into account the energy losses of the winding for dissipation in copper, which is formally expressed by a somewhat abstract parameter of the winding's own voltage drop;
• We set the stacking coefficient Ku = 0.8, add 3-5 mm each to a and b of the magnetic circuit, calculate the number of layers of the winding, the average length of the turn and the length of the wire
• We calculate in a similar way the secondary 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

Wire diameters in the calculation of windings are usually more than 3 mm, and varnished winding wires with d> 2.4 mm are rare on the market. In addition, the welder's windings experience strong mechanical loads from electromagnetic forces, therefore, finished wires are needed with an additional textile winding: PELSH, PELSHO, PB, PBD. They are even more difficult to find and very expensive. The length of the wire per welder is such that cheaper bare wires can be insulated on their own. An additional advantage - twisting several stranded wires to the desired S, we get a flexible wire, which is much easier to wind. Anyone who has tried to manually lay a tire of at least 10 squares on the carcass will appreciate it.

Isolation

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

1. Masking tape with 75-80% overlap, i.e. in 4-5 layers.
2. Mitcal tape with an overlap of 2 / 3-3 / 4 turns, that is, 3-4 layers.
3. Cotton tape with an overlap of 50-67%, 2-3 layers.

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

Winding

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

• We are preparing a wooden boss with a height along 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 fasten temporary plywood cheeks to it;
• We wrap the temporary frame in 3-4 layers with a thin plastic wrap with an approach to the cheeks and a twist on their outer side so that the wire does not stick to the tree;
• We wind a pre-insulated winding;
• On the winding, we soak twice before flowing through with liquid varnish;
• after the impregnation dries, carefully remove the cheeks, squeeze out the lug and tear off the film;
• we tie the winding in 8-10 places evenly around the circumference with a thin cord or propylene twine - it is ready for testing.

Lapping and homework

We load the core into a biscuit and tighten it with bolts, as expected. The winding tests are carried out completely similar to the tests of the dubious finished transformer, see above. Better to use LATR; Iхх at an input voltage of 235 V should not exceed 0.45 A per 1 kVA of the overall power of the transformer. If it is more, the primary organization will be killed. Winding wire connections are made on bolts (!), Insulated with a heat-shrinkable tube (HERE) in 2 layers or cotton tape in 4-5 layers.

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

After finishing, the core is disassembled; 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 we soak it again with liquid varnish; when dry - twice undiluted. This biscuit is ready, you can make a secondary one. When both are on the core, we once again test the transformer on Ixx (suddenly it curled somewhere), fix the biscuits and saturate the entire transformer with normal varnish. Phew, the most dreary part of the work is behind.

Pull VX

But we still have it too cool, have you forgotten? It 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 will dissipate by heat. If we have a welder for 10 or more kVA, and we need to weld thin metal, a resistor is needed. Whatever the current is set by the regulator, its emissions during arc striking are inevitable. Without active ballast, they will burn through the seam in places, and the resistor will extinguish them. But for us, weak ones, he will not be of any use to him.

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

We will go the other way: we will use active-reactive ballast, in the old welders, in common parlance, called the gut, see fig. on right. Material - steel wire rod 6 mm. The diameter of the loops is 15-20 cm. How many of them are shown in Fig. it can be seen that this gut is correct for power up to 7 kVA. 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 clip-clothespin. By selecting the attachment point, you can, together with switching to the secondary taps, fine-tune the operating mode of the arc.

Note: active-reactive choke in operation can be heated red-hot, so it needs a non-combustible thermo-resistant dielectric non-magnetic lining. In theory, a special ceramic lodgment. It is permissible to replace it with a dry sand pillow, or already formally in violation, but not rough, the welding gut is laid on bricks.

But other?

This means, first of all, the electrode holder and the return hose connector (clamp, clothespin). They, since we have a transformer at the limit, you need to buy ready-made, and such as in Fig. on the right, don't. For a welding machine for 400-600 A, the quality of contact in the holder is not perceptible, and it will also withstand just winding the return hose. And our home-made, working with an effort, can go awry, it seems to be incomprehensible why.

Further, the body of the device. It needs to be made of plywood; desirably bakelite impregnated as described above. The bottom - from 16 mm thick, the panel with the terminal block - from 12 mm, and the walls and lid - from 6 mm, so that they do not come off during carrying. Why not sheet steel? It is a ferromagnet and in the stray field of the transformer can disrupt its operation, because we are drawing out everything that is possible from it.

As for the terminal blocks, the terminals themselves are made from bolts from M10. The basis is the same textolite or fiberglass. Getinaks, bakelite and carbolite are not suitable, they will soon crumble, crack and exfoliate.

Trying a constant

DC welding has a number of advantages, but the VC of any DC welding transformer is toughened. And ours, designed for the minimum possible power reserve, will become unacceptably tough. The choke-gut will not help here, even if it worked on direct current. In addition, expensive 200 A rectifier diodes must be protected from current and voltage surges. We need a return-absorbing infra-low frequency filter, FINCH. Although it looks reflective, the strong magnetic coupling between the halves of the coil must be taken into account.

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

With the magnetic core, the coils are easier, although not entirely. Suitable for him are 2 PLs of the TS-270 power transformer from old tube TVs - "coffins" (data is in reference books and in the Russian Internet), or similar, or SHL with similar or large a, b, c and h. SL is assembled from 2 submarines with a gap, see fig., 15-20 mm. Fix it with textolite or plywood spacers. Winding - insulated wire from 20 sq. mm, how much will fit in the window; 16-20 turns. They wind it in 2 wires. The end of one is connected to the beginning of the other, this will be the midpoint.

The filter is adjusted along an arc at the minimum and maximum values ​​of Uхх. If the arc is at least sluggish, the electrode sticks, the gap is reduced. If the metal burns at maximum, they increase or, which will be more effective, cut off part of the side rods symmetrically. So that the core does not crumble from this, 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 micro-arc welding was mentioned at the beginning. The “equipment” for it is extremely simple: a step-down transformer 220 / 6.3 V 3-5 A. One electrode - the wire twisting itself (copper-aluminum, copper-steel can be used); the other is a graphite rod, like the lead from a 2M pencil.

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

Video: homemade twist welding machine

Video: do-it-yourself welding machine from capacitors

Contact! There is a contact!

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

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

Nevertheless, resistance spot welding is much more economical than arc welding: the open-circuit voltage of the welding transformer for it is 2 V. It is the sum of 2-contact steel-copper potential differences and the ohmic resistance of the penetration zone. The transformer for resistance welding is calculated similarly to it for arc welding, but the current density in the secondary winding is taken from 30-50 and 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.

Runet has a lot of descriptions of homemade pulse-point welders from unusable microwaves. They are, in general, correct, but in repetition, as it is written in "1001 Nights", there is no benefit. And the old microwave ovens do not lie in heaps in the trash heaps. Therefore, we will deal with constructions less known, but, by the way, more practical.

In fig. - device of the simplest device for pulse spot welding. It can weld sheets up to 0.5 mm; for small crafts, it fits perfectly, and magnetic cores of this and larger standard size are relatively affordable. Its advantage, in addition to simplicity, is the clamping of the running rod of the welding tongs with a load. A third hand would not hurt to work with a contact-welding impulse, and if one has to squeeze the pliers with force, then it is generally inconvenient. Disadvantages - increased risk of accidents and injuries. If you accidentally give an impulse when the electrodes are brought together without the parts to be welded, then plasma will hit from the tongs, metal splashes will fly, the wiring protection will be knocked out, and the electrodes will fuse tightly.

Secondary winding - 16x2 copper bus. It can be drawn from strips of thin sheet copper (it will turn out to be flexible) or made from a piece of a flattened pipe for supplying the refrigerant of a household air conditioner. Manually insulate the bus as described above.

Here in fig. - drawings of an impulse spot welding apparatus are more powerful, for welding sheet up to 3 mm, and more reliable. Thanks to a rather powerful return spring (from the carapace of the bed), accidental convergence of the pliers is excluded, and the eccentric clamp provides a strong stable compression of the pliers, which significantly determines the quality of the welded joint. In which case the clamp can be instantly reset with one blow to the eccentric lever. The disadvantage is the insulating nodes of the ticks, there are too many of them and they are complicated. Another one is the aluminum pliers rods. Firstly, they are not as strong as steel, and secondly, they are 2 unnecessary contact differences. The heatsink on aluminum is certainly excellent though.

About electrodes

In an amateur environment, it is more expedient to insulate the electrodes at the installation site, as shown in Fig. on right. The house is not a conveyor belt, the device can always be allowed to cool down so that the insulating sleeves do not overheat. Such a design will make it possible to make the rods from a durable and cheap steel professional pipe, and also lengthen the wires (up to 2.5 m this is permissible) and use a contact welding gun or remote pliers, see Fig. below.

In fig. on the right, one more feature of electrodes for spot resistance welding is visible: a spherical contact surface (heel). Flat heels are more durable, which is why 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 to be welded, otherwise the penetration spot will be burned out either in the center (wide heel) or along the edges (narrow heel), and corrosion will go from the welded joint even on stainless steel.

The last thing about electrodes is their material and dimensions. Red copper quickly burns out, so purchased electrodes for resistance welding are made of copper with a chromium additive. These should be used, with current copper prices this 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. The length of the electrode under the conditions of heat transfer is not less than 3 of its diameters from the heel to the root (the beginning of the shank).

How to give impetus

In the simplest home-made devices for pulse-contact welding, a current pulse is given manually: they simply turn on the welding transformer. This, of course, is not good for him, and welding is either lack of penetration or burnout. However, it is not so difficult to automate the feeding and normalization of welding pulses.

A diagram of a simple, but reliable and proven by long-term practice of the welding pulse generator is given in Fig. The auxiliary transformer T1 is a conventional power transformer of 25-40 W. Winding voltage II - according to the backlight lamp. You can instead put 2 LEDs connected in antiparallel with a damping resistor (normal, 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 (ordinary electrolytic) is needed for a voltage of 40 V. Diodes V1-V4 and V5-V8 are any rectifier bridges for 1 and from 12 A, respectively. Thyristor V9 - for 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 that regulates the pulse duration. Transformer T2 - welding.

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

Modern technology offers a huge selection of models, differing in power and size. Reliable designs have a fairly high cost. Budget options tend to have a short lifespan.

Our material provides detailed instructions on how to make a do-it-yourself welding machine. Before starting the work process, it is recommended that you familiarize yourself with the type of welding equipment.

Types of welding machine

The devices of this technique differ into 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
• invector.

The AC model is considered the simplest mechanism that you can easily make 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 of these parts can be purchased from specialized stores. Detailed consultation of specialists helps to make the right choice.

AC design

Experienced welders call this a step-down transformer.

How to make a welding machine with your own hands?

The first thing to do is to make the right core. For this model, it is recommended to select the bar part type.

For its manufacture, you will need plates made of transformer steel. Their thickness is 0.56 mm. Before proceeding with the assembly of the core, its dimensions must be observed.

How to calculate the parameters of a part correctly?

Everything is simple enough. The dimensions of the center 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. For this, thin transformer plates are taken, which are interconnected to the required thickness of the part.

Next, we wind a step-down transformer consisting of turns of a thin wire. For this, 210 turns of thin wire are made. On the other hand, 160 turns are wound. The third and fourth primary windings should contain 190 turns. After that, a thick plate is attached to the surface.

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

Note!

The finished structure should contain 4 bolts with a different number of turns.

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

You can control the supply of electrical energy by switching the 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 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 often used to work on an industrial scale.

The main welding invector is made from a printed circuit board. Such a semiautomatic welding machine can withstand power surges during long-term operation.

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

Diy welding machine photo

Note!