The basis of the welding machine of the first design— laboratory transformer LATR for 9 A. The casing and all fittings are removed from it, only the winding remains on the core. In the welding machine transformer it will be primary (network). This winding is insulated with two layers of electrical tape or varnished cloth. A secondary winding is wound on top of the insulation - 65 turns of wire or a set of wires with a total cross-section of 12-13 mm 2. The winding is reinforced with electrical tape.The transformer is installed on an insulating stand made of textolite or getinax inside a casing made of sheet steel or duralumin with a thickness of no more than 3 mm. Holes with a diameter of 8-10 mm are made in the casing cover, on the back and side walls for ventilation. A handle made of steel rod is strengthened on top.

An indicator light, a 220 V, 9 A switch and secondary winding terminals are installed on the front panel - a cable with an electrode holder is connected to one of them, and a cable is connected to the other, the second end of which is pressed against the part being welded during welding. In addition, this last terminal must be grounded during operation. The AC indicator light type CH-1, CH-2, M.N-5 signals that the device is turned on.

Electrodes for this device must have a diameter of no more than 1.5 mm.

For welding machine of the second design(Fig. 126) it is necessary to make a transformer. A core with a cross section of about 45 cm 2 is assembled from W-shaped transformer iron, and the primary (network) winding is wound on it - 220 turns of 1.5 mm PEL wire. Taps are made from the 190th and 205th turns, after which the winding is insulated with two or three layers of electrical tape or varnished cloth.

A secondary winding is wound on top of the insulated primary winding.

It contains 65 turns of wire or a set of wires with a total cross-section of 25-35 mm 2. In the set it is best to use wires of the PEL or PEV type 1.0-1.5 mm. As in the first design, the finished transformer is mounted on an insulating stand and placed in a casing. The walls of the casing must be at least 30 mm away from the transformer. On the front panel, in addition to the light bulb, switch and terminals, there is a switch that regulates the current.

In a welding machine of this design, electrodes with a diameter of 1.5 and 2 mm can be used.

When working, you must wear a mask. This device cannot be connected to the home network, as it consumes about 3 kW. You can use the device in a workshop if available. electrical network, to which it is allowed to connect devices with a power of up to 5 kW.

Attention! Before starting work, check the grounding.

Wear dry tarpaulin overalls and gloves when welding. Place a rubber mat under your feet. Don't work without a mask.

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

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

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

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

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

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

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

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

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

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

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

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

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

Current regulator circuit for a welding machine

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

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

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

Conversion of LATR 2 into a homemade welding machine

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

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

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

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

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

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

An excellent welding machine can be made on the basis of a laboratory LATR autotransformer and a homemade thyristor mini-regulator with a rectifier bridge. They make it possible not only to safely connect to a standard 220 V network, but also to change the voltage on the electrode, and therefore select the required amount of welding current.

Inside the housing there is a toroidal autotransformer (ATR), made on a large cross-section magnetic core. It is this magnetic core that will be needed from LATR for the manufacture of a new welding transformer (ST).

We will need two identical magnetic core rings from large LATRs. LATRs were produced in the USSR different types with a maximum current of 2 to 10 A. Welding transformers for its manufacture are suitable for those whose magnetic core dimensions make it possible to place required amount turns. The most common among them is the ATR type LATR 1M.

The magnetic core from LATR 1M has the following dimensions: outer diameter 127 mm; internal 70 mm; ring height 95 mm; cross section 27 cm2 and mass 6 kg. You can make an excellent welding transformer from two rings from this LATR.

In many ATRs, the magnetic core has a larger outer diameter of the ring, but a smaller height and diameter of the window. In this case, it must be increased to 70 mm. The magnetic circuit ring is made of pieces of iron tape wound on each other, welded at the edges.

In order to adjust the inner diameter of the window, it is necessary to disconnect the end of the tape from the inside and unwind required quantity. Don't try to do it all in one go.

The welding transformer begins the manufacturing operation, firstly it is necessary to insulate both rings. Paying attention to the corners of the edges of the rings, if they are sharp, they can easily damage the applied insulation and then short-circuit the winding wire. It is better to glue some elastic tape or cambric cut lengthwise to the corners. The top of the ring is wrapped with a small layer of insulation. Next, the insulated rings are fastened together.

The rings are tightly twisted with thick tape, and secured on the sides with pegs secured with electrical tape. Now the core for ST is ready.

Let's move on to the next point manufacturing a welding transformer, namely laying the primary winding.

Welding transformer windings - wound as shown in figure three - the primary winding is in the middle, both sections of the secondary are placed on the side arms. The primary winding requires about 70-80 meters of wire, which will have to be pulled with each turn through both windows of the magnetic circuit. In this case, I can recommend using the device shown in Figure 4. First, the wire is wound on it and in this form is easily pulled through the windows of the rings. The winding wire can be in pieces, ten meters long, but it is better to use a whole one.

In this case, it is wound in parts, and the ends are fastened without twisting and soldered together, and then insulated. The diameter of the wire used in the primary winding is 1.6-2.2 mm. in the amount of 180-200 turns.

Let's start winding the ST. We attach the cambric to the end of the wire using electrical tape to the beginning of the first layer. The surface of the magnetic circuit is rounded, so the first layers will have fewer turns than each subsequent layer, to level the surface, see Figure 5. The wire must be laid turn to turn, in no case should the wire overlap the wire.

The layers of wire must be insulated from each other. To save space, the winding should be laid as compactly as possible. On a magnetic circuit made of small rings, the interlayer insulation must be used thinner, for example using regular tape. Do not rush to wind the primary winding once. It's easier to do this in 2-3 approaches.

Let us determine the number of turns of the secondary winding of the CT for the required voltage. First, let's connect the already wound primary winding to an alternating voltage of 220 volts. Current idle move In this option, the CT is low - only 70-150 mA, the CT hum should be quiet. Wind 10 turns of wire around one of the side arms and measure the output voltage on it with a voltmeter. Each of the side arms receives only half of the magnetic flux generated on the central arm, so here for each turn of the secondary winding there will be 0.6-0.7 V. Based on the result obtained, we calculate the required number of turns in the secondary winding, focusing on the voltage level at 50 volts, this is usually about 75 turns. The easiest way is to wind it with 10 mm2 stranded wire in synthetic insulation. You can assemble a secondary winding from several strands of copper wire. Half the turns should be wound on one arm, half on the other.

Having wound the windings on both arms of the CT, you need to check the voltage on each of them; a difference of 2-3 volts is allowed, but no more. Then the windings on the arms are connected in series, but so that they are not in antiphase, otherwise the output will be near zero.

At standard mains voltage, a welding transformer on a magnetic core made of LATR can produce a current in arc mode of up to 100-130 A; during a short circuit, the secondary circuit current reaches 180 A.

The arc starts very easily at XX voltage, about 50 V or higher, although the arc can be started at lower voltages without any problems. On rings from LATRs, you can also assemble ST in a toroidal pattern.

For this you will also need two rings, preferably from large LATRs. The rings are connected and insulated: one large ring-magnetic circuit is obtained. The primary winding contains the same number of turns as described above, but it is wound around the entire ring and usually in two layers. The layers need to be insulated with as thin materials as possible. Thick winding wires should not be used.

The advantage of the toroidal CT circuit is its high efficiency. Each turn of the secondary winding contains 1 V of voltage, therefore, the secondary winding will contain fewer turns, and the output power will be higher than in the previous case.

Obvious disadvantages include the problem with winding, the limited volume of the window and the inability to use large-diameter wire.

Using hard wires for secondary use is problematic. It is better to use soft stranded

The arc burning characteristic of the toroidal CT is an order of magnitude higher than that of the previous version.

Diagram of a welding machine based on ST on a magnetic core from Latrov

Operating modes are set by potentiometers. Together with capacitors C2 and C3, it forms classic phase-shifting chains, each of which will operate in its own half-cycle and open its thyristor for a given period of time. As a result, an adjustable 20 - 215 V will appear on the primary winding of the CT. Transforming in the secondary winding, they easily ignite the arc for welding on alternating or rectified current to the desired voltage.

To make a welding transformer, you can use a stator from an asynchronous motor. The size of the core is determined in this case by the cross-sectional area of ​​the stator, which must be at least 20 cm 2.

Domestic color TVs used large, heavy network transformers, for example, TS-270, TS-310, ST-270. They have U-shaped magnetic cores, they are easy to disassemble by unscrewing just two nuts on the tightening pins, and the magnetic core breaks up into two halves. For older transformers TS-270, TS-310, the cross-section of the magnetic core has dimensions of 2x5 cm, S = 10 cm2, and for newer ones - TS-270, the cross-section of the magnetic core has S = 11.25 cm2 with dimensions of 2.5x4.5 cm. This means that the window width of old transformers is several millimeters larger. Older transformers are wound copper wire, a wire from their primary windings may be useful.

Welding transformer other possible types and design options

In addition to special production, ST can be obtained by converting ready-made transformers for various purposes. Powerful transformers of a suitable type are used to create networks with a voltage of 36, 40 V, usually in places with increased fire hazard, humidity and for other needs. For these purposes they use different types transformers: different powers, connected to 220, 380 V according to a single or three-phase circuit.

No craftsman or homely owner will refuse a compact and at the same time quite reliable, cheap and easy-to-manufacture “welder”. Especially if he finds out that the basis of this device is easy to modernize 9 amp(familiar to almost everyone with school lessons physics) laboratory autotransformer LATR2 and a homemade thyristor mini-regulator with a rectifier bridge. They not only allow you to safely connect to your household lighting network alternating current with a voltage of 220V, but also change Usv on the electrode, which means choosing the desired value of welding current.

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.

Welding transformer based on the widely used LATR2 (a), its connection to the main circuit electrical diagram 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 board made of 10 mm getinax or fiberglass with a packet switch SB1, a thyristor voltage regulator (with resistor R6), an HL1 light indicator for turning on the device in the network and output terminals for welding on alternating (X2, X3) or constant (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 welding current on the voltage on the secondary winding of the transformer and on the diameter 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. Workpieces 250-350 mm long are coated liquid glass- a mixture of silicate glue and crushed chalk, leaving the 40 mm ends required 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 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: best results welding with direct current of reverse polarity at a minimum (but sufficient for stable arc burning) voltage will give.

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, it’s impossible would be better suited stranded copper (total cross-section about 20 mm2) in rubber insulation. 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!

M.VEVIOROVSKY, Moscow region. Modeler-constructor 2000 No. 1.