Do-it-yourself welding machine 220v. Homemade welding machines

Housework always requires a certain set of tools, fixtures, as well as a variety of equipment. This is especially felt by the owners of private houses and those involved in various types of repairs in their own workshops and garages. The acquisition of expensive equipment is not always justified, since its use will not be permanent, but it is quite possible for every craftsman to assemble a welding machine with his own hands.

Before starting the process, it is necessary to determine the power of the device, because its dimensions and capabilities will depend on this. To get acquainted with the assembly procedure, you can watch the corresponding video, which shows how you can make a practical welding machine with your own hands. Its manufacture will require some theoretical training, as well as experience in electromechanical work. The assembly of the electric device at home is carried out according to preliminary calculations, taking into account both the input and output parameters of the device.

This electric device is useful not only for welders who perform some work at home or in the garage, but also for ordinary craftsmen who use a welding device to build various devices.

Features of homemade transformers

Self-assembled devices differ from factory equipment in their technical design. Do-it-yourself welding is made from available elements and assemblies, for which a welding transformer circuit is used. With exact observance of the parameters of the component parts, the electric device will serve reliably for many years. Before you make a welding transformer device with your own hands, you need to decide on the available components. The basis is a transformer consisting of a magnetic circuit, as well as primary and secondary windings. It can be purchased separately, adapted to an existing one, or made independently. To make a welded electric device with your own hands, transformer iron and wire for windings will be added to a variety of tools from improvised materials. The manufactured transformer must be able to be connected to a 220 V household power supply and have an output voltage of about 60-65 V for welding thick metals.

Features of homemade rectifiers

Self-made rectifiers allow you to weld thin sheet metal with high quality seam joints.

The scheme of the welding machine using the rectification of electric current is very simple. It contains a transformer to which a rectifier unit is connected, as well as a choke. This simplest design ensures stable combustion of the welded arc. A coil of copper wires wound around a core is used as a choke. The rectifying device is connected directly to the outputs of the step-down transformer winding.

Depending on the goals, you can independently build a mini welded electric device. It will perfectly cope with metals of small thickness, which do not require the use of high currents when connecting. A spotter can be made from a welded electric device, which will greatly expand the possibilities of its application.

How to make a welding machine

A self-made electric welding device is designed to perform small jobs around the house, household or in the garage. At the first stage, the necessary calculations are performed and assembly parts and assemblies are prepared. To assemble a welding transformer with your own hands, it is advisable to determine in advance the place of assembly of the device. This will streamline the manufacturing process. Next to it, the layout units are folded, allowing you to assemble the simplest electric welding machine with your own hands. In addition to the main voltage converter, you will need a choke that can be used from the elements of a fluorescent lamp. In the absence of a finished element, it is made independently from a magnetic circuit from a powerful starter and wire from copper conductors with a cross section of about 1 mm square. A self-made electric welding machine will differ from its counterparts not only in appearance, but also in characteristics. To decide how to make it, check out similar devices in the photo or video.

Calculation of the welding transformer

Electric welding home-made devices are made according to the simplest scheme, which does not involve the use of additional nodes. The power of the assembled electric apparatus will depend on the required value of the welded electric current. Welding in the country with a do-it-yourself electric device will directly depend on the technical characteristics of your own product.

When calculating the power for welding, take the strength of the required welding current and multiply this value by 25. The resulting value, when multiplied by 0.015, will show the required cross-sectional diameter of the magnetic circuit for welding. Before making calculations for the windings, you will have to remember other mathematical operations. To get the cross section of the higher voltage winding, the power value is divided by two thousand, after which it is multiplied by 1.13. The calculation method for the primary and secondary windings is different.

To obtain the winding values ​​\u200b\u200bof the lowest voltage of the transformer, you will have to spend a little more time. The size of the cross section of the secondary winding depends on the density of the welded electric current. For values ​​​​of 200 A, this will be 6 A / mm sq., With numbers 110-150 A - up to 8, and up to 100 A - 10. When determining the cross section of the lower winding, the strength of the welded electric current is divided by density, after which it is multiplied by 1.13.

The number of turns is calculated by dividing the cross-sectional area of ​​the transformer magnetic circuit by 50. In addition, the output voltage will affect the final result of welding. It affects the characteristic of the process and can be increasing in current, gently sloping or steeply falling. This affects the fluctuations of the arc during operation, in which the minimum current changes are important when working at home.

Scheme of the welding transformer

The figure below shows a diagram of a welding transformer of the simplest form.

You can find wiring diagrams that will be supplemented with devices for rectification and other elements to improve the welded electrical apparatus. However, the main component is still a conventional transformer. The wiring diagram for connecting its wires is quite simple. The connection of the welded device is carried out through a switching electric device and fuses to a 220 V household electrical network. The use of electrical protective devices is mandatory, as this will protect the network from overloads in emergency conditions.

a - network winding on two sides of the core;
b - the corresponding secondary (welding) winding, connected in anti-parallel;
c - network winding on one side of the core;
g - the secondary winding corresponding to it, connected in series.

Defining parameters

To make an electric welding machine, you need to understand the principle of operation. It converts the input voltage (220 V) to a lower one (up to 60-80 V). In this process, the low strength of the electric current in the primary winding (about 1.5 A) increases in the secondary (up to 200 A). This direct dependence of the operation of transformers is called the step-down current-voltage characteristic. The operation of the device depends on these indicators. On its basis, calculations are carried out, and the design of the future apparatus is determined.

Rated operating mode

Before welding, it is necessary to determine its future nominal mode of use. It shows how long do-it-yourself welding fixtures can continuously cook and how much they must cool. This indicator is also called the duration of the inclusion. For homemade electrical appliances, it is located in the region of 30%. This means that out of 10 minutes, he is able to continuously work 3, and rest 7 minutes.

Rated operating voltage

The operation of a transformer welded device is based on lowering the input voltage to the nominal operating value. When manufacturing a welding machine, you can make any value of the output parameters (30-80 V), which directly affects the range of working electric currents. Unlike a 220 V power supply, the output value can be about 1.5-2 Volts in products for spot electric welding. This is due to the need to obtain a high level of current.

Mains voltage and number of phases

The current wiring diagram for a home-made welding transformer is designed for connection to a household single-phase power supply. For powerful welding devices, an industrial network with three phases at 380 V is used. The rest of the calculations are performed from the value of this input parameter. Do-it-yourself mini welding uses the inclusion in the home electrical network and does not require large supply voltages.

Open circuit voltage

A do-it-yourself household welder must have an x ​​/ x voltage value sufficient to ignite an electric arc. The larger this value, the easier it will appear. The manufacture of the device must comply with current safety regulations, which limit the output voltage to a maximum of 80 V.

Rated welding current of the transformer

Before you make an electric welding machine yourself, you need to decide on the size of the rated current. The possibility of performing the work itself on metals of various thicknesses will depend on it. With household electric welding, a value of 200 A is enough, which allows you to make a fully functional device. Exceeding this indicator will require an increase in the power of the electric transformer, which affects both the growth of its dimensions and weight.

Assembly process

The manufacture of a home-made welding machine begins with the necessary calculations. The input and output voltages, as well as the required electric current, are taken into account. The size of the device and the amount of materials needed directly depend on this. An electric welding machine, like other equipment, is not very difficult to make with your own hands. With the right calculation and the use of high-quality components, it can reliably serve for decades. For the base, a wire with copper conductors is used, as well as a core made of magnetically permeable iron. The remaining components are not so significant and can be selected from those that can be easily obtained.

How to start the preparatory stage

After the calculation part is completed, materials are prepared, and a workplace is equipped for assembling the structure. To build a home-made welding machine, you will need wires for the primary as well as the secondary winding, for the core - a suitable transformer iron, insulating materials (varnished cloth, textolite, glass tape, electric cardboard). In addition, you should take care in advance of the winding machine for the manufacture of windings, metal elements for the frame and a switching electric device. During the assembly process, you will need a set of conventional locksmith tools. Choose a more spacious workplace to freely wind the coils and engage in the assembly process.

Construction assembly

Having completed the preparatory measures, proceed directly to the manufacture of the electric apparatus. Homemade electric welding requires a lot of time during assembly. It is not as heavy as long and painstaking, requiring precise observance of the calculated values. The procedure begins with the manufacture of a frame for the windings. For this, textolite plates of small thickness are used. The inside of the boxes should fit the transformer core with a small gap.

After assembling the two frames, it is necessary to insulate them to protect the electrical wire. This is done using any electrically insulating material of a heat-resistant type (varnished cloth, glass tape or electric cardboard).

A wire with heat-resistant insulation is wound onto the resulting frames. This will protect the product from possible breakdown during overheating in operation. It is necessary to accurately count the number of turns so that there is no difference with the calculated values. Each wound layer is necessarily isolated from the next. Reinforced insulation is laid between the primary and secondary windings. Remember to make the necessary taps on the required number of turns. After winding is completed, external insulation is performed.

At the next stage, the wound windings are mounted on the transformer core, and its blending is performed (assembly of a single structure). At the same time, it is undesirable to drill sheets of transformer iron during installation. Metal plates are connected in a checkerboard pattern and are well tightened. Assembling a simple U-shaped welder with your own hands is not particularly difficult. At the end of the assembly procedure, the integrity of the windings is checked for possible damage. The final stage is the assembly of the case and the connection of the switching electric device. Additional equipment includes a rectifier unit, as well as an electric current regulator.

Be attentive to all processes, from calculations to the assembly of home-made welding. The final parameters of the manufactured device will depend on this.

1. What will we be about
2. What we won't talk about
3. Transformer
4. Trying a constant
5. microarc
6. Contact! There is a contact!

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

The second - a purchased welding machine is expensive. Rent is also not cheap, because. the probability of its failure with unskilled use is high. Finally, in the outback, getting to the nearest point where you can rent a welder can be just long and difficult. Generally, it is better to start the first steps in metal welding with the manufacture of a welding machine with your own hands. And then - let him stand in a barn or garage until the case. It's never too late to spend money on branded welding, if things go well.

What will we be about

This article discusses how to make equipment at home for:

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

What we won't talk about

First, skip the gas welding. Equipment for it costs pennies compared to consumables, gas cylinders cannot be made at home, and a home-made gas generator is a serious risk to life, plus carbide is now, where it is still on sale, expensive.

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

The third is argon-arc welding. From whose light hand the assertion that it is a hybrid of gas and arc went for a walk 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 welding seam is chemically clean, free from impurities of metal compounds with oxygen and nitrogen. Therefore, non-ferrous metals can be boiled under argon, incl. heterogeneous. 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 in the order of routine economic activity. And if you really need it, it’s easier to rent argon welding - compared to how much (in money terms) the gas will go back into the atmosphere, these are pennies.

Transformer

The basis of all "our" types of welding is a welding transformer. The procedure for its calculation and design features differ significantly from those of power supply (power) and signal (sound) transformers. The welding transformer operates in intermittent mode. If you design it for maximum current like continuous transformers, it will turn out to be prohibitively large, heavy and expensive. Ignorance of the features of electrical transformers for arc welding is the main reason for the 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 zaumi;
2. features of the magnetic circuits of welding transformers with recommendations for choosing from randomly turned up ones;
3. testing of available second-hand;
4. calculation of a transformer for a welding machine;
5. preparation of components and winding of windings;
6. trial assembly and fine-tuning;
7. commissioning.

Theory

An electrical transformer can be likened to a water storage tank. This is a rather deep analogy: the transformer operates due to the energy reserve of the magnetic field 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 that for water losses due to infiltration. Electricity losses in copper windings are formally similar to pressure losses in pipes due to viscous friction in a liquid.

Note: the difference is in evaporation losses and, accordingly, magnetic field scattering. 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 (VVC) 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, the VX is rigid (curve 1 in the figure); they are like a shallow vast pool. If it is properly insulated and covered with a roof, then 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 paddles, the water is drained. With regard to transformers, the power man must keep the output voltage as stable as possible up 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.
• Constructive measures (core configuration, calculation method, winding configuration and arrangement) 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 transfer of the current form, because. its distortion reduces the efficiency.

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

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 the electrode in the wrong way, it goes out. Therefore, the welding transformer is already made similar to a conventional water tank. Its VC is soft (normal dissipation, curve 2): as the load current increases, the secondary voltage drops smoothly. The normal scattering 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. reduce the weight and size 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 begin to heat up. Quite long: thermal time constant of welding transformers 20-40 min. If you then let it cool down and there was no unacceptable overheating, you can continue to work. The relative drop in the secondary voltage? U2 (corresponding to the range of the arrows in the figure) of normal dissipation increases smoothly with an increase in the range of oscillations of the welding current Iw, which makes it easy to hold the arc in any type of work. These properties are provided as follows:

1. The steel of the magnetic circuit is taken with a hysteresis, more "oval".
2. The reversible scattering losses are normalized. 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. Induction is chosen close to the limiting overheating, this allows by reducing cos? (a parameter equivalent to efficiency) at a current that is significantly different from sinusoidal, take more power from the same steel.

Note: reversible scattering loss means that part of the lines of force penetrates the secondary through the air, bypassing the magnetic circuit. The name is not entirely successful, as well as "useful scattering", because. "Reversible" losses are no more useful for the efficiency of a transformer than irreversible ones, but they soften the VX.

As you can see, the conditions are completely different. So, is it necessary to look for iron from a welder? Optional, for currents up to 200 A and peak power up to 7 kVA, and this is enough on the farm. By calculation and constructive measures, as well as with the help of simple additional devices (see below), we will obtain, on any hardware, a VX curve 2a that is somewhat more rigid than the normal one. In this case, the efficiency of welding energy consumption is unlikely to exceed 60%, but for episodic work, this is not a problem for yourself. But on thin work and low currents, it will not be difficult to hold the arc and the welding current, without having much experience (? U2.2 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.

• According to the formula from paragraph 2 before. the list we find the overall power;
• We find the maximum possible welding current Iw \u003d Pg / Ud. 200 A are provided if 3.6-4.8 kW can be removed from the iron. True, in the 1st case, the arc will be sluggish, and it will be possible to cook only with a deuce or 2.5;
• We calculate the operating current of the primary at the maximum network voltage allowed for welding I1rmax \u003d 1.1Pg (VA) / 235 V. In general, 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 I1rmax, we find the diameter of its copper wire d = (4S / 3.1415) ^ 0.5. Its full diameter with self-isolation D = 0.25 + d, and if the wire is ready - tabular. To work in the "brick bar, mortar yok" mode, you can take J1 \u003d 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 W and P, k2 = 40 for PL, SHL and k2 = 35 for O, OL;
• We find the total number of its turns W = 195k3w, where k3 = 1.03. k3 takes into account the energy losses of the winding due to leakage and in copper, which is formally expressed by a somewhat abstract parameter of the winding's own voltage drop;
• We set the stacking factor Ku = 0.8, add 3-5 mm to a and b of the magnetic circuit, calculate the number of winding layers, the average length of the coil and the wire footage
• We calculate the secondary in the same way at J1 = 6 A/sq. mm, k3 \u003d 1.05 and Ku \u003d 0.85 for voltages of 50, 55, 60, 65, 70 and 75 V, in these places there will be taps for rough adjustment of the welding mode and compensation for fluctuations in the supply voltage.

Winding and finishing

The diameters of the wires in the calculation of the windings are usually obtained more than 3 mm, and varnished winding wires with d> 2.4 mm are rare in wide sale. In addition, the welder's windings experience strong mechanical loads from electromagnetic forces, so finished wires are needed with an additional textile winding: PELSh, PELSHO, PB, PBD. Finding them is even more difficult, and they are very expensive. The footage of the wire per welder is such that cheaper bare wires can be insulated on their own. An additional advantage is that by 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 on the frame at least 10 squares will appreciate it.

isolation

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

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

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

winding

A thin-walled home-made frame will not withstand the pressure of thick wire turns, 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, impregnated with liquid varnish (see above) bakelite plywood. The instruction for winding the windings of the welding transformer is as follows:

• We are preparing a wooden boss with a height in winding height 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 film with a call on 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;
• After winding, we impregnate twice until it flows through with liquid varnish;
• after the impregnation dries, carefully remove the cheeks, squeeze out the boss and tear off the film;
• we tightly tie the winding in 8-10 places evenly around the circumference with thin cord or propylene twine - it is ready for testing.

Finishing and domotka

We shift the core into a biscuit and tighten it with bolts, as expected. The winding tests are carried out in exactly the same way as those of the dubious finished transformer, see above. It is better to use LATR; Iхх at an input voltage of 235 V should not exceed 0.45 A per 1 kVA of the overall power of the transformer. If more, the primary is homemade. 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 Ixx got back to normal 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, we disassemble the core; we tightly wrap the biscuit with the same masking tape, calico or “rag” electrical tape in 5-6, 4-5 or 2-3 layers, respectively. Wind across the turns, not along them! Now once again impregnate 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 for Ixx (suddenly it curled somewhere), fix the biscuits and impregnate the entire transformer with normal varnish. Phew, the most dreary part of the work is over.

Pull VX

But he is still too cool with us, remember? Needs to be softened. The simplest way - a resistor in the secondary circuit - does not suit us. Everything is very simple: at a resistance of only 0.1 ohms at a current of 200, 4 kW of heat will be dissipated. 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 when the arc is ignited are inevitable. Without an active ballast, they will burn the seam in places, and the resistor will extinguish them. But to us, low-powered 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 dissipation control. And for him - the core is almost the same as that of the transformer, and rather complex mechanics, see fig.

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

Note: an active-reactive inductor can get red hot in operation, so it needs a fireproof, heat-resistant, non-magnetic dielectric lining. In theory, a special ceramic lodgment. It is acceptable to replace it with a dry sand cushion, or already formally with a violation, but not rough, the welding gut is laid on bricks.

But other?

This means, first of all, an electrode holder and a connection device for the return hose (clamp, clothespin). They, since we have a transformer at the limit, need to be bought ready-made, but such as in fig. right, don't. For a 400-600 A welding machine, the quality of the contact in the holder is not very noticeable, and it will also withstand simply winding the return hose. And our self-made, working with an effort, can go wrong, it seems to be unclear why.

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

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

Trying a constant

DC welding has a number of advantages, but the VX of any DC welding transformer is tightened. And ours, designed for the minimum possible power reserve, will become unacceptably tough. The inductor-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 filter of infra-low frequencies, Finch. Although it looks reflective, you need to take into account the strong magnetic connection between the halves of the coil.

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

With a magnetic circuit, the coil is simpler, although not quite. For it, 2 PLA of the TS-270 power transformer from old tube TVs-"coffins" (the data is available in reference books and in Runet), or similar, or SL with similar or large a, b, c and h. From 2 PLs, a SL is assembled with a gap, see Fig., 15-20 mm. Fix it with textolite or plywood gaskets. 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 middle point.

The filter is adjusted along the arc at the minimum and maximum Uхх values. If the arc is sluggish at the minimum, the electrode sticks, the gap is reduced. If the metal burns at the maximum, increase it or, which will be more efficient, cut off part of the side rods symmetrically. So that the core does not crumble from this, it is impregnated with liquid, and then with normal varnish. Finding the optimum inductance is quite difficult, but then welding works flawlessly on alternating current.

microarc

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

Now more computer power supplies are used for microarc welding, or, for pulsed microarc welding, capacitor banks, see the video below. At 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!

Contact 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 the part is a coin or less, then the softest arc will burn it entirely.

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

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. A transformer for contact welding is calculated similarly to it for arc welding, but the current density in the secondary winding is 30-50 or more A / sq. mm. The secondary of the contact-welding transformer contains 2-4 turns, it cools well, and its utilization factor (the ratio of welding time to idling and cooling time) is many times lower.

In RuNet there are many descriptions of home-made pulsed spot welders from unusable microwaves. They are, in general, correct, but in repetition, as it is written in "1001 Nights", there is no use. And old microwave ovens don't lie around in heaps. Therefore, we will deal with less well-known designs, but, by the way, more practical.

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

The secondary winding is made of a 16x2 copper bus. It can be made from strips of thin sheet copper (it will turn out flexible) or made from a segment of a flattened refrigerant supply pipe for a domestic air conditioner. The tire is isolated manually, as described above.

Here in fig. - drawings of a pulsed spot welding machine are more powerful, for welding a sheet up to 3 mm, and more reliable. Thanks to a fairly powerful return spring (from the armored mesh of the bed), accidental convergence of the tongs is excluded, and the eccentric clamp provides a strong stable compression of the tongs, which significantly affects the quality of the welded joint. In which case, the clamp can be instantly reset with one blow on the eccentric lever. The disadvantage is the insulating knots of the pliers, there are too many of them and they are complex. Another one is aluminum pincer bars. Firstly, they are not as strong as steel ones, and secondly, these are 2 unnecessary contact differences. Although the heat dissipation of aluminum is certainly excellent.

About electrodes

In amateur conditions, it is more expedient to isolate the electrodes at the installation site, as shown in fig. on right. There is no conveyor at home, the apparatus can always be allowed to cool down so that the insulating sleeves do not overheat. This design will make it possible to make rods from a durable and cheap steel professional pipe, and also extend the wires (up to 2.5 m is acceptable) and use a contact welding gun or remote tongs, see fig. below.

On fig. On the right, one more feature of electrodes for resistance spot welding is visible: a spherical contact surface (heel). Flat heels are more durable, so electrodes with them are widely used in industry. But the diameter of the flat heel of the electrode must be equal to 3 thicknesses of the adjacent welded material, otherwise the penetration spot will burn 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 point about the 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, at current copper prices it is more than justified. The electrode diameter 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 according to the conditions of heat transfer is at least 3 of its diameters from the heel to the root (beginning of the shank).

How to give impetus

In the simplest home-made pulse-contact welding machines, a current pulse is given manually: they simply turn on the welding transformer. This, of course, does not benefit him, and welding is either lack of fusion, or burnout. However, it is not so difficult to automate the feed and normalize the welding pulses.

A diagram of a simple, but reliable and long-term proven welding pulse shaper is shown in fig. Auxiliary transformer T1 is a conventional power transformer for 25-40 watts. Winding voltage II - according to the backlight. Instead of it, you can put 2 LEDs connected in anti-parallel with a quenching resistor (normal, 0.5 W) 120-150 Ohms, then the voltage II will be 6 V.

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

Finally

And finally, something that may seem like a joke: welding in saline solution. In fact, this is not idle entertainment, but the thing is quite useful for some purposes. And you can make welding equipment for salt welding with your own hands on the table in 15 minutes, see the video:

Video: do-it-yourself welding in 15 minutes (on saline solution)

1.1. General information.

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

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

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

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

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

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

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

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

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

The rated welding current must be:

I St \u003d KK 1 * d e, where

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

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

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

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

Fig.2 Falling external characteristic of the welding machine:

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

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

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

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

1. 2. Choice of core type.

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

Fig.3 Rod-type magnetic circuit:

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

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

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

Rice. 4 Toroidal type magnetic core:

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

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

1. 3. Choice of winding wire.

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

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

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

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

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

k 2 - constant coefficient;

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

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

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

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

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

1.4. Features of winding windings.

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

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

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

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

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

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

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

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

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

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

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

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

1.5. Setting up the welding machine.

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

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

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

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

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

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

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

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

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

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

2. Portable welding machine based on "Latra".

2.1. Design feature.

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

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

2.2. Improvements "Latra".

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

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

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

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

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

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

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

Rice. eleven Schematic diagram of the welding machine.

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

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

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

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

3. Welding machine from a three-phase transformer.

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

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

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

3.1. Details.

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

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

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

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

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

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

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

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

4. Electrode holder.

4.1. Holder for electrodes made of d¾" pipe.

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

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

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

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

4.2. The holder of electrodes from steel corners.

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

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

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

5. Electronic current regulator for welding transformer.

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

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

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

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

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

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

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

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

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

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

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

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

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

Also on this topic you can see:

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

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

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

All the best, write to © 2005

Welding work at home has long been commonplace. The availability of devices and consumables, the ability to inexpensively study at welding courses, various manuals for obtaining independent skills. All these factors make it possible to save on the wages of a professional welder, and increase the efficiency of work.

However, if you carefully study the market for welding machines, unpleasant moments are revealed:

• High-quality welders have a high cost, it is more profitable to hire a specialist several times (unless, of course, you do this work all the time).
• Affordable units have a number of disadvantages: low reliability, poor quality of the seam, dependence on the supply voltage and type of consumables.

Hence the conclusion: if you need high quality equipment at an affordable price, you will have to make a welding machine from available materials with your own hands.

Before considering the options for homemade welders, we will analyze the principle of their work.

Ohm's law is at the heart of the operation of any unit. At constant power, there is an inverse relationship between current and voltage. For normal operation, a current of 60–150 A is required. Only in this case, the metal in the welding zone will melt. Imagine a welding machine that works directly with a voltage of 220 volts. To achieve the required current strength, a power of 15–30 kW is required. Firstly, for this it will be necessary to lay a separate power supply line: most inputs to residential premises are limited by technical conditions at the level of 5–10 kW. In addition, for such a current strength, wiring with a cross section of at least 30 mm² is required. You will have to cook in compliance with protective measures when working in electrical installations up to 1000 volts: rubber boots, gloves, workplace fencing, and so on.

Of course, it is impossible to provide such conditions in reality.

Therefore, any welding machine converts the voltage (downward): at the output we get the desired current while maintaining reasonable power.

The optimal voltage value is 60 volts. With a welding current of 100 A, this is quite acceptable 6 kW of power. How to convert voltage?

There are four main types of welding machines

Any of these devices can be assembled independently. Let's review manufacturing technologies by models:

Transformers (with or without rectifier)

The heart of a transformer is the core. It is recruited from transformer steel plates, which are quite problematic to make manually. By hook or by crook, the source material is mined in factories, in construction teams, at scrap metal collection points. The resulting structure (usually in the form of a rectangle) must have a cross section of at least 55 cm². This is a rather heavy construction, especially after laying the windings.

When assembling, it is imperative to provide an adjusting screw with which you can move the secondary winding relative to the stationary primary.

In order not to go into the complexity of calculating the cross section of wires, we take typical parameters:

• current strength on the secondary 100–150 A;
• open circuit voltage 60–65 volts;
• operating voltage when welding 18–25 volts;
• current strength on the primary winding up to 25 A.

Based on this, the cross section of the primary wire should be at least 5 mm², if done with a margin, you can take a wire of 6–7 mm². The insulation must be heat-resistant, of a material that does not support combustion.

The secondary winding is recruited from a wire (or preferably a copper bus), with a cross section of 30 mm². Rag insulation. Don't let the thickness scare you, the number of turns on the secondary is small.

The number of turns of the primary winding is determined by a factor of 0.9–1 turns per volt (for our parameters).

The formula looks like this:

W(number of turns) = U(voltage) / factor.

That is, with a network voltage of 200–210 volts, it will be about 230–250 turns.

Accordingly, at a secondary voltage of 60–65 volts, the number of its turns will be 67–70.

From a technical point of view, the transformer is ready. For ease of use, it is recommended to make a small margin for the secondary winding, with several branches (on 65, 70, 80 turns). This will allow you to work confidently in places with low mains voltage.

Hiding the unit in the case, or leaving it open is a matter of safe use. A typical manufactured do-it-yourself welding transformer looks like this:

The optimal material for the case is textolite 10–15 mm.

Adding a rectifier

A home-made powerful welding transformer from the point of view of circuitry is a conventional power supply. Accordingly, the rectifier is arranged as simply as in a mains charger for a mobile phone. Only the element base will look several orders of magnitude more massive.

As a rule, a couple of capacitors are added to a simple diode bridge circuit to dampen the rectified current pulses.

You can assemble a rectifier without them, but the smoother the current, the better the welding seam is obtained. To assemble the bridge itself, powerful diodes of the D161–250 (320) type are used. Since a lot of heat is generated on the elements under load, it must be dissipated using heatsinks. Diodes are attached to them with a bolted connection and thermal paste.

Of course, the radiator fins must either be blown by a fan or protrude above the case. Otherwise, instead of cooling, they will heat the transformer.

mini welding transformer

If you do not need to weld rails or channels from 4–5 mm steel, you can assemble a compact welder for soldering steel wire (making frames for homemade products) or welding thin sheet metal. To do this, you can take a ready-made transformer from a powerful household appliance (ideally, a microwave oven), and rewind the secondary winding. Wire cross section 15–20 mm², power consumption no more than 2–3 kW.

The scheme is calculated in the same way as for more powerful units. When assembling the rectifier, you can use less powerful diodes.

micro welder

If the scope of application is limited to soldering copper wires (for example, when installing junction boxes), you can limit yourself to a design the size of a couple of matchboxes.

It is performed on the transistor KT835 (837). The transformer is made independently. In fact, this is a high-frequency boost converter.

Unlike traditional welders, this circuit uses high voltage, up to 30 kV. Therefore, care must be taken when working.

We wind the transformer on a ferrite rod. Two primary windings: collector (20 turns 1 mm), base (5 turns 0.5 mm). Secondary (step-up) winding - 500 turns of 0.15 wire.

We assemble the circuit, solder the resistor piping according to the circuit (so that the transformer does not overheat at idle), the device is ready. Powered from 12 to 24 volts, with the help of such a device you can weld wire harnesses, cut thin steel, connect metals up to 1 mm thick.

A thick sewing needle can be used as welding electrodes.

Inverter (switching power supply for welding)

A homemade inverter welding machine cannot be made simply “on the knee”. This will require a modern element base and experience with the repair and creation of electronic devices. However, the scheme is not as terrible as it is painted. There are a great many such devices, and they all work no worse than factory counterparts. In addition, in order to create a pulse welding machine with your own hands, it is not necessary to purchase dozens of expensive radio components and ready-made assemblies. Most of them, especially high-frequency elements for the power supply, can be borrowed from old TVs or a PSU from a computer. The cost is close to zero.

The considered inverter has the following characteristics:

• Load current on electrodes: up to 100 A.
• Power consumption from a 220 volt network - no more than 3.5 kW (current about 15 A).
• Used electrodes up to 2.5 mm.

The illustration shows a finished scheme, which has been repeatedly tested by many home craftsmen.

Structurally, the inverter consists of three elements:

1. Power supply for the converter and control circuit. Made on an affordable element base, using an optocoupler from an old computer power supply. With the independent manufacture of the transformer, the cost is almost zero: the parts are cheap. Denominations and names of radioelements in the illustration.
2. Capacitor charge delay unit (for the starting arc). Made on the basis of KT972 transistors (absolutely not a shortage). Of course, transistors are mounted on radiators. For switching, an ordinary automobile relay with a current load on the contacts of up to 40 A is sufficient. For manual control, conventional circuit breakers (bags) of 25 A are installed. Output 300 volts - idle. When loaded, the voltage is 50 volts.
3. The current transformer is the most critical node. When assembling, special attention should be paid to the accuracy of the inductors. Some tuning can be done using a variable resistor (highlighted in red in the diagram). However, if the parameters are not consistent, the required arc power cannot be achieved. PWM is implemented on the US3845 chip (one of the few parts that you have to buy). Power transistors - all the same KT972 (973). Some elements in the diagram are imported, but they can be easily replaced with available domestic ones by looking for analogues on the datasheet website. The high-frequency unit is made from parts of a horizontal transformer from a TV.

Working wires no more than 2 meters long are connected to the output of the welding inverter. The cross section is at least 10 squares. When working with electrodes up to 2.5 mm, the current drop is minimal, the seam is smooth and even. The arc is continuous, not worse than the factory counterpart.

In the presence of active cooling (fans from the same computer power supply), the design can be compactly packed into a small case. Considering high frequency transducers, it is better to use metal.

Outcome

The more complex the homemade welding machine, the greater the savings. It is simple transformers that are more expensive due to the use of expensive copper in the windings or transformer iron. Switching power supplies, especially if there are old parts from typical electrical appliances in stock, are almost free.

Related videos

In construction, installation and repair work, a welding machine is used. Usually the design is purchased ready-made, but you can make it yourself. In this case, there is a significant savings in money. Moreover, this process can captivate those who like to engage in the manufacture of something new.

Connections, electrodes and windings

In order to assemble the welding machine with your own hands, you need to decide on the scheme on the basis of which the work will be carried out. Even before the start of the main work, it is worth considering how the unit will be powered. If the voltage is higher, then the use of the device may harm human health.

Usually, a single-phase 220 V network is used to power the equipment. In this case, it is necessary to use an additional winding (special ballast), with the help of which the periodically changing electric current is regulated during the welding period.

Before assembling a welding inverter with your own hands, you need to purchase:

• Transformer magnetic circuit.
• Remote capacitor devices.
• Welding mode switch.
• Several types of windings (primary, secondary, additional).
• Regulatory devices that help to establish the optimal welding mode.
• Special heat sensors.
• A device that notifies you with sounds about the optimal mode of operation.

Why Use Concrete

Before you make an inverter welding machine with your own hands, you need to make a case. It is made of specially prepared concrete, characterized by a high degree of plasticity. This material is able to quickly harden and become the desired shape.

The hull is made from fine-grained sand and cement in certain proportions. You should take 75 percent sand, 20 percent cement. In addition to these components, it is necessary to add an equal amount of PVA glue and glass wool. Sometimes the glue is replaced with a water-soluble latex material.

Novice craftsmen believe that the unit is quite easy to assemble with their own hands, in comparison with the creation of its body. With sequential work, the structure is assembled quite quickly.

The body must be at least 1 cm thick. The welding machine is cleaned, followed by drying, after which the body is started to be made. After waiting for the concrete to harden, the unit is externally processed using an organic monomer.

To cope with this task, experts recommend using styrene or methyl methacrylate. They help to heat treat the surface of the device. In this situation, a temperature above 70 degrees Celsius should be applied.

As a result of monomer polymerization, a waterproof layer is formed on the surface of the unit body. It is he who protects the surface of the structure from environmental influences.

Simple design

For the layout of the welding machine, you can use faulty household appliances. For example, you can use a failed microwave oven. Together with it, you should take electrical wiring, clamps, wooden parts and tips.

Taking all these components, it is possible in a short time, even with minimal knowledge in the field of technology, to produce the design of an apparatus for spot welding.

Parts inside the unit are fixed with self-tapping screws, washers or brackets of appropriate sizes. It is optimal to use a serviceable transformer of a broken microwave oven, from which equipment is made by hand.

Assembly process

They begin work by removing the secondary winding from the transformer. This operation requires accuracy. It is carried out with an angle grinder.

Next, the lamellar core is removed from the surface of the secondary winding. After carrying out the operation on the transformer, parts cut off on both sides can be found. With their help, the work will be better. Ideally, it is necessary to ensure that the insulating layer on the core is free of any defects.

Then the magnetic shunt is attached. During its normal functioning, the work of a do-it-yourself welding machine is carried out. Then the transformer is rewound using a thick wire made of copper material. If the core is damaged, it needs to be repaired. If the defect is minimal, then the site is isolated.

At the next stage, it is necessary to put the transformer on a wooden block, securing the top and bottom of the workstation with brackets. If the electrodes are attached qualitatively, then the unit will work better. If there are defects in the contacts, it will be difficult to weld the elements.

The fixation of the electrodes on the upper and lower parts of the bar is carried out with self-tapping screws. Then winding wires are connected to them. It is necessary to properly fix the copper terminals using pliers, which is usually very difficult for beginners. The structure is ready. Then it is necessary to check whether something can be welded using the unit, while it is important to follow the safety regulations.

Usually, it is not difficult to assemble a welding machine even for those people who have minimal technical knowledge. To do this, you can use the step-by-step instructions with photos at all stages, of which there are a large number on the Internet.

DIY welding machine photo