Homemade welding. DIY DC welding machine: my diagram

If a person plans to perform living conditions small volumes of any simple welding work, he can easily make a welding machine with his own hands, without spending money on purchasing a factory unit.

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In order to make a welding unit from readily available materials and parts, it is necessary to clearly understand the key principles of its operation and only then begin assembly. First of all, you should decide on the current power of your homemade welding machine. To connect massive reinforcement, of course, a high current intensity is required, and for welding thin metal products (no more than 2 mm) a lower current intensity is required.

The current indicator is directly related to which electrodes are planned to be used. Welding of sheets and structures with a thickness of 3 to 5 mm is carried out with 3–4 mm rods, and with a thickness of less than 2 mm – with 1.5–3 mm rods. If you use four-millimeter electrodes, the current strength homemade installation should be 150–200 A, three-millimeter – 80–140 A, two-millimeter – 50–70 A. But for very thin parts (up to 1.5 mm), a current of 40 A is quite sufficient.

The formation of an arc for welding from mains voltage in any welding machine is achieved through the use of a transformer. This device includes in its design:

• windings (primary and secondary);
• magnetic circuit

It's easy to make a transformer yourself. The magnetic core, for example, is assembled from transformer steel plates or other material. The secondary winding is necessary directly for welding work, and the primary winding is connected to a 220-volt electrical network. Professional units necessarily have in their design some additional devices that improve and enhance the quality of the arc and allow you to smoothly adjust the current intensity.

Homemade welding machines, as a rule, are made without additional devices. The power of the transformer is selected based on the current strength. To obtain the calculated power, you need to multiply the current used for welding by 25. The resulting product, when multiplied by 0.015, gives us the required diameter of the magnetic core. And to calculate the required winding cross-section (primary), the power should be divided by two thousand and multiplied by 1.13.

Determining the cross-section of the secondary winding will have to “suffer” a little longer. Its value depends on the density of the welding current used. With a current strength of around 200 A, the density is 6A/square millimeter, from 110 to 150 A - 8, less than 100 A - 10. To set the required cross-section of the secondary winding you need:

• divide the welding current by its density;
• multiply the resulting value by 1.13.

The number of turns of wiring can be determined by dividing the cross-sectional area of ​​the magnetic circuit by 50. Another important point, which those who plan to know need to know self-production welding machine, is that the welding process can be “soft” or “hard” depending on the voltage available at the output terminals (at their clamps) of the unit.

The specified voltage establishes the features of the external characteristics of the current for welding, which can be gently or steeply decreasing, as well as increasing. In self-assembled welders, experts advise using current sources that are described by a flat or steeply falling characteristic. They show minimal changes in current when the electric arc oscillates, which is optimal for welding at home.

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Now that we know the main features of the welder, we can begin assembling a homemade welding machine. Now on the Internet there are many diagrams and instructions for performing such a task, which make it possible to create almost any equipment for welding - AC and DC, pulsed and inverter, automatic and semi-automatic.

We will not go into complex technical “wilds”, and will tell you how to make a welding machine of the simplest transformer type. It will operate on alternating current, providing an efficient and quite decent welded joint in terms of seam quality. Such a unit will allow you to perform any household work, which require welding of metal and steel products. To make it you will need the following materials:

• a couple of tens of meters of thick (preferably copper) cable (wire);
• iron for core transformer device(iron must have a sufficiently high magnetic permeability).

It is most convenient to make the core a rod, in a traditional U-shape. In principle, it is also possible to use a core of a different configuration, for example, a round one from the stator of any burnt electric motor, but be prepared for the fact that round design windings are much more difficult to wind. The recommended cross-sectional area of ​​the core for a standard household welding unit, made independently, is about 50 square centimeters.

This area is enough for the installation to use rods with a diameter of 3–4 millimeters.

There is no point in making a larger cross-section, since the unit will become much heavier, but you will not achieve a real technical effect. If you are not satisfied with the recommended cross-sectional area, you can calculate its value yourself using the diagram given in the first part of our article.

The primary winding must be made of copper wire with high thermal resistance characteristics (during welding, the winding is exposed to high temperatures). This wire, in addition, must have cotton or fiberglass insulation. As a last resort, it is allowed to use a wire in a rubber-fabric or ordinary rubber insulating sheath, but in no case in a polyvinyl chloride sheath.

By the way, you can make the insulation yourself by cutting two-centimeter wide strips of cotton or fiberglass. You wrap a copper cable with these strips, and then impregnate the wire with homemade insulation with any electrical varnish. Believe me, such insulation will not overheat when using 6-7 welding rods (when they are burned during the average duration of welding work).

The cross-sectional areas of the windings are calculated according to the principles that were outlined earlier. It seems that you will not have any problems with these calculations. Typically, the cross-sectional area of ​​the “secondary” wire is taken at the level of 25–30 square millimeters, the “primary” – 5–7 (values ​​for homemade units that will work with rods with a diameter of 3–4 millimeters).

It is also easy to determine the length of a piece of copper wire and the number of turns for both windings. And then they begin to wind the coils. Their frame is made according to the geometric parameters of the magnetic circuit. The dimensions are selected in such a way that the magnetic circuit fits onto the core, made of textolite or cardboard used in electrical engineering, without any difficulty.

The winding of the coils has a small peculiarity. The primary winding is wound in half, then half of the secondary is placed on it. After this, the second part of the coil is processed in a similar way. To improve the insulating properties, it is advisable to lay pieces of cardboard strips, fiberglass or thick paper between the layers.

After assembling a do-it-yourself welding installation, it must be adjusted. To do this, you need to plug it into the network and measure the voltage on the secondary winding. Its value should be 60–65 V. If the voltage is different, you will need to wind (or wind) part of the winding. Such procedures will have to be performed until the specified voltage value is reached.

The primary winding of the assembled transformer is connected to an internal laying cable (IRP) or to a two-core hose wire (SHRPS), which will be connected to a 220 volt network. The secondary winding (its leads) is connected to insulated PRG wires, one of them is then in contact with the product being welded, and the welding rod holder is attached to the second. The homemade welding unit is ready!

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In his practice, any radio amateur often needs to strongly heat or carefully weld one or another part. There is no point in using a conventional welding unit for these purposes, since even without it you can form a high-temperature flow quite simply and without expense.

If you have an old autotransformer lying around, which was previously used to regulate the supply voltage of Soviet lamp-based televisions, it is easy to adapt it to create voltaic arc. To do this, you need to connect graphite electrodes between its terminals. Such a simple design will make it possible to perform simple welding work, for example, the following:

• repair or production of thermocouples: a welder from an autotransformer allows you to repair thermocouples in which the so-called “ball” breaks, and other equipment for similar repair work simply does not exist;
• connecting the power buses to the filament element of a conventional magnetron;
• welding of any wires and cables;
• heating structures made of springs and similar parts to high temperatures;
• hardening of all kinds of devices made from (they are heated with an arc and then immersed in machine oil).

If you decide to make a welder based on an autotransformer, you need to handle it extremely carefully, since it does not have galvanic isolation from the electrical network. This means that misuse homemade device may result in electric shock.

To perform all the above “minor” work, it is recommended to use an automatic transformer with a voltage (output) of 40–50 volts with low power (about 200–300 watts). Such a device is capable of delivering 10–12 amperes of operating current, which is quite enough for welding wires, thermocouples and other elements. The electrodes for the described mini-welding machine are ordinary pencil leads.

It is better if they are soft, however, medium and hard pencils are also suitable. Holders for such graphite rods can be made from old terminal blocks found on any electrical devices. The holder is connected to the winding (as you understand, secondary) of the autotransformer through one of the existing terminals, and the product that needs to be welded is also connected to it, but through a different terminal.

The handle of the electrode holder can be easily made from an ordinary fiberglass washer or from another heat-resistant element. Finally, let’s say that the arc on a welding machine from an autotransformer does not burn for very long. On the one hand, this is bad, on the other hand, it is very good, since the short duration of its operation eliminates the risk of overheating of the transformer device.

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

Modern technologies offer a huge selection of models that differ in power and size. Reliable designs have a fairly high cost. Budget options, as a rule, have short term operation.

Our material presents detailed instructions how to make a welding machine with your own hands. Before starting the work process, it is recommended to familiarize yourself with the type of welding equipment.

Types of welding machine

The devices of this technology come in several types. Each mechanism has some features that are reflected in the work performed.

Modern welding machines are divided into:

• models direct current;
• with alternating current
• three-phase
• vector

The AC model is considered the most simple mechanism, which you can easily do yourself.

A simple welding machine allows you to perform complex work with iron and thin steel. To assemble such a structure, you must have a certain set of materials.

These include:

• wire for winding;
• core made of transformer steel. It is necessary for winding the welder.

All these parts can be purchased in specialized stores. Detailed consultation with specialists helps you make the right choice.

AC design

Experienced welders call this design a step-down transformer.

How to make a welding machine with your own hands?

The first thing you need to do is to correctly manufacture the main core. For this model, it is recommended to choose a rod type of part.

To make it you will need plates made of transformer steel. Their thickness is 0.56 mm. Before you begin assembling the core, you must observe its dimensions.

How to correctly calculate the parameters of a part?

Everything is quite simple. The dimensions of the central hole (window) must accommodate the entire winding of the transformer. The photo of the welding machine shows a detailed diagram of the assembly of the mechanism.

The next step is to assemble the core. To do this, take thin transformer plates, which are connected to each other to the required thickness of the part.

Next, we wind a step-down transformer consisting of turns of thin wire. To do this, make 210 turns of thin wire. On the other side, a winding of 160 turns is made. The third and fourth primary windings should contain 190 turns. After this, a thick platinum is attached to the surface.

The ends of the wound wire are secured with a bolt. I mark its surface with the number 1. The following ends of the wire are secured in a similar way with the corresponding markings applied.

Note!

IN finished design There should be 4 bolts with different numbers of turns.

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

Control the supply electrical energy possible by switching wires to required amount windings It is not recommended to overheat the welding mechanism during operation.

DC apparatus

These models allow you to perform complex work on thick steel sheets and cast iron. The main advantage of this mechanism is its simple assembly, which does not take much time.

The welding invector is a secondary winding design with an additional rectifier.

Note!

It will be made of diodes. In turn, they must withstand an electric current of 210 A. For this, elements marked D 160-162 are suitable. Such models are quite often used for work on an industrial scale.

The main welding injector is made from printed circuit board. This semi-automatic welding machine can withstand power surges during long-term operation.

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

Photo of a do-it-yourself welding machine

Note!

A welding machine is highly specialized equipment, but almost every man has had to look for a similar unit more than once in his life to repair home appliances or a car. It is quite easy to make a welding machine with your own hands, but you should understand that the equipment is suitable for working on small structures. This will be electric arc welding from an AC or DC source.

Argon and gas welding require special knowledge and equipment. You can make a gas generator at home, but if the master does not have a specialized education, there is a high risk of making a mistake. It is easier to rent an argon-arc welding machine; it costs tens of times less than making the equipment yourself.

Welding machine for home use- This is a simplified design with the simplest components and a simple assembly diagram. The main part is a welding transformer, which you can make yourself or use a unit household appliance(for example, a microwave oven).

The inverter welding unit is designed according to the following diagram:

• power supply;
• rectifier;
• inverter

You can make a transformer yourself using waste wire cables and copper tape of the required length.

If the transformer uses round copper wire, the operation of the device is limited to 2-3 welding rods. Transformer oil is used for cooling.

The seam on the parts being connected is formed due to heat, the source of which is an electric arc that occurs between two electrodes. One of the electrodes is the material being welded. A short circuit, which is required to heat up the electrode (cathode), will lead to a stable discharge with a temperature of up to 6000°C. Under its influence, the metal will begin to melt. This is a rough description of the welding process for non-specialists who, in everyday life, simply need to quickly fix the required profile or part.

Product contents

Welding inverters are rarely made independently. This electronic device requires repeated testing, specific knowledge and experience. It is easier to make a homemade product based on a transformer, and since it must work from a household network (usually 220 V), this device will be quite sufficient for minor home repairs.

The welding inverter for a 220 V network is assembled according to the scheme that is used for devices operating from industrial three-phase network. You need to know that these devices will have an efficiency 60% higher than equipment adapted for a single-phase network.

The transformer welder is manufactured without additional components, the package includes:

• transformer (you can make it yourself);
• insulating material;
• welding rod holder;
• PRG cable.

More complex products inverters are equipped with:

• transformer;
• inverter;
• ventilation system;
• ampere regulator.

After assembly, the voltage of the secondary winding is measured: the values ​​should not exceed the parameters of 60-65 V.

Power supply for a simple welder

Homemade welding transformers are simple equipment for rare repairs. The stator can serve as a magnetic core. The primary winding will be connected to the network, the secondary winding is designed to receive an electric arc and perform work. The transformer winding consists of copper wire or tape (up to 30 meters).

The primary winding is made of copper strip with cotton insulation. You can use a “bare” magnetic core and insulate it separately. The wire is wrapped in strips of cotton fabric and impregnated with any varnish for electrical work. The secondary winding is wound after insulating the primary. The cross-section of the primary winding is 5-7 square meters. mm, secondary section - 25-30 sq. mm. After insulation, the parameters are tested: a larger number of turns may be required.

An inverter-type welding machine has a more complex device, can operate on direct or alternating current and provides better weld quality. But if in everyday life you only need to carry out spot welding(for example, when repairing household appliances), then manufacturing an inverter welder is impractical. If you are using a transformer from a vacuum cleaner or microwave oven, it is important not to damage the primary winding. In 80% of cases, the secondary winding must be removed and redone so that the unit does not overheat.

Rectifier block

The rectifier unit converts the AC signal voltage into a DC signal and consists of a small number of small parts:

• diode bridges;
• capacitors;
• throttle;
• Voltage boost.

The rectifier is assembled on the principle of a bridge circuit, where alternating current is supplied at the input, and direct current comes out from the output terminals. Both devices - a transformer and a rectifier for a welder - are equipped with a forced cooling unit. You can use a cooler from the computer power supply.

Inverter block

The inverter unit converts direct current from the rectifier into alternating current and produces a voltage of up to 40 V and a current of up to 150 A.

The inverter operates according to the following scheme:

1. From the outlet, alternating current (frequency 50-60 Hz) is supplied to the rectifier, where the frequency is equalized. The current is supplied to transistors, where the constant signal is converted into alternating current with an increase in the oscillation frequency to 50 kHz.
2. Reducing the voltage of the high-frequency flow on the step-down transformer from 220 to 60 V. At the same time, the current increases. Due to the increase in frequency, only the minimum permissible number of turns is used in the inverter coil.
3. At the output rectifier, the final conversion of the electric current into a constant one occurs with great force and low voltage, which is optimal for high-quality welding.

In addition to the main stages, the welding device adjusts the current strength and ensures optimal ventilation. You can make an inverter yourself, guided by a detailed diagram.

Required Tool

To assemble the welding machine and manufacture you will need the following tools and devices:

• hacksaw;
• fasteners;
• soldering iron;
• knife, chisel, tweezers and screwdrivers;
• sheet metal for the frame;
• electrodes;
• assembly elements for a transformer, asynchronous stator.

The parts of the device are assembled on a textolite base; sheets of aluminum or industrial steel are used for the body.

Manufacturing

All parts in the scheme for manufacturing a transformer welder at home will be arranged in the following order:

• rectifier;
• network filter;
• converter;
• transformer;
• power rectifier.

You can exclude the power filter and rectifier from the circuit, but the electric arc will be poorly controlled, and the seam will be of poor quality (uneven, with large torn edges that will require cleaning).

Assembly steps:

1. Winding transformer coils. For an inverter welder that will operate on alternating and direct current, you will need a high-frequency transformer with a conversion module.
2. Varnishing of winding insulation.
3. Assembly of the magnetic circuit. The best option- asynchronous stator from an electric motor with a power of 4-5 kW.
4. Soldering the connections of the coils and output.
5. Checking the transformer.
6. Assembly of the diode bridge and connection in the circuit. You will need 5 diodes of the KVRS5010 or B200 class.
7. Installing a cooling radiator on each diode bridge.
8. Mounting the inductor on the same board with the rectifier.
9. Installing the current regulator on the control panel.
10. Ensuring ventilation of the entire structure. Fans are installed around the perimeter of the welding machine body.
11. The output to the working electrodes and holder is installed on the front wall, the power cord is on the opposite.
12. It is recommended to install a threshold between the board with the power supply and the power unit. sheet metal, a voltage capacitor that will stabilize the current in the electric arc.

The weight of the assembled device for minor repairs is from 10 kg. It is recommended to manufacture the diode bridge with a choke in a separate housing to reduce weight. This unit will need to be connected to the welding machine of stainless steel. With alternating mains voltage, semi-automatic equipment is practically not required for welding iron profiles, body repairs or spot clamps.

AC

A homemade welding machine operating on alternating current has the following advantages:

1. Reliable seam. With alternating current, the arc does not deviate from its original axis, this helps beginners make an even and high-quality seam.
2. A simple way to assemble the device.
3. Budget cost of components.
4. It only needs to be connected to a single-phase network; a household outlet is sufficient.

The main disadvantage of a resistance welding machine is metal spattering during operation due to interruption of the electric arc sinusoid and rapid overheating of the transformer. To weld parts up to 2 mm thick, the electrode diameter should be 1.5-3 mm. Welding of sheets from 4 mm is carried out with 3-4 mm rods at a machine current of at least 150 Amperes.

DC

Homemade DC devices are widely used for home use, but require skill, time and more small parts to assemble. Among the advantages of the equipment:

• a stable arc allows you to weld complex and thin-walled structures;
• absence of ungrabbed areas;
• there is no metal spatter, cutting off burrs and cleaning seams is not required.

It is recommended to check the complete DC welding machine with your own hands several times for overheating of the transformer, capacitor and diode bridge in test mode before main operation.

Changes can be made to the design of homemade welding machines and constantly improved. You can make a unit that operates on direct current, a minimal design that operates on an alternating signal with a minimum power of up to 40A, or a massive stationary unit for installation in a workshop.

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

Welding machines come in permanent and alternating current.

S.A. direct current are used for low current welding of thin sheet metal (roofing steel, automotive, etc.). The DC welding arc is more stable; direct and reverse polarity welding is possible. You can weld on direct current using electrode wire without coating and electrodes designed for welding on both direct current and alternating current. To make the arc burning stable at low currents, it is desirable to have an increased voltage idle move Uxxwelding winding (up to 70 - 75 V). To rectify alternating current, the simplest “bridge” rectifiers on powerful diodes with cooling radiators are used (Fig. 1).

To smooth out voltage ripples, one of the outputs of S.A. And they are connected to the electrode holder through inductor L1, which is a coil of 10 - 15 turns of a copper bus with a cross section of S = 35 mm 2, wound on any core, for example, from. To rectify and smoothly regulate the welding current, more complex circuits are used using powerful controlled thyristors. One of the possible circuits based on thyristors of type T161 (T160) is given in the article by A. Chernov “It will charge and weld” (Model Designer, 1994, No. 9). The advantages of DC regulators are their versatility. The range of their voltage changes is 0.1-0.9 Uxx, which allows them to be used not only for smooth adjustment of welding current, but also for charging batteries, power supply of electric heating elements and other purposes.

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

Rice. 1. Bridge rectifier for welding machine. Connection shown S.A. for welding thin sheet metal with “reverse” polarity - “+” on the electrode, “-” on the part being welded U2: - output alternating voltage of the welding machine

AC welding machines are used when welding with electrodes whose diameter is more than 1.6 - 2 mm, and the thickness of the welded products is more than 1.5 mm. In this case, the welding current is significant (tens of amperes) and the arc burns quite steadily. Electrodes designed for welding with alternating current only are used. For normal operation welding machine you need:

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

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

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

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

When designing an amateur SA, one should not strive to completely cover the range of welding currents. It is advisable at the first stage to assemble a welding machine for working with electrodes with a diameter of 2 - 4 mm, and at the second stage, if it is necessary to work at low welding currents, supplement it with a separate rectifier device with smooth control of the welding current. Amateur welding machines must satisfy a number of requirements, the main of which are the following: relative compactness and low weight; sufficient operating time (at least 5 - 7 electrodes dе = 3 - 4 mm) from a 220V network.

The weight and dimensions of the device can be reduced by reducing its power, and the operating time can be increased by using steel with high magnetic permeability and heat-resistant insulation of the winding wires. These requirements are easy to meet if you know the basics of welding machine design and adhere to the proposed technology for their manufacture.

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

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

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

Figure 4. Diagram of a toroidal magnetic circuit.

The cross section of the core should be S = 45 - 55 cm 2. The welding machine will be somewhat heavier, but it will not let you down! Amateur welding machines on toroidal-type cores, which have higher electrical characteristics, are about 4 to 5 times higher than those of a rod type, and electrical losses are low, are becoming increasingly widespread. The labor costs for their manufacture are more significant and are associated primarily with the placement of the windings on the torus and the complexity of the winding itself.

However, with the right approach they give good results. The cores are made from transformer strip iron, rolled into a torus-shaped roll. An example is a core from a 9 A “Latr” autotransformer. To increase the internal diameter of the torus (“window”) with inside unwind part of the steel tape and wind it onto outside core. But, as practice shows, Latra alone is not enough to produce high-quality SA. (small section S). Even after working with 1 - 2 electrodes with a diameter of 3 mm, it overheats. It is possible to use two similar cores according to the scheme described in B. Sokolov’s article “Welding Baby” (Sam, 1993, No. 1), or to produce one core by rewinding two (Fig. 4).

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

Amateur SAs made on the basis of stators of high-power asynchronous three-phase electric motors (more than 10 kW) deserve special attention. The choice of core is determined by the cross-sectional area of ​​the stator S. Stamped stator plates do not fully correspond to the parameters of electrical transformer steel, therefore it is not advisable to reduce the cross-section S to less than 40 - 45 cm.

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

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

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

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

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

A larger number of network winding taps, as practice shows, is impractical. And that's why. By reducing the number of turns of the primary winding, both the power SA and Uxx increase, which leads to an increase in arc voltage and a deterioration in welding quality. Consequently, it is impossible to cover the range of welding currents without deteriorating the quality of welding by simply changing the number of turns of the primary winding. To do this, it is necessary to provide for switching the turns of the secondary (welding) winding W 2.

The secondary winding W 2 must contain 65 - 70 turns of an insulated copper bus with a cross-section of at least 25 mm (preferably a cross-section of 35 mm). Suitable and flexible stranded wire(for example, welding) and three-phase power multi-core cable. The main thing is that the cross-section of the power winding should not be less than required, and the insulation should be heat-resistant and reliable. If the wire cross-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.

Rice. 5. Fastening the terminals of the CA windings: 1 - CA housing; 2 - washers; 3 - terminal bolt; 4 - nut; 5 - copper tip with wire.

The difficulty of purchasing switches for high currents, and practice shows that it is easiest to insert the welding winding leads through copper lugs under terminal bolts with a diameter of 8 - 10 mm (Fig. 5). Copper tips are made from copper tubes of a suitable diameter 25 - 30 mm long and attached to the wires by crimping and preferably soldering. Let us especially focus on the order of winding the windings. General rules:

1. Winding should be done along an insulated core and always in the same direction (for example, clockwise).
2. Each layer of the winding is insulated with a layer of cotton wool. insulation (fiberglass, electrical cardboard, tracing paper), preferably impregnated with bakelite varnish.
3. The winding terminals are tinned, marked, and secured with cotton wool. braid, additionally put cotton on the terminals of the network winding. cambric.
4. In case of doubt about the quality of insulation, winding can be carried out using a cotton cord, as if in two wires (the author used cotton thread for fishing). After winding one layer, winding with cotton. the thread is fixed with glue, varnish, etc. and after drying, wind the next row.

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

Let's consider the order of arrangement of windings on a rod-type magnetic core. The network winding can be positioned in two main ways. The first method allows you to obtain a more “hard” welding mode. The network winding in this case consists of two identical windings W 1 W 2, located on different sides of the core, connected in series and having the same wire cross-section. To adjust the output current, taps are made on each of the windings, which are closed in pairs (Fig. 6a, c).

The second method involves winding the primary (network) winding on one side of the core (Fig. 6 c, d). In this case, the SA has a steeply falling characteristic, welds “softly”, the arc length has less influence on the value of the welding current, and therefore on the quality of welding. After winding the primary winding of the CA, it is necessary to check for the presence of short-circuited turns and the correctness of the selected number of turns. The welding transformer is connected to the network through a fuse (4 - 6A) and preferably an AC ammeter. If the fuse burns out or gets very hot, then this is a clear sign of a short-circuited turn. Consequently, the primary winding will have to be rewound, paying special attention to the quality of the insulation.

Rice. 6. Methods for winding CA windings on a rod-type core: a - network winding on both sides of the core; b - the corresponding secondary (welding) winding, connected back-to-back; c - network winding on one side of the core; g - the corresponding secondary winding, connected in series.

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

Figure 8. Connection diagram for measuring instruments.

For the second winding method, the main welding winding W 2 1 is wound on the side of the core free from windings and makes up 60 - 65% of the total number of turns of the secondary winding. It serves mainly to ignite the arc, and during welding, due to a sharp increase in the magnetic dissipation flux, the voltage on it drops by 80 - 90%. An additional welding winding W 2 2 is wound on top of the primary one. Being a power source, it maintains the welding voltage and, consequently, the welding current within the required limits. The voltage across it drops in welding mode by 20 - 25% relative to the no-load voltage. After manufacturing the SA, it is necessary to set it up and check the quality of welding with electrodes of different diameters. The setup process is as follows. To measure welding current and voltage, you need to purchase two electrical measuring instruments - an AC ammeter for 180-200 A and an AC voltmeter for 70-80 V.

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

Their connection diagram is shown in Fig. 8. When welding with different electrodes, take the values ​​of the welding current - Iw and welding voltage Uw, which must 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, either by switching the primary and secondary windings, the required values ​​are set, or the number of turns of the secondary winding is redistributed (without increasing them) towards increasing the number of turns wound on top network winding. After welding, you can make a break or saw the edges of the welded products, and the quality of the weld will immediately become clear: the depth of penetration and the thickness of the deposited layer of metal. It is useful to create a table based on the measurement results.

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

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

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

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

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

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

1. The power delivered at the time of welding should be maximum, but not more than 5-5.5 kW. In this case, the current consumed from the network will not exceed 25 A.
2. The welding mode must be “hard”, and therefore, the winding of the windings S.A. should be carried out according to the first option.
3. The currents flowing in the welding winding reach values ​​of 1500-2000 A and higher. Therefore, the welding voltage should be no more than 2-2.5V, and the no-load voltage should be 6-10V.
4. The cross-section of the primary winding wires is at least 6-7 mm, and the cross-section of the secondary winding is at least 200 mm. This cross-section of wires is achieved by winding 4-6 windings and then connecting them in parallel.
5. It is not practical to make additional taps from the primary and secondary windings.
6. The number of turns of the primary winding can be taken as the minimum calculated due to the short duration of the operation of the SA.
7. It is not recommended to take a cross-section of the core (core) less than 45-50 cm.
8. Welding tips and underwater cables to them must be copper and pass appropriate currents (tip diameter 12-14 mm).

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

And finally, some technological tips.

The welding machine must be connected to the network using a wire with a cross-section of 6-7 mm through an automatic machine with a current of 25-50 A, for example AP-50. The diameter of the electrode, depending on the thickness of the metal being welded, can be selected based on the following relationship: da= (1-1.5)L, where L is the thickness of the metal being welded, mm.

The arc length is selected depending on the diameter of the electrode and is on average 0.5-1.1 d3. It is recommended to weld with a short arc of 2-3 mm, the voltage of which is 18-24 V. Increasing the length of the arc leads to a violation of the stability of its combustion, increased losses due to waste and spatter, and a decrease in the depth of penetration of the base metal. The longer the arc, the higher the welding voltage. The welding speed is selected by the welder depending on the grade and thickness of the metal.

When welding with straight polarity, the plus (anode) is connected to the part and the minus (cathode) to the electrode. If it is necessary for less heat to be generated on the parts, for example, when welding thin-sheet structures, reverse polarity welding is used (Fig. 1). In this case, the minus (cathode) is connected to the part being welded, and the plus (anode) is connected to the electrode. This not only ensures less heating of the part being welded, but also accelerates the process of melting the electrode metal due to more high temperature anode zone and greater heat input.

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

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

20 years ago, at the request of a friend, I built him a reliable welder to work on a 220-volt network. Before this, he had problems with his neighbors due to a voltage drop: an economical mode with current regulation was required.

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

This article is based on personal experience I’m telling you how I assembled and set up a DC welding machine with my own hands based on a homemade one toroidal transformer. It came out in the form of a small instruction.

I still have the diagram and working sketches, but I can’t provide photographs: there were no digital devices then, and my friend moved.

Versatile capabilities and tasks performed

A friend needed a machine for welding and cutting pipes, angles, sheets of different thicknesses with the ability to work with 3÷5 mm electrodes. ABOUT welding inverters They didn’t know at the time.

We settled on the DC design, as it is more universal and provides high-quality seams.

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

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

• made on a board from thick getinaks;
• covered with a dielectric casing;
• mounted on the housing with the output of the adjusting potentiometer handle.

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

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

Simple design of DC welding machine

Based on the installation principle, the following parts can be distinguished:

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

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

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

Theoretically, you can use any model of transformer to power the welding machine. The main requirements for it:

• provide arc ignition voltage at idle speed;
• reliably withstand the load current during welding without overheating the insulation from prolonged operation;
• meet electrical safety requirements.

In practice I have met different designs homemade or factory transformers. However, they all require electrical engineering calculations.

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

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

Features of core manufacturing

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

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

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

They began to wind the wire on top of the reinforced insulating layer.

Secrets of the power winding device

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

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

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

The core donuts were mounted tightly: this way they have smaller dimensions and weight. However, the flow area for the winding wire is also limited. Installation is difficult. Therefore, each power half-winding was separated into its own magnetic circuit rings.

In this way we:

• doubled the cross-section of the power winding wire;
• saved space inside the donuts to accommodate the power winding.

Wire alignment

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

We figured out the required length in our minds. Of course it wasn't enough. Each winding had to be made from two parts and spliced ​​with a screw clamp directly on the donut.

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

Technology of winding wire on a torus

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

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

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

This work is difficult, painstaking, and requires perseverance and attention. The wire must be laid tightly, counted, the process of filling the internal cavity must be monitored, and the number of turns wound must be recorded.

How to wind a power winding

We found it for her copper wire suitable section - 21 mm 2. We estimated the length. It affects the number of turns, and the no-load voltage necessary for good ignition of the electric arc depends on them.

We made 48 turns with the middle terminal. In total, there were three ends on the donut:

• middle - for direct connection of the “plus” to the welding electrode;
• the extreme ones - to the thyristors and after them to ground.

Since the donuts are fastened together and the power windings are already mounted on them along the edges of the rings, the winding of the power circuit was carried out using the “shuttle” method. The aligned wire was folded like a snake and pushed through the holes of the donuts for each turn.

The middle point was unsoldered using a screw connection and insulated with varnished cloth.

Reliable welding current control circuit

The work involves three blocks:

1. stabilized voltage;
2. formation of high-frequency pulses;
3. separation of pulses into circuits of thyristor control electrodes.

Voltage stabilization

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

In principle, any power supply with similar electrical characteristics current and voltage at the output.

Pulse block

The stabilized voltage is smoothed by capacitor C1 and supplied to the pulse transformer through two bipolar transistors of direct and reverse polarity KT315 and KT203A.

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

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

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

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

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