Today, the welding inverter is actively used not only for industrial needs, but also at home. This is due to its excellent functional and manufacturing advantages.

If you are well versed in electronics, then having diagrams and manufacturing instructions, you can make an inverter welding machine with your own hands, while spending money only on consumables. This option is suitable for people who like to buy good quality equipment. Inverter devices from well-known companies are very expensive, and cheap ones will only bring disappointment from use.

In order to start constructing a homemade welding inverter, you need to carefully work on its circuit: study the entire design, understand the electronics, and prioritize the work.

The structure of a homemade inverter

Almost all home-made welding inverters have the following basic elements:

1. Power unit;
2. Power key drivers;
3. Power part.

When designing a welding inverter, it is important take a look at its characteristics:

• The maximum current consumption is 32 A;
• During operation, a current of no more than 250 A is used;
• To perform welding work, a sufficient mains voltage of 220 V;
• For work, electrodes with a diameter of 3-5 mm and a length of 10 mm are used.
• The resulting device will have efficiency indicators no less than the professional version of the device.

DIY welding machine diagram

When you have decided that the inverter apparatus will be built independently, the first thing to do is drawing up a diagram.

You need to consider and provide for ventilation of the device’s mechanisms, as this is extremely important to avoid overheating of the parts inside. The simplest and optimal solution would be to use radiators from Pentium 4 and Athlon 64 system units. These components are commercially available and have a low price.

The diagram must provide for the presence and location of brackets that will secure the transformer.

Preparatory work before assembling the device

When the device diagram has been drawn up, it is necessary to proceed to the preparation of components and parts. To assemble an inverter with your own hands, you will The following materials are needed:

To avoid problems with voltage drops, it is necessary to wind across the entire width of the frame. In the specifically proposed version of the device there will be 4 windings:

1. Primary. It will include 100 turns, PEV 0.3 mm;
2. Secondary first - 15 turns, PEV 1 mm;
3. Secondary second - 15 turns, PEV 0.2 mm;
4. Secondary third - 20 turns, PEV 0.3 mm.

The board and power supply are installed separately from each other, with a sheet of metal located between them. To attach it to the housing of the welding inverter, it is necessary to use welding seams.

To control the shutters, it is necessary to install conductors. Their length should be no more than 15 cm; there are no special requirements for the cross-section. When assembling the device, it is necessary to study the diagram for it in detail, to understand all the important points of connecting the parts to each other.

The power supply is required after the primary winding covered with shielding winding. It is made from a similar wire. All turns of the cover must have the same direction as the primary ones and completely overlap them. There must be insulation between each winding. You can use varnished cloth or masking tape for it.

When putting the power supply into operation, you need to work on selecting the required resistance. It must be balanced so that the power supplied to the relay is within 20-25 V.

Carefully select radiator elements for input rectifiers. They must be powerful and reliable. Used computer parts have proven themselves to be excellent. They are available for sale on the radio market.

For a welding inverter it is necessary presence of 1 thermal sensor. It is installed inside the radiator. To regulate the current in the arc, a PWM controller is purchased and installed on the control unit. The capacitor will produce a PWM voltage, and the parameters of the welding current will depend on this.

Assembling an inverter welding machine

Having purchased all the necessary parts for the welding inverter, we proceed to its assembly. Before installing parts, check that they are in good condition. Find a ready-made inductor and start winding it. For this it is necessary use PEV-2 wire. The required number of turns is 175. The selected capacitor must have a voltage of at least 1000 V. If you cannot buy one capacitor with this voltage, you can install several so that their total capacity is 1000 V.

Try not to use one powerful transistor in the installation; it is better to replace it with several, less powerful ones. These indicators affect the operating frequency, which leads to the formation of large noise effects during welding work. If you incorrectly calculate the required power of the device, this will lead to rapid breakdown and repair work.

When assembling the welding inverter begins, it is imperative keep distance between the winding and magnetic cores. A PCB plate must be placed between the layers of the winding. This will help increase the electrical safety of the device and achieve fast and sufficient cooling.

Next, we move on to attaching the transformer to the very base of the homemade inverter. For this, 2-3 staples are used. They can be made of copper wire with a diameter of 3 mm. For boards, you can use foil PCB with a thickness of 0.5-1 mm. Be sure to make narrow cuts in the plates; they will help to freely remove the diodes to avoid overloads.

When all the main elements of the device have been assembled, you can proceed to attaching it to the base. The base itself can be made from getinax plates. For normal operation a plate 0.5 cm thick is suitable. Be sure to cut a round window in the center of the plate; a fan will be fixed there, which must be protected with a protective grille. When installing magnetic cores, do not forget to leave gaps for free air flow.

On the front side you need to install a toggle switch handle and LEDs, cable clamps and a variable resistor handle. This will be the design of an almost finished welding machine. It is placed in a casing 4 mm thick. A button is installed on the electrical wire holder. Thoroughly insulate the cable that is connected to it and the wires.

Setting up the welding inverter for operation

Having assembled the entire mechanism, it is necessary configure it correctly and competently and put into operation. There are situations where it is difficult to resolve the issue on your own and you have to seek the help of a specialist.

1. The first step is to connect the device to a 15V PWM power supply; one of the convectors is also connected in parallel. This will help avoid overheating of the device, and the noise level will be significantly lower.
2. In order for the resistor to close, a relay must be connected. It is put into operation after the capacitors have finished charging. This will help to avoid large voltage fluctuations when connecting to a 220V network. If you neglect to connect the resistor directly, an explosion may occur.
3. Next, careful monitoring of the operation of the resistor closure relay is necessary when it is connected to the current on the PWM board. It is imperative to diagnose the presence of pulses on the board after the relay is activated.
4. Then we supply 15V power to the bridge. This helps to check its normal and proper operation and correct installation. The current on the device should not exceed 100A. In this case, the speed should be idle.
5. It is imperative to check the correct installation of transformer phases. You can use a 2-beam oscilloscope for this. To do this, you need to supply 220V power to the bridge from the capacitors through the lamp, setting the PWM frequency to 55 kHz. Having installed the oscilloscope, look at the signal form and observe that the voltage should not exceed 330V. Calculate oscillation frequency transformer is easy. It is necessary to gradually reduce the PWM frequency until the lower IGBT switch produces a slight turn. This indicator must be divided by 2, and the resulting quotient added to the value of the supersaturation frequency. The current consumption parameters of the bridge should not be higher than 150 mA. Follow the light from the light bulb. Very bright indicates problems with the winding; a breakdown is possible in it. There should be no noise effects coming from the transformer. If there is any noise, pay attention to the correct polarity. As a test control on the bridge, you can use a 220V electric kettle. All conductors from PWM must be crowded together and located away from sources of interference.
6. Using resistors, it is necessary to gradually increase the current. At the same time, listen to extraneous noises and sounds, watch the oscilloscope readings. The readings of the lower key are no more than 500V. The norm is 240V.
7. Welding work must begin within 10 seconds. Then the radiators are checked. If they are cold, then the work lasts another 20 seconds. Further, the time increases to 1 minute.

Rules for maintenance and repair of welding equipment

For proper and long-term operation of the device, it is necessary to periodically check and monitor each structural element. This will make your repair work easier and reduce it to a minimum. If the unit breaks down, find the cause of the problem and carry out repair work.

To perform these works it is necessary have the following tools:

The first and main cause of failure may be the rectifier. Through it, alternating current is converted into direct voltage. A surge protector makes it possible to smooth out voltage fluctuations. The transistor circuit is responsible for generating a single-phase high-frequency voltage. The unit regulates the operation of the keys using feedback signals, so it can change the operating mode of the inverter. The cooking transformer is responsible for reducing the voltage, then the valve blocks rectify it and supply it to the electrode.

DIY welding inverters

If the welding machine breaks down, remove the housing cover and blow with a regular vacuum cleaner. Areas that are difficult to clean using this method should be treated with a brush or cloth. Begin diagnosing the input circuit. Check if the inverter is receiving voltage. If it is not there, then repair the power supply. The fuses may have blown. It’s not difficult to create a welding inverter with your own hands, but repairs, if diagnosed incorrectly, can take a lot of time.

Next, start diagnosing the temperature sensor. Compare the nominal indicators with the existing ones. This element cannot be repaired and must be replaced with a new one. Then, the basic elements of the apparatus are studied. If you see darkening on one of them, this means that the soldering was performed poorly during assembly. Use a tester to check connection circuits.

If the contacts are made poorly, this leads to overheating, breakdown and expensive repairs of the inverter. Check the connectors, if they are loose - tighten them, if there is a bad connection - solder them. If during welding work there is spattering of metal, sticking of the electrode, or burning of an arc, then it is necessary to adjust the current supply or replace the electrodes.

Make sure the cable is in good condition; if it is bent, replace it with a new one immediately. Only in this case will an inverter welding machine, created with your own hands, work efficiently and reliably.

In order to assemble a welding inverter with your own hands, it is not necessary to have deep knowledge of physics, or have a professional understanding of technology, electricity, etc.

You just need to carry out everything according to the scheme and know, at least at a minimum level, the mechanism of operation of this equipment. Those wishing to create an inverter in a more economical and simpler version should know that the technical features and efficiency are essentially the same from analogue designs.

One of the important questions for welding specialists is how to do it yourself. The process can be performed using the circuitry of welding inverters.

Before assembling an effective welding inverter, it is necessary to highlight the following technical characteristics of the equipment:

• on one of the transistors, the current that passes through the input should be 32 amperes;
• 250 amperes is an indicator of the current strength that is created when leaving the device;
• the voltage should be up to 220 volts.

In order to create the simplest welding inverter, it is necessary to combine the following elements into one mechanism:

• power block;
• thyristor power supply unit;
• drivers for power switches.

Materials for its assembly

Drawing of an inverter welding machine.

Before starting to assemble, the master must prepare the necessary tools and materials that he may need in his work.

First of all:

• various types of screwdrivers;
• a soldering device to connect parts in an electronic circuit;
• tool for cutting on a metal surface;
• thread, as a fastener;
• surface with a small thickness of metal;
• parts that form the electrical circuit of an inverter welding machine;
• copper wire and strips to wind the transformer will be required;
• fiberglass;
• mica;
• textolites;
• ordinary thermal paper used in cash registers.

The welding machine circuit is used to assemble equipment at home with an electrical voltage of 220 volts.

But if there is a need, then they use welding machine circuits operating on a three-phase power supply with a voltage of 380 volts. Such equipment has advantages, among which is a high efficiency rate, in contrast to single-phase designs.

Unit power supply

In the power supply of a welding inverter, the most important part is the one that swings with ferrite in Ш7*7 or 8*8.

Inverter power supply.

Using this mechanism, a regular voltage is supplied and is created by 4 windings:

1. Primary.
   One hundred circles of PEV wire with a diameter of 0.3 millimeters.
2. The first is secondary.
   15 circles of PEV wire with a diameter of 1 millimeter.
3. The second is secondary.
   15 circles of PEV with a diameter of 0.2 millimeters.
4. The third is secondary.
   20 circles with a diameter of 0.3 millimeters.

After the primary winding is completed and its sides are insulated using fiberglass, it is also wrapped in shielding wire. Each turn must completely cover the protective layer.

The shield wire winding should be in the same direction as the primary winding. It is worth paying attention to the same diameters of the two types of windings.

The same rule is used for other types: when winding the transformer frame, insulating wires from each other using fiberglass, or using simple masking tape.

To stabilize the voltage in the region of 20-25 volts, which enters the power supply through a relay, a resistor is selected for electronic circuits. The main feature of the mechanism under consideration is the change from alternating current to regular current.

This can be achieved by using a diode formed when performing an “oblique bridge” circuit. It happens that during operation of the device the diode overheats, which is why it is necessary to install it on radiators and often repair the power supply. An alternative to radiators is a cooling part from old equipment.

Installation of a diode bridge involves the use of 2 radiators: the top is connected to one battery through a mica gasket, and the bottom is connected to the second battery through the surface of thermal paste.

The bridge of diodes should be output in the direction where the transistor output is directed. Due to this, direct current turns into alternating current with high frequencies.

The connecting wire of these terminals can reach a maximum length of 15 centimeters. The metal sheet must be placed between the power supply and the inverter part of the device and welded to the “body” of the equipment.

Power block

Manufacturing of a welding inverter.

The power unit is the basis of the transformer in the welding inverter. With its help, the voltage indicator at high frequencies decreases, and the power, on the contrary, increases. To create a power block in a transformer, the use of cores is required. To create a small gap, it is recommended to use regular newsprint.

With each applied layer, to ensure thermal insulation, it is necessary to wind cash register tape to achieve good wear resistance. The secondary winding is created on the basis of 3 strip layers of copper, insulated from each other by a fluoroplastic tape.

Most craftsmen wrap a step-down transformer with a thick copper wire, however, this is a mistaken action. With such a transformer, a simple welding inverter will work with high-frequency current, displacing the conductor outside without heating the parts inside.

It is best to form windings using a conductor with a wide surface, in other words, use a wide copper strip.

Instead of a thermal insulating surface layer, experts sometimes replace it with plain paper. It is not as stable as thermal insulation tape or cash register tape. Elevated temperature only affects the darkening of the tape, but its wear resistance remains at the original level.

Inverter unit

The main function of the simple one is to convert direct current, which is generated using the rectifier of the device, into alternating high-frequency current.

To solve this situation, experts use a power transistor and high frequencies with an opening and closing channel. The mechanism in question in the equipment is responsible for changing direct current into alternating current at high frequencies.

You can make an inverter welding machine with your own hands according to the electrical diagram, which indicates how to connect the capacitors in series.

They are used in the following cases:

1. Minimizing surge in the transformer.
2. Minimization of losses in the transformer block that appear when the device is disconnected from the network.
   This occurs due to the fact that the transistor opens at a higher speed than it closes - the current loses its power, which entails overheating of the switches in the transistor block.

Unit cooling system

Electrical circuit of an inverter for welding.

It is worth noting that most power elements in welding equipment tend to become very hot during operation, which can cause it to break.

In order to avoid such situations, it is most effective to install a fan in all units of the device, in addition to the radiator, a cooling mechanism during operation - a kind of cooling system.

You can do it yourself if you have a powerful fan. Often one is used with the air flow directed towards the step-down power transformer.

With a fan that has little power from a computer, for example, you may need up to 6 pieces, of which three devices are installed near the power transformer with the air flow directed in the opposite direction.

To avoid overheating, a homemade welding inverter must work together with a temperature sensor. It is installed on a heating radiator. If the radiator reaches the maximum temperature, it automatically turns off the current supply.

For more efficient functionality of the cooling system of the unit, the housing must be equipped with an air intake with its correct implementation. Air flow passes through its grilles into the internal systems of the device.

DIY inverter assembly

The important question remains, how to do it? First of all, you need to choose a case with reliable protection or form it yourself using sheet metal, where the thickness should be no less than 4 millimeters.

For the base where it is mounted for inverter welding, getinax sheets with a thickness of no less than 5 millimeters are used. The structure itself will be located on the base thanks to brackets made independently from copper wires with a diameter of 3 millimeters.

To create electronic circuit boards in the electrical circuits of a welding machine, foil-coated textolite is used, the thickness of which reaches 1 millimeter. When installing magnetic cores, which tend to heat up during operation, it is necessary to remember the gaps between them. They are needed so that air can circulate freely.

In order to automatically control the welding inverter, the welder must buy and connect to it a special controller that is responsible for the stability of the current. It also determines whether the supply voltage will be powerful.

For more convenient operation of a homemade unit, a control element is mounted in the outer part. It can act as a toggle switch to activate the device, a knob in a variable resistor, thanks to which it controls the supply of current or a cable clamp and a signal LED.

Assembling a welding inverter with your own hands is quite simple if you adhere to all the rules, follow the instructions and strictly follow the prescribed scheme.

Do-it-yourself inverter manufacturing diagram.

Diagnostics of a homemade inverter and its preparation for operation

Assembling a homemade one is not the whole process. The preparatory stage is also considered an important part of the entire work, where it is necessary to check whether all its systems are working correctly and how to configure the necessary parameters.

First of all, equipment diagnostics are carried out, namely, supplying a voltage of 15 volts to the controller and cooling system of the welding machine in order to check their endurance. Thanks to this, the functionality of the mechanisms is checked and the avoidance of overheating during operation of the unit.

When the capacitors in the unit are fully charged, a relay is connected to the electrical network, which is responsible for closing the resistors. With direct supply, without a relay, there is a risk of the device exploding.

When the relay is functioning, voltage is supplied to the device for up to 10 seconds. It is quite important to find out how long the inverter can function during welding. To do this, it is tested for 10 seconds. If the radiator remains at the same temperature, then the time can be set to 20 seconds, etc. up to a full minute.

Maintenance of a homemade welding inverter

Drawing of a welding inverter for DIY assembly.

In order for a simple homemade welding inverter to work for a long time, it requires proper care. If the welding equipment breaks down, you need to remove the housing and carefully clean the mechanism with a vacuum cleaner. In parts where it cannot be reached, you can use a brush and a dry cloth.

First of all, you need to diagnose all welding equipment - check the voltage, its input and flow. If there is no voltage, it is necessary to monitor the functionality of the power supply.

The problem may also be burnt fuses in the structure. The sensor that measures the temperature, which is not repaired but replaced, is also considered a weak point.

After diagnostics, it is necessary to pay attention to the quality of the connection of the electronic systems of the equipment. Then identify poor-quality fastening by eye or using a special tester.

When these problems are identified, they are eliminated immediately using available parts, so as not to provoke overheating and breakdown of all welding equipment.

Bottom line

It is a mistake to assume that a device you create yourself will not allow you to effectively perform the necessary work. With a homemade device with an easy assembly circuit, you can weld elements using an electrode with a diameter of up to 5 millimeters and an arc length of up to 10 millimeters.

After the homemade equipment is connected to the circuit, it is necessary to set the automatic mode with a specific current value. The voltage in the wire may be about 100 volts, which indicates some kind of problem.

To fix the problem, you need to find the circuit diagram of the welding inverter, disassemble it and check how correctly it was assembled.

Thanks to such a homemade apparatus, the welder can not only weld homogeneous, dark metal, but also non-ferrous and various alloys. When assembling such a device, in addition to the basics of electronics, you also need to have a free period of time to implement your plan.

The welding process using an inverter is a necessary thing in every man’s home for any domestic and industrial purposes.

The designer and famous scientist Yuri Negulyaev at one time invented an almost irreplaceable device - a welding inverter. We suggest you consider how to make a welding inverter with your own hands using a pulse transformer and powerful MOSFET transistors.

The most important thing when constructing or repairing a purchased or homemade inverter is its circuit diagram. For the manufacture of our inverter, we took it from Negulyaev’s project.

Manufacturing of transformer and choke

To work we will need the following equipment:

1. Ferrite core.
2. Frame for transformer.
3. Copper bar or wire.
4. Bracket for fixing the two halves of the core.
5. Heat-resistant insulating tape.

First you need to remember a simple rule: the windings are wound only over the full width of the frame; with this design, the transformer becomes more resistant to voltage surges and external influences.

A high-quality pulse transformer is wound with a copper busbar or a bundle of wires. Aluminum wires of the same cross-section are not able to withstand a sufficiently high current density in the inverter.

In this version of the transformer, the secondary winding must be wound in several layers, according to the sandwich principle. A bundle of wires with a cross-section of 2 mm, twisted together, will serve as the secondary winding. They must be isolated from each other, for example, with a varnish coating.

Winding rings

There must be two or three times more insulation between the primary and secondary windings so that the mains voltage, which in rectified form is 310 volts, does not reach the secondary winding. PTFE heat-resistant insulation is best suited for this.

The transformer can also be made not on a standard core, by using for these purposes 5 transformers from horizontal scanning of faulty TVs, combined into one common core. It is also necessary to remember about the air gap between the windings and the core of the transformer, this makes it easier to cool.

An important note: the uninterrupted operation of the device directly depends not only on the magnitude of the direct current, but also on the thickness of the wire of the secondary winding of the transformer. That is, if we wind the winding thicker than 0.5 mm, we will get a skin effect, which does not have a very good effect on the operating mode and thermal characteristics of the transformer.

A current transformer is also made on a ferrite core, which will then be attached to the positive power wire; the outputs from this transformer come to the control board to monitor and stabilize the output current.

To reduce the ripple at the output of the device and reduce the amount of noise emissions into the power supply network, a choke is used. It is also wound on a ferrite frame of any design, with a wire or bus, the thickness of which corresponds to the thickness of the secondary winding wire.

Welding machine design

Let's look at how to construct a fairly powerful pulsed welding inverter at home.

If you repeat the design according to the Negulyaev system, then the transistors are screwed to the radiator with a plate specially cut for this purpose, thus improving the heat transfer from the transistor to the radiator. Between the radiator and the transistors it is necessary to lay a thermally conductive gasket that does not allow current to pass through. This provides short circuit protection between the two transistors.

The rectifier diodes are attached to a 6 mm thick aluminum plate; the fastening is carried out in the same way as the transistors are fastened. Their outputs are connected to each other with a bare wire with a cross-section of 4 mm. Be careful not to let the wires touch.

The choke is attached to the base of the welding machine with an iron plate, the dimensions of which follow the shape of the choke itself. To reduce vibration, a rubber seal is placed between the throttle and the body.

Video: DIY welding inverter

All power conductors inside the inverter housing must be routed in different directions, otherwise there is a possibility of a short circuit. The fan cools several radiators simultaneously, each of which is dedicated to its own part of the circuit. This design allows you to get by with just one fan installed on the rear wall of the case, which significantly saves space.

To cool a homemade welding inverter, you can use a fan from a computer case; it is optimal in both size and power. Since ventilation of the secondary winding plays a large role, this should be taken into account when positioning it.

Diagram: disassembled welding inverter

The weight of such an inverter will range from 5 to 10 kg, while its welding current can range from 30 to 160 amperes.

How to configure the inverter

Making a homemade welding inverter is not that difficult, especially since it is an almost completely free product, except for the costs of some parts and materials. But to configure the assembled device, you may need the help of specialists. How can you do this yourself?

Instructions that make it easier to independently set up a welding inverter:

1. First, you need to apply mains voltage to the inverter board, after which the unit will begin to emit the characteristic squeak of a pulse transformer. Voltage is also supplied to the cooling fan, this will prevent the structure from overheating and the operation of the device will be much more stable.
2. After the power capacitors are fully charged from the network, we need to close the current-limiting resistor in their circuit. To do this, you need to check the operation of the relay, making sure that the voltage across the resistor is zero. Remember, if you connect the inverter without a current-limiting resistor, an explosion may occur!
3. The use of such a resistor significantly reduces current surges when the welding machine is connected to a 220-volt network.
4. Our inverter is capable of producing current in excess of 100 amperes, this value depends on the specific circuit used in the design. It is not difficult to find out this value using an oscilloscope. It is necessary to measure the frequency of incoming pulses to the transformer; they should be in the ratio of 44 and 66 percent.
5. The welding mode is checked directly on the control unit by connecting a voltmeter to the output of the optocoupler amplifier. If the inverter is low-power, the average amplitude voltage should be about 15 volts.
6. Then the correct assembly of the output bridge is checked; for this, a voltage of 16 volts is supplied to the inverter input from any suitable power supply. At idle, the unit consumes a current of about 100 mA, this must be taken into account when carrying out control measurements.
7. For comparison, you can check the operation of an industrial inverter. Using an oscilloscope, the pulses on both windings are measured; they must correspond to each other.
8. Now you need to check the operation of the welding inverter with connected power capacitors. We change the supply voltage from 16 volts to 220 volts, connecting the device directly to the electrical network. Using an oscilloscope connected to the output MOSFET transistors, we monitor the waveform; it should correspond to tests at reduced voltage.

Video: welding inverter under repair.

A welding inverter is a very popular and necessary device in any activity, both in industrial enterprises and in households. In addition, due to the use of a built-in rectifier and current regulator, with the help of such a welding inverter it is possible to achieve better welding results compared to the results that can be achieved when using traditional devices whose transformers are made of electrical steel.

Even a home craftsman who does not have deep knowledge of electrical processes can assemble a homemade inverter welding machine. The main requirement is compliance with installation technology, compliance with the diagram and understanding of the operating principle of the device. If you create an inverter with your own hands, then its parameters and performance will not differ significantly from factory models, but the savings can be decent.

A simple homemade inverter-type device will allow you to carry out high-quality welding operations. Even an inverter with a simple circuit allows you to work with an electrode from 3 to 5 mm and an arc up to 1 cm.

Characteristics

A similar welder for home use may have the following parameters:

• Voltage level – 220 volts.
• Input current - 32 amperes;
• Output current - 250 amperes.

An inverter that operates from a 220 V household power supply is suitable for domestic use. If necessary, it is possible to assemble a more powerful device operating from 380 V. It has higher productivity compared to a single-phase inverter welding machine.

Features of operation

First you need to understand how the inverter functions. Essentially, it is a computer power supply. In it you can observe the transformation of electricity in the following sequence:

• The input AC voltage is transformed into DC.
• The 50 Hz current consumption is converted to high frequency.
• The output voltage decreases.
• The output current is rectified, the required frequency is maintained.

Such transformations are necessary to reduce the weight of equipment and its dimensions.

Transformer welding machines have sensitive weight and dimensions. Due to the significant current strength, arc welding can be carried out in them. To increase the current and lower the voltage, the secondary winding involves the presence of fewer turns, and the cross-section of the wire increases. As a result, the transformer welder is heavy and bulky.

The inverter principle makes it possible to reduce these figures significantly. The circuitry of such a device involves increasing the frequency to 60-80 kHz, which helps reduce its size and weight. To implement such a conversion, power field-effect transistors are used. They communicate with each other precisely at this frequency. They are powered by direct current coming from a rectifying device, which is a diode bridge. The voltage value is equalized by capacitors.

After the transistors, the current is transferred to a step-down transformer. It is a small coil. The small dimensions of the inverter transformer coil are ensured by a frequency that is greatly increased by field-effect transistors. The result is characteristics similar to those of a transformer device, but with less weight and size.

What is needed for assembly

To create such a homemade product, it is necessary to take into account the characteristics of the circuit, i.e., consumed voltage and current. An output current of 250 amps is enough to create a durable seam. To implement the idea you will need the following details:

• Transformer.
• Primary winding (100 turns with wire ⌀ 0.3 mm).
• 3 windings. In the outer: 20 turns, ⌀ 0.35 mm. On average: 15 and ⌀ 0.2. In internal 15 and ⌀ 1 mm.

In addition, before starting to assemble the inverter, it is necessary to prepare tools and elements for developing electronic circuits. You will need:

• Screwdrivers;
• Soldering iron;
• Hacksaw for metal;
• Fasteners;
• Electronic elements;
• Copper wires;
• Thermal paper;
• Electrical steel;
• Fiberglass;
• Textolite;
• Mica.

Scheme

The electrical circuit diagram of an inverter is one of the most critical moments when designing or repairing an inverter apparatus. Therefore, we recommend that you first study the options in detail and then begin to implement them.

List of radioelements

Power part

The power supply plays one of the leading roles in the inverter apparatus. It is a transformer wound on ferrite. It provides a stable decrease in voltage and increase in current value. You need 2 cores Ш20х208 2000 nm.

Thermal paper is used to create thermal insulation between the inverter windings. To minimize the negative impact of constant voltage drops in the electrical network, the winding should be carried out across the entire width of the core.

For the winding of the transformer, experts recommend the use of copper sheet having a width of 40 mm and a thickness of 0.3 mm. It needs to be wrapped in 0.05 millimeter thermal paper (cash register tape). Experts explain this by the fact that during welding, high-frequency current is displaced onto the surface of thick wires, while the core is not used and a lot of heat is released. Therefore, ordinary conductors are not suitable. This effect can be eliminated by using conductors with a significant surface area.

An analogue of copper sheet that can be used is PEV wire with a cross-section of 0.5-0.7 mm. It is multi-core with air gaps between the cores, which reduces heating.

After creating the primary layer, a shielding wire with fiberglass is wound in the same direction. This wire (of similar diameter) must completely cover the fiberglass. It is necessary to proceed in the same way with other windings of the transformer. They must be isolated from each other using the above insulators.

In order for the voltage from the transformer to the relay to be at the level of 20 - 25 volts, it is necessary to select the correct resistors. The main task of the inverter power supply is to change alternating current into direct current. This is implemented by a diode bridge circuit of the “oblique bridge” type.

During operation, the diodes of the inverter device will heat up. Therefore, they must be placed on the radiator. It is allowed to use radiators from computers. Fortunately, they are now widespread and inexpensive. You will need 2 radiators. The upper element of the bridge is fixed on one, and the lower element on the second. In this case, when installing the first one, it is necessary to use a mica gasket, and in the second case, thermal paste.

The output of the diode bridge is in the same direction as the output of the transistors. Use wires no longer than 15 cm. The basis of the inverter unit is transistors. The bridge must be separated from the power supply by a sheet of metal, which is subsequently attached to the case.

Installation of diodes on a radiator

Inverter unit

The main task of this inverter unit is to transform the rectified current into a high-frequency alternating component. Power transistors that open and close at high frequencies are designed to perform this function.

It is better to create a converting unit of an inverter apparatus not with one more powerful transistor, but with the use of several weaker ones. Due to this, the frequency of the current is stabilized and the noise effect during welding is minimized.

The inverter circuit must contain capacitors. Connected in a series circuit. Perform 2 main tasks:

• Minimize resonant emissions of the power supply.
• Reduce losses of the transistor unit that occur after switching on. This is explained by the fact that the transistor opens faster. The closing speed is noticeably slower. In this case, a loss of current occurs and the switches in the transistor unit heat up.

Cooling system

The power elements of the converter will heat up significantly during welding. This may cause a breakdown. To eliminate this, in addition to the radiators mentioned above, you should use a fan that eliminates overheating and ensures stable cooling.

One fan of sufficient power may be enough. However, when using elements of an old PC, you may need up to 6 pieces, 3 of which must be placed near the transformer.

To completely protect a homemade inverter from overheating, you can use a temperature sensor. It should be mounted on the hottest element with a radiator. The element will be able to turn off the power when a certain temperature is reached, and the indication will signal a critical level.

For efficient and stable operation of the inverter ventilation system, it is necessary to ensure constant correct air intake. To do this, the holes through which air will be taken in should not be blocked by anything. A sufficient number of holes should be provided in the inverter housing. In this case, they need to be placed on opposite surfaces of the body.

Control

When placing the electronic boards of the device, it is possible to use foil-coated PCB with a thickness of 0.5 - 1 millimeter.

To ensure automatic control of inverter welding, you should buy and install a PWM controller. It will stabilize the welding current and voltage level. For convenient control, all controls and connection points are located on the front part.

Frame

After creating the main elements of inverter welding, you can begin preparing the body parts. When planning, you need to take into account the width of the transformer, since it must be placed unobstructed in the housing. Based on this size, approximately 70% of the space should be added for the remaining parts. The protective casing can be made from sheet iron, 0.5-1 millimeters thick. The elements can be connected using welding or bolts. A more sophisticated option would be a one-piece design made from curved raw materials. Handles and belt mounts are required to carry the device.

When designing an inverter, consideration should be given to the possibility of easy disassembly to access internal components for easy repair. The front side must also contain:

• Current switch;
• A button that will turn the device on/off;
• Light indication elements;
• Connectors for connecting cables.

Factory inverters are powder coated. You can use regular paint at home. It is worth applying a coating to prevent the appearance of rust.

Connection

The assembled welding machine must be connected to the electrical network. When connecting to an outlet, be sure to have a fuse or circuit breaker. For protection, a 25 amp circuit breaker can be installed at the inverter input.

If the connection point is remote, you can use an extension cord.

The device is turned on according to the standard scheme - using the “on/off” button. The indication should light up, usually a green LED is used for this.

The connection to the network must be made with a wire having a cross-section of at least 1.5 mm 2 . However, the optimal cross-section will be a wire of 2.5 mm 2.

Before connecting the device to the electrical network, you should check that all high-voltage elements are insulated from the housing parts.

Functionality check

After all assembly and debugging work has been completed, it is necessary to check the functionality of the created inverter.

According to the recommendations of specialists, it is necessary to check the current and voltage of the device using an oscilloscope. The lower voltage loop should be up to 500 volts, not exceeding 550 V. If all design requirements are met, the voltage level will be 330 - 350 volts. But this method is not always available, because not every home has its own similar measuring device.

Often the inspection is carried out in action directly by the welder. To do this, a test seam is created with complete burnout of the electrode. At the end of the test welding, you need to check the temperature on the transformer. If it goes off scale, then there are some deficiencies in the circuit and everything should be double-checked.

If the temperature of the power unit is normal, then you can carry out another 2-3 test runs. After this, check the temperature of the radiators. They may also overheat. If after two to three minutes they return to normal, then you can safely continue working.

The assembly procedure of the device is not complicated. The most important step is setting up the inverter device. You may need to seek help from a specialist.

1. First you need to connect 15 volts to PWM while simultaneously connecting one convector. This way you can reduce heat and noise during operation.

2. To close the resistor you need to connect a relay. It is connected when the capacitors have finished charging. Due to this, you can significantly reduce voltage fluctuations when connecting to a 220 volt power supply. Without a resistor, an explosion is possible when connected directly.

3. Check the operation of the resistor closure relay a couple of seconds after current is supplied to the PWM board. Check for the presence of a rectangular pulse on the board after the relay has been tested.

4. Supply 15 volt power to the bridge to check its functionality and correct assembly. The current should be no higher than 100 mA at idle.

5. Checking the correct placement of phases. Use an oscilloscope. The bridge circuit is supplied with 200 volts from the capacitors through the lamp with a load of 200 W. The PWM frequency is set to 55 kHz. An oscilloscope is connected, the signal shape and voltage level are checked (no more than 350 volts).

To determine the frequency of the device, you should slowly lower the PWM frequency until a slight turn occurs on the IGBT switch. The resulting frequency value must be divided by 2 and the oversaturation frequency added. The result is an operating frequency oscillation of the transformer.

The transformer of the device should not make any noise. If they are present, the polarity must be checked. The diode bridge can be connected to power for the test through suitable household appliances. For example, a kettle with a power of 3000 W is suitable.

The conductors going to the PWM must be short. They need to be twisted and placed further from the source of interference.

6. The current is gradually increased using a resistor. In this case, you need to listen to the inverter and monitor the values ​​on the oscilloscope. There should be no more than 500 volts on the lower key. The average value is 340. If noise is present, the IGBT may fail.

7. Start welding after 10 seconds. The radiators are checked, if they have not heated up, then extend the work for another 20 seconds. After re-checking, welding can last from one minute or longer.

Safety

All operations performed, with the exception of performance testing, must be carried out exclusively on de-energized equipment. It is recommended to check each element in advance so that after installation it does not fail due to overvoltage. Basic electrical safety rules are also mandatory.

Thus, almost anyone can do homemade inverter welding. The proposed description should help you understand all the nuances. If you study video tutorials and photo materials, then assembling the device will not be difficult.

Welding inverter– a convenient mobile device operating from a 220V network. Its light weight and small size make it possible to work at any construction and repair sites and at home.

It is intended for direct current welding of ferrous and non-ferrous metals. The package includes 2 welding cables, a brush and instructions. Installing a special burner will allow the device to operate in a protective gas environment.

The main technical parameters that most inverters meet:

• welding current adjustment ranging from 20 to 250A;
• voltage XX 50-70V;
• industrial frequency 50Hz;
• electrode diameter 1.6-5mm;
• power used is approximately 4-12 kW;
• duty cycle at 200A is 60%;
• Efficiency 85%;
• weight from 3 to 12 kg;

In addition to the parameters, the equipment must meet the basic requirements:

1. Soft ignition and uniform arc burning.
2. Power control and current strength.
3. Protection triggered in case of short circuit.
4. Quality formation weld bead.

Advantages:

1. Energy saving.
2. Easy to use.
3. Reliability and safety.

Before assembly you need to know the device

Various types and types of welding inverters are produced all over the world. In a short period of time, they have gained popularity among people. Affordability played an important factor in this.

Let's take a closer look at what the most common low-power units are made of, using the COLT 1300 from an Italian manufacturer as an example:

1. The case is made from a metal protective casing 1mm thick. It's wearing side panels.
2. On the front wall connectors for connecting cables, a current regulator, a network and protection indicator are provided.
3. On the back there is a switch.
4. Throughout the shell Technological openings for ventilation have been made.
5. There is an electrical board inside, on which all the details of the circuit are fixed.

This assembly option is the most convenient.

The Chinese make the filling from 4.5 plates. This is not a disadvantage, but when designing your device, let’s take a simpler idea.

The set consists of the following units:

• electric stove;
• capacitors;
• radiators;
• fan;
• absorption filter;
• diode rectifier;
• transistors;
• Control block;

The rest is shown in the specification.

Scheme

One of the first steps in manufacturing an inverter is determining its operating circuit. Since there is a large amount of choice on the Internet, there is no need to come up with something new.

We will continue to use information about the inverter model COLT1300 as a basis; the working diagram is shown in Figure 1:

Fig 1.

Figure 2 shows a diagram of the control unit for the processes taking place in the power section. For the type of device under consideration, the circuits are squeezed onto one board. Let's change this and make the control unit on a separate board.

Fig.2

Let's divide the main diagram into several parts and get:

To make electrical 4 boards, you will need the following:

• textolite FR4 150×250mm (2mm);
• permanent black marker;
• citric acid and hydrogen peroxide;
• soldering flux LTI-120;
• drill with a diameter of 1mm and 2mm;

In the Dip Trace program we draw a power circuit:

Convert to board:

At the end you will get a drawing:

An example is shown in a simpler diagram. You can download a tutorial for working in Dip Trace on the website Full-Chip.net. It sequentially describes each operation for printing microcircuits.

The resulting image of the layout must be printed on a laser printer, this is a prerequisite, ink will not give the desired effect:

1. Let's prepare the textolite. Sand lightly with fine-grit sandpaper to a bright surface. We attach the printed layout to the plate and wrap it with another layer of newsprint on top.
2. Apply a hot iron and wait 15-20 seconds. Let it cool gradually, then soak it in water to make it easy to peel off. If in some area the connection is poorly printed, we fill it in with a black marker.
3. Preparing a bath for etching the board. The solution includes citric acid, hydrogen peroxide and water. The container is large enough for the board to fit completely into it. You must be careful with this mixture and wear rubber gloves. Stir only with wooden objects, not metal ones.
4. Next, all this needs to be put in a warm place. or in a bowl of warm water. By controlling the process, you can see when the unpainted copper coating comes off, then you can remove the part.
5. Drying the circuit and remove the marker with sandpaper. We cover the surface with LTI-120 flux. In order to allow the tracks to oxidize, they must be carefully polished to a pleasant shine.

So, we get two boards for the power circuit and the control unit.

Required materials, parts and tools

To assemble a homemade inverter you will need:

• screwdriver;
• pliers;
• wire cutters;
• grinder with cutting and notching wheels;

Material List:

• metal 1 mm thick, for the manufacture of the body and casing;
• self-tapping screws;
• copper wires;
• ready-made boards for parts;
• tin, solder;
• ferrite rings for transformer;
• thermal conductive paste KPT-8;
• ferrite core;
• PETV wire coil d=1.5 for transformer winding;

And a list of parts:

• power VS-150 EBUO4;
• transistors IRG4PC50UDPBF IGBT 600V 55A 60kHz;
• high-speed PWB controller for switching power supplies UC3825N;
• Finder soft start relay, 3.5 steps 16A 250V;
• power resistor SQP3BT 47 Ohm;
• EMI suppression filter B82731-N2102-A20;
• capacitors 470mKf 450V LS series 35×45;
• radiators Hs 113-50 50x85x24;
• fan DEEPCOOL WIND BLADE 80, 80mm;
• diode bridge KTs405 90-92;

Assembly, step by step instructions

We begin assembly with the body structure. We mark two parts of the shell on a metal sheet. The picture shows U-shaped factory halves.

It is impossible to make exactly such casings at home, but following the example you can try:

Explanation:

1. Marked sheet mode with a grinder, and then bend it on a homemade bending machine.
2. Inside the base install the jumpers on which the boards will be located.
3. On W - shaped plates wind the windings. The primary winding is 100 turns; between the layers we place a gasket, thin, thick paper. The secondary winding is 50 turns.
4. Install using a soldering iron and solder the parts onto the prepared boards according to the circuits.
5. Transistors and diodes install on radiators. Between them we apply heat-conducting paste KPT-8.
6. We connect the circuits with insulated conductors. The diameter is not as important as the length, which should not exceed 140mm. The wires must be twisted together.

A similar assembly example is shown in the image:

Inverter setup

We will configure the converter in the range of 20-85 kHz:

1. We give the load to the winding of a step-down transformer.
2. Comparing the type of signal with the right pattern

Explanations:

1. Polarity change step must be at least 1.2 µs.
2. It is important to set up the device under load to obtain maximum parameters of the assembled equipment.
3. To the exits We connect an approximate resistance of 0.14 Ohm.
4. Next we connect generator, to the diode bridge, calculating the phases.
5. Nutrition there should be 12-25V; connect a light bulb to the secondary winding of the power transformer.
6. By adjusting the frequency, we achieve the brightest arc burning.
7. In case of transistor failure or the diode will have to replace the burnt part.
8. Settings carry out again.

If the output parameters do not meet the required parameters, the reason may be an incorrect or poor-quality transformer winding. The gaps between the windings are not maintained or the lining between the layers is poor.

The voltage at the output of the stabilizers should be +15V and -15V.

On the resistor in front of the driver we connect the current regulator potentiometer to minimum.

We simulate an increase in current. At the output, the voltage rises to 5V. The PWM signal produces a frequency of 30 kHz.

As the current increases, the voltage increases and the frequency signal becomes smaller. At the end. Carry out the settings with the inverter. We adjust the maximum current, then using a potentiometer we set the frequency of the PWM signal to 30 kHz.

Terms of use

Welding equipment requires a responsible attitude:

1. Before work prepare the workplace. It's normal to have a lot of free space.
2. Inverter reacts poorly to temperature changes and weather conditions.
3. Avoid dust. It conducts current very well. Industrial plants have compressed air that can be used to blow through equipment.
4. Do not overheat the device. Intense electrical processes occurring in circuits lead to great heating. A burnt-out part is a common breakdown problem. On average, continuous operation lasts 5-6 minutes.
5. Selecting wires for cables depends on the thickness of the electrode. For household needs, use a 3mm diameter. Welding with this diameter will allow the use of thin and light cables. Their length should not be more than 1.5 m.
6. Before work All wire connections are checked to avoid interruptions in the current supply.
7. Attach the plus to the metal, the minus to the holder. Plug in the device and press the start button on the back panel. Set the welding current. Its strength should be sufficient to melt, but not burn through the metal.
8. Work required in special, fire-resistant clothing, gloves and a shield.

Self-assembly costs

This section provides a calculation of the funds invested in the assembly of the welding inverter. The list shows the main pieces of equipment. Anything not included in the list is of little importance.

The price, on the contrary, is indicated for one unit:

• thermal conductive paste – KPT-8 200r;
• ferrite core – 170r;
• wire coil - PETV d=1.5 for transformer winding 550r;

And a list of parts:

• power diodes VS-150 EBUO4 390r-1pcs;
• transistors IRG4PC50UDPBF IGBT 600V 55A 60kHz 230-1pcs;
• high-speed PWB controller for switching power supplies UC3825N 300r-1pcs;
• Finder soft start relay, in steps of 3.5 16A 250V 70r;
• power resistor SQP3BT 47 Ohm 9p;
• EMI suppression filter B82731-N2102-A20 57р;
• capacitors 470mKf 450V series LS 35×45 770r-1pcs;
• radiators Hs 113-50 50x85x24 180r-1pcs;
• fan DEEPCOOL WIND BLADE 80, 80mm 260r;
• diode bridge KTs405 90-92 27r;

Operating principle

Inverter– electric arc power source. Having small dimensions, it ensures stable burning of the electrode. These processes can be supported by rectified and converted voltage several times.

Let's compare a conventional transformer with its competitor. The first serves to reduce the network voltage to 60V. The powerful copper winding then allowed a high current to pass through. The simple design has disadvantages - copper consumption, heavy weight.

These 2 drawbacks were eliminated by increasing the operating pulse from 0.05 kHz to 65 kHz.

A simplified diagram of energy changes is shown in the figure:

Explanations of the diagram:

1. Mains voltage 220V with an oscillation of 50 Hz pass through a diode rectifier. This is done to power the transistors on which the inverter circuit is assembled.