How to make a choke for a welding inverter

DIY choke for DC welding

It is difficult to imagine, in our time, any work with metal without the use of a welding machine. Using this device, you can easily connect or cut iron of various thicknesses or dimensions.

Naturally, to perform high-quality work you will need certain skills, but first of all you need the welder itself.

Nowadays, of course, you can buy it, as well as, in principle, hire a welder, but in this article we will talk about how to make a welding machine with your own hands.

Moreover, with all the wealth of choice of models, reliable ones are quite expensive, and cheap ones do not shine with the quality of the work performed. But even if you decide to buy a welding machine, reading this article will help you choose the machine you need. There are several types of welders: direct current, alternating current, three-phase and inverter.

In order to determine which option you need, let’s consider the design and structure of the first two, which you can assemble with your own hands at home without any specific skills.

AC

This type of welding machine is one of the most common options, both in industry and in private households.

It is easy to use and, compared to others, can be made quite easily at home, as evidenced by the photo below.

To do this, you need to have a wire for the primary and secondary windings, as well as a transformer steel core for winding the welder. In simple words, an AC welding machine is a step-down transformer.

The optimal voltage when operating a welding machine assembled at home is 60V. The optimal current is 120-160A. Now it’s easy to calculate what cross-section the wire should have in order to make the primary winding of the transformer (the one that will be connected to the 220 V network). The minimum cross-sectional area of ​​the copper wire should be 3-4 square meters. mm, the optimal is 7 sq.

mm, because it is necessary to take into account voltage drops and possible additional load. We find that the optimal diameter of the copper core for the primary winding of a step-down transformer should be 3 mm. If you decide to take an aluminum wire in order to make a welding wire yourself, then the cross-section of the copper wire must be multiplied by a factor of 1.6.

It is important that the wires are in a rag sheath; you cannot use conductors in PVC insulation - when the wires heat up, it will melt and a short circuit will occur. If you do not have a wire of the required diameter, you can use thinner wires by winding them in pairs. But then it should be taken into account that the thickness of the winding will increase, and, accordingly, the dimensions of the device itself.

For the secondary winding, you can use a thick stranded copper wire - the same as the core on the holder.

The first step is to make a transformer core for a homemade welding machine. The best option would be a rod-type core as shown in Figure 1:

This core must be made from transformer steel plates. The thickness of the plates should be from 0.35 mm to 0.55 mm. Before assembling the core, it is necessary to calculate its dimensions, this is done as follows: firstly, the size of the window, i.e. dimensions c and d in Figure 1 must be chosen such as to accommodate all the windings of the transformer, secondly, the roll area, which calculated by the formula Skren=a*b, must be at least 35 square meters. cm.

If Skren is greater, then the transformer will heat up less and, accordingly, work longer. It is better that the Skrena is equal to 50 square meters. see. Next, we proceed to assembling the plates of a homemade welding machine. It is necessary to take the L-shaped plates and fold them, as shown in Figure 2, until you can make a core of the required thickness. Then we fasten it with bolts at the corners.

Finally, it is necessary to process the surface of the plates with a file and insulate them by wrapping them with rag insulation.

Next, we proceed to winding the welding machine from the step-down transformer. First, we wind the primary winding, which will consist of 215 turns, as shown in Figure 3.

It is advisable to make a branch from 165 and 190 turns. We attach a thick textolite plate to the top of the transformer.

We fix the ends of the windings on it using a bolted connection, noting that the first bolt is a common wire, the second is a branch from the 165th turn, the 3rd is a branch from the 190th turn and the 4th is from the 215th.

This will make it possible to subsequently regulate the current strength during welding; the greater the number of turns in the primary winding, the higher the current strength of your welding device will be. Then we proceed to winding 70 turns of the secondary winding, as shown in Figure 4.

A smaller number of turns are wound on the other side of the core - where the primary winding is wound. The ratio of turns should be approximately 60% to 40%.

This ensures that after you catch the arc and start welding, the eddy currents will partially turn off the work of the winding with a large number of turns, which will lead to an increase in the welding current, and accordingly improve the quality of the seam.

We will also secure the ends of the winding with bolts to the textolite plate. Now your homemade welding machine is ready.

Having connected the holder and ground to the secondary winding, it is necessary to connect the network to the common wire and the wire extending from the 215th turn of the primary winding. If you need to increase the current, you can make fewer turns of the primary winding by switching the second wire to a contact with fewer turns. The characteristics can be reduced using a resistance made from a piece of transformer steel bent in the form of a spring and connected to a holder.

It is always necessary to ensure that the welding machine does not overheat.

This is how you can make a welding machine from a step-down transformer with your own hands. As you can see, the instructions are not too complicated and even an inexperienced electrician can assemble the device on their own.

DC

Some types of welding require a DC welder. This tool can be used to weld cast iron and stainless steel. You can make a DC welding machine with your own hands in no more than 15 minutes by converting a homemade product to AC. To do this, you need to connect a rectifier assembled with diodes to the secondary winding.

As for the diodes, they must withstand a current of 200 A and have good cooling. D161 diodes are suitable for this. Capacitors C1 and C2 with the following characteristics of 15000 μF and a voltage of 50V will help us equalize the current. Next, we assemble the circuit shown in the drawing below. Inductor L1 is needed to regulate the current.

Contacts x4 are for connecting the holder, and x5 are for supplying current to the part to be welded.

Now you know the basic principles of the design of welders and, using them, you can make a welding machine with your own hands, both constant and alternating current.

We also recommend watching the video lessons provided below, which will help you clearly see how to assemble a simple welder yourself from scrap materials.

Visual master classes

So, if you decide to make a welding machine at home, perhaps these video lessons will inspire you to make your own tool:

Also read:

Source: https://respect-kovka.com/drossel-dlya-svarki-postoyannym-tokom-svoimi-rukami/

Do-it-yourself choke for DC welding - Metalworker's Handbook

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 an electrical control circuit using thyristors and installed it.

In this article, based on personal experience, I tell you how I assembled and configured a DC welding machine with my own hands based on a homemade 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. Welding inverters were not known at that 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 getinax;
• 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 come across different designs of homemade or factory-made 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 an article about making a transformer soldering iron Moment with your own hands. 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 cm2.

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, durable insulation, designed to withstand long-term operation 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 large-diameter ring is made of wire and 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

For it, we found a copper wire of a suitable cross-section - 21 mm2. 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.

Typically reference books recommend 60-70 volts. One experienced welder told us that in our case 50 would be enough. We decided to check it, and if it wasn’t enough, then increase the winding further.

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 outer 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 of current and output voltage can work here.

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.

  Classification of electric fusion welding

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. We checked the appearance of the pulses with an oscilloscope.

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

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

Welding current regulation

Variable resistor R2, with its resistance, determines the position of each pulse passed through the control electrode of the thyristor. The shape of the pulsating current at the output of the power circuit of the welding machine depends on it.

Half-sine ripples can pass through completely when the welding current is set to maximum or be cut off to almost zero.

Personal impressions of use

When the DC welding machine was made with our own hands, we began to study its capabilities. First of all, we experimented with the polarity of the electrode connection and identified a pattern.

The electrode can be supplied with “plus” - direct polarity or “minus” - reverse polarity. In this case, the depth of weld penetration changes. With reverse polarity it increases by about 40-50%.

Our welding machine allows you to weld with 3 mm electrodes, providing a welding current of 80 amperes for quite a long time. The heating of the structure does not exceed operating conditions. At the same time, the load in the household wiring network is maintained at a level of up to 20 A.

The cooling system can be enhanced by forced ventilation by blowing. But we did not deal with this issue.

I show the scanned handwritten text of a preserved document. It may be useful for repetition.

And now I recommend watching the video by the owner of zxDTCxz “Welding machine based on a toroidal magnetic core.” It contains many useful recommendations.

Source: https://ssk2121.com/drossel-dlya-svarki-postoyannym-tokom-svoimi-rukami/

How to wind a choke for a welding machine

Electric welding is widely used in large industries and small workshops. Devices for joining metals with an electric arc also vary in size and power.

But they all have one possible problem in common - a voltage drop interferes with the ignition of the arc and the welding. It can also be difficult to adjust the required current value for a specific metal thickness. To solve all this, a choke is used as part of the equipment.

What it is? How does it function? How to make a throttle for your device yourself?

What it is?

It is quite possible to make a choke for a welding machine with your own hands. It consists of a core and two windings with a specific cross-section, designed to operate with a specific current value. A choke from a large welding equipment will not fit a small unit, and vice versa, a small model will not be effective on a large welding machine.

The choke receives and accumulates current from the step-down transformer, which facilitates smooth ignition of the electrode. During welding, the arc burns more softly and the metal of the weld pool is less splashed. If the incoming voltage is too high, the inductor takes over part of the resistance function. This allows you to more accurately tune the machine and weld thin metal.

The advantage of a homemade throttle

To weld metal of various thicknesses, several methods are used to adjust the current:

• Changing the distance between transformer elements. Welding machines have two windings, between which electromagnetic induction occurs. Due to this, Volts decrease and Amps increase. If the current is too high for normal welding on a given thickness of material, then the windings are separated from each other using a threaded screw. This dissipates induction and reduces current. The degree of adjustment depends on the length of the screw and the size of the device body. The wider the settings for this parameter, the larger the welding unit itself.
• Step adjustment on the transformer winding allows you to cut off part of the coil, allowing the current to flow along a shorter path. To reduce the force of the welding arc, set the longest voltage path possible. But this depends on the number of turns of the step-down transformer.
• A resistance made of a steel spring with terminals attached at a certain interval allows you to regulate the current strength in small “steps”, but has a significant drawback in the form of rapid overheating of the resistance, which is constantly under the welder’s feet.

The introduction of a choke into the circuit solves all these problems at the same time. This small electrical device partially compensates for the missing resistance, so there is no need to use large transformers with wide adjustment parameters. The current adjustment occurs smoothly without steps, and there is no hot spring under your feet.

Application

A self-made choke interacts well with transformers. Since alternating current is characterized by crackling and splashing of metal, adding this element to the circuit will allow you to cook more gently. This is especially felt when working on heating pipes, where water continues to leak from the system.

The choke for a welding inverter and semi-automatic device is also useful in facilitating rapid ignition of the arc. For example, if the inverter should produce 48 V no-load, then when the voltage in the network drops or surges, this value will be even less.

When you need to weld with an MP-3 electrode, the optimal current value for which is 70 V, and at 48V it ignites with difficulty, then in the event of a voltage drop it will be very difficult to initiate an arc.

As a result, planned welding work will have to be postponed until normal voltage is restored.

The choke, in combination with a rectifier, is capable of producing a self-induction emf, which penetrates the air space and easily ignites the electrode. In the case of a semi-automatic machine, this facilitates easy start of work at the slightest approach of the wire coming from the nozzle to the product.

Combining two functions (resistance compensation and arc stabilization), this device allows you to weld thin metal under conditions of surge voltage. Thus, devices with a choke are widely used for welding car bodies at service stations, or stainless steel thin containers.

DIY choke

To know how to wind a choke correctly, it is important to understand its structure. Although it is simple, following each part carefully step by step will ensure a quality result. For a semi-automatic machine or inverter used in a private home or country house, a choke made as follows is suitable:

1. An old transformer is used as a basis. The optimal model is a boost element on a tube TV marked “TSA 270-1”. Similar ones can be found in elderly friends' garages. The dimensions of its internal part are ideal for a welding machine for home use.
2. The transformer is disassembled by cutting off the bolts to release the coils. Or you can rotate the row of heads at the top of the device and remove the coils directly.
3. It is necessary to install gaskets on empty horseshoes that will form an inductive gap of the choke. They can be made from cardboard with a sheet thickness from 0.8 to 1.0 mm. The spacers are glued to the base of the horseshoe.
4. The winding is made with soft aluminum wire with a cross-section of 36 mm. Each coil should have 24 turns. Using the specified core from an old TV, you can make three layers of eight turns each. Between layers it is necessary to perform high-quality insulation with paper and bakelite varnish. This is done due to the device’s ability to generate self-induction emf, which appears when the arc breaks. Then the discharge follows the path of least resistance and breaks through the air, which renews the burning of the electrode. If the least resistance is between the turns of the winding, then a breakdown will occur there, which will lead to damage to the element.
5. The wire must be wound in one direction on each coil. Thanks to the same direction, you will get a structure on which at the top there will be a jumper between the taps connecting the coils, and at the bottom there will be an input and an output.
6. If an error was made during winding and the coils turned out to be opposite in the direction of winding, then you can get out of this situation by installing an oblique jumper between the upper and lower taps diagonally. The second pair of taps forms the inlet and outlet.
7. It is recommended to install the inductor in the circuit after the diodes. A cable from the diode bridge is connected to the input, and a ground cable supplied to the product is attached to the output.

Throttle check

After assembly, the device is tested. To do this, it is necessary to weld on metal whose thickness will be used most often in everyday work. The current strength is checked, which should be sufficient for good penetration, but without burn-through.

It is also necessary to pay attention to the behavior of the welding arc, its stability, moderate crackling, and smooth combustion without excessive spatter. Easy ignition of the electrode and good arc characteristics will indicate proper assembly. If the current strength has dropped significantly, then it is worth rewinding the device and removing several turns of the winding on each coil.

The introduction of a choke into the circuit of a semi-automatic device, inverter or conventional transformer makes it easier to work with the device. It becomes more convenient to apply sutures, and the electrode ignites smoothly and stably. This is especially practical in the private sector, where power surges are commonplace. It is easy to make a homemade device following the sequence given in the article.

Source: https://steelfactoryrus.com/kak-namotat-drossel-dlya-svarochnogo-apparata/

Making a choke for a welding machine with your own hands

RUSENUKR

A step-down transformer is the basis of a simple welding machine. A more complex welding machine is one that has a rectifier at the output that converts alternating voltage into direct voltage. Such welding machines are called rectifiers.

There are three types of transformers: toroidal, rod and armored, the differences between them can be seen in the figure above.

The most complex is the welding machine, which first converts the input power frequency of 50 Hz into a direct voltage, like rectifiers, and then converts it into an alternating voltage, the frequency of which is measured in kilohertz. This is an inverter.

Only someone who is well versed in radio electronics and the element base used there can make an inverter with their own hands. For this specialist, there is no need to explain why the inductor is needed and where its place is in the circuit. It would be advisable to explain to an unprepared person what a transformer and a rectifier for it are.

Calculation of the cross-section of the wires of the primary winding of the transformer

Diagram of a welding transformer.

The theory of transformers is complex in that it is based on the laws of electromagnetic induction and other phenomena of magnetism. However, without using complex mathematical apparatus, it is possible to explain how a transformer works and whether it can be assembled independently.

The transformer can be manually wound on a metal core assembled from transformer steel plates. It is easier to wind on a rod or armored core than on a toroidal one. You should immediately note that the image clearly shows the difference in the thickness of the wires: the thin wire is located directly on the core, and a larger number of turns is clearly visible in it. This is the primary winding. The thicker wire with fewer turns is the secondary winding.

Without taking into account the power losses inside the transformer, let's calculate what the current I1 should be in its primary winding. The ideal network voltage is U=220 V. Knowing the power consumption, for example, P=5 kW, we have:

I1 = P:U= 5000:220=22.7 A.

Based on the current in the primary winding of the transformer, we determine the diameter of the wire. The current density for a household welding transformer should be no more than 5 A/mm2 of wire cross-section. Therefore, for the primary winding you will need a wire with a cross section of S1 = 22.7:5 = 4.54 mm2.

Using the cross-section of the wire, we determine the square, its diameter d without taking into account the insulation:

d2=4S/ =4 4.54/3.14=5.78.

Taking the square root, we get d=2.4 mm. These calculations were performed for copper wire cores. When winding wires with an aluminum core, the obtained result must be increased by 1.6-1.7 times.

For the primary winding, copper wire is used, the insulation of which must withstand high temperatures well. This is fiberglass or cotton insulation. Rubber and rubber-fabric insulation is suitable. Wires with PVC insulation should not be used.

Calculation of the cross-section of the wires of the secondary winding of the transformer

Diagram of a transformer with primary and secondary windings.

The voltage at the output of the welding machine transformer in the absence of a welding arc (idle mode) is usually 60-80 V. The higher the idle voltage, the more reliably the arc is ignited. The welding arc voltage is usually 1.8-2.5 times less than the no-load voltage.

Attention. It is necessary to constantly remember that in the absence of an arc the voltage at the transformer output is life-threatening.

For welding in everyday life, an electrode with a diameter of 3 mm is usually used, which is sufficient to provide an arc current of approximately 150 A. With an open circuit voltage of 70 V, the arc voltage will be approximately 25 V, and the power consumption P of the welding machine must be at least

Р=25 150=3750 W =3.75 kW.

It is advisable to design the transformer for higher power, that is, higher welding arc current. For example, with an arc current of 200 A, the power consumption will be approximately 5 kW. This is the power the transformer should be designed for.

The single-phase voltage in the house should be 220 V, but it can vary by ±22 V. This is one of the reasons why the arc current may change and will need to be adjusted.

The cross-section of the wire in the secondary winding of the transformer is determined based on the current density equal to 5 A/mm2. For a current of 200 A, the wire cross-section is 40 mm2, that is, it can only be a busbar that is wound with layer-by-layer insulation. Based on existing standard sizes, you can select the required tire both in length and cross-section.

Typical sizes of copper busbars produced by industry:

Manufacturing diagram of a welding choke

• length from 0.5 to 4 m with intervals of 0.5 m;
• width from 2 to 60 cm with intervals of 1 cm (with widths from 4 to 10 cm) and with intervals of 5 cm (with widths from 10 to 60 cm);
• thickness from 3 to 10 mm.

You can also use a stranded wire, the cross-section of which corresponds to the calculated value. To increase the cross-section, the wire can be folded in half or three. For aluminum wire, the cross-section must be increased by 1.6-1.7 times.

For a choke that is connected at the output of the transformer, the cross-section of the wire must be the same as in the secondary winding of the transformer.

Rectifier for welding machine

Electrical circuit of a welding machine rectifier.

To weld with direct current, an AC-to-DC converter must be connected to the output winding of the transformer. Such a device is called a rectifier, which is why a welding machine with this device is called a rectifier.

The top graph represents the sinusoidal voltage at the output of the transformer secondary winding. The horizontal t-axis is the time axis. The time interval between zero voltage values ​​is determined by the oscillation period. It consists of positive and negative half-cycles.

It can be seen that the current is not constant, but pulsating. The only way to reduce ripple is by increasing the capacitance of the capacitor.

To regulate the arc current, the choke must be connected between the transformer output and point 3 of the rectifier.

Methods for regulating welding arc current

Let's consider one of the methods of regulating the welding arc current, based on the use of a choke in the secondary winding of the transformer. The arc current is regulated by changing the air gap provided in the core on which the busbar is wound.

Let's consider three modes in which a transformer can be.

Diagram of no-load and short circuit of a transformer.

1. Idle mode. Alternating voltage is supplied to the input of the transformer. An emf is induced in the secondary winding, but there is no current in the output circuit.
2. Load mode. As a result of ignition of the arc, it closes the output circuit, consisting of the secondary winding of the transformer and the inductor winding. A current flows, the magnitude of which is determined by the inductive reactance of these windings. If there were no choke, the current would be maximum. The degree of impact depends on the size of the air gap in the rod on which the winding is wound.
3. Short circuit mode. This is the moment the electrode touches the parts of the workpiece being welded. An alternating magnetic flux is created in the transformer core, and an emf is induced in the secondary winding. The current in the circuit is determined by the inductive reactance of the inductor and the secondary winding of the transformer.

As the gap increases, the resistance increases. This leads to a decrease in the magnetic flux and, accordingly, to a decrease in the inductive resistance of the choke coil and the total resistance of the circuit. The arc current increases. This method allows you to smoothly regulate the current.

Transformer assembly diagram.

However, the moving system has the disadvantage that as a result of the vibration of the metal when passing alternating current through the coil, it becomes not very reliable.

You can, sacrificing the smoothness of the adjustment, make it stepwise. To do this, it is necessary to make the choke so that there is no air gap in the magnetic core. During the winding process, taps must be made through a certain number of turns. In this option, the current can be adjusted in steps, through contacts that must be made powerful in order to carry a current of hundreds of amperes.

There is another reason why the throttle must be turned on to create normal manual welding conditions.

The characteristic of the dependence of arc voltage on its current is called falling. An inexperienced welder will have to believe that such a relationship is useful when welding if it is difficult to maintain a constant distance between the electrode and the parts being welded. To provide such a characteristic, the inductive reactance of the secondary winding of the transformer alone is not enough. The immediate task of a choke for a welding machine is to add the missing resistance.

How to make a choke and wind it correctly?

To wind the choke coil, you can use a UI series magnetic core. Table 1 shows the dimensions corresponding to the maximum values ​​of parameters a and b.

Table 1.

Name	a, mm	b, mm	c, mm	d, mm	e, mm	f, mm	h, mm	i, mm	k1, mm	k2, mm	Holes, mm
UI 90	90	120	90	30	30	30	7,8	60	15	105	4
UI 120	120	160	120	40	40	40	11,0	80	20	140	4

Before winding, it is necessary to insulate the yoke. During the winding process, its direction does not change. The next layer is isolated from the previous one with cotton insulation. You can use fiberglass or cardboard designed for insulation. The insulating gasket is impregnated with bakelite varnish. If conclusions are drawn during winding, they should be marked immediately.

The welding arc current can be adjusted stepwise by turning on a load ohmic resistance at the output in the form of a nichrome spiral, with periodic taps. However, this method is inconvenient due to the possible high heating of the filament (even red hot).

For smooth adjustment, movable windings of the transformer are created. By changing the distance between the primary and secondary windings, they change the magnitude of the magnetic flux and, consequently, the resistance in the secondary winding of the transformer.

But for a welding machine used in everyday life, the most suitable method is a smooth adjustment using a throttle.

Source: https://stroystory.ru/kovka/instrumenty-6/6515-izgotovlenie-drosselja-dlja-svarochnogo-apparata.html

Do-it-yourself welding inverter: diagram, video - Asutpp

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.

Schematic diagram of a welding inverter

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.

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.

Inverter from computer

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.

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.

Source: https://www.asutpp.ru/samodelnyj-svarochnyj-invertor.html

Homemade choke for welding inverter

Making a homemade welding inverter is not difficult, especially if you are comfortable with electronics. The main thing is that you have free time (5-6 hours) and the desire to do this work. This device will be useful to all owners. Welding inverters are new modern welding machines that are now coming to the fore.

The device of an inverter welding machine.

You can find many different types of inverters on the market. But a device made independently may turn out to be of better quality and a DIY inverter will cost less than buying a new device.

Some information about welding machines

Now it is very difficult to imagine any structure that would not require welding. Various voltages are used for this work. Depending on it, welding machines are divided into two groups: direct current and alternating current. It is allowed to weld with direct current using uncoated electric wire and electrodes.

To make the arc burn at low currents, it is necessary to have an increased open-circuit voltage on the winding up to 70 V. A DC welding machine is better to use; it is used for thin sheet metals, especially for automobile and roofing steel.

The welding arc is stable at this stage, so welding occurs with both direct and reverse polarity of the voltage supplied.

Classification of welding inverters.

What does a welding machine consist of? The main composition of the welding device includes:

• transformer is the main part;
• primary and secondary coils;
• housing for the welding machine;
• fans;
• stationery paper or a roll from a cash register;
• copper strip;
• copper tape.

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How to make a homemade welding machine

The most important part in working on an inverter is the circuit. The manufacture of a welding device begins with the selection of a transformer, onto which a copper strip of sheet metal (length 40 mm, thickness 0.3 mm) is wound.

You also need a thermal layer, which can be used as stationery paper or a roll from a cash register. It should be strong and not break when wound. Do not wind with thick wire, because

This device will operate at high frequencies, which will lead to overheating of the transformer.

To prevent this from happening, take copper tape - this will be the second winding of three strips of copper. They will be separated by a fluoroplastic layer. For the second winding, take the paper again, as with the first. True, the paper will darken, but it will not lose its color. Don't forget to put a fan in the transformer so that the winding does not heat up and cool down. You can take a cooler from your computer with 220 V and 0.15 A. The diagram will help you understand the idea.

Electrical circuit of the welding equipment.

Next, continue manufacturing the inverter based on your circuit. The next step should be a cooling system that protects the welding machine from overheating. It is better to take it from a computer processor. A total of 6 such fans will be required, 3 of them should be directed towards the motor winding. Don't forget to install air intakes opposite the coolers.

After this, you need to install a power oblique bridge. It will be located on two radiators. The upper edge of the bridge will be on one side, and the lower edge should be attached through a spacer to the other bridge. The diodes need to be brought out and placed towards the transistors. To reduce emissions, capacitors should be soldered onto the board (14 pieces of 0.15 μm and 630 V), and they should be distributed over the entire power line.

In order for the splashes to increase and the losses of the IGBT to become minimal, it is worth inserting snubbers into the chain, which contain capacitors C15, C16. IGBTs open faster, but the opposite process takes longer. And at this moment C15 and C16 will begin to receive a charge through the diode that was installed. All this is done so that the snubber takes on all the power and reduces heat consumption by 4-5 times.

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How to connect a welding inverter with your own hands

Making this device is not as difficult as setting it up. It will take longer. A sequential connection diagram will help:

Methods for connecting a welding inverter.

1. The welding inverter should be connected to the mains. You will hear loud sounds, this unit will begin to transmit current. Electricity is supplied to the fan, making the welding machine quieter and generating less heat.
2. Next, you should close the resistor. To do this, after charging the capacitors, you need to connect the relay. Current surges when turned on are reduced.
3. Please note that you cannot connect a transformer without a resistor part, as an explosion may occur. To find out the level of the welding machine, you need to turn on the device in ammeter mode, the incoming pulses should be equal to 44%.
4. With the help of an amplifier and optocoupler that transmit a signal to the unit, you can check the welding itself. The amplitude should be 15 V.
5. Using an oscilloscope, you can check the operation of the welding machine. If the pulses that come from different windings are the same, then the inverter is working correctly.
6. Finally, you need to check the inverter transformer under the control of the capacitors. To do this, increase the pass level to 200 W, connect an oscilloscope and observe the sound signals that the collector-emitter will produce.

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Safety precautions when working with a welding inverter

Welding is a very dangerous and traumatic type of work. And electric welding can give the welder an electric shock. Therefore, all equipment, that is, the welding machine with which the welder works, must be properly grounded. This helps protect against electrical injury.

The next danger to human health is the ultraviolet spectrum of an electric arc. It can harm the eyes, skin and cause severe burns. Therefore, people who work with a welding machine must use special clothing and a mask designed for welding. It is advisable to protect other people from welding, because... If you just look at a welder’s work, you can also get eye burns.

If safety rules are followed, welding work will not cause harm to human life and health.

The welding inverter has many advantages, the main one of which is its low weight.

You can use both AC and DC electrodes in it.

Source: moiinstrumenty.ru

Source: https://stroyka.ahuman.ru/samodelnyj-drossel-dlja-svarochnogo-invertora/