DC welding machine bd 310 stationary. Do-it-yourself DC welding machine: my scheme

20 years ago, at the request of a friend, he assembled a reliable welder to work from a 220 volt network. Before that, he had problems with his neighbors due to a voltage drop: he needed an economical mode with current control.

After studying the topic in reference books and discussing the issue with colleagues, I prepared an electrical thyristor control circuit and mounted it.

In this article, based on personal experience, I tell you how I assembled and set up a DC welding machine with my own hands based on a home-made toroidal transformer. It turned out in the form of a small instruction.

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

Versatile Capabilities and Tasks

A friend needed an apparatus for welding and cutting pipes, angles, sheets of different thicknesses with the ability to work with electrodes 3 ÷ 5 mm. About welding inverters at that time did not know.

We settled on the design of direct current, as a more universal one, providing high-quality seams.

The negative half-wave was removed with thyristors, creating a pulsating current, but they did not begin to 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, which are necessary when cutting with electrodes. She:

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

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

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

Simple structure of DC welding machine

According to the principle of installation, the following parts can be distinguished:

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

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

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

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

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

In practice, I have come across different designs of home-made or factory transformers. However, they all require an electrical calculation.

I have been using a simplified technique for a long time, which allows you to create fairly reliable designs for a medium-precision transformer. This is quite enough for domestic purposes and power supplies for amateur radio devices.

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

Features of the manufacture of the core

Craftsmen make magnetic wires from electrical steel of various profiles: rectangular, toroidal, double rectangular. They even wind coils of wire around the stators of burned 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, made two rings out of them - donuts. The cross-sectional area of each was calculated to be 47.3 cm 2 .

They were isolated with varnished cloth, fastened with a cotton ribbon, forming the figure of a lying eight.

A wire was wound on top of the reinforced insulating layer.

Secrets of the power winding device

The wire for any circuit must be with good, durable insulation, designed for long-term operation when heated. Otherwise, during welding, it will simply burn out. We proceeded from what was at hand.

We got 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 bagels were mounted tightly: so they have smaller dimensions and weight. However, the flow area for the winding wire is also limited. Installation is difficult. Therefore, each half-winding of the power supply was smashed into its rings of the magnetic circuit.

In this way we:

doubled the cross section of the power winding wire;
saved space inside the bagels 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 twisted.

Figured out the required length. Of course, it wasn't enough. Each winding had to be made from two parts and spliced with a screw clamp right on the donut.

The wire was stretched on the street along its entire length. They took the pliers in hand. They clamped opposite ends with them 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 from the wire and wound inside the torus by rotating one turn at a time.

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

This process was well shown by Alexey Molodetsky in his video "Winding the torus on the rim".

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

How to wind a power winding

For her, we found a copper wire of a suitable section - 21 mm 2. Figured out the length. It affects the number of turns, and the open-circuit voltage necessary for a good ignition of the electric arc depends on them.

We made 48 turns with an average output. In total, there were three ends on a donut:

middle - for direct connection of the "plus" to the welding electrode;
extreme - to thyristors and after them to ground.

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

The tapping of the middle point was performed by a screw connection with its insulation with varnished cloth.

Reliable welding current control circuit

Three blocks are involved in the work:

stabilized voltage;
formation of high-frequency pulses;
separation of pulses on the circuit of control electrodes of thyristors.

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 D814V zener diodes.

In principle, any power supply with similar electrical characteristics of the output current and voltage can work here.

Impulse block

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

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

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

Windings II and III are included in the control circuit of 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 trigger current is 200 mA and the trigger voltage is 3.5 volts.

Welding is a simple and reliable way to connect one-piece metal. Welding works are carried out with the help of special equipment, ranging from microelectronics to heavy construction.

Today, welding is carried out using direct and alternating voltage. In AC welding installations, a transformer of any structure is used as the main element. And in welding devices with a constant flow energy, power rectifier blocks. Properly selected electric welding electrodes are the key to quality work.

What is alternating current in welding

Variable voltage got its name, as the flow of electrons continuously changes its direction of movement. During an AC welding process, the arc jumps continuously. This happens due to the regular deviation from the axis of the welding arc. Of course, this affects the quality of the resulting seam. As a result, the scar is wide, and metal droplets form at the junction. If the arc goes out, then the ignition can be resumed by increasing the voltage.

With all this, equipment for electric welding with a change has its advantages:

Simple construction.
Great working resource.
You can adjust the strength of the welding current.

Transformers are still very popular.

DC welding

Welding machines on a constant basis supports 2 modes of operation - the process of connecting with straight and reverse polarity. Using such installations, it is necessary to regularly monitor their mode of operation, since some metals seize on direct, while others on reverse polarity.

Most widely used straight polarity. The welded crater is deep and narrow. The heat supply decreases, the passage speed increases. It is used for cutting metal, has a stable arc, resulting in a high-quality connection. Used when working with steel, thickness from 4 mm. Most materials are welded on straight polarity.

Reverse polarity is used to connect thin metals of medium thickness. The electric welding seam is not deep, but wide enough. With this polarity, do not use electrodes that are sensitive to overheating.

The main advantages of welding with constant voltage are:

No splashes of molten metal.
Electric current arc stability.

Differences between DC and AC electrodes

electrodes conditionally do not differ. But a constant power flow is not suitable for AC connection. Electric welding materials, which are designed for a change, are also successfully used for electric welding using direct electricity. Experts call the resulting electrodes universal.

Universal electrodes are characterized by:

A good and stable arc that even re-ignites easily.
Volume production of work.
High profitability.
Slight spatter.
Good separation of impurities.
Possibility to weld contaminated, oxidized, rusty and wet materials with high quality.
The simplest requirements for the device and the employee.

A feature of universal electric welding electrodes is the ability to make a joint of metal products, even if there is large distance between metal parts. They are excellent for electric welding of short seams and spot welding.

Comparing welding with direct and alternating voltage, more advantages for devices with a constant flow of energy. Welded materials are saved as spatter is minimal. Standing is simple and easy to use in work, it is used for thin-walled products. The impact of weather conditions does not affect the stability of the arc, ensuring high performance. All areas on the structure are boiled, as a result, the specialist receives a high-quality and neat scar.

Variable device provides good connection quality, simplicity and convenience of the welding process. Equipment that operates on this type of voltage is much cheaper.

The main difference between AC and DC electricity is that during operation, a current is supplied to the electrode or variable with a frequency 50 Hz or constant. In the design of the constant flow welding machine, there are rectifiers in the form of diodes that rectify the electricity at the output and create a constant-sign pulsating value. Modern semiconductor rectifiers guarantee high performance and high efficiency. Therefore, better welding will be obtained using a constant flow. As practice has shown, change electrodes are the last century.

Welding current is the most important parameter on which a quality connection depends. It is necessary to select the electrode diameter taking into account the thickness of the metal. And starting from its diameter, electricity is set. This information can be found on the packaging. There are no exact and specific voltage settings - each master focuses on his feelings and sets the desired voltage parameter.

In specialty stores there is a very wide selection of electrodes for electric arc welding. When buying, pay attention to the quality of products and the availability of a license.

There are many types of welding machines, among which the following are best known: mechanical welding devices using consumable electrodes; equipment for argon-arc welding with non-consumable electrodes; for welding using flux with automatically consumable electrodes. In addition, there are generators for welding, transformers, inverters and devices for resistance spot welding. To work with each type of metal, well-defined electrodes are provided.

In terms of its design, an apparatus for working with direct current is much more complicated than an alternating current unit, since a rectifier with a diode or thyristor bridge is installed in it to obtain a constant voltage at the output. However, the power of the welding machine at the output is much less than that consumed due to its drop on the rectifier itself.

In other words, its efficiency is low, and this is a serious disadvantage in terms of energy savings. However, due to the stable arc and the ability to work with various metals, it could be classified as a professional equipment.

AC welding machine - what is its feature?

Much cheaper than the previous model AC welding machine, also working with consumable electrodes. It is great for working with ferrous metals, allows you to weld them with an overlap and butt.

If this welding machine is used, 220 volts is the operating voltage, however, at idle, it may vary depending on the electrodes used, which can be either calcium fluoride or rutile coated. The device is very easy to operate, provides for smooth adjustment of the current strength, which depends on the electrode chosen for operation.

This transformer welding machine can be successfully used both at home and in the factory. Electric welding machines are designed to operate from a 220 or 380 volt network and are respectively called single- or three-phase. Depending on this, the scheme for connecting welding wires changes.

The single-phase welding machine is connected by connecting one welding wire to the “phase”, the other to the “neutral” connector and the third to the “zero” ground. Otherwise, a three-phase welding machine is connected. Two ends of the welding cable are connected to any two "phases", and the third - to the protective "zero".

It should be noted that if a 380 volt welding machine is used, then it is considered more powerful than one connected to a 220 volt network, but this is not the only way to increase productivity.

Inverters - increase the power of the welding machine

So far, we have considered welding machines in which a conventional power transformer is used as an input voltage converter. It is he who determines the solid dimensions and heavy weight of this type of equipment. However, it is reliable and inexpensive.

But there are other types of devices in which the so-called inverters- semiconductor amplifiers. Small dimensions and weight have made them perhaps the most popular type of welding units.

With an efficiency level of up to 85%, the device works with different metals, guaranteeing high speed, quality and accuracy of welding. Inverter devices have different power and can be connected to both 220 and 380 volt networks.

The welding machine is one of the most demanded equipment in the world. Welding works are carried out everywhere and on a very large scale.

Of course, there are a large number of varieties of these devices, which differ in the principle of operation, dimensions, output amperage and other technical characteristics. There is also equipment operating on alternating and direct current.

The DC welding machine is the most common, because. supports 2 modes of operation - welding of direct (on the electrode minus, and on the part plus) and reverse (on the contrary, on the electrode plus, on the part minus) polarity. Very often it is required to change operating modes, because. some metals are well seized on a straight line, while others on the reverse polarity.

The choice of one or another apparatus is closely related to what goals the welder himself adheres to:

What metal will be welded (type and thickness);
What current (its voltage and strength) is present at the work site;
How long will the welding machine have to work without rest;
And other situations.

Welding machines used in industry, manufacturing, construction, etc. different from those used at home. The main difference between them is the power and, accordingly, the cost.

Today, the so-called inverters - electric arc welding machines - are very successful on the market. They are perfect for almost any welding work, of any complexity and volume. They are also most often used in everyday life for two simple reasons - they have small dimensions and low cost. In addition, inverters are easy to handle and easy to repair. And an electronics engineer, even with a basic set of knowledge, is able to create a homemade DC welding machine from numerous circuits available on the network.

Consider the above criteria for selecting inverters in more detail.

Some facts about inverters and which one to choose for your home

Let's start with the metal being welded. For example, in manufacturing or construction, it is often necessary to weld thick metal parts or metals with a low weldability coefficient (the ability of metals to be weldable). In such situations, one cannot do without a powerful welding machine with an output amperage of the order of 300-500 A or more. However, in everyday life, metal sheets or parts with a thickness of more than 5 mm are very rare. And for their welding, an inverter with a current strength of 160 A is quite suitable.

The voltage that a house, garage, etc. is equipped with is often not enough for the normal functioning of high-power welding machines, because. they require 380 V (3 phases). Before buying this or that inverter, it is necessary to measure the voltage in the place where welding will be carried out. It often happens that the owner checks the product before buying it in the store for performance, and when he comes home it turns out that it does not work. It's all about lack of tension. Therefore, you need to buy an inverter with such technical characteristics that are suitable for its normal operation at home.

An inverter is most often a DC welding machine, especially if it will be used at home. In order to obtain a constant voltage at the output, special high-voltage converters are used. It is they who during their work are very hot, which requires the use of high-quality cooling. In cheaper models, inverters use metal (aluminum or copper) heat sinks - radiators. In more expensive models, air or water cooling is used, thanks to which the devices are able to work for a very long time without turning off. However, for domestic purposes, inverters with radiator cooling of electronic elements are quite suitable.

When choosing welding, buyers have a question: buy a DC or AC inverter welding machine? Both types of inverters have their advantages and disadvantages, but it is worth noting that today AC welding is a thing of the past, they are being replaced by more advanced rectifier or DC welding machines.

Which device to choose?

What to choose - a rectifier or a transformer?

AC welding machines have the following advantages:

simple design;
minimum breakdowns, large working resource;
the ability to regulate the strength of the welding current.

The disadvantages of such devices are quite significant:

low efficiency;
spattering of metal during welding;
large dimensions.

- modern welding inverters that convert current into direct current. Advantages of rectifiers:

high quality welds;
high efficiency;
the ability to regulate the current strength, a protective block;
welding of any metals, incl. low-alloyed, etc.

DC inverters have practically no drawbacks, and are affordable for every consumer group.

How to measure the current strength of a welding inverter?

The main characteristic of welding inverters is the current strength, the higher it is, the more productive the device will be. The cost of welding also directly depends on this indicator.

For domestic use, an inverter with parameters up to 160 A, connected to a 220 V power supply, is sufficient. If there are power surges in the mains, it is recommended to purchase a semi-professional device with current characteristics of 200 A. It is not difficult to measure the current of the device. Usually, this indicator of a serviceable inverter corresponds to that declared by the manufacturer, but if there is any doubt about the health of the device, then the readings can be measured using a digital millivoltmeter or a pointer microammeter. However, please note that the readings of the instruments depend on the length of the welding arc, the diameter of the electrode, and the correctness of the measurement.

Also an important indicator is the power of the welding machine. As a rule, it is not indicated in the passport, but knowing the maximum current output by welding and other parameters, you can calculate the amount of kW consumed.