If you need a power supply with a non-standard voltage, but you didn’t find the one you need, then don’t worry - you can make it yourself! If this is not a switching power supply, then one of the important elements of the power supply will be a high-quality transformer. You can make a transformer for the required voltages with your own hands; often, if all winding rules are followed, a homemade transformer will be much better than a factory-made one.

For winding a transformer, there are simplified calculation methods that have proven themselves quite well in amateur radio activities. We will discuss how to wind a transformer from scratch using one of these methods in the following articles, but in this one we will only touch on step-by-step rewinding of a transformer with an existing primary winding. So before reading a lengthy article, brew a couple of cups of coffee/tea and be patient :)

A few important points to know before you start rewinding the transformer:

1) Before measuring the voltages of the secondary windings, it would not be amiss to measure the voltage in the 220V network (write down in a notebook at what voltage the measurements were made). Changing the value of the supply network leads to a change in the voltage on the secondary windings of the transformer.

Changes in network voltage occur mainly due to its load by consumers in your home, depending on the time of day. A similar situation is observed when changing substations. For example, the voltage of the 220V network at your home, dacha or work may be different. Also, voltage drop on the secondary windings may be due to the quality indicators of the transformer.

This circumstance was mentioned for the reason that when designing the anode-heat transformer, I had to take this fact into account and make additional taps on the secondary winding (it is possible on the primary winding, for a certain network voltage). The transformer was intended for a radio tube tester and it was important to provide the device with certain supply voltages. If the required voltage did not match, the supply wires were connected to other taps of the secondary windings of the transformer.

2) All actions with a transformer connected to a 220V network must be carried out with a 60-80W incandescent light bulb connected to the break of one wire, between the power plug and the transformer. The light bulb acts as a fuse. If suddenly you have connected the windings incorrectly and a short circuit occurs in the windings, the light will light up and prevent the consequences of the error; if everything is fine, the light will not light. After making sure that everything is in order, the light bulb can be removed.

3) One more nuance regarding factory-made transformers. Often, in order to reduce production costs in order to save copper wire, the primary winding is not wound at the factory, as a result of which transformers operate with increased induction. In these cases, the magnetic circuit of the transformer will be on the verge of saturation: it will hum, get very hot and have a large no-load current. Also, the output voltages will drop significantly under load. After all, the current value XX is one of the important indicators of a high-quality transformer. The lower the current, the better.

To measure the no-load current, a microammeter is connected to the primary winding circuit. The microammeter is connected in series to one wire between the power plug and the transformer itself, while the load on the secondary windings must be turned off. Depending on the overall power of the transformer, the appropriate XX current for this transformer is determined.

4) When assembling the transformer, it is imperative to insulate the tension pins with a dielectric (cambric, paper tube) from the magnetic circuit plates. Assemble the package of magnetic circuit plates tightly without gaps.

A poorly assembled transformer can negate the correct design of the transformer windings, thereby increasing eddy currents (Foucault currents), and they will lead to a large no-load current with all its “charms”.

5) When rewinding a transformer, you should take into account the filling of the magnetic circuit window with copper wire. A situation may arise when an incorrectly selected magnetic core with a small window will not allow you to wind the required number of turns with wire of the calculated diameter. Almost all Soviet brochures or manuals for radio amateurs on winding provide formulas for calculating the occupancy of a magnetic circuit window.

6) The number of wound turns of wire in the winding can be approximately determined without disassembling the transformer. For toroidal transformers, everything is much simpler in terms of counting turns per volt. It is enough to wind several turns of insulated wire around the donut over all the windings, plug the transformer into the network and measure the voltage.

For W-shaped ones, almost everything is the same, but provided that there is a gap between the magnetic core and the coil. If it is possible to thread a wire and wrap it around the transformer coil, then in this case you can carefully insert a flexible, insulated long wire into the gap and make several turns (as long as the wire is enough). Laying the wire on the coil must be done tightly, with even turns to each other. Straighten the ends of the winding you just made so that they do not short out. All that remains is to insert the power plug into the socket and measure the voltage with a multimeter.

The voltage will correspond to the number of turns made by the wire. Then the simple laws of mathematics come into play for calculating the number of turns per volt. You count how many turns are wound, and measure the voltage, then calculate how many turns are needed for one volt. Then you multiply the resulting number of turns (per volt) by the required voltage in the winding - it’s simple!

How to determine the primary winding?

If you don't know how to connect a transformer, then the first thing you need to do is find the primary winding. The primary winding in a step-down transformer can be determined using a multimeter in resistance measurement mode. In most cases, the network winding has the highest resistance, since it is wound on a large number of turns.

Please note that the primary winding in low-power transformers is wound with a thin winding wire and is located (as a rule, but there are exceptions) closest to the magnetic core. Consider the contact petals on the transformer coil frame; the ends of the windings come out and are sealed onto the contact petals. This way you can visually assess the thickness of the wire and which winding terminals are closest to the inside of the coil frame.

The high-voltage anode winding in a step-up anode-heat transformer may also have high resistance, but in any case it is necessary to check through a light bulb and measure the voltage on other windings. For example, apply a voltage of 6.3V to the filament winding and measure the voltage on the other windings. The network (primary) winding is wound at 220-230V, it should have approximately the same voltage.

You can determine the windings using a multimeter in the “continuity” mode (also measuring resistance). On the contact pad of the transformer coil, place the probe on one petal and alternately touch the other petals with the second probe. When you find the second end of the winding, the multimeter notifies you of this with a sound signal (resistance readings on the screen). This way you “ring out” the windings. To avoid confusion, you should first draw the location of the contacts on the coils and mark them during the process of determining the windings for short circuits. If the winding has several terminals, then the beginning and end can be recognized by the highest resistance for a given winding (the middle point will have an average resistance value).

By following simple steps to identify the windings, you can independently connect a transformer unknown to you. This is much easier if the transformer coils have factory markings on them. In this case, using information from the reference book, you can determine the parameters and numbering of the terminals of the transformer windings.

Rewinding a transformer with your own hands. Case Study

Now, having understood some points that you need to know, let's start rewinding the transformer. Next, an example of rewinding in a “live story format” will be described, if I were to record all my actions in chronological order for you under a dictaphone :). So, the “Record” button is turned on, the cassette film with a characteristic rustling winds the film from one reel to another. It’s evening, the table lamp is burning on the table, and the smell of rosin is in the air... :)

A friend asked me to assemble a bipolar power supply to power the Yunost-21 synthesizer. It was necessary to obtain stable +/- 10 volts at the output. I did not find a specific transformer in my amateur radio stocks. It was decided to manufacture it ourselves to the required parameters. The basis for the modification was an armor-type transformer with an Ш-shaped magnetic core, which previously worked in the power supply of a single-channel amplifier. According to preliminary calculations, the total load on the transformer in the amplifier was 3A, which corresponded with a margin for the load of the designed power supply.

Taking into account the overall power of the transformer and the thickness of the wire of the secondary winding, I figured that the primary winding should be wound with wire of a suitable diameter (measurements with a micrometer after winding the secondary winding confirmed this). Measuring the no-load current also confirmed the suitability of the selected transformer (there was no need to rewind the primary). All that remained was to deal with the secondary winding.

For a bipolar power supply, it is necessary to have two symmetrical windings designed for 1 Ampere load (the transformer for conversion already has them). We connect the transformer to a 220V network and measure the voltage at the taps of the windings. We write down the obtained values ​​on a draft for subsequent calculations. Next, we disassemble the transformer to rewind it.

Unscrew the studs and remove the transformer brackets. Before us is a W-shaped armored magnetic circuit. It consists of W-shaped plates and I-shaped plates, which alternate with each other and are rearranged in a certain way.

To make the disassembly process easier, carefully remove the varnish/paint. Removal of the paint coating (if necessary) is carried out extremely carefully so as not to damage the surface of the plates and not to leave a burr that can short circuit the magnetic circuit plates. If possible, we do without these manipulations.

First, the I-shaped plates must be removed. Carefully pry it up with a knife or a flat thin screwdriver, pry it up and pull them all out. After this, we remove the W-shaped plates from the transformer coil frame one by one.

After the transformer coil has been separated from the magnetic circuit, we proceed to further actions. We are now faced with the task of counting the number of turns in the secondary windings. We do not touch the primary winding.

Based on the measurement results, the two secondary windings have the same voltages and are symmetrical to each other (they mirror the number of turns). If we find out the number of turns of one winding, we will know how many there are in the other. After counting, you won’t have to completely wind up all the turns; we’ll just calculate how much wire needs to be wound in order to get the desired voltage.

This counting of turns will help us verify the correctness of the previous measurements, when we wound wire onto a coil to count how many turns there are per volt.

Having sat down at the table in a calm environment, we place in front of us a piece of paper, a pen (pencil) and a transformer coil. We begin to unwind the wire and count the turns being wound. After every ten winding turns, we mark a piece of paper with a mark, for example, a vertical line, which will correspond to 10 turns. We will do the same when winding wire onto a reel. This is necessary in order not to get confused and lose count. You can also use a simple calculator, adding the values ​​of the turns.

Some tips:

Before work, make sure that there are no sharp surfaces of furniture around you on which the winding wire could rub or get caught (do not damage the enamel insulation of the winding wires!);

Wind the wire onto a separate spool. This way it will be laid evenly without damage, which will allow it to be reused;

It is also important to carefully wind the wire to avoid the formation of loops and creases in the process - this way we will keep the wire relatively straight and will not damage the enamel coating of the copper wire when bending it.

Method of rewinding the secondary windings of a transformer

We have the first secondary winding measured at 2.02 volts. We wind the wire and count the turns. 2.02 volts corresponds to 12 turns. We divide 12 turns by 2.02 volts and get 5.94 turns per volt. Further, when calculating, we will multiply the voltage that we must obtain by 5.94 turns. The resulting value will be equal to how many turns we will need to wind to obtain the required voltage.

Let's continue winding the second secondary winding. According to measurements, it corresponded to a voltage of 19.08 volts. Let's check the previous calculations in practice. The second secondary winding turned out to be 112 turns. Divide 112 by 5.94 and we get 18.85 volts.

I assume that a small discrepancy appeared due to the fact that the values ​​of the second decimal place and the length of the wire for tapping the second end of the secondary winding were not taken into account. A piece of wire for tapping the secondary winding ran at a right angle from the bottom cheek of the coil frame to the top. An EMF is also induced on this segment (approximately ¼ of a turn), which is reflected in the discrepancy. Perhaps I was wrong by one turn and didn’t count it. This error should also be taken into account when designing a transformer.

We wind up the third secondary winding. It is worth noting that during measurements, the third winding, according to the voltmeter readings, had the same voltage value as the second secondary winding. This means that our fourth secondary winding corresponds to the voltage of the first winding and has the same number of turns.

The output of the designed bipolar power supply requires a voltage of plus/minus 10 volts of DC voltage. In order for the output of the power supply to be 10 volts, you need to take into account some points, namely the voltage drop across the elements of the power supply and “drawdowns” in the 220V power supply network. According to rough estimates, the transformer for powering the power supply circuit should produce 13-14 volts of alternating voltage. Based on this, we wind two secondary windings at 14 volts.

We have not touched the third secondary winding yet. The third and fourth windings give us a total of 21.1 volts, which is 124 turns for two windings. We multiply 14 volts by 5.94 turns and get the value 83.16 - this is the required number of winding turns to achieve 14 volts. From 124 turns (21.1V) we subtract 83.16 turns (14V) and get 40.84 - this is the value of the number of turns that should be wound to ultimately obtain a winding whose output will be 14 volts. We unwind and get the first necessary secondary winding.

To increase the reliability of the transformer and prevent electrical breakdown of the varnish insulation of the wire, it is necessary to tightly wrap the insulator around the coil over the first secondary winding. As an insulator, you can take the paper that is used to wrap the windings of a factory-made transformer like TS-180 or others; if you don’t have one, you can look for baking paper in your kitchen. We cut a strip of paper the width of the transformer coil with a small margin and make accordion-shaped cuts along the edges measuring 3-4 millimeters. We lay the paper and wrap it around the spool in several layers (no more than 2-3).

We wind 83.16 turns on top of the paper insulation for the second secondary winding of 14 volts. We wind it exactly turn to turn, trying to repeat the factory laying on the reel. At the end of winding, we wrap the coil with insulating paper, similar to how we did the interlayer insulation between the windings.

Now we assemble the transformer in the reverse order as we disassembled it. Don’t forget to isolate the tension pins from the magnetic circuit plates (after assembly you can ring them with a tester). When tightening a package of plates, the main thing is to maintain balance, not to overtighten (the thread may be damaged or the pin will burst) and not to tighten the nuts properly along the threads. Insufficient tightening of the magnetic circuit plates can lead to transformer hum and increased no-load current.

Now we connect the transformer to the network through a light bulb and measure the voltage at the ends of the windings. You may have to repeat the transformer assembly and disassembly procedure several times to achieve the desired result.

Thank you for reading this lengthy article! There are many examples of rewinding transformers on the Internet; this article described my own experience in rewinding a transformer with my own hands; you should also not take the article as a scientific work.

I also advise you to find brochures in electronic form from the Soviet period, where everything is sensibly and competently presented on this topic.

In the following articles I will try to describe in detail the calculation and winding of a transformer from scratch, I will tell you. Good luck!

About the author:

Greetings, dear readers! My name is Max. I am convinced that almost everything can be done at home with your own hands, I am sure that everyone can do it! In my free time I like to tinker and create something new for myself and my loved ones. You will learn about this and much more in my articles!

Fedotov Alexey Gennadievich (UA3VFS)
Gus-Khrustalny

Winding method for toroidal transformers.

The winding technology and the insulation method are actually very simple and in no case involve any kind of winding, varnished fabric, or anything else. The fact is that with any winding with varnished cloth or other insulators, the inner window of the TORA is instantly filled, since on the outside there is one layer, and on the inside there are 5-10 layers, and even uneven ones. I have long been planning to write an article about a method for high-quality winding of tori. This takes quite a long time to explain and is better shown in the photo. Moreover, after winding, the windings do not turn into a wheel, and the transformer itself does not become egg-shaped and wire consumption is minimal. In view of all this, the efficiency of the transformer is maximum. And what comes out of this, you can see in my.

Let me make a reservation right away: we are talking about powerful toroidal transformers. Overall power, which is more than 500W. Which are wound with wires from 1 to 3mm. naturally turn to turn. And, as a rule, the network winding of which lies in the range from 100 to 400 turns, in total, that is, 0.5-2 turns per volt. Winding less powerful transformers in this way is troublesome, but it is possible if desired.

What is needed for winding.

1) You need to make a stand for winding the toroid; this is done very simply. Take a square piece of chipboard or plywood 10-15mm thick. With dimensions of 200X200mm, we also need two wooden blocks 200mm long and 20X20mm square. We need to either glue these two bars in the center of our site, parallel to each other, with a distance of 100mm between them. Better yet, screw these bars to the platform using screws, but with countersunk heads and recess the heads into the plywood, otherwise they will scratch the table. Now if you place a toroid on this stand, it will stand firmly and steadily.
2) You need a shuttle, I cut the shuttle out of plexiglass 5-6mm thick. The width is usually 30-40mm. length 300-400mm. I make the end cuts not at an angle, but in a semicircle and process them with a file so that the insulation of the wire does not deteriorate, and I even glue one or two strips of electrical tape, again to protect the wire.
We wind the wire onto the shuttle; it’s okay if there isn’t enough wire, you can carefully solder the wire and wind it further. But it’s better to calculate it so that there is enough wire.
3) Now we need material for insulation between the layers, it’s very easy to find
thin cardboard (packaging), for example, I use speaker boxes for cars. The main thing is that it is not a thick, but not thin material, the thickness of the cardboard is about 0.5 mm. If it is glossy on one side, then that is also good.
4) We also need thick threads, number 10-20. But at worst, number 40 is possible.
The winding itself is carried out away from you to the right.

And now the most important thing is the manufacture of the insulating gaskets themselves between the layers.
We will need a caliper, with sharp ends.
We measure the outer diameter of our torus, add 20mm. (for overlap) and divide in half. For example, the outer diameter of the torus is 150mm + 20mm = 170mm. 170mm./2 = 85mm.
We set the bar to 85mm. and fix it with a screw. We will use the rod itself as a compass for drawing circles on cardboard. Why use a barbell and not a regular compass, which is both simpler and more convenient? And everything is very simple, when we draw on the cardboard with the sharp and durable end of the rod, a depressed groove will remain on the cardboard and it will help us. This groove is very useful for making it easier to bend the inner cut circle of our gaskets. In general, you yourself will understand that a barbell is better than a convenient compass.
And so we draw the outer circle on the cardboard and cut it out with scissors; in principle, the outer circle can be drawn with an ordinary compass.
Next, measure the internal diameter of the torus We don’t add anything, we don’t subtract anything, we just divide it in half. For example, diameter 60mm/2 = 30mm.
We set the caliper caliper to 30mm. fix it with a screw and draw the internal diameter on cardboard.
Next, we take a pencil and a ruler and work on the inner circle, first we draw a cross, that is, we divide the circle into 4 parts, then into 8 parts, if the inner diameter of the TOR is more than 60mm. then also into 16 parts.
>Next, we draw another circle with a regular compass, which is half the size of the inner one, that is, we move the compass apart by 15mm.

And now we need a flat piece of plywood or chipboard on which we will place our cardboard blank for cutting through our parts drawn with a pencil with the end of a sharp scalpel or knife. You need to cut in a circle from the outer edge of the circle to the central point, no further, otherwise the cardboard will ride up. You need to cut right through the cardboard. Next, using scissors, we cut out the inner circle we drew with a regular compass. Bend the resulting slices perpendicular to the workpiece.
It is clear that two such blanks are needed for each layer, each time the diameters are measured again, since their value changes from layer to layer.
Next, measure the height of the torus and cut out two strips of cardboard of the same width.
We insert one strip inside the torus, so that the overlap is no more than 10mm.
We wind the second strip in one layer onto the outer side of the torus with the same overlap.
We put both round blanks on the ends of the torus, fasten them with thread in three or four places in a circle.
And then we begin to wind.

The most dangerous places for breakdown are the external and especially internal corners of the TOR circles. Therefore, if during winding we see that the wire can come into contact with the wire of the inner layer, especially along the inner corner of the TORA circle. Then you need to place strips of the same cardboard 10mm wide under the wire. and 20-30mm long, where necessary. On the outer side, as a rule, this does not have to be done, since the outer side of the workpiece is layered on the edge and well protects the wire from short-circuiting.

All marking and cutting of cardboard blanks is done on the matte side of the cardboard, It is not advisable to use glossy cardboard on both sides.
Before you start winding the torus, you need to wrap two layers of electrical tape on your fingers on both bends of the little finger and on the bend of the index finger, otherwise there will be huge water calluses.

The fact is that the number of turns will depend on the quality of the iron, but the approximate calculation is done simply, like with a conventional transformer, we only take a coefficient of 20-30.
Well, for example, we measure the height, it = 10cm.
We measure the wall thickness, it = 5 cm.
10x5=50cm.
25/50=0.5 turns per 1 volt.
220x0.5=110 turns of the network winding.
Now we begin to wind the network winding, having wound approximately 90 turns, we try to connect it to the network, while measuring the no-load current.
It is not at all difficult to connect the tip of the wire directly to the shuttle.
Gradually winding the wire, we bring the no-load current to 50-100mA. and at this point we stop winding, the resulting number of turns will be realistic. Now we divide this real amount by 220 and get the real value of the number of turns per 1 volt.
And in accordance with this figure we calculate all output windings.

Keep in mind that when the transformer is connected to the network, the initial instantaneous current surge is very large. And in order not to burn the tester, you need to do this. We connect the network cable through a closed toggle switch parallel to the toggle switch, turn on the tester, plug the plug into the socket and only then open the toggle switch to see the no-load current.

By the way, it is precisely because of the powerful primary inrush current that transformers with a power of more than 1 kW must be turned on using a soft switching circuit. Moreover, this scheme is very simple.

Illustrations

There are situations in life when you need a transformer with special characteristics for a specific case. For example, the network adapter in your favorite receiver burned out, and you don’t have one to replace it. But there are other unnecessary parts from old equipment that are lying around, so you can try to convert them yourself to specific parameters. Next, we will tell you how to calculate and make a transformer with your own hands at home, providing all the necessary calculation formulas and assembly instructions.

Calculation part

So, let's begin. First you need to understand what such a device is. A transformer consists of two or more electrical coils (primary and secondary) and a metal core made of individual iron plates. The primary winding creates a magnetic flux in the magnetic core, which in turn induces an electric current in the second coil, as shown in the diagram below. Based on the ratio of the number of turns in the primary and secondary coils, the transformer either increases or decreases the voltage, and the current changes in proportion to it.

The maximum power that the transformer can deliver depends on the size of the core, so the design is based on the presence of a suitable core. The calculation of all parameters begins with determining the overall power of the transformer and the load connected to it. Therefore, first we need to find the power of the secondary circuit. If there is more than one secondary coil, then their power must be summed. The calculation formula will look like:

• U2 is the voltage on the secondary winding;
• I2 is the secondary winding current.

Having received the value, you need to make a calculation of the primary winding, taking into account transformation losses, the estimated efficiency is about 80%.

P1=P2/0.8=1.25*P2

Based on the power value P1, the core and its cross-sectional area S are selected.

• S in centimeters;
• P1 in watt.

Now we can find out the coefficient of effective energy transfer and transformation:

• 50 is the network frequency;
• S is the cross section of iron.

This formula gives an approximate value, but for ease of calculation it is quite suitable, since we are making the part at home. Next, you can begin to calculate the number of turns; this can be done using the formula:

Since our calculation is simplified and a slight voltage drop under load is possible, increase the number of turns by 10% of the calculated value. Next, we need to correctly determine the current of our windings; this must be done for each winding separately using this formula:

We determine the diameter of the required wire using the formula:

Based on Table 1, select a wire with the required cross-section. If there is no suitable value, you need to round up to the table diameter.

If the calculated diameter is not in the table, or the window is filled too much, then you can take several wires of a smaller cross-section and get the required amount in total.

To find out whether the coils will fit on our homemade transformer, you need to calculate the area of ​​the transformer window, this is the space formed by the core into which the coils are placed. We multiply the already known number of turns by the wire cross-section and fill factor:

We perform this calculation for all windings, primary and secondary, after which we need to sum up the area of ​​the coils and make a comparison with the area of ​​the magnetic circuit window. The core window must be larger than the cross-sectional area of ​​the coils.

Manufacturing procedure

Now, having the calculations and material for assembly, you can start winding. We lay the first layer of winding on the prepared cardboard reel. To do this, it is convenient to use an electric drill, clamping the coil in the chuck using a special device (it can be a bolt with two washers and a nut). Having secured the drill to a table or workbench, at low speeds, we lay the wire, turn to turn without overlap. Between the layers of wire we place one layer of insulation - capacitor paper. Between the primary and secondary windings, two layers of insulation must be made to avoid breakdown.

It is much easier if you plan to rewind the finished transformer to the desired voltage. In this case, it is enough to count the number of turns of the secondary winding when unwinding, and knowing the transformation ratio:

Before checking, ring the windings, make sure that their resistance is not too low, and that there are no breaks or breakdowns in the product body. The first switch-on must be carried out with extreme caution; it is advisable to switch on an incandescent lamp with a power of 40-90 Watts in series with the primary winding.

Test work

This article provides instructions that clearly explain how to make a transformer with your own hands at home. As an example, we described the sequence of calculation and assembly of an armored model, as the most common type of converter. Its popularity is due to the simplicity of manufacturing winding units, ease of assembly, repair and alteration. Based on this homemade product, you can easily make a charger for charging a car battery, or make a booster charger for a laboratory power supply, an electric wood burner, a hot knife for cutting foam plastic, or another device for the needs of a home craftsman.

A transformer is a unit designed to transmit electricity with changed parameters through the network to the end consumer. This equipment has a specific design. Transformers can step down or step up voltage.

Over time, the core may need to be rewinded. In this case, the radio amateur is faced with the question of how to wind a transformer. This process takes a lot of time and requires concentration. However, there is nothing complicated about rewinding a circuit. There are step-by-step instructions for this.

Design

The transformer operates on the principle of electromagnetic induction. It may have a different magnetic drive design. However, one of the most common is the toroidal coil. Its design was invented by Faraday. To understand how to wind a toroidal transformer or a device of any other design, you must initially consider the design of its coil.

Toroidal devices convert alternating voltage from one power to another. There are single-phase and three-phase designs. They consist of several elements. The structure includes a ferromagnetic steel core. There is a rubber gasket, primary and secondary winding, as well as insulation between them.

The winding has a screen. covered and core. A fuse and fasteners are also used. To connect the windings into a single system, a magnetic drive is used.

Winding device

Toroidal transformers can be of different types. This must be taken into account when creating the outline. Wind transformer 220/220, 12/220 or other varieties can be done using a special tool.

To simplify the process, you can make a special device. It consists of which are fastened together with a metal rod. It is shaped like a handle. This skewer will help you quickly wind the outlines. The twig should be no thicker than 1 cm. It will pierce the frame right through. Using a drill will make this process easier.

The drill is mounted on the surface of the table. It will be parallel. The handle should rotate freely. The rod is inserted into the drill chuck. Before this, you need to put a block with the frame of the future transformer on the metal pin. The rod may have a thread. This option is considered preferable. The block can be clamped on both sides using a nut, textolite plates or wooden planks.

Other tools

To wind the transformer 12/220, pulse, ferrite or other types of designs, you need to prepare a few more tools. Instead of the design presented above, you can use an inductor from a telephone, a device for rewinding film, or a machine for a bobbin with thread. There are many options. They must ensure a smooth, uniform process.

You will also need to prepare the device for unwinding. In principle, such equipment is similar to the devices presented above. However, in the reverse process, rotation can be performed without a handle.

In order not to count the number of turns yourself, you should purchase a special device. It will take into account the number of turns on the coil. An ordinary water meter or bicycle speedometer may be suitable for these purposes. Using a flexible roller, the selected metering device is connected to the winding equipment. You can count the number of turns of a coil orally.

Calculations

To understand how to wind a pulse transformer, calculations need to be made. If you are rewinding an existing coil, you can simply remember the original number of turns and purchase a wire of identical cross-section. In this case, you can do without calculations.

But if you need to create a new transformer, you need to determine the quantity and type of materials. For example, for a device with a working load from 12 to 220 V, a device with 90 to power will be required. You can take a magnetic drive, for example, from an old TV. The conductor cross-section is determined in accordance with the power of the unit.

The number of turns of the coils is determined for 1V. This figure is equivalent to 50 Hz. The primary (P) and secondary (B) windings are calculated as follows:

• P = 12 x 50/10 = 60 turns.
• B = 220 x 50/10 = 1100 turns.

To determine the currents in them, the following formula is used:

• Tp = 150: 12 = 12.5 A.
• TV = 150: 220 = 0.7 A.

The obtained result must be taken into account when choosing materials for creating a new device.

Layer insulation

To wind ferrite transformer or another type of device, it is necessary to study one more nuance. Conductors should be installed between certain layers. Most often, condensate or cable paper is used for this. All necessary materials can be purchased in specialized stores. The paper must have sufficient density and be smooth without gaps or holes.

Between the individual coils, insulating layers are created from stronger materials. Lacquered fabric is most often used. It is covered with paper on both sides. This is also necessary to level the surface before winding. If you couldn’t find varnished fabric, you can use paper folded in several layers instead.

The paper is cut into strips, the width of which should be greater than the outline. They should extend beyond the edges of the winding by 3-4 mm. Excess material will be folded up. This will keep the edges of the reel well protected.

Frame

To understand how to wind a transformer correctly, attention should be paid to every detail of this process. Having prepared the insulation, wire and tools, you should make a frame. You can use cardboard for this. The inside of the frame must be larger than the core rod.

For an O-shaped magnetic drive, you need to prepare 2 coils. For an W-shaped core, one circuit will be required. In the first option, the round core must be covered with an insulating layer. Only after this do they begin winding.

If the magnetic drive is W-shaped, the frame is cut out from the sleeve. Brushes are cut out of cardboard. In this case, the coil will need to be wrapped in a compact box. The brushes are put on the sleeves. Having prepared the frame, you can begin winding the conductor.

Step-by-step winding instructions

It will be quite simple. To do this, a reel of wire should be installed in the unwinding equipment. The old wire will be removed from it. The frame of the future transformer must be placed in the winding equipment. Then you can make rotational movements. They should be measured, without jerking.

During this procedure, the wire from the old coil will be moved to the new frame. The distance between the wire and the table surface should be at least 20 cm. This will allow you to place your hand and fix the cable.

You need to lay out all the necessary tools and equipment on the table in advance. You should have insulating paper, scissors, sandpaper, a soldering iron (plugged into the mains), a pen or pencil on hand. With one hand you need to turn the handle of the winding device, and with the other you need to fix the conductor. It is necessary that the turns are laid evenly and evenly.

Looking at the step-by-step instructions, how to wind a transformer, attention should be paid to subsequent operations. After laying the conductor, the frame will need to be insulated. Through its hole it is necessary to pass the end of the wire removed from the circuit. The fixation will be temporary.

Experienced radio amateurs recommend practicing first before winding. When you can apply the turns evenly, you can start working. The tension angle and wires must be constant. Each subsequent layer does not need to be wound all the way. Otherwise, the conductor may slip from its intended place.

During the winding process, you need to set the counter to zero. If it is not there, you need to pronounce the number of turns of the wire out loud. At the same time, you should concentrate as much as possible so as not to lose count.

The insulation will need to be pressed with a soft rubber ring or glue. Each subsequent layer will be 1-2 turns less than the previous one.

Connection process

Considering how to wind a transformer, it is necessary to study the process of connecting wires. If the core breaks during winding, the soldering process should be performed. This procedure may also be required if you initially plan to create a circuit from several separate pieces of wire. Soldering is performed in accordance with the thickness of the wire.

For wire up to 0.3 mm thick, the ends need to be cleared to 1.5 cm. They can then simply be twisted and soldered using the appropriate tool. If the wire is thick (more than 0.3 mm), you can solder the ends directly. In this case, twisting is not required.

If the wire is very thin (less than 0.2 mm), it can be welded. They are twisted without undergoing a stripping procedure. The connection point is brought into the flame of a lighter or alcohol lamp. An influx of metal should appear at the junction. The junction of the wires must be insulated with varnished cloth or paper.

Trial

Having studied the procedure, how to wind a transformer, There are a few more recommendations to consider. The number of turns of a thin conductor can reach several thousand. In this case, it is better to use special counting equipment. The winding is protected from above with paper. For thick conductors, external protection is not required.

To assess the reliability of the insulation, it is necessary to touch each output of the network circuits with the lead-out conductor in turn. The verification procedure must be performed very carefully. Avoid the possibility of electric shock.

After reviewing the step-by-step instructions for winding a transformer, you can repair an old one or create a new device. If all its points are strictly followed, it is possible to create a reliable, durable unit.

Transformer is translated from Latin as “converter”, “converter”. This is a static type electromagnetic device designed to convert alternating voltage or electric current. The basis of any transformer is a closed magnetic circuit, which is sometimes called a core. Windings are wound onto the core, of which there can be 2-3 or more, depending on the type of transformer. When an alternating voltage appears on the primary winding, a magnetic current is excited inside the core. It, in turn, causes an alternating current voltage with exactly the same frequency on the remaining windings.

The windings differ from each other in the number of turns, which determines the coefficient of change in voltage. In other words, if the secondary winding has half as many turns, then an alternating voltage appears on it, two times less than on the primary winding. But the current power does not change. This makes it possible to work with high currents at relatively low voltage.

Depending on the shape of the magnetic circuit There are three types of transformers:

Plate materials

Transformer cores are made of either metal or ferrite. Ferrite, or ferromagnetic, is iron with a special crystal lattice structure. The use of ferrite increases the efficiency of the transformer. Therefore, most often the transformer core is made of ferrite. There are several ways to make a core:

• Made from stacked metal plates.
• Made from wound metal tape.
• In the form of a monolith cast from metal.

Any transformer can operate in both step-up and step-down modes. Therefore, all transformers are conditionally divided into two large groups. Boost: The output voltage is greater than the input. For example, it was 12 V, it became 220 V. Step-down: the output voltage is lower than the input. It was 220, but became 12 volts. But depending on which winding the primary voltage is supplied to, it can be turned into a boost voltage, which will turn 10 A into 100 A.

DIY toroidal transformer

A toroidal transformer, or simply a torus, is most often made at home as the main part for a home welding machine and more. In fact, this is the most common type of transformer, first manufactured by Faraday in 1831.

Advantages and disadvantages of the torus

Thor has undoubted advantages compared to other types:

The simplest torus consists of two windings on its ring-shaped core. The primary winding is connected to the source of electric current, the secondary winding goes to the electricity consumer. By means of a magnetic circuit, the windings are combined and their induction is enhanced. When the power is turned on, an alternating magnetic flux appears in the primary winding. Connecting with the secondary winding, this flux generates electromagnetic force in it. The magnitude of this force depends on the number of wound turns. By changing the number of turns, you can convert any voltage.

Calculation of the power of a toroidal transformer

Making a welding toroidal transformer at home begins with calculating its power. The main parameter of the future torus is the current that will be supplied to the welding electrodes. Most often, electrodes with a diameter of 2–5 mm are sufficient for domestic needs. Accordingly, for such electrodes the current power should be in the range of 110–140 A.

The power of the future transformer is calculated using the following formula:

U - open circuit voltage

I - current strength

cos f - power factor equal to 0.8

n - efficiency equal to 0.7

Next, the calculated power value is compared with the cross-sectional area of ​​the core using the appropriate table. For home welding transformers, this value is usually 20−70 sq. cm depending on the specific model.

After this, using the following table, the number of turns of the wire is selected in relation to the cross-sectional area of ​​the core. The pattern is simple: the larger the cross-sectional area of ​​the magnetic circuit, the fewer turns are wound on the coil. The direct number of turns is calculated using the following formula:

U is the current voltage on the primary winding.

I - secondary winding current, or welding current.

S is the cross-sectional area of ​​the magnetic circuit.

The number of turns on the secondary winding is calculated using the following formula:

Toroidal core

Toroidal transformers have a rather complex core. It is best made from special transformer steel (an alloy of iron and silicon) in the form of a steel strip. The tape is pre-rolled into a dimensional roll. Such a roll, in fact, already has the shape of a torus.

Where can I get a ready-made core? A good toroidal core can be found on an old laboratory autotransformer. In this case, it will be necessary to unwind the old windings and wind new ones onto a ready-made core. Rewinding a transformer with your own hands is no different from winding a new transformer.

Features of torus winding

The primary winding is made of copper wire in glass cloth or cotton insulation. Under no circumstances should rubber-insulated wires be used. For a current on the primary winding of 25 A, the wound wire must have a cross-section of 5-7 mm. On the secondary, it is necessary to use a wire of a much larger cross-section - 30-40 mm. This is necessary due to the fact that a much higher current will flow on the secondary winding - 120-150 A. In both cases, the wire insulation must be heat-resistant.

In order to properly rewind and assemble a homemade transformer, you need to understand some details of the process of its operation. It is necessary to correctly wind the wires. The primary winding is made using a wire of a smaller cross-section, and the number of turns themselves is much larger, this leads to the fact that the primary winding experiences very heavy loads and, as a result, can get very hot during operation. Therefore, the installation of the primary winding must be done especially carefully.

During the winding process, each wound layer must be insulated. To do this, use either a special varnished cloth or construction tape. The insulating material is pre-cut into strips 1-2 cm wide. The insulation is laid in such a way that the inner part of the winding is covered with a double layer, and the outer part with a single layer. After this, the entire insulating layer is coated with a thick layer of PVA glue. The glue in this case has a dual function. It strengthens the insulation, turning it into a single monolith, and also significantly reduces the humming sound of the transformer during operation.

Winding devices

Winding a torus is a complex and time-consuming process. In order to somehow lighten it, special winding devices are used.

• The so-called fork shuttle. The required amount of wire is first wound onto it, and then, using shuttle movements, the wire is sequentially wound onto the transformer core. This method is suitable only if the wire being wound is sufficiently thin and flexible, and the internal diameter of the torus is so large that it allows the shuttle to be pulled through freely. At the same time, winding occurs quite slowly, so if you need to wind a large number of turns, you will have to spend a lot of time on it.
• The second method is more advanced and requires special equipment for its implementation. But with its help you can wind a transformer of almost any size and at a very high speed. In this case, the quality of winding will be very high. The device is called a “breakable rim”. The essence of the process is as follows: the winding rim of the device is inserted into the hole of the torus. After this, the winding rim is closed into a single ring. Then the required amount of winding wire is wound onto it. And finally, the winding wire is wound from the rim of the device onto the torus coil. Such a machine can be made at home. His drawings are freely available on the Internet.