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 tr-ry from old technology, which are lying around idle, so you can try to remake 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 electric 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. 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:

Determining the diameter required wire according to the formula:

Based on Table 1, select a wire with the required cross-section. If suitable value no, 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 more area coil sections.

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 turn 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 thermometer for charging a car battery, or make a boosting thermometer for a laboratory power source, an electric wood burner, hot knife for cutting foam plastic or other device for the needs of a home craftsman.

Based on the shape of the magnetic circuit, transformers are divided into rod, armored and toroidal. It would seem that there is no difference, because the main thing is the power that the transformer is capable of converting. But if you take three transformers with magnetic cores different shapes to the same overall power, then it turns out that the toroidal transformer will show the best performance characteristics of all. It is for this reason that most often for food various devices In many industrial areas, the choice is, of course, toroidal transformers due to their high efficiency.

Today, toroidal transformers are used in various fields industry, and most often toroidal transformers are installed in sources uninterruptible power supply, in voltage stabilizers, they are used to power lighting and radio equipment; toroidal transformers can often be seen in medical and diagnostic equipment, in welding equipment, etc.

As you understand, when we say “toroidal transformer,” we usually mean a network single-phase transformer, power or measuring, step-up or step-down, whose toroidal core is equipped with two or more windings.

A toroidal transformer works in principle the same way: it lowers or increases the voltage, increases or decreases the current - it converts electricity. But a toroidal transformer, with the same transmitted power, is smaller in size and lighter in weight, that is, has better economic indicators.

The main feature of a toroidal transformer is the small total volume of the device, reaching up to half in comparison with other types of magnetic cores. twice the volume of a toroidal strip core with the same overall power. Therefore, toroidal transformers are more convenient to install and connect, and it is no longer so important whether we are talking about internal or external installation.

Any specialist will say that the toroidal shape of the core is ideal for a transformer for several reasons: firstly, it saves materials in production, secondly, the windings evenly fill the entire core, distributed over its entire surface, leaving no unused spaces, thirdly, Since the windings are shorter, the efficiency of toroidal transformers is higher due to the lower resistance of the winding wires.

Winding cooling is another important factor. The windings are effectively cooled by being arranged in a toroidal shape, hence the current density can be higher. Losses in the iron are minimal and the magnetizing current is much lower. As a result, the thermal load capacity of the toroidal transformer turns out to be very high.

Energy savings are another plus in favor of a toroidal transformer. Approximately 30% more energy is saved at full load, and approximately 80% at idle, compared to laminated magnetic cores of other forms. The dissipation index of toroidal transformers is 5 times less than that of armored and rod transformers, so they can be safely used with sensitive electronic equipment.

With a power of a toroidal transformer up to a kilowatt, it is so light and compact that for installation it is enough to use a metal pressure washer and a bolt. All the consumer needs to do is select a suitable transformer based on load current and primary and secondary voltages. When manufacturing a transformer at the factory, the cross-sectional area of ​​the core, the area of ​​the window, the diameters of the winding wires are calculated, and the optimal dimensions of the magnetic circuit are selected, taking into account the permissible induction in it.

To convert current they are used different kind special devices. Toroidal transformer TPP for welding machine and other devices, you can wind it with your own hands at home, it is an ideal energy converter.

Design

The first bipolar transformer was made by Faraday, and according to the data, it was a toroidal device. A toroidal autotransformer (brand Shtil, TM2, TTS4) is a device designed to transform alternating current one voltage to another. They are used in various linear installations. This electromagnetic device can be single-phase or three-phase. Structurally consists of:

1. Metal disk made of rolled magnetic steel for transformers;
2. Rubber gasket;
3. Primary winding terminals;
4. Secondary winding;
5. Insulation between windings;
6. Shield winding;
7. An additional layer between the primary winding and the shielding winding;
8. Primary winding;
9. Insulating core coating;
10. Toroidal core;
11. fuse;
12. Fastening elements;
13. Cover insulation.

A magnetic circuit is used to connect the windings.

This type of converter can be classified by purpose, cooling, type of magnetic circuit, windings. By purpose there is impulse, power, a frequency converter(TST, TNT, TTS, TT-3). For cooling – air and oil (OST, OSM, TM). By the number of windings - two-winding or more.

Photo - the principle of operation of the transformer

A device of this type is used in various audio and video installations, stabilizers, and lighting systems. The main difference between this design and other devices is the number of windings and the shape of the core. Physicists believe that the ring shape is the ideal design for an anchor. In this case, the winding of the toroidal converter is carried out evenly, as well as the heat distribution. Thanks to this arrangement of the coils, the converter cools quickly and even during intensive operation does not require the use of coolers.

Photo - toroidal ring converter

Advantages of a toroidal transformer:

1. Small dimensions;
2. The output signal on the torus is very strong;
3. The windings are short in length, resulting in reduced resistance and increased efficiency. But also because of this, a certain background sound is heard during operation;
4. Excellent energy saving characteristics;
5. Easy to install yourself.

The converter is used as a network stabilizer, Charger, as a power supply halogen lamps, tube amplifier ULF.

Photo - finished TPN25

Video: purpose of toroidal transformers

Principle of operation

The simplest toroidal transformer consists of two windings on a ring and a steel core. The primary winding is connected to the source electric current, and the secondary one – to the electricity consumer. Due to the magnetic circuit, the individual windings are connected to each other and their inductive coupling is strengthened. When the power is turned on, an alternating magnetic flux is created in the primary winding. Meshing with individual windings, this flux creates an electromagnetic force in them, which depends on the number of turns of the winding. If you change the number of windings, you can make a transformer to convert any voltage.

Photo - Operating principle

Also, converters of this type are either buck or boost. A toroidal step-down transformer has a high voltage on the secondary winding terminals and a low voltage on the primary winding. Increasing is the opposite. In addition, the windings can be high voltage or lower, depending on network characteristics.

How to do

Even young electricians can make a toroidal transformer. Winding and calculation are not complicated. We suggest considering how to properly wind a toroidal magnetic circuit for a semi-automatic machine:

Considering that 1 turn carries 0.84 Volts, the winding circuit of a toroidal transformer is carried out according to the following principle:

So you can easily make your own 220 to 24 volt toroidal transformer. The described circuit can be connected either to arc welding, and semi-automatic. The parameters are calculated based on the wire cross-section, number of turns, and ring size. The characteristics of this device allow for stepwise adjustment. Among the advantages of the assembly principle: simplicity and accessibility. Among the disadvantages: heavy weight.

Price overview

You can buy a toroidal transformer HBL-200 in any city Russian Federation and CIS countries. It is used for various audio equipment. Let's look at how much the converter costs.

I'm already tired of assembling low-frequency amplifiers on microcircuits, my hands are itching, and I wanted to solder something serious. I decided to solder a transistor amplifier with bipolar power supply. The power source will be a linear power supply with a toroidal transformer, the winding of which I will talk about in this article.

First we need to decide on the power of the amplifier, the number of channels and load resistance.

I will have two channels, the output power will be approximately 100W per channel, the load resistance will be 4 Ohms.

You don’t have to bother and take a 300W transformer, but this is extra size and weight. Fortunately, if a class AB amplifier has an efficiency of approximately 50%, then in order to get 100W at the output, you need to consume 200W. If two channels are 100W each, then the consumption will be 400W. This is all approximate, and with the condition that the input signal will be a sinusoid with a constant amplitude. I don't think among reasonable people There are people who like to listen to terrible squeaking in the speakers.

The music we listen to has a sine wave waveform that varies in both frequency and amplitude. This signal will not always have a maximum amplitude; at such moments the electrolytic capacitor of the power source will be charged, and discharged at maximum amplitudes, thereby saving on transformer power. Again, if you are not a fan of listening to squeaking in the speaker system.

Let's calculate the power and voltage of our future transformer. Download and run the program.

We fill in all the fields at the top of the program, set the quiescent current to 10mA, the preamplifier current to 0mA, select the purpose and type of signal according to the taste of the music you are listening to. Click “Apply”.

The program calculated the voltage idle move power source, as well as capacitor capacity, these ratings are advisory in nature and are given for one arm.

Next, fill in the two lower windows in accordance with the recommended values ​​and click “Calculate”. We got the output voltage of the transformer windings, I have 34.5V on each arm, the current of the secondary windings is 1.7A, diode parameters and connection diagram.

We have decided on the transformer parameters, now we download and run the program. We will calculate the winding data.

My core is toroidal and has dimensions of 130*80*25. Fill in the fields of the program.

We set the induction amplitude to 1.2 T, or maybe one and a half (as in my case), this is for strip cores, and for plate cores we set it to 1 T. This parameter depends on the hardware.

Current density for class AB is from 3.5-4 A/mm2, for class A 2.5 A/mm2.

We set the currents and voltage of the secondary windings, click calculate.

So, we got the number of turns of the primary and secondary windings, as well as the diameters of the wires.

You can do without calculations, wind approximately 900 turns, and periodically connect the winding to a 220V network in series through an incandescent lamp with a rated voltage of 220V.

If the lamp stays on, even at half heat, then we move on, checking periodically. As soon as the lamp stops glowing, it is necessary to measure the no-load current (but without the lamp, we connect the winding directly to the network), which should be 10-100 mA.

If the no-load current is less than 10mA, then this is not very good. Due to the high resistance, the transformer will heat up under the load. If the current exceeds 100mA, the transformer will heat up at idle. Although there are transformers with no-load current and 300mA, they heat up without load and hum terribly.

You can start winding the transformer itself. I need to wind 1291 turns of the primary winding with a wire whose diameter is 0.6 mm. Notice the diameter, not the cross-section! I have a 0.63mm wire.

I wrap it with rag tape. Once I wrapped the core with one lavsan tape, without electrical tape (or cardboard), and after winding several layers a breakdown occurred. Apparently the lower layers of the wire were crushed, and the varnish was damaged by the sharp edge of the core. Now, when winding toroidal transformers, I always wind the core with rag tape.

Mylar tape can be bought in the store, in the form of a baking sleeve, which is cut into ribbons using a razor blade and a metal ruler.

We take a 40cm wooden ruler, saw through both edges so that the wire can be wound around it. We reel in a large number of wires (I had to wind 1300 turns several times).

I wind all the windings clockwise, as in the picture.

We secure the free end of the wire with tape, or thread, and wind the winding layer turn to turn.

Solder the wires of the primary winding. We isolate the areas of soldering and stripping of varnish.

I'll give you one little advice. When soldering wires to the terminals of the primary winding, choose high-quality and durable wires, or do not solder them, but place them in dielectric tubes (heat shrink, cambric). While I was winding the secondary windings, my leads broke off due to repeated bending. I took the wires from the PC power supply.

We overlap 4-5 layers of lavsan tape taken from the baking sleeve.

Don’t forget to write down the number of turns in each layer on a piece of paper so you don’t forget. After all, winding a transformer can last not 1-2 days, but a month or several months, when there is no time, and you can forget everything.

We wind the remaining layers of wire in the same direction, between which we place layers of lavsan tape insulation.

The connection points must be soldered and insulated with heat shrink tubing.

When you reel it in required amount turns of the primary winding of a toroidal transformer, you need to connect the winding in series through a 220V lamp to the network, as mentioned above. The lamp should not glow. If it lights up, it means you have a small number of turns, or short circuit between layers or turns (if the wire is bad).

My no-load current is 11mA.

Solder the tap. We isolate the primary winding from the secondary well, maybe 6-8 layers of Mylar tape.

The secondary winding can be wound according to the calculations made above, or using the following method.

We take a thin wire and wind two or three dozen turns over the “primary”. Next, we connect the primary winding to the network and measure the voltage on our experimental winding. I got 18 turns of 2.6V.

Dividing 2.6V into 18 turns, I calculated that one turn is equal to 0.144V. The more turns on the experimental winding are wound, the more accurate the calculation. Next, I take the voltage I need on one of the secondary windings (I have 35V) and divide by 0.144V, I get the number of turns of the secondary winding equal to 243.

Winding the “secondary” is no different. We wind it in the same direction, with the same shuttle, only we take the diameter of the wire from the calculations above. My wire diameter is 1.25mm (I didn’t have a smaller one).

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 it is not pulse block nutrition, then one of important elements The power supply will be a high-quality transformer. You can make a transformer for the required voltages with your own hands, often, subject to all winding rules, homemade transformer will be much better than factory made.

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. Similar situation 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 tie rods with a dielectric (cambric, paper straw) 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, as 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 inside 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 the average resistance value).

Having completed simple steps With the definition of 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 recording in chronological order all my actions are for you :). So, the “Record” button is turned on, the cassette film with a characteristic rustling winds the film from one reel to another. Evening, the table is lit desk lamp, 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 armor-type 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 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.

Sitting down at the table in calm atmosphere In front of us we place 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 may 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 in order to end up with 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 of 3-4 millimeters in size. 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 stud 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 in electronic format 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 free time I love making things and creating something new for myself and my loved ones. You will learn about this and much more in my articles!