Transformer is translated from Latin as “converter”, “converter”. This is a static type electromagnetic device designed to convert AC 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, it is excited inside the core. magnetic current. 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. It does possible work with currents great strength 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 structure crystal lattice. 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

The toroidal transformer, or simply torus, is most often made at home as the main part for the home welding machine and not only. 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 to 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 for household needs Electrodes with a diameter of 2−5 mm are quite sufficient. 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—coefficient useful action, 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 carried out copper wire in fiberglass or cotton paper insulation. Under no circumstances should the wires be used rubber insulation. 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 significant current will flow on the secondary winding greater strength- 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. Previously insulating material cut into strips 1−2 cm wide. The insulation is laid in such a way that inner part The windings are covered with a double layer, and the outer winding, respectively, with one 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 the torus - difficult process, which takes a lot of time. In order to somehow lighten it, special winding devices are used.

• The so-called fork shuttle. It is pre-wound on it required amount wires, and then, using shuttle movements, the wires are sequentially wound onto the transformer core. This method is only suitable if the wire being wound is thin and flexible enough, and inner diameter 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 this.
• 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 with 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.

If you have a power transformer with a suitable(in this case S = 10.4 cm²) in terms of power cross-section of the core, but its secondary winding is designed for a different voltage, you can rewind the transformer.

In this case, you can not carry out such labor-intensive work as winding a multi-turn primary winding, but use a ready-made, old primary winding.

We determine the location of the primary and secondary windings on the frame. The primary winding is usually located on the frame closer to the core and is wound thin wire With big amount turns.
Next you need to determine the number of turns per volt w for this steel core. You cannot use the value of the number of turns per volt previously calculated for the previous article.
Let's connect the transformer to a 220 volt network. Let's measure the voltage on all secondary windings. Let's choose the winding with the lowest voltage. For example, it will be equal to U = 30 volts. Let's mark its location on the frame.
Next, you need to disassemble the transformer, removing the core plates and freeing the frame. You need to rewind the transformer, wind the old secondary (or secondary, if there are several) windings and count the number of turns in the selected winding.
We leave only the primary winding and inter-winding insulation.
Let's say the number of turns in the selected winding will be n = 140.

Then the number of turns per volt w for this transformer will be:

w = n: U = 140: 30 = 4.67 turns.

If there is no secondary winding at all, or there is no way to calculate it, we will proceed in a different way.
Wind 100 turns over the primary winding insulated wire any diameter is a “measuring” winding.
Let's assemble the transformer again, connect it to a 220-volt network and measure the voltage on the “measuring” winding with a voltmeter. Let's say it will be 21.5 volts.

Let's calculate the number of turns per 1 volt for this transformer:
w = n: U = 100: 21.5 = 4.65 turns.
Then the number of turns in the new 36 volt secondary winding will be:

U_2 = 36 4.65 = 167.8 turns. Let's round up to 170 turns.
The “measuring” winding should be removed and wound with a wire of the appropriate diameter.

How to wind a transformer on an W-shaped core?

This article is a continuation of the articles:

Winding the windings of the transformer frame on an W-shaped core must be done on a winding machine equipped with a revolution counter and special device for attaching the frame and bobbin with wire. But, as a rule, there is no such machine at hand.

We use a regular one for winding hand drill. Before winding, you need to remove and put the frame on the mandrel several times so that the frame sits more freely on the mandrel. Next, we put the frame back on the mandrel, reinforce it with two plywood planks (the planks are needed so that the cheeks of the frame do not spread out to the sides when winding the wire), tighten it with a bolt or pin and secure it in the chuck of a hand drill.The drill must be secured in a table vise.

It is necessary to calculate the gear ratio of the chuck and the drill handle. To do this, let's count the number of revolutions of the drill chuck per revolution of the handle. Or, if possible, count the number of teeth on both gears. The ratio of their number will give the conversion factor n.

For example: the number of teeth on the handle gear is 35 pcs., the number of teeth on the chuck is 7 pcs., then the coefficient n = 35 / 7 = 5. With one revolution of the drill handle, 5 turns of wire are wound onto the frame.

When winding the transformer frame on an W-shaped core, you need to count not the number of revolutions of the chuck, but the number of revolutions of the drill handle, which is much simpler and more convenient. Let's determine the number of turns of the handle for the network primary winding.
K = 1050/5 = 210 rpm.
To wind the primary winding you need to make 210 revolutions of the drill handle.

One practical advice: in order not to lose count of the number of revolutions when winding the coil, after every 10 revolutions of the drill handle, somewhere on the paper you need to make a mark - a tick.
I counted the number of ticks equal to 21 - that’s when the primary winding is ready.

It is necessary to make a hole in the cheek of the frame for the wire to exit. The hole is made with an awl in the cheek, which goes outside the transformer.
The enameled winding wire is connected to the stranded wire. The junction is covered with a piece thick paper as in the picture...

When winding transformer coils on an W-shaped core, it is best (I highly recommend) to wind it turn to turn, laying capacitor paper between the layers for insulation between the layers.

The width of the condenser paper should be 4-5 mm wider than the distance between the cheeks of the frame and have cuts along the entire length, as in the figure….
The reason for increasing the width of the paper is this: when winding, the turns of the wire press the paper, it becomes deformed and narrows in size. The turns of the lower layer are exposed, and interturn breakdown between the layers is possible.

Having wound the primary winding and brought out the end with a stranded wire, lay 2-3 layers of paper or varnished cloth (inter-winding insulation) to protect the wires of the network winding from accidental contact with the wires of the output winding.

Winding the secondary winding using a drill is not convenient, because the secondary winding wire is thick - 1 mm in diameter... It is best to wind the secondary winding manually by removing the workpiece with the frame from the drill chuck.

The secondary winding is also wound turn to turn with a strip of paper (the same as the primary winding) placed between the layers. Number of turns of the secondary winding at 36 volts there will be 180 turns.

The ends of the secondary winding are removed from the frame by the wire itself, without soldering to a stranded wire. You can only, for strength, put a thin vinyl chloride tube on the wire.

After winding the secondary winding, 2-3 layers of thick paper are laid again to protect the wire from external damage. Then the finished frame with windings is carefully removed from the mandrel, being careful not to damage it.

Then we assemble the transformer completely, insert the magnetic circuit plates across the roof, from different sides of the frame. First, we assemble without plates - jumpers, it’s more convenient. After all the W-shaped plates are inserted, we insert the jumper plates.

By lightly tapping the ends with a hammer, we trim the plates on a level surface. Then the entire magnetic circuit must be tightened with stud bolts or crimped with corners with mounting holes.

Finally we got to interesting moment- launching his creation - a transformer on an W-shaped core into the electrical network.

To test the transformer, we connect the power cable with a plug (through a 1 ampere fuse) to the primary winding of the transformer.

Voltmeter alternating current you need to check the presence of voltage on the secondary winding of the transformer. It should be 35 - 37 volts.

If all the work is done correctly, then after 5-10 minutes of operation, the transformer should not heat up. After connecting a 36 volt light bulb, the voltage may drop to 33-35 volts, this is normal.

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 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, 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 upon step by step rewind 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 it happens short circuit in the windings, then the light will light up and prevent the consequences of the error; if everything is fine, then 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, to reduce production costs in order to save copper wire, the primary winding is under-winded at the factory, as a result of which the 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 by 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. Next come simple laws mathematics to calculate 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 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, then the multimeter sound signal(resistance readings on the screen) notifies you about this. 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).

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 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 estimates total load per 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.

Having sat down at the table in a calm atmosphere, 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 may rub or get caught (do not damage the enamel insulation of the winding wires!);

Wind the wire onto separate coil. 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 loops and creases formed in the process - this way we will keep the wire relatively straight and not damage enamel coating copper wire when it is bent.

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!

Making a homemade transformer is a worthwhile endeavor so as not to waste money on buying transformers.

Selection of materials

Let's take a Russian wire, its insulation is stronger. The wire from old coils is used if there is no damage to the insulation. For insulation, paper or FUM film is suitable. For insulation between the windings, it is better to use varnish fabric and several layers of insulation. For superficial external insulation suitable cable paper, varnish cloth. You can also wind the transformer using PVC electrical tape.

The frame is made of fiberglass or similar material.

Calculations of parameters of a homemade transformer

On a simple transformer the primary winding has 440 turns for 220 volts. It turns out 1 volt for every two turns. Formula for counting turns by voltage:

N = 40-60 / S, where S is the cross-sectional area of ​​the core in cm 2.

The constant 40-60 depends on the quality of the core metal.

Let's make a calculation for installing the windings on the magnetic circuit. In our case, the transformer has a window 53 mm in height and 19 mm in width. The frame will be textolite. Two cheeks at the bottom and top 53 - 1.5 x 2 = 50 mm, frame 19 - 1.5 = 17.5 mm, window size 50 x 17.5 mm.

We are counting required diameter wires The power of the transformer core with your own hands is 170 watts in size. On the network winding the current is 170 / 220 = 0.78 amperes. Current density is 2 amperes per mm 2, standard wire diameter according to the table is 0.72 mm. The factory winding is made of 0.5 wire, the factory saved money on this.

• Winding of a simple transformer high voltage 2.18 x 450 = 981 turns.
• Low voltage for filament 2.18 x 5 = 11 turns.
• Low voltage filament 2.18 x 6.3 = 14 turns.

Number of turns of the primary winding:

we take a wire of 0.35 mm, 50 / 0.39 x 0.9 = 115 turns per layer. Number of layers 981 / 115 = 8.5. It is not recommended to draw conclusions from the middle of the layer to ensure reliability.

Let's calculate the height of the frame with windings. Primary of eight layers with 0.74 mm wire, 0.1 mm insulation: 8 x (0.74 + 0.1) = 6.7 mm. It is better to shield the high-voltage winding from other windings to prevent high-frequency interference. In order to wind the transformer, we make a screen winding from one layer of 0.28 mm wire with two layers of insulation on each side: 0.1 x 2 + 0.28 = 0.1 x 2 = 0.32 mm.

The primary winding will take up space: 0.1 x 2 + 6.7 + 0.32 = 7.22 mm.

Step-up winding of 17 layers, thickness 0.39, insulation 0.1 mm: 17 x (0.39 + 0.1) = 6.8 mm. On top of the winding we make layers of insulation 0.1 mm.

It turns out: 6.8 + 2 x 0.1 = 7 mm. Height of the windings together: 7.22 + 7 = 14.22 mm. 3 mm left for filament windings.

You can make a calculation internal resistance windings To do this, the length of the turn is calculated, the length of the wire in the winding is taken, the resistance is determined, knowing resistivity according to the table for copper.

When calculating the resistance of the primary winding section, a difference of about 6 ohms is obtained. This resistance will give a voltage drop of 0.84 volts at a nominal current of 140 milliamps. To compensate for this voltage drop, we add two turns. Now during loading the sections are equal in voltage.

Making a transformer coil frame with your own hands

The angles on the parts and the accuracy in dimensions are important, which will affect the assembly of a simple transformer.

On the cheeks we allocate places for attaching the output contacts of the windings, and drill holes according to calculations. When the frame is assembled, now we round off the sharp edges that the winding wire will touch. We use a needle file for this purpose. The wires should not be bent sharply, as the insulation enamel will crack. Now let's check whether the plate is inserted into the frame window. It should not dangle or fit tightly. We place the frame on a special machine or prepare to wind the transformer manually. Thick wires are always tossed around by hand.

Winding a transformer with your own hands

We lay the first layer of insulation. Insert the end of the wire into the hole in the output terminal. We begin to wind the wire, not forgetting about its tension. You can check this way: the wound coil will not bend under your finger. The wire cannot be stretched, as the insulation will be damaged. It is recommended to soak the finished coil with paraffin so as not to damage the wire. If the winding hums while the transformer is operating, the wire insulation wears off, the wire bends and breaks. For this reason, the tension of the wire during winding is of great importance.

During winding, we move the coils closer to each other and compact them. The first layer is the most important.

There is no need to leave empty space on the layer. The highest voltage on the last turns is for the primary 60 + 60 / 2, 18 + 55 V. The varnish insulation will withstand the voltage; if the wire falls into the void of the layer, the insulation may be damaged. We saturate the first layer, then the second and so on. The insulation between the windings must be treated conscientiously. It must withstand up to 1000 volts. At the top of the insulation, it is recommended to write the number of turns and the size of the wire; this will be useful during repairs.

The layers of a homemade transformer must have correct form. As you wind the coil, it will bend at the edges. To do this, the layers need to be equalized during winding without damaging the insulation.

It is better to make forced wire joints on the edge of the frame behind the core. Connect the wire by twisting with soldering, overlay with soldering. The length of the contact when connecting is made more than 12 wire diameters. The joint must be insulated with paper or varnish cloth. Soldering must be without sharp corners.

The terminal ends of the windings are made in different ways. The main thing is to have reliability and quality.

Completing the manufacture of the transformer with your own hands

We solder the lead ends of the windings, insulate the surface of a simple transformer, sign these characteristics on it and assemble the core. After this, you need to check this simple transformer with your own hands.

We measure the idle current of the homemade transformer; it should be minimal. Let's look at the heating. If the core heats up, then the iron is selected incorrectly. If the windings get hot, it means there is a short circuit. If it’s normal, then we short-circuit the secondary winding; there should be no crackling or strong buzzing.

An example of how to make a homemade transformer

Let's move on to the manufacture of the transformer itself. Based on the finished core, we will calculate the power of the transformer, turns and wire, wind the primary and secondary windings, and assemble the transformer completely.

To wind a transformer with a voltage of 220 to 12 volts, we need to select a magnetic core. We select a W-shaped magnetic core and a frame from an old transformer. To determine the power delivered a simple transformer, it is necessary to make a preliminary calculation.

Transformer calculation

We calculate the diameter of the primary winding wire. Transformer power P 1 = 108 W:

P 1 = U 1 x I 1

where: I 1 – current in the primary winding;

then the current in the primary winding is:

I 1 = P 1 / U 1 = 108 W / 220 V = 0.49 A.

Let's take I 1 = 0.5 ampere.

From the table, select the wire diameter depending on the current permissible current 0.56 A, diameter 0.6 mm.

You can wind a homemade transformer with your own hands without a machine. This will take two to three hours, no more. Let's prepare strips of paper to lay between the layers of wire. We cut out a strip with a width equal to the distance between the cheeks of the transformer coil plus a couple of millimeters so that the paper lies tightly and the turns do not overlap each other at the edges.

We make the length of the strip with a margin of two centimeters for gluing. Lightly cut along the edges of the strip with scissors so that the paper does not tear when bending.

Then we glue a strip of paper onto the frame, smoothing it tightly.

Winding the primary winding

Now we take the wire from an old coil, which has a wire with good, non-cracked insulation. We insert the end of the wire into a flexible tube of insulation from an old used wire of the appropriate suitable diameter. We insert the end of the winding into the hole in the coil frame (they are already present in the old frame).

The coil winds tightly, turn to turn. Having wound 3-4 turns, you need to press the turns against each other so that the winding of the turns is tight. To wind the transformer after winding the first layer, it is necessary to count the number of turns in the row. We got 73 turns. We make a gasket with a strip of paper. We wind the second layer. During winding, you need to keep the wire taut at all times so that the winding is tight. After the second layer we also make a paper gasket. If the length of the wire is not enough, then we connect another wire to it by soldering. We tin the varnished wire by heating the end with a soldering iron on an aspirin tablet. At the same time, the varnish is easily removed.

When the winding of the primary winding is completed, we insulate the end of the wire into a tube and bring it out to the outside of the coil. We make winding insulation between the primary and secondary windings. You can wind the transformer further.

Secondary winding

Let's calculate the diameter of the wire of the secondary winding of a homemade transformer. Let us take the power of the secondary winding:

P 2 = 100 watts

P 2 = U 2 x I 2

U 2 = 18 volts;

The permissible current in the secondary winding will be equal to:

I 2 = P 2 / U 2 = 100 W / 18 V = 5.55 A.

From the table, diameter depending on current: diameter for a current of 5.55 A - the closest value in the table is 6.28 amperes. For such a current, a wire diameter of 2 mm is required.

We take the wire that we got when winding up the old transformer. We wind the wire of the secondary winding according to the same principle as the primary winding. The wire of the secondary winding is much stiffer, therefore, in order for it to lie evenly when winding, it must be periodically upset by hammer blows through wooden block so as not to damage the insulation. We got 3 layers of secondary winding. The result is a finished wound frame of a simple transformer.

DIY transformer assembly

To speed up assembly, we take two W-shaped plates. We insert them inside the frame alternately on both sides, two pieces at a time.

We are not installing the covering plates yet. They will be installed later. If you insert all the plates at once as a whole package, then gaps appear between the plates and the inductance of the entire core drops. After assembling the W-shaped plates of the homemade transformer, we insert the overlapping plates, also two pieces each.

After assembling the core, carefully tap its planes with a hammer to align the plates. Using racks and pins we will tighten the core. According to the rules, paper sleeves are put on the studs to reduce losses in the core.

We clean and tin the ends of the windings. Then we solder to the lead strips, which can be attached to the transformer frame. The result is a ready-made transformer with your own hands.

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Rewinding transformers is a complex and labor-intensive type of technological operation when repairing this type of electrical equipment. All types of transformers produced by industry are highly reliable. These static electromagnetic devices have no moving parts and are designed for a long period of operation. Most common reasons failures may be, in particular:

• factory defects (components, assembly)
• critical deviation of operating modes
• violation of prescribed operating rules
• installation errors
• natural aging of insulating materials.

As a rule, in such cases there is a break in the transformer winding with its complete refusal. Another manifestation of a failure is an interturn short circuit on the housing, during which the power drops, and significant heating of the windings occurs. In the above cases, the transformer needs major renovation with complete (partial) disassembly of the active part.

When a transformer fails, in most cases it is overhauled rather than replaced. This is due to economic reasons. Thus, restoring functionality by rewinding the transformer coil costs about 30% less than purchasing a new device. On the technical side, repairing a power transformer has positive aspect it is possible to modernize the transformer by changing (improving) it consumer properties, technical parameters. The restored transformer can still serve for a long period.

The transformer rewinding service in Moscow provided by our company can be used for the purpose of repair, modernization, or changing technical parameters various types this electrical equipment. Rewinding means the following types of work: disassembling the transformer, troubleshooting it, actually rewinding the transformer coils, applying insulation (impregnation with varnish), general assembly, bench testing.

Rewind technology pulse transformer different from other species. In order to reduce interference and losses, its design uses a complex sectional winding. Rewinding only the primary or secondary winding of a pulse transformer is impossible; both must be rewinded at once. When rewinding such devices, the sequence of operations must be strictly followed; the slightest deviations can significantly change its characteristics and even lead to failure.

In the event that there is a need to manufacture a device with non-standard voltage and current parameters, a careful calculation and rewinding of a transformer of a suitable (unified) type is made. In this case, the existing structural elements (winding frame, core) are taken as a basis and the old winding is replaced with a new one. For example, this way you can rewind the TS 180 transformer (secondary winding), which is equivalent to manufacturing a new one with the given characteristics.

In the process of rewinding a transformer, it becomes possible to improve its technical and operational parameters. Using the method of dividing the windings into sections instead of additional insulation improves heat removal, and therefore helps to increase the rated power of the transformer. Air cooling The winding will be more efficient the more separate sections it contains. Application effective ways winding can, by reducing the cross-section of the wires, reduce the size of the windings (coils), their weight and the total cost of the device.

Prices for rewinding transformers