Do-it-yourself toroidal transformer - calculation of turns, winding technology. DIY toroidal welding transformer Toroidal core

Most electronic devices require a certain type of power to function, which is different from that supplied by the industrial network. One of the types of such devices is a toroidal transformer. The device has found wide application in various fields of energy, electronics and radio engineering. Most often, transformers are used in electrical networks and in power supplies of all kinds of electronic equipment.

Design and principle of operation

Transformer - the name of the word comes from the Latin transformare, which means to transform. The generally accepted definition for it is as follows: a transformer is a device that, using the phenomenon of electromagnetic induction, is able to change the amplitude of the voltage without changing the shape and frequency of the signal.

A transformer is an electrical device that reduces or increases an alternating electrical voltage. Such transformers are called step-down or step-up. It should be noted that there are also such devices that leave the value of the sinusoidal signal unchanged, they are called galvanic or throttle.

Any transformer in its design contains the following components:

• magnetic circuit (core);
• windings;
• frame for the location of the windings;
• insulator;
• various additional elements (brackets for fastening, strips for outputting contacts, etc.).

The transformer in its design has two or more inductively coupled windings. They are available in both wire and tape types and are always covered with a layer of insulation. The windings are fixed on a magnetic circuit made of soft ferromagnetic material. The primary winding is connected to the voltage source, and the secondary to the load.

The general principle of operation of the device, regardless of its type and purpose, is as follows. An alternating signal is applied to the primary winding of the device, which leads to the appearance of an alternating current in it. This current, in turn, induces an alternating magnetic field in the core, under the action of which an alternating electromotive force (EMF) occurs in the windings. When a load is connected to the secondary winding, an alternating current begins to flow through it. The winding to which the signal is applied is called the primary. The winding connected to the load is called the secondary.

According to the method of cooling, toroidal devices are divided into those using air and liquid cooling. In addition, there are transformers with combined cooling - liquid-air. The main technical parameters of the device include:

1. Input voltage value: allowable voltage value supplied to the primary.
2. The value of the output voltage. Determined by the transformation ratio.
3. The type of transformation. There is an increase or decrease in the signal level.
4. Number of phases. Depending on the network in which transformers are used, they are divided into single-phase or three-phase.
5. The number of windings. There are two-winding or multi-winding devices.

The main parameters of the device include: rated power and transformation ratio. The unit of measure for power is Volt-Amps (VA). The transformation ratio shows the ratio of voltage levels at the input of the device to its output. Its value is directly proportional to the ratio of the number of turns of the primary to the secondary.

In a toroidal transformer, a ring core is used as a basis, which is geometrically a torus. The advantage of this type of magnetic circuit lies in the simple rewinding of the transformer with your own hands and obtaining the highest coefficient of performance (COP) compared to other types of transformers with the same overall values. The disadvantages of tori include increased heating during operation.

Current transformer

In addition to the standard type of voltage transformers, there is a special type called a current transformer. Its main purpose is to change the value of the current relative to its input. Another name for this type of device is current.

Current transformer - a measuring device designed to measure the strength of alternating current. Current devices are used when it is necessary to measure a high current or to protect semiconductor devices from abnormal values ​​\u200b\u200bthat have arisen on the line.

The current device in appearance is no different from a voltage transformer, its differences are in the connection and the number of turns in the winding. The primary is performed using one or a pair of turns. These turns are passed through a toroidal magnetic circuit, and it is through them that the current is measured. Current devices are made not only of the toroidal type, but can also be made on other types of cores. The main condition is that the measured wire makes a full turn.

The secondary winding in this design is shunted with a low-resistance resistor. In this case, the voltage on this winding should not be large, since during the passage of the largest currents, the core will be in saturation mode.

In some cases, measurements are carried out on several conductors that are passed through the torus. Then the magnitude of the current will be proportional to the strength of the sum of the currents.

Calculation of product parameters

Before winding a toroidal transformer at home, you will need to calculate its values. To do this, you need to know the source data. These include: the magnitude of the output voltage, the outer and inner diameter of the core.

The power of the device is determined by the product of the areas S and So, multiplied by the coefficient: P \u003d 1.9 * S * Sok.

The cross-sectional area is calculated by the formula: S=h*(D-d)/2, where:

• S- cross-sectional area;
• h is the height of the structure;
• D- outer diameter;
• d - inner diameter.

To calculate the window area, the formula is used: Sok=3.14*d2/4.

The number of turns in the secondary winding is equal to the product of W2=U2*50/Soc.

This calculation technique can be applied to almost any type of toroidal transformer. But for the calculation of some products there is a methodology.

welding device

This type of transformer is characterized by a large output current. The maximum current and voltage are used as input parameters. For example, for a device with a welding current of 200 amperes and a voltage of 50 volts, the calculation is as follows:

1. The power of the transformer is calculated: P \u003d 200 A * 50 V \u003d 1000 W.

2. The window section is calculated: Sok \u003d π * d2 / 4 \u003d 3.14 * 144 / 4 (cm2) ≈ 113 cm².

3. Cross-sectional area: Sc = h * H = 2 cm * 30 cm = 60 cm².

4. Core power: Rc = 2.76 * 113 * 60 (W) ≈ 18712.8 W.

5. Number of turns of the primary winding: W1 = 40 * 220 / 60 = 147 turns.

6. Number of turns for the secondary winding: W2 = 42 * 60 / 60 = 42 turns.

7. The area of ​​the secondary wire is based on the highest operating current: Spr = 200 A / (8 A / mm2) ≈ 25 mm².

8. The area of ​​\u200b\u200bthe primary wire is calculated: S1 \u003d 43 A / (8 A / mm2) ≈ 5.4 mm².

This calculation option is applicable not only for welders, but can also be successfully used for other types. As you can see, there should not be any difficulties in the calculation.

Current transformer device

It is not difficult to make a current transformer with your own hands, but before making it you will need to perform a calculation. This calculation differs from the generally accepted one due to the design features of the product. It starts with the required secondary current (ampere unit): Iam = Iper / Ivt, where:

Iper - the value of the current of the primary winding, multiplied by the number of turns in it;

Ivt - the number of turns in the secondary winding.

In order to figure out how to correctly perform the calculation, it is easier to consider a practical example of a home-made current device. Let it be necessary to obtain 4 volts at the output of the current device, and limit the current to 5 amperes.

The step-by-step calculation method looks like this:

1. A ferrite ring is taken, for example 20 × 12x6 from 2000hM.
2. 100 turns of wire are wound. These turns make up the secondary, since the primary is just one turn of wire passed through the ferrite.
3. The value of the current in the secondary will be: I / Ktr \u003d 5 / 100 \u003d 0.05 A. where Ktr is the transformation ratio of the transformer (the ratio of the number of primary winding to secondary).
4. The value of the load shunt is calculated according to Ohm's law: R = U/I. It turns out R \u003d 4 / 0.05 \u003d 80 Ohms.

Thus, it is possible to perform the calculation for any required parameters. Regardless of the shape of the current at the input, the voltage at the output of the current device is always bipolar. It is the resistance, not the diode, that is used as the shunt of the secondary winding. If there is a need for a diode, then the resistor is connected first, and then the diode or diode bridge. In the second case, the resistance is included in the diagonal of the bridge.

Self-manufacturing

The price of finished products is high, and it is not always possible to find a device with the required parameters. Therefore, it is advisable to make a transformer or autotransformer with your own hands. In addition to manufacturing a transformer from scratch, it is possible to rewind a faulty device.

For the manufacture of the product, transformer iron and wire are required. Iron is a plate assembled in the form of a torus and forming a magnetic circuit. You can buy it or take it from old disassembled devices. For example, take plates from industrial transformers and, using a device in the form of a cut ring, roll plates from metal in the form of a donut. Assemble the plates, cover the core with fiberglass and fill with varnish.

The turns of the windings are made of copper wire of the desired diameter. The winding itself does not cause difficulties:

If during the winding process it is necessary to perform a retraction, then the wound wire is broken. A tap is soldered to the place of the break, and the main wire is wound further. The place of withdrawal, as a rule, is carefully isolated. The fastening of the ends of the windings is usually carried out with the help of threads, with which the wires are tied to the surface of the core or the laid wire. It is better to place a strip of wire to be threaded on the "shuttle". It is made of a small plastic profile with slots in the ends for fixing the wire.

Such work requires care and accuracy, especially when winding the primary winding. For the manufacture of several devices, it is advisable to use a machine for winding toroidal transformers. It is difficult to make such a device with your own hands, but it is possible.

DIY winding machine

One possible option is to make a machine equipped with an adjustable stacker and coil counter, using the principle of a bicycle wheel.

The wheel is put on a pin in the wall, while its rim is supplied with a rubber ring. In order to put the core on the rim, you first need to cut it, and then fasten it again, getting a solid circle. Having wound the required length of wire on it, one end of it is connected to a core freely located on the rim. The coil moves along the rim in full circles, as a result of which the wire is laid on the frame. In this case, a bicycle counter is used to count the revolutions.

Creating a more advanced device will require the use of stepper motors with positioning of their position. For this, microcontrollers and an electronic counter are used. Such design requires certain skills in radio electronics.

Winding a transformer with your own hands is a simple task if you prepare for it in advance. People who make various radio equipment or power tools have a need for transformers for specific needs. Since it is far from always possible to purchase certain products, craftsmen often wind toroidal transformers on their own. Those who are trying to wind for the first time face difficulties: they cannot determine the correctness of the calculations, select the appropriate parts and technology. It must be understood that different types are wound in different ways.

Also fundamentally different toroidal devices. The calculation of the toroidal transformer and its winding will be special. Since radio amateurs and craftsmen create parts for power equipment, but do not always have sufficient knowledge and experience to manufacture them, this material will help this category of people deal with the nuances.

Preparation for winding

Necessary materials

Winding materials require careful selection Every detail matters. In particular, you will need:

1. Transformer frame. It is used to isolate the core from the windings and also holds the winding coils. It is made of strong and thin dielectric materials so as not to take up too much space in the intervals (“windows”) of the core. You can use cardboard, microfiber, textolite. The thickness of the material should not exceed 2 mm. The frame is glued using ordinary joinery glue (nitro glue). Its shape and dimensions are completely dependent on the core, the height is slightly greater than that of the plate (winding height).
2. Core. This role, as a rule, is performed by magnetic circuits. The best solution is to use plates from disassembled transformers, since they are made from suitable alloys and are designed for a certain number of turns. Magnetic circuits have a variety of shapes, but most often there are products in the form of the letter "Ш". In addition, they can be cut from various blanks that are available. To determine the exact dimensions, the winding wires are pre-wound.
3. Wires. Here you need to use two types: for winding and for conclusions. The optimal solution for transforming devices is copper wires with enamel insulation (PEL or PE type). They are enough even for power transformers. A wide selection of sections allows you to choose the most suitable option. PV wires are also often used. For output, it is best to take wires with multi-colored insulation so as not to get confused when connecting.
4. Insulating pads. Help to increase the insulation of the winding wire. As a rule, thin and thick paper is used (tracing paper is perfect), which should be laid between the rows. But the paper must be intact, tears and punctures, even the most insignificant ones, must be absent.

How to speed up your workflow

Many radio amateurs have in their arsenal simple special units, with which the winding is done. In many cases, we are talking about simple structures in the form of a small table or table stand, on which several bars with a rotating longitudinal axis are installed. The length of the axis itself must exceed the length of the winding frame by 2 times. A handle is attached to one of the exits from the bars, allowing you to rotate the device.

Coil frames are put on the axis, which are stopped on both sides by pins-limiters (they prevent the frame from moving along the axis).

To convert the current, various types of special devices are used. The CCI toroidal transformer for a welding machine and other devices can be wound 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 just a toroidal device. A toroidal autotransformer (brand Stihl, TM2, TTS4) is a device designed to convert alternating current of one voltage to another. They are used in various linear installations. This electromagnetic device can be single-phase and three-phase. Structurally consists of:

1. Metal disc made of rolled magnetic steel for transformers;
2. rubber gasket;
3. Conclusions of the primary winding;
4. secondary winding;
5. insulation between windings;
6. Shielding winding;
7. An additional layer between the primary winding and the shielding;
8. Primary winding;
9. Insulating coating of the core;
10. toroidal core;
11. fuse;
12. fasteners;
13. Cover insulation.

A magnetic circuit is used to connect the windings.

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

This type of device is used in various audio and video installations, stabilizers, 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 performance of the anchor. In this case, the winding of the toroidal converter is uniform, as is the heat distribution. Due to this arrangement of coils, the converter cools down quickly and even with intensive work does not need to use coolers.

Advantages of a toroidal transformer:

1. Small dimensions;
2. The output signal on the torus is very strong;
3. The windings are short, and as a result, reduced resistance and increased efficiency. But also because of this, a certain sound background is heard during operation;
4. Excellent energy saving performance;
5. Ease of self-installation.

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

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 a source of electric current, and the secondary - to the consumer of electricity. 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. Interlocking with individual windings, this flux creates an electromagnetic force in them, which depends on the number of winding turns. If you change the number of windings, then you can make a transformer to convert any voltage.

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

How to do

Even young electricians can make a toroidal transformer. Winding and calculation are not difficult. We propose to consider how to properly wind a toroidal magnetic circuit for a semiautomatic device:

Considering that 1 turn carries 0.84 volts, the winding circuit of a toroidal transformer is performed according to this principle:

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

Price overview

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

The winding technology and the insulation method are actually very simple and in no case imply any winding, varnished cloth, or anything else. The fact is that with any winding of the transformer core with varnished cloth or other insulators, the inner window of the TORA is instantly filled, since one layer is obtained on the outer side, and 5-10 layers on the inner side, and even uneven ones.
For a long time I was going to write an article about the method of high-quality winding of toroidal transformers. This is quite a long explanation and it is better to show in the photo. Moreover, after winding, the windings do not turn into a wheel, and the transformer itself does not become egg-shaped and the wire consumption is minimal. In view of all this, the efficiency of the transformer is maximum. And what comes out of it, you can see in my amplifier.
I’ll make a reservation right away, we are talking about powerful toroidal transformers. Overall power, which is more than 500 watts. Which are wound with wires from 1 to 3 mm. naturally turn to turn. And, as a rule, the network winding of which lies in the aisles 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 you can if you wish.
What you need for winding:
1) It is necessary to make a stand for winding the toroid, this is done very simply. We take a square piece of chipboard or plywood 10-15mm thick. With dimensions of 200X200mm, we also need two wooden bars 200mm long and with a square of 20X20mm. We need to either glue these two bars in the center of our site, parallel to each other, at a distance of 100 mm between them. Better yet, screw these bars to the site with screws, but with countersunk heads and drown heads in plywood, otherwise they will scratch the table. Now, if you put a toroid on this stand, it will stand firmly and stably.
2) We need a shuttle, I cut the shuttle out of plexiglass 5 mm thick. The width is usually 30-40mm. length 300-400mm. I make end cuts not at an angle, but in a semicircle and process them with a file so that the wire insulation does not deteriorate and even glue with one or two strips of electrical tape again to protect the wire. We wind the wire on the shuttle, it’s not scary if the wire is not enough, you can carefully solder the wire and wind it further. But it is better to calculate all the same, so that the wire would be enough.
3) Now we need material for insulation between layers, it is very simple to find thin cardboard (packaging), for example, I use car speaker boxes. The main thing is that it would not be thick, but not thin material - the thickness of the cardboard is somewhere around 0.5 mm. If it is glossy on one side, then this is also good.
4) We also need thick threads 10-20 number. But at worst, you can also number 40. The winding itself is carried out from itself to the right side.

And now the most important thing is the manufacture of the insulating gaskets themselves between the layers. We need a caliper-compass, 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 150 mm + 20 mm = 170 mm. 170mm./2 = 85mm.
Set the bar to 85mm. and fix with a screw. We will use the bar itself as a compass for drawing circles on cardboard. Why exactly with a barbell, and not with an ordinary compass, which is both easier and more convenient? And everything is very simple, when we draw on cardboard with a sharp and strong end of the rod, then a squeezed groove will remain on the cardboard and it will help us. This groove is very useful for the convenience of bending the inner split circle of our pads. In general, you yourself will understand that a barbell is better than a convenient compass.

And so we draw, the outer circle on cardboard and cut it out with scissors, in principle, the outer circle can be drawn with an ordinary compass.
Next, we measure the inner diameter of the torus, do not add anything, do not subtract, but simply divide in half. For example, diameter 60mm./2 = 30mm. We expose, namely the compasses, by 30mm. fix with a screw and draw the inner 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 TORA is more than 60mm. then also into 16 parts.
Next, we draw another circle with an ordinary compass, which is half the size of the inner one, that is, we expand the compass by 15 mm.
And now we need an even piece, plywood or chipboard, on which we will put our cardboard blank for cutting with the end of a sharp scalpel or knife, applied with a pencil of our parts. You need to cut in a circle from the outer edge of the circle to the center point, no further, otherwise the cardboard will bulge. You need to cut through the cardboard.

Then, with scissors, we cut out the inner circle drawn by us with an ordinary compass. We 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 10 mm. We wind the second strip in one layer on the outer side of the torus with the same overlap. We put both round blanks on the ends of the torus, fasten with a thread in three or four places in a circle. And then we start to wind.

The most dangerous places for breakdown are the outer and especially the inner corners of the TORA 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 circle of the TORA. Then it is necessary to put strips of the same cardboard 10 mm wide under the wire. and 20-30 mm long, where necessary.

On the outside, as a rule, this is not necessary, since the outer side of the workpiece is layered on the edge and well protects the wire from shorting. All marking and cutting of cardboard blanks is done from 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 both folds of the little finger and on the fold of the index finger on the fingers, otherwise there will be huge water blisters.

The fact is that the number of turns will depend on the quality of the iron, but an approximate calculation is done simply, like with a conventional transformer, only we take a coefficient of 20-30.
Well, for example, we measure the height, it = 10 cm.
We measure the wall thickness, it \u003d 5 cm. 10x5 \u003d 50 cm.
25/50=0.5 turns per 1 volt.
220x0.5=110 turns of network winding.
Now we begin to wind the network winding of the transformer, having wound approximately 90 turns, we try to connect it to the network, while measuring the no-load current.
It is not difficult to connect the tip of the wire directly on the shuttle. Gradually winding the wire, we bring the idle current to 50-100 mA and stop winding at this, the resulting number of turns will be real.
Now we divide this real number by 220 and get the real value of the number of turns per 1 volt. And in accordance with this figure, we calculate all the output windings.
Keep in mind that when the transformer is connected to the network, the primary instantaneous inrush current is very large. And in order not to burn the tester, you need to do this: connect the network wire through a closed toggle switch parallel to the toggle switch, turn on the tester, plug the plug into a 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 current surge that transformers with a power of more than 1 kW must be switched on using a soft switching circuit. Moreover, this scheme is very simple.

Fedotov Alexey Gennadievich. (UA3VFS)

Many amateur welders dream of a toroidal transformer. After all, it has long been known that the weight and size characteristics of toroids are much better than those of "Sh" and "P"-shaped transformers. So, with the same characteristics, the toroid is 1.3-1.5 times smaller. The reason why many do not undertake the manufacture of such a transformer is the lack of iron. This article will help you find a way out of this situation.

The design involves the manufacture of a toroidal transformer from a used industrial welding transformer. To do this, it is disassembled, and a donut is assembled from plates measuring 90X450 mm. The required cross-sectional area of ​​the core depends on the number of plates.

In principle, the plates can also be used from the power transformers of old tube color TVs. Transformer TC270, TCA310 are being reassembled. U-shaped cores are broken into plates with a hammer blow, which are straightened on an anvil.
To make a donut, you first need to rivet a hoop of plates with an outer diameter of 260 mm. Then the first plate is inserted inside the hoop, holding it with your hand so that it does not unwind, the second plate is inserted end-to-end to it, and so on, until the inner diameter of the donut is 120 mm. If the bagel is made from TS270 transformers, then the diameter must be recalculated to achieve the required cross-sectional area. You can make two bagels and put them together. In this case, the outer and inner diameters of the donut can be left unchanged.

The edges of the toroid are processed with a file. From electric cardboard we make two rings with an outer diameter of 270 mm, an inner diameter of 110 mm, and a strip 90 mm wide. We apply the blanks from the electric cardboard to the donut and wrap it with tape on a woven basis, you can wrap it with tape from the degaussing loop of kinescopes. The primary winding is wound with a PEV-2 wire with a diameter of 2.0 mm, the number of turns for 220 V is approximately 170. This largely depends on the assembly density of the plates. The exact number of turns can be verified experimentally. If the no-load current is more than 1-2 A, then it is necessary to wind the turns, if less - unwind. The secondary winding is wound with a PV3 wire with a cross section of 15-20 mm, 30 turns. The third winding also contains 30 turns, but wound with MGTF 0.35 wire. Tape insulation is laid between the windings.

After testing the transformer, you can begin to manufacture the control circuit. It is a phase current regulator. The alternating voltage taken from the third winding of the transformer is rectified by a bridge on diodes VD5-VD8. Capacitor C1 is charged by a positive half-wave through resistors R1 and R2. When the voltage on it reaches about six volts, a breakdown occurs of an analog of a low-voltage dinistor assembled on a zener diode VD6 and a thyristor VS3, and the thyristor VS1 opens through the VD3 diode. The capacitance C1 is discharged. The same thing happens with a negative half-wave, only the VD4 diode and the VS2 thyristor open. Resistor R3 serves to limit the current through the analogue of the dinistor.
The adjustment consists in adjusting the required welding current control zone with the resistor R1.

As SA1, you can use any automatic machine for 25 A KD209A can be replaced with KD202V-KD202M or any others for a current of more than 0.7 A and a voltage of more than 70 V. The KUKLA thyristor can be replaced with KU201-KU202. Resistors R1 and R2 - for a power of at least 10 watts. C1 - K50-6. VD1, VD2, VS1, VS2 for current 160-250 A with any voltage group. They must be installed on radiators with a cooling area of ​​at least 100 cm2.

Winding 3 of the transformer is designed for a voltage of 40 V, and the secondary, if necessary, can be increased.