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How to wind a transformer: step by step instructions. How to wind a transformer: step by step instructions Finishing the manufacture of a transformer with your own hands

Even a novice radio amateur can independently make a transformer from 220 to 12 Volts. This device belongs to AC machines, the principle of operation is vaguely reminiscent of an asynchronous motor. Of course, you can buy a ready-made transformer, but why spend money, especially in cases where there is enough steel for the core and wire for the coils on hand? It remains only to study a little theory and you can start manufacturing the device.

How to choose materials

In the manufacture of a step-down transformer from 220 to 12 volts, it is important to use high-quality materials - this will ensure high reliability of the device, which you will subsequently assemble on it. It should be noted that the transformer allows you to make an isolation from the network, so it can be installed to power incandescent lamps and other devices that are in rooms with high humidity (showers, basements, etc.). When making the coil frame yourself, you need to use durable cardboard or textolite.

It is recommended to use domestic wires, they are much stronger than Chinese counterparts, they have better insulation. You can use wire from old transformers, as long as there is no damage to the insulation. To isolate the layers from each other, you can use both plain paper (preferably thin) and FUM tape, which is used in plumbing. But for the insulation of the windings, it is recommended to use a fabric impregnated with varnish. It is imperative to apply insulation over the windings - lacquer fabric or cable paper.

How to carry out the calculation?

Now that all the materials are ready, you can calculate the transformer from 220 to 12 volts (for a lamp or any other household appliance). In order to calculate the number of turns of the primary winding, you need to use the formula:

N = (40..60) / S.

S is the cross-sectional area of ​​the magnetic circuit, the unit of measurement is sq. see In the numerator there is a constant - it depends on the quality of the core metal. Its value can range from 40 to 60.

Example calculation

Let's say we have the following settings:

  1. The window is 53 mm high and 19 mm wide.
  2. The framework is made of textolite.
  3. Upper and lower cheeks: 50 mm, frame 17.5 mm, therefore, the window has a size of 50 x 17.5 mm.

Next, you need to calculate the diameter of the wires. Let's say you want the power to be 170 watts. In this case, the current on the network winding will be equal to 0.78 A (we divide the power by the voltage). In the design, the current density turns out to be 2 A/sq. mm. With these data, you can calculate that you need to use a wire with a diameter of 0.72 mm. It is also allowed to use 0.5 mm, 0.35 mm, but the current will be less.

From this we can conclude that to power radio equipment on lamps, for example, you need to wind 950-1000 turns for a high-voltage winding. For glow - 11-15 turns (the wire only needs to be used with a larger diameter, depending on the number of lamps). But all these parameters can be found empirically, which will be discussed later.

Calculation of the primary winding

When making a transformer from 220 to 12 Volts with your own hands, you need to correctly calculate the primary (network) winding. And only after that you can start doing the rest. If you incorrectly make the calculation of the primary, then the device will start to warm up, buzz strongly, it will be inconvenient to use it, and even dangerous. Let's say a wire with a cross section of 0.35 mm is used for winding. One layer will fit 115 turns (50 / (0.9 x 0.39)). The number of layers is also easy to calculate. To do this, it is enough to divide the total number of turns by how much fits in one layer: 1000/115 = 8.69.

Now you can calculate the height of the frame along with the windings. The primary one has eight full layers, plus insulation (0.1 mm thick): 8 x (0.1 + 0.74) = 6.7 mm. To prevent high-frequency interference, the network winding is shielded from the rest. For the screen, you can use a simple wire - wind one layer, insulate it and connect the ends to the body. It is also allowed to use foil (of course, it must be strong). In general, the primary winding of our transformer will take 7.22 mm.

A simple way to calculate secondary windings

And now about how to calculate the secondary windings, if the primary is already available or ready. You can use such a transformer 220 to 12 volts for LED strips, just be sure to install a voltage stabilizer. Otherwise, the brightness will be inconsistent. So what do you need to calculate? A few meters of wire and only wind a certain number of turns over the primary winding. Let's say you wound 10 (and you don't need more, that's enough).

Next, you need to assemble the transformer and connect the primary winding to the network through a circuit breaker (for safety reasons). Connect a voltmeter to the secondary winding and click the machine. See what voltage value the device shows (for example, it showed 5 V). Therefore, each turn gives out exactly 0.5 V. And now you just focus on what voltage you need to get (in our case it is 12 V). Two turns is 1 volt of voltage. And 12 V is 24 turns. But it is recommended to take a small margin - about 25% (which is 6 turns). Nobody canceled the voltage loss, so the 12 V secondary winding should contain 30 turns of wire.

How to make a coil frame

It is extremely important in the manufacture of the frame to achieve a complete absence of sharp corners, otherwise the wire may be damaged, an interturn circuit will appear. On the cheeks, you need to take away the places to which the output contacts from the windings will be attached. After the final assembly of the frame, it is necessary to round off all sharp edges with a needle file.

Plates made of transformer steel should fit into the holes as tightly as possible, free play is not allowed. For winding thin wires, you can use a special device with a manual or electric drive. And thick wires need to be wound exclusively by hand without additional devices.

Rectifier block

By itself, a 220 to 12 volt transformer will not produce direct current; additional devices must be used. This is a rectifier, filter and stabilizer. The first is performed on one or more diodes. The most popular scheme is the bridge. It has a lot of advantages, among the main ones are minimal voltage losses and high quality of the output current. But it is allowed to use other rectifier circuits.

As filters, a conventional electrolytic capacitor is used, which allows you to get rid of the remnants of the variable component of the output current. A zener diode installed at the output allows you to keep the voltage at the same level. In this case, even if there are ripples in the 220 V network and in the secondary winding, the voltage at the rectifier output will always have the same value. This is good for the devices that connect to it.

The voltage in the household electrical network, as you know, is 220 or 380 V. However, such a power supply is not “digestible” for all appliances.

Some require a voltage of only 12 V and such devices have to be connected through a special device - a transformer.

How the 220 transformer changes to 12 volts and how you can assemble this device yourself - our conversation will be devoted to this topic.

So, a transformer is an electrical device that converts electrical energy, namely, a change in voltage. If the output, that is, the changed, voltage is less than the input, the transformer is called step-down. If, on the contrary, as a result of the conversion, the voltage increases, then the transformer is called step-up.

Step-down transformer 220/12

Why do you need a step-down transformer in everyday life? Low-voltage electricity powers laptops and mobile phones, but they are always sold with transformers, colloquially referred to as "power supplies." Another thing is low-voltage lighting, which uses halogen or ultra-modern LED lamps.

Today, many people want to acquire one - because of a number of advantages:

  • there is no danger of electric shock and fire (it is especially desirable to equip bathrooms and other rooms with high humidity with such lighting);
  • compared to traditional low-voltage lamps, they are much more economical: for example, LEDs at the same luminosity consume 15 times less energy than a 220 V incandescent lamp;
  • low-voltage lamps last much longer than 220 V analogues: LED manufacturers promise 50 thousand hours of operation and even give a guarantee for 3 years.

To connect such a lighting system, the transformer has to be purchased separately. But in the simplest version, you can do it yourself.

Principle of operation from 220 to 12 V

The simplest transformer consists of two coils of wire with different numbers of turns. One coil - it is called the primary - is connected to an alternating current source, which is usually the household power supply.

As you know, a conductor through which an alternating current flows becomes a generator of an electromagnetic field, and if it is also wound into a coil, then the field is denser. Moreover, since the current is variable, then the electromagnetic field is the same.

Further, in strict accordance with the law of electromagnetic induction, an alternating electromagnetic field generated by the primary coil induces an EMF in the secondary coil. It is important to understand that EMF appears precisely when the number or intensity of field lines penetrating the conductor changes.

The principle of operation of the voltage converter

That is, either the field must be constantly changing (such a field is called variable), or the conductor must move in it (this is what happens in electric generators). Hence the conclusion: if the primary coil is connected to a DC source, the transformer will not function.

In order for the primary coil to have a high inductance, as well as to concentrate the magnetic flux inside the coils, they are wound on a ferromagnetic steel core.

In the absence of such a core, the transformer connected to the household network will not only not function, but will simply burn out.

How the voltage at the output of the transformer changes depends on the ratio of the number of turns in the coils. If there are fewer of them in the secondary coil, the voltage will be reduced, while it will be as much less than the input voltage as the number of turns in the secondary coil is less than in the primary. That is, for example, if the primary coil consists of 2 thousand turns, and the secondary coil consists of 1 thousand turns, and at the same time a voltage of 220 V is applied to the primary coil, then an EMF of 110 V will appear in the secondary.

Voltage transformer

Accordingly, in order to convert the voltage from 220 V to 12 V, the number of turns in the secondary coil must be 220/12 = 18.3 times less than in the primary.

Since the power from one coil is transferred to another almost in full (the proportion of losses depends on the efficiency of the transformer), and the power is the product of voltage and current strength (W \u003d U * I), the opposite picture is observed with the current strength in the coils: how many times the voltage in the secondary coil decreases, by the same amount the current strength in it will be greater than in the primary.

Therefore, the secondary coil in a step-down transformer must be wound with a thicker wire than the primary.

Assembly order

The design of a transformer begins with the calculation of its parameters. We set the following values:

  1. Input voltage: 220 V.
  2. Output voltage: 12 V.
  3. The cross-sectional area of ​​​​the core: we accept S = 6 square meters. cm.

N = K*U/S,

  • N is the number of turns;
  • K - empirical coefficient. You can take K \u003d 50, but in order to avoid saturation of the transformer, it is better to take K \u003d 60. This will slightly increase the number of turns and the transformer itself will become a little larger, but losses will decrease.
  • U is the voltage in the winding, V.
  • S - cross-sectional area of ​​the core, sq. cm.

Do-it-yourself car voltage converter 12-220 V

Thus, in the primary coil, the number of turns will be:

N1 \u003d 60 * 220/6 \u003d 2200 turns,

in the secondary:

  • copper wire enclosed in silk or paper insulation: for the primary coil - with a cross section of 0.3 square meters. mm, for the secondary - 1 sq. mm (when the current in the load circuit is less than 10 A);
  • several cans (tin will be used to make the core);
  • thick cardboard;
  • varnished cloth (tape insulation);
  • paraffin-impregnated paper.

Power inverter circuit

The manufacturing process of the transformer looks like this:

  1. 80 strips of 30x2 cm in size must be cut out of the cans. The tin must be annealed: it is placed in an oven, heated to a high temperature, and then left to cool with the oven. The essence of the treatment is precisely in the gradual cooling, as a result of which the steel softens and loses its elasticity.
  2. Next, the plates must be cleaned of soot and varnished, after which each of them is glued on one side with thin paper - cigarette or paraffin.
  3. From thick cardboard it is necessary to make a frame for windings, consisting of a trunk and cheeks. It should be wrapped in several layers of paraffin-impregnated paper, you can also use drawing tracing paper.
  4. On the frame turn to turn you need to wind the wire. To speed up this operation, you can make a simple winding machine: put the frame on a steel bar, insert the latter into the grooves made in two boards, and then bend one end in the form of a handle. When laying the wire, every two or three turns, you need to lay paper with paraffin - for insulation. When the winding of the primary coil is completed, you need to fix the ends of the wire on the cheeks of the frame and wrap the coil with paper in 5 layers.
  5. The winding direction of the secondary coil must match the direction of the primary coil.

It is possible to make a transformer capable of lowering the voltage to both 12 and 24 volts, which are required by some lamps and other devices. To do this, you need to wind 240 turns on the secondary coil, but from the 120th make a conclusion in the form of a loop.

  1. Having fixed the conclusions of the secondary coil on the second cheek of the frame, it (the coil) is also wrapped with paper.
  2. Half the length of the tin plates must be inserted into the coil, after which they go around the frame so that the ends are connected under the coil. It is obligatory to have a gap between the plates and the frame.
  3. Now the home-made transformer needs to be fixed on the base - a fragment of a wooden board with a thickness of about 50 mm. For fastening, use staples that should cover the bottom of the core.

At the end, the ends of the windings are brought to the base and equipped with contacts.

Connection

To connect the transformer, you need to connect the load to the contacts of the secondary winding, and then apply the voltage of the household mains to the contacts of the primary coil.

The connection scheme to the secondary winding depends on what voltage you need to get at the output: if 24 V - we connect to the extreme terminals, if 12 V - to one of the extreme terminals and the output from the 120th turn.

Wiring diagram for 12V spotlights through a transformer

If the consumer operates on direct current, a rectifier must be connected to the terminals of the secondary coil. In this capacity, a diode bridge is used, equipped with a capacitor (it plays the role of a filter, smoothing out ripples).

Choice of ready solution

Today, a transformer with any parameters can be found in electronics or welding equipment stores. Along with traditional devices, new generation devices are also sold - inverter transformers. In such devices, the current first passes through the rectifier before entering the primary winding.

And then - through an inverter assembled on the basis of a microcircuit and a pair of key transistors, again turning the current into alternating, but with a much higher frequency: 60 - 80 kHz instead of 50 Hz. This transformation of the input current can significantly reduce the size of the transformer and greatly reduce losses.

Box with step-down transformer YaTP 0.25

The transformer should be selected according to the following characteristics:

  1. Input voltage and current frequency: the characteristics of the device must indicate "220 V" or "380 V" if it is purchased for a 3-phase network. The frequency should be 50 Hz. There are transformers that are designed, for example, for a frequency of 400 Hz or more - when connected directly to a household power supply, such a device will burn out.
  2. Output voltage and current type: everything is clear with the output voltage - it must correspond to the voltage for which the electrical consumer is designed. But at the same time, it is important not to forget to look at what current the transformer produces. Many of them today are equipped with rectifiers, as a result of which the output current is not alternating, but constant.
  3. Rated power: it is very important that the maximum power with which the transformer can operate (it is called the nominal power) is approximately 20% more than the load power. If this margin is not available, and even more so if the rated power of the transformer is less than the power consumed by the load, the converter windings will overheat and burn out.

Transformers are:

  1. open: equipped with a non-hermetic casing, inside which moisture and dust can get. But there is the possibility of forced cooling with a fan.
  2. Closed: equipped with a sealed housing with a high degree of moisture and dust protection, so they can be installed in rooms with high humidity.

Models with an aluminum body can be used outdoors (street lighting with LED lamps, advertising). Due to the inability to apply forced cooling, the power of closed transformers is limited.

Transformer OSM-1-04

There are also transformers

  • rod: coils can only be placed in a vertical position;
  • armored: work in any position.

The cost of transformers varies greatly and primarily depends on the power. Here are some examples:

  1. YATP-0.25. A device with a rated power of 250 W, equipped with a housing. The cost is 1700 rubles.
  2. OSM-1-04. Can work with input voltage 220 V or 100 - 127 V, output is 12 V. There is no case. Cost - 2600 rubles.
  3. OSZ-1 U2 220/12. Transformer for 1 kW. It costs 5300 rubles.
  4. TSZI-4.0. Converter with housing, rated power is 4 kW. Input voltage - 220 or 380 V, output - 110V or 12 V. Cost - 10.5 thousand rubles.

Portable transformer in the case TSZI-2.5 kW. can be connected to both 220 V and 380 V, the output is 12 V. The cost is 13.9 thousand rubles.

Related video

In this article I want to talk about winding a transformer for a powerful 12-220 automotive inverter.
This transformer was wound to work in conjunction with a Chinese automotive voltage converter board.

Such inverters have recently found wide popularity due to their light weight, compact size and low price, an indispensable thing if you need to connect network loads in a car that need a 220-volt power source, and even alternating current with a frequency of 50 Hz, the inverter can fully provide such conditions. A few words about the converter itself, its approximate circuit is shown below.

The diagram is provided only to show the principle of operation, but this thing works in a rather simple way.

Two generators, both TL494, the first of which operates at a frequency of about 60 kHz and is designed to drive the power transistors of the primary circuit, which in turn drive the power pulse transformer. The second generator is tuned to a frequency of about 100 Hz and drives high-voltage power transistors.

The rectified voltage after the secondary winding of the transformer is supplied to high-voltage field devices, which, operating at a given frequency, turn direct current into alternating current - with a frequency of 50 Hz. The shape of the output signal is a rectangular, or more correctly speaking, a modified sine wave.

Our transformer is the main power component of the inverter and its winding is the most crucial moment.

The primary winding is in the form of a bus (unfortunately I can’t indicate the exact length), the width of this bus is about 24mm, the thickness is 0.5mm.

Operating frequency and type of master oscillator.
Inverter input voltage
Overall dimensions and type (brand) of the transformer core

First, the primary winding was wound. Two shoulders were wound with one solid tape, the number of turns is 2x2 turns. After winding the first two turns, a tap was made, then the remaining two turns were wound.

On top of the primary winding, it is imperative to put insulation, in my case, ordinary electrical tape. The number of insulation layers is 5.

The secondary winding is wound in the same direction as the primary, for example, clockwise.


To obtain a 220 Volt output voltage, in my case, the winding contains 42 turns, moreover, the winding of the winding was done in layers - the first layer of 14 turns, on top of two more layers that contain exactly the same number of turns.
The winding was wound with two parallel strands of 0.8 mm wire, an example of the calculation is shown below.

After all this, we assemble the transformer - we fasten the halves of the core using any electrical tape or adhesive tape, I do not recommend glue, since it can penetrate between the halves of the ferrite and form an artificial gap, which will lead to an increase in the quiescent current of the circuit and to the combustion of the input transistors of the inverter, so that you need to pay a lot of attention to this factor.




In operation, the transformer behaves very calmly, the current consumption without load is around 300 mA, but this is taking into account the consumption of the high-voltage part.

The maximum overall power of the core that I used is around 1000 watts, of course the winding data will be different depending on the type of core used. By the way, winding can be done both on W-shaped cores and on ferrite rings.

On this basis, exclusively all transformers are wound in both industrial and home-made pulse voltage converters, by the way - the designs of home-made inverters are very often repeated by radio amateurs in projects of subwoofer amplifiers and not only, so I think the article was interesting for many.

To convert the voltage from low to high, and vice versa, step-up or step-down transformers are used. They are electrical machines with high efficiency and are used in many areas of technology.

Is it possible to make a transformer with your own hands at home? What materials and devices should be used in the production of such work? In order to properly assemble a step-up transformer, it is necessary to accurately complete the entire technological process and recommendations for assembling this type of electrical machines, which will be given below.

What you need to know and have for self-winding a transformer?

If there is a need for this device, then you need to have answers to the following questions:

  1. Why do you need a transformer: to increase or decrease the voltage?
  2. What voltages should be at the input and output of the device?
  3. Does the device operate on AC 50 Hz or should it be rated for a different frequency?
  4. What will be the power of a homemade transformer?

After receiving the answers, you can start buying the necessary materials. To do this, they buy tape insulation (varnished fabric) for the future transformer, a core for it (if there is a suitable power from an old, burned-out TV, then you can use it), the required amount of wire in enamel insulation.

For winding windings, you can make a simple winding machine. To do this, take a board 40 cm long and 100 mm wide. Two bars of 50 x 50 millimeters are attached to it with screws so that the distance between them is 30 cm. They must be drilled at the same height with a drill with a diameter of 8 mm. A rod is inserted into these holes, on which the coil of the future transformer is first put on.

On the one hand, a thread should be cut to a length of 3 cm on the pin and a handle is fixed to it with the help of two nuts, which rotates the rod with the coil when winding the transformer.

The dimensions of the winding machine described above are not critical - it all depends on the size of the core. If it is made of ferroalloys and has the shape of a ring, then the winding will have to be done manually.

A preliminary calculation of the number of turns can be made based on the required power of the device. For example, if you need a step-up transformer from 12 to 220 V, then the required power of such an apparatus will be in the range of 90-150 watts. We choose an O-shaped type of magnetic circuit from an old TV or buy a similar one in a store. Its cross section must be selected according to the formula from the electrical reference book. In this example, it is approximately 10-11 cm².

The next step is to determine the number of turns per volt, which in this case is 50 Hz divided by 10-11, something like 4.7-5 units per volt. Now you can calculate the number of turns of the primary and secondary windings: W1 \u003d 12 X 5 \u003d 60 and W2 \u003d 220 X 5 \u003d 1100.

Then it is necessary to determine the currents in them: I1 = 150:12=12.5 A and I2=150:220=0.7 A.

Let's find the sections and diameters of the wires of the windings according to the formulas from the reference book.

The step-up transformer is pre-calculated, you can start winding it.

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Coil cage manufacturing workflow

They are made from cardboard. The inner part should be slightly larger than the core rod, and the cheeks should freely enter the transformer window. When using an O-shaped core, two coils must be made, and when using W-shaped plates, one.

When using a round core from LATRA, it is pre-wound with tape insulation and then the wire is directly wound on it, distributing the required number of turns around the entire ring. After the winding of the primary winding is completed, it is covered with 3-4 layers of varnished cloth and then the turns of its secondary part are wound on top. After that, the wire is closed with tape insulation, having previously brought out the ends of the windings. When using conventional magnetic circuits, the coil frame is done as follows:

  • a sleeve pattern is made with lapels on the sides of the ends;
  • cheeks are cut out of cardboard;
  • roll the body of the coil along the marked lines into a small box and seal it;
  • the upper parts (cheeks) are put on the sleeve and, having folded back the lapels, they are glued.

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Production of step-up transformer windings

The coil is put on a wooden block with the dimensions of the magnetic core rod. A hole for the winding rod is pre-drilled in it. This part is inserted into the machine, and the winding manufacturing process begins:

  • 2 layers of varnished cloth are wound on the coil;
  • one end of the wire is fixed on the cheek and the handle of the machine begins to slowly rotate;
  • the turns must be laid tightly, isolating each wound layer from the adjacent varnished cloth;
  • after the primary winding coil is wound, the wire is cut off and its second end is fixed on the cheek next to the first;
  • Insulating tubes are put on both terminals, and the outside of the winding is covered with insulation;
  • In the same sequence, the coil of the secondary winding is wound.

The household electrical network has a voltage of 220 volts, which most electrical appliances are designed for. In this case, it often becomes necessary to power individual consumers - low-voltage heaters, halogen lamps and power other devices (LED strips, etc.) designed for alternating current. This is provided by a transformer, which is small in size and has a one-piece housing.

The device can be picked up and purchased in retail chains, and, if necessary, made by hand.

A standard step down transformer consists of 2 windings (primary and secondary) wound around a ferromagnetic core with copper wire. The primary is connected to the network, and the secondary to the load. Principle of operation such a device is as follows:

  1. The voltage applied to the primary winding generates an alternating field around the core.
  2. Magnetic induction, when connected to a load, creates voltage in the turns of the secondary winding, and energy will be supplied from the primary winding, which will be transferred to the secondary circuit.

The value of the output voltage is affected by the ratio and the number of turns of each winding. By adjusting this indicator, you can achieve any current value on the secondary winding, and get both step-down and. In this case, it must be borne in mind that the device connected to a 220 V household network will give out an alternating voltage, which, if necessary, can then be converted by a rectifier.

At present, electronic-type step-down devices are widely used, made based on semiconductors, the work of which is complemented by an integrated circuit. They have certain advantages in the form of small size, high efficiency, low weight, lack of heating and noise, the possibility of adjusting the current, short circuit protection. But the traditional transformer continues to be actively used because of the reliability and simplicity of design.

Choice of ready-made solution, criteria

Electrical and electronics stores offer ready-made household transformers for various needs. Choosing the right device should be guided by the following criteria:

  1. Input voltage parameters. The case of the device must be marked with 220 or 380 V. In this case, a household version for a 220 volt network is required.
  2. The input voltage parameters, which must correspond to 12 V.
  3. Power. To do this, pre-calculate the total load that will be powered through the transformer. This indicator of the device must exceed the calculated value by at least 20%.
With the help of a transformer that converts 220 to 12 V, you can save a lot on protective materials and cables by implementing a household lighting system on its basis using halogen lamps and LED strips. This is a safe circuit in terms of electric shock, and is also protected from voltage surges and short circuits. Such systems eliminate the possibility of fires.

In the video, a story about the purchase of a turnkey solution

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