When building a receiver, amplifier or other radio equipment, a radio amateur has to deal with the work of reworking an old or manufacturing a new transformer. Radio amateurs who begin such work for the first time often do not quite understand how to wind, what material to choose and how to test the manufactured transformer. Information on these issues, gleaned from magazine articles and books, is usually insufficient, and the radio amateur has to do most of the work, relying on his ingenuity or resorting to the help and advice of a more experienced comrade. On this page, recommendations will be given for the independent manufacture of a network transformer.

WINDING DEVICES

In factories with mass serial or in-line production, transformers are usually wound on special, often automated machines. It is difficult for radio amateurs, of course, to rely on a special winding machine, and therefore the winding of transformers is usually done either directly by hand or using simple winding devices.
Consider how you can make simple winding devices from improvised materials and using ordinary tools.
The simplest such device is shown in Fig. 1. It consists of two racks / (or a metal bracket) mounted on a board 2, and an axis 3 of a thick (diameter 8-10 mm) metal bar, threaded through the holes in the racks and bent at one end in the form of a handle.
To wind the wire on the finished frame 4, a wooden block 5 is made, slightly smaller in size than the frame window. A hole is drilled in the block for fitting it onto the axle. The frame is put on a block, which is then placed on the axis and fixed there with a pin 5. In order for the frame not to hang out and move out of the block, a sealing wedge 7 made of hard cardboard or thin plywood must be inserted between them. In order to avoid axial play during winding, which is very important for even laying of turns, it is necessary to put on free sections of the axis between the block and the uprights pieces of tubes 8, which can be made from metal sheets by wrapping them around axis 3.
To remove the wound frame, you need to remove the pin 5 and pull out the axle 3.
A more convenient and reliable winding device is made from a hand drill / (Fig. 2), which must be clamped in a vise 2 or attached to the table so that nothing interferes with the free rotation of the drill handle. A metal rod 3 is clamped into the drill chuck, on which a block with a frame is mounted. It is best to cut a rod with a diameter of 4-6 mm, and then the block with the frame can be clamped between two nuts 4. In this case, you can do without the block, clamping the frame with two cheeks made of plywood or textolite with holes in the center.
As a winding device, it is also convenient to use a ready-made machine for textile spools, a film winder, a telephone inductor, etc. A film winder is especially convenient (after a slight alteration), since it is made firmly and has a soft, backlash-free move. Its alteration consists in replacing a short roller with a lock for reels of film with a long axis with threads and winglets for fixing various frames.

No less important for winding work than the winding machine itself is the unwinding device, on which the coil with wire or the frame of the old transformer is put on, the wire of which is used for new winding. So that the insulation of the unwound wire does not deteriorate, and also that there are no shocks (which is important when laying the turns in an ordinary way), the wire must go completely evenly.

The simplest device for unwinding wire is shown in Fig. 3. This is an ordinary metal bar /, threaded through the holes of wooden racks 2, mounted on a board 3. The manufacture of a wooden block for the frame of the unwinding coil 4 is not necessary in this case. In order for it not to beat or jump during unwinding, it is possible to roll tube 5 of the required diameter from thick cardboard or paper, pass a rod through it and insert it tightly enough into the frame window.
It is better, however, to make a special unwinding device, shown in Fig. 4. From a strip of mild steel or other suitable material, a bracket / is bent, which is attached to board 2 (or table). In vertical racks, brackets make holes (5-6 mm in diameter) with threads (M-5 or M-6 thread), into which bolts 3 sharpened from the ends to a cone are screwed. hairpin 4, from the ends of which shallow holes (3-4 mm) are drilled. The cones and the stud are completed with appropriate nuts (preferably with wing nuts) 5 and cheeks 6 for clamping the coil or frame with wire.

Very important in the winding process is the ability to accurately count the number of turns. A simple, but requiring special attention, method is the oral count of each revolution (or after one revolution) of the machine handle. If the winding must contain a large number of turns, then it is more convenient, after counting a hundred turns, to make a mark on paper (in the form of a stick), then summing up all the marks. In a machine with a gear transmission, the gear ratio is taken into account, which should always be remembered.
It is much better to use a mechanical counter, which can be used as a bicycle speedometer or a counting mechanism from an electric meter, water meter, etc.
The articulation of the counter with the machine can be done using a flexible roller (a piece of thick-walled rubber tube) connecting the axis of the counter with the axis of the machine (Fig. 5a). In this case, every time you install a new frame, you have to disconnect the joint of the axles, removing the flexible roller, and after installing the new frame, put it on again. A more convenient, but also more complicated way of articulation is that the counter is connected to the machine through a pair of identical gears (Fig. 5b). With this method, the counter is linked to the machine all the time.

FRAMEWORK

The frame of the transformer (or inductor) is needed to isolate the windings from the core and to keep the windings, insulating gaskets and leads in order. Therefore, it must be made of sufficiently strong insulating material. At the same time, it must be made of a sufficiently thin material so as not to take up much space in the core window. Usually, the material for the frame is thick cardboard (pressboard), fiber, textolite, getinaks, etc. Depending on the size of the transformer or inductor, the thickness of the sheet material for the frame is taken from 0.5 to 2.0 mm.
For gluing the cardboard frame, you can use office universal glue or ordinary carpentry glue. Nitroglue (enamelite, hercules) should be considered the best glue with good moisture resistance. Getinax or textolite frames are usually not glued, but are assembled “in a castle”.

The shape and dimensions of the frame are determined by the dimensions of the core, after which its parts are drawn and then cut. If transformer plates with a middle core notch are used, then the height of the frame is made a few millimeters less than the height of the window so that the core plates can be inserted without difficulty. To avoid errors, the dimensions of the core plates must be carefully measured (if they are unknown) and a sketch should be drawn on paper with the dimensions of the individual parts of the frame. It is especially important to coordinate the individual parts of the frame when assembling it “into the castle”. The ratios of the dimensions of the frame and the core plates for different types of plates are given in Fig. 6.
A conventional frame for a transformer can be made like this. First, the cheeks of the frame are cut out and a sleeve with lapels on the end sides is cut out according to Fig. 7. Having made cuts at the folds, the pattern is rolled up into a box, with side / glued to side 5. After that, both cheeks are put on the sleeve. Then you need to bend the lapels of the sleeve and, spreading the cheeks to the edges of the sleeve, glue the lapels to the outer planes of the cheeks. In the corners on the outer side of the cheeks, you can glue pieces of the same cardboard from which the frame sleeve was made. If the glue is strong enough and reliable, then the sleeve can be made without lapels, gluing the cheeks directly on the edges of the sleeve.

A prefabricated frame is more difficult to manufacture, but it has great strength and does not require gluing. The details of the prefabricated frame are shown in Fig. 8. They are made in the following way. The dimensions from the sketch are transferred by marking to a sheet of material (textolite, getinax, fiber). If the material is not too thick, then the parts are cut out with scissors. Then the grooves are cut into them with a file. In the cheeks /, after drilling several holes in them, windows are cut out. After that, having laid out the parts on the table, sides 2 and 3 of the sleeve are adjusted so that when assembling the frame, all the cuts and protrusions of the “lock” converge. When marking and manufacturing parts 2, one of them can have a “lock” part of a much larger size (the outlines are shown by dotted lines in Fig. 8) to place contacts or petals on it for soldering the winding leads. In order not to confuse the parts, they should be numbered before assembly. The order of assembly of the frame is clear from Fig. nine.

Immediately after making the cheeks, it is better to pre-drill holes for the leads in them “in reserve”. When assembling the frame or gluing the cheeks, it is necessary to take into account which side of the transformer (or both) and on which side of the cheeks the leads will be made in order to correctly position the sides of the cheeks with holes for the leads. It is necessary to pay attention to the fact that the sides of the cheeks with holes in the case of a square core section are not closed by the core plates.
The finished glued or assembled frame must be prepared for winding, for which it is necessary to round the corners of the sleeve and cheeks with a file, and also remove the burrs. It is useful (but not necessary) to coat or impregnate the frame with shellac, bakelite, etc.

INSULATING GASKETS

In some cases, a large voltage is formed between adjacent rows of transformer windings, and then the insulation strength of the wire itself is insufficient. In such cases, between the rows of turns, it is necessary to place insulating pads made of thin thick paper, tracing paper, cable, capacitor or tissue paper. The paper should be flat and when viewed through the light, it should not have visible pores and punctures.
The insulation between the windings in a transformer must be even better than between the rows of turns, and the better the higher the voltage. The best insulation is varnished cloth, but in addition to it, thick cable or wrapping paper is also needed, which are also laid in order to level the surface for ease of winding the next winding on top. One layer of varnished cloth is always desirable, but it can be replaced with two or three layers of tracing paper or cable paper.
Having measured the distance between the cheeks of the finished frame, you can proceed to the preparation of insulating paper strips. In order to prevent the extreme turns of the winding from falling between the edges of the strips and the cheeks, the paper is cut into somewhat wider strips than the distance between the cheeks of the frame, and the edges are cut by 1.5-2 mm with scissors or simply bent. When winding, notched or bent strips cover the extreme turns of the winding. The length of the strips should provide overlapping of the winding perimeter with an overlap of ends by 2-4 cm.

To isolate the leads, places of soldering and winding taps, pieces of cambric or vinyl chloride tubes and pieces of varnished cloth are used.
To tighten and secure the beginning and end of thick windings (filament and output), pieces (10-15 cm) of twill tape or strips cut from varnished fabric and folded three or four times for strength are prepared.
If the outer row of the winding comes close to the core, then rectangular plates are cut out of thin sheet textolite or cardboard, which are inserted between the winding and the core after the transformer is assembled.

WINDING AND OUTPUT WIRES

The windings of transformers that a radio amateur has to deal with are most often made with enamel-insulated wire of the PE or PEL brand.
In power transformers, only PE wire is used for mains and step-up windings, and for the filament windings of lamps, the same wire or, with a large diameter (1.5-2.5 mm), a wire with double paper insulation of the PBD brand.
The conclusions of the ends and taps from the windings made with a thin wire are made with a wire of a slightly larger cross section than the winding wire. For them, it is better to take a flexible stranded wire with elastic insulation (for example, vinyl chloride or rubber). If possible, it is advisable to take wires with different colors, so that you can easily recognize any conclusion from them later. Conclusions from overcasting, made with a thick wire, can be made with the same wire. Pieces of thin-walled insulating tubes must be put on the ends or taps of these windings. The lead wires must be of such length that they can be freely connected to the elements of the circuit or to the joint bar (comb).

WINDING

The coil with the wire intended for the next winding is clamped between the removable cheeks of the threaded pin of the unwinding device. The hairpin with the coil is installed in the cones of this device (Fig. 4). Depending on the diameter of the wire, the pressure of the cones and the degree of braking of the unwinding coil are adjusted.
The coil must be clamped so that it does not hit during unwinding, since the success and ease of laying the wire coil to coil depend on this. The unwinding device is located in front of the winding machine no closer than 1 m (further is better).
The prepared frame of the transformer is clamped between two cheeks loosely mounted on a hairpin. The pin is then inserted into the drill chuck or clamped onto the winder shaft. The frame, as well as the coil with wire, must be well centered so that it rotates evenly during winding and does not hit. The clamping brushes must be positioned in such a way that they do not close the openings for the leads in the frame.
It is necessary to install the coil with wire on the unwinding device and the winding machine on the table as shown in Fig. 10. The wire should go from the top of the coil to the top of the transformer frame. The machine or drill is located above the table at such a height that there is a distance of 15-20 cm between the axis of the machine and the plane of the table; then, when winding, the left hand can be freely placed on the table without interfering with the rotation of the machine with the frame.
Before you start winding, you need to prepare insulating gaskets, lead wires, an insulating tube for leads, a sheet of paper and a pencil for marking when counting turns, if there is no counter, scissors for cutting gaskets, a piece of fine sandpaper for stripping insulation and a heated soldering iron for soldering leads. You yourself need to freely sit down against the table (workbench) and practice hand interactions. With the right hand, it is necessary to rotate the winding machine so that the wire lies on the frame from above, and with the left hand, hold and pull the wire, directing its movement so that it lies evenly round to round (for this, the left hand must be placed on the table under the axis of the machine or attachment by pulling it forward as far as possible). The farther from the frame to direct the wire, the more accurately and easier the wire fits.

The frame, verified and fixed on a machine or drill, is wrapped with a thin paper strip. To strip
held, it can be slightly glued.
The lead conductor or the end of the wound wire itself can be fixed in two ways. If the wire is thin, then the conclusion is made with a different, flexible wire. Such a lead must be long enough so that, by passing it through a hole in the frame, it is possible to wrap it (with one turn) around the frame sleeve. The stripped end of the wound wire is soldered to the tip of the lead wire that has been previously stripped and tinned by 2-3 mm, and, having isolated the place of soldering with a piece of paper or varnished cloth folded in half, winding is started (Fig. 11, a). The insulating pad is pressed when winding with subsequent turns (Fig. 11.6). The output threaded into the frame hole must be wrapped several times around the axis (stud) of the winding machine or tied to it so that it does not pull out of the frame during further winding. For greater reliability, the conclusions can be tied to the sleeve with several turns of strong thread. Another way is that the output wire, after passing it through the holes in the cheek of the frame, is captured by a strip of cushioning paper, the edge of which is bent under the wire (Fig. 11, c). Then a strip, which should have the width of the frame, wraps around the sleeve and presses the lead wire. At the same time, under the strip (at the end of the lead wire), you need to put an insulating pad, which will then cover the place of soldering of the lead wire and the wound wire.
To the tinned end of the lead wire protruding from under the gasket, located at the other cheek of the frame, solder the stripped tip of the wound wire and wind it. In this case, the insulating pad will be pressed by the first turns of the winding, and the output end - by the turns of its first row (Fig. 11, d).

Winding must be done slowly at first, adjusting the hand so that the wire goes and lies coil to coil with some tension. In the process of winding this row, the left hand should be evenly moved behind the laying of turns, trying to maintain the tension angle. Thus, subsequent turns of the first row press the previous ones. Each row should not be wound up to the cheek of the frame by 2-3 mm, in order to prevent the turns from falling along the cheek. This is especially important when winding high-voltage windings (for example, step-up in power or anode in output transformers).
Before winding starts (when the first output is filled and soldered), the revolution counter must be set to zero or its readings recorded. In the absence of a counter, the revolutions are counted silently or aloud, with each hundred revolutions marked on paper with a stick.
After winding each row, the wire must be left taut so that during the application of the paper strip, the wound part of the winding does not unravel. To do this, you can press the wire to the cheek of the frame with a linen clip. The gasket must cover the entire row of windings. It is glued together or temporarily (until it is held by the turns of the next row) is pressed against the winding with a rubber ring, which can be made from a thin corded elastic band.
The last winding conclusion can be made in the same way as the first. Before winding the last full or incomplete row, this lead conductor, together with a paper gasket (Fig. 11.0), must be laid on the frame and, wrapping the frame with a gasket strip, press the conductor with a rubber ring. After winding the last row, the wound wire is cut off and, after stripping, soldered to the tinned tip of the lead wire (Fig. 11,e). If the output end must come out of the cheek, near which the last row of the winding ends, then the output end blank is made in the form of a loop (Fig. 11, e), which fits on the frame in the same way as a conventional output conductor.
Taps from a part of the turns of the winding wound with a not too thin wire (from 0.3 mm or more) can be made in the form of a loop with the same wire (without cutting it), as shown in Fig. 12, a. The loop in this case is passed through the hole of a paper strip folded in half, which is tightened after pressing it to the winding with subsequent turns (Fig. 12.6). You can get by without a paper strip if you put an insulating tube on the loop-shaped outlet. Taps from a winding made with a thin wire (less than 0.3 mm) are usually made with a flexible lead wire, which is soldered to the wire, as shown in Fig. 12, c.

The beginning and end of the thick wire windings are led out directly (without separate output wires) through the holes in the cheeks of the frame. On the ends emerging from the frame, you only need to put on flexible insulating tubes. The winding ends are fastened with a narrow cotton tape. The tape is folded in half, forming a loop into which the first output end of the wire is passed. Then, holding the tape with your hand and winding 6-8 turns tightly on it, the loop is tightened (Fig. 13, a). The second output end of the winding is also fixed. In this case, without winding the last 6-8 turns, a tape folded in a loop is placed on the frame, the last turns are wound, which press this tape to the frame, and, having passed the end of the winding into the loop, the loop is tightened (Fig. 13.6). If the thick wire winding contains a small number of turns (no more than 10), then the lead ends can be fixed with a tape by double-sided tightening, as shown in Fig. 13, c.
In multilayer windings of thick wire, it is recommended to make paper spacers after each row. If the frame is not particularly strong, then each subsequent row should be made one or two turns less, and then fill the voids between the winding and the cheeks of the frame with twine or thread. This is important when there are still other windings on top.
If the wire breaks during winding or when the winding is made from separate pieces of wire, the ends of the wires are connected as follows. For wires of small diameter (up to 0.3 mm), the ends of 10-15 mm are cleaned with sandpaper, carefully twisted and soldered. The junction of the wires is then insulated with a piece of slip paper or varnished cloth. The ends of thicker wires are usually soldered without twisting. Thin wires (0.1 mm or less) can be welded by twisting the ends by 10-15 mm (without stripping the insulation) and then placing them in the flame of an alcohol lamp, gas, or several matches. The connection of wires in this case is considered reliable if a small ball is formed at the end of the twist.
Windings made of thin wire with a number of turns of several thousand can be wound not turn to turn, but “in bulk”. However, the turns should be laid evenly so that the winding does not have bumps and dips. Approximately every millimeter of the thickness of such a winding, paper spacers must be made.
To balance two windings or half windings, frames are often used, partitioned off in the middle with a cheek. First, one half of the winding is wound, and then the frame is turned over 180 ° and the other half is wound. Since the turns of each half of the winding will be wound in different directions, then when the halves are connected in series, their beginnings or ends must be connected. In this case, it is more convenient to make conclusions from the windings from opposite sides of the frame.
The windings of a transformer or inductor can be made without a frame. The winding is basically the same as with the frame, but the spacers between the windings (or rows) are made very wide (three times wider than the windings).
At the end of the winding of each section, the protruding edges of the gasket are cut at the corners with scissors or a safety razor blade and, bending them, close the wound section (Fig. 14). End sides of wound windings
then you need to fill it with tar (from dry elements and batteries! Ray).

Outside, if the top row of turns of the last winding is wound with a thick wire and made neatly enough, the coil can be wrapped with nothing. If the upper winding is made of a thin wire, and even wound not a turn to a turn, then the coil should be wrapped with paper or leatherette.
In order to make it easy to understand the leads and taps during the installation of the transformer, it is advisable to use multi-colored lead wires. For example, make the outputs of the network winding of the transformer yellow, the beginning and end of the step-up winding - red, the tap from the middle of the step-up winding and the wire from the screen - black, etc. You can, of course, use single-color lead wires, but then you need to put on each output cardboard tag with the appropriate designation.

CORE ASSEMBLY AND TERMINAL INSTALLATION

Having finished winding the transformer, proceed to the assembly of its core. If the conclusions of the windings are made on one side of the cheek of the frame, then it is placed on the table with the conclusions down. If the conclusions are made on both sides of the cheeks, then the frame must be positioned so that the largest number of conclusions and the thickest of them are at the bottom; the upper conclusions must be folded several times and tied temporarily to the winding so that they do not interfere with the assembly of the core (Fig. 15, i). This is especially important when the shape of the core plates is notched on the middle core.
The power transformer core plates are assembled without a gap, into a cover (alternately on the left, then on the right), as shown in Fig. 15.6. The cores of output transformers or filter chokes are often assembled with an air gap, inserting plates from one side only (Fig. 15, e). To keep this gap unchanged, a strip of paper or cardboard is inserted into the joint between the plates and the overlays of the core. In inserts with a notch on the middle core, the thickness of the gap is determined by the thickness of the notch.
If the frame is not very strong, then it is necessary to fill it with plates (especially at the end of assembly) very carefully, since otherwise it is possible to cut the sleeve with the sharp edge of the middle core and damage the winding. To prevent this, it is desirable to insert and bend a protective strip of mild steel into the frame window (Fig. 15.6).

When assembling the core from plates with a middle core notch, it is necessary to use an auxiliary guide plate (Fig. 15, d), cutting it out, for example, from one core plate.
The frame window is filled with as many plates as possible. If the transformer was disassembled and rewound, then when reassembling it, all the plates removed earlier must be used. During the assembly process, the core should be pressed several times by inserting a ruler or bar into the frame window for this. The last plates, if they are tight, can be driven in with a hammer, lightly hitting it through the wooden lining. After that, turning the transformer in different directions and placing it on a flat surface, it is necessary to trim the core with light hammer blows through a wooden lining.
The core, after its assembly, should be well tightened. If there are holes in the plates, then it is pulled together with bolts through overhead strips or squares (Fig. 16, a and b). Along with this, you can also install a screw with petals for soldering the output ends of the windings.
A small core, assembled from plates without holes, can be pulled together with one common bracket cut from thin mild steel (Fig. 16, c).

It is very convenient to fasten the transformer and tighten its core to use the chassis on which the transformer is to be installed. A window is cut out in the chassis for the passage of the lower part of the coil with leads, a transformer is installed and the core is pulled together with bolts through a common patch frame (Fig. 16,d). In this case, the output ends are connected to the corresponding sections of the circuit either directly or through a shield mounted on the chassis with contact petals.

SIMPLE TESTS

The transformer, after winding and assembly, must be tested.
Power transformers are tested by connecting the primary (mains) winding to the mains.
To check the absence of short circuits in the transformer windings, the following simple method can be recommended. An electric lamp L (Fig. 17) is switched on in series with the primary winding / of the transformer under test, designed for the corresponding mains voltage. For transformers with a power of 50-100 W, they take a lamp of 15-25 W, and for transformers of 200-300 W - a lamp of 50-75 W. With a working transformer, the lamp should burn approximately “a quarter of the heat”. If, at the same time, one of the transformer windings is short-circuited, the lamp will burn with almost full heat. In this way, the integrity of the windings, the correctness of the conclusions and the absence of short-circuited turns in the transformer are checked.

After that, after making sure that the winding terminals are not closed, the primary winding of the transformer must be connected directly to the network for one or two hours (by closing the L lamp with the Vk switch). At this time, you can measure the voltage on all transformer windings with a voltmeter and make sure that their values ​​\u200b\u200bare consistent with the calculated ones.
In addition, it is necessary to test the reliability of the insulation between the individual windings of the transformer. To do this, one of the output ends of the step-up winding // must in turn touch each of the outputs of the network winding /. In this case, the voltage of the step-up winding, together with the voltage of the mains winding, will act on the insulation between these windings. In the same way, touching the output end of the step-up winding // to the output ends of other windings, the insulation of these windings is also tested. The absence of a spark or weak sparking (due to the capacitance between the windings) at the same time shows the adequacy of the insulation between the transformer windings.
The test of the transformer must be done carefully, being careful not to get under the high voltage of the step-up winding.
Other types of transformers (output, etc.) with windings of a sufficiently large number of turns are tested in the same way. By measuring the voltage on the windings of the transformer, it is possible to determine the transformation ratio.
Convinced as a result of the test that the manufactured transformer is in good condition, the latter can be considered ready for installation and installation.

The program for calculating the transformer can be

Do-it-yourself winding a transformer is in itself a simple procedure, but it requires significant preparatory work. Some people involved in the manufacture of various radio equipment or power tools have a need for transformers for specific needs. Since it is not always possible to purchase a specific transformer for specific cases, many wind them on their own. Those who make a transformer for the first time with their own hands often cannot solve the problems associated with the correct calculation, selection of all parts and winding technology. It is important to understand that assembling and winding a step-up transformer and a step-down transformer are not the same thing.

The main parts of the transformer design.

The winding of the toroidal device is also significantly different. Since most radio amateurs or craftsmen who need to create a transforming device for the needs of their power equipment do not always have the appropriate knowledge and skills on how to make a transforming device, therefore this material is aimed specifically at this category of people.

Preparation for winding

Scheme of winding a welding transformer.

The first step is to make the correct calculation of the transformer. Calculate the load on the transformer. It is calculated by summing all connected devices (motors, transmitters, etc.) that will be powered by the transformer. For example, a radio station has 3 channels with a power of 15, 10 and 15 watts. The total power will be equal to 15 + 10 + 15 = 40 watts. Next, take the correction for the efficiency of the circuit. So most transmitters have an efficiency of about 70% (more precisely, it will be in the description of a specific circuit), so such an object should be powered not with 40 W, but with 40 / 0.7 = 57.15 W. It is worth noting that the transformer also has its own efficiency. Typically, the efficiency of the transformer is 95-97%, but you should take the correction for homemade and take the efficiency equal to 85-90% (selected independently). Thus, the required power increases: 57.15 / 0.9 = 63.5 watts. Standard transformers of this power weigh about 1.2-1.5 kg.

Next, they are determined with input and output voltages. For example, let's take a step-down transformer with voltages of 220 V input and 12 V output, the frequency is standard (50 Hz). Determine the number of turns. So, on one winding their number is 220 * 0.73 = 161 turns (rounded up to an integer), and on the bottom 12 * 0.73 = 9 turns.

After determining the number of turns, proceed to determine the diameter of the wire. To do this, you need to know the flowing current and current density. For installations up to 1 kW, the current density is chosen in the range of 1.5 - 3 A / mm 2. The current itself is approximately calculated based on the power. So, the maximum current for the selected example will be about 0.5-1.5 A. Since the transformer will operate with a maximum of 100 W load with natural air cooling, we take the current density to be about 2 A / mm 2. Based on these data, we determine wire cross section 1/2 = 0.5 mm 2. In principle, the cross section is sufficient to select the conductor, but sometimes a diameter is also required. Since the cross section is found according to the formula pd 2 / 2, the diameter is equal to the root of 2 * 0.5 / 3.14 = 0.56 mm.

In the same way, the cross section and diameter of the second winding are found (or, if there are more of them, then all the others).

Winding materials

Winding a transformer requires careful selection of the materials used. So, almost every detail is important. You will need:

Scheme of a continuous winding of a transformer.

1. Transformer frame. It is necessary to isolate the core from the windings, it also holds the coils of the windings. Its manufacture is carried out from a durable dielectric material, which must necessarily be quite thin so as not to take up space in the intervals ("window") of the core. Often, special cardboard boxes, textolite, fibers, etc. are used for these purposes. It should have a minimum thickness of 0.5 m, and a maximum of 2 mm. The frame must be glued; for this, ordinary joinery adhesives (nitro-adhesives) are used. The shapes and dimensions of the frames are determined by the shapes and dimensions of the core. In this case, the height of the frame should be slightly greater than the height of the plates (winding height). To determine its dimensions, it is necessary to make preliminary measurements of the plates and estimate approximately the height of the winding.
2. Core. A magnetic core is used as a core. The plates from the disassembled transformer are best suited for this, since they are made of special alloys and are already designed for a certain number of turns. The most common form of the magnetic circuit resembles the letter "Ш". At the same time, it can be cut from various blanks available. To determine the dimensions, it is necessary to pre-wind the wires of the windings. To the winding, which has the largest number of turns, determine the length and width of the core plates. To do this, take the length of the winding + 2-5 cm, and the width of the winding + 1-3 cm. Thus, an approximate determination of the size of the core occurs.
3. The wire. Here the winding and wires for the leads are considered. The best choice for winding the coils of a transforming device are copper wires with enamel insulation (type "PEL" / "PE"), these wires are enough to wind not only transformers for amateur radio needs, but also for power transformers (for example, for welding). They have a wide selection of sections, which allows you to purchase the wire of the desired section. The wires that come out of the coils must have a larger cross section and be insulated with PVC or rubber. Often used wires of the "PV" series with a cross section of 0.5 mm 2. It is recommended to take wires with insulation of different colors for the output (so that there is no confusion when connecting).
4. Insulating pads. They are necessary to increase the insulation of the winding wire. Usually thick and thin paper is used as spacers (tracing paper is well suited), which is laid between rows. In this case, the paper must be complete, without breaks and punctures. Also, windings are wrapped with such paper after they are all ready.

Ways to speed up the process

Scheme of a homemade device for winding transformers.

Many radio amateurs often have special primitive devices for winding windings. Example: a primitive winding machine is a table (often a stand) on which bars with a rotating longitudinal axis are installed. The length of the axis is chosen 1.5-2 times the length of the frame of the coils of the transforming device (the maximum length is taken), at one of the exits from the bars, the axis must have a handle for rotation.

A reel frame is put on the axis, which is stopped on both sides by restrictive pins (they prevent the frame from moving along the axis).

Next, a winding wire is attached to the coil from one of the ends and winding is carried out by rotating the axis knob. Such a primitive design will significantly speed up the winding of the windings and make it more accurate.

Winding process

The winding of the transformer consists in winding the windings. To do this, the wire that is planned to be used for windings is wound tightly on any coil (to simplify the process). Further, the coil itself is installed either on the device indicated above, or it is wound “manually” (this is difficult and inconvenient). After that, the end of the winding wire is fixed on the winding coil, to which the lead wire is soldered (this can be done both at the beginning and at the end of the operation). Then the coil starts to rotate.

In this case, the coil should not move anywhere, and the wire should have a strong tension for tight laying.

The winding of the turns of wire should be carried out longitudinally so that the turns fit together as tightly as possible. After the first row of turns has been wound along the length, it is wrapped with special insulating paper in several layers, after which the next row of turns is wound. In this case, the rows should fit snugly against each other.

In the process of winding, you should control the number of turns and stop after winding the desired amount. It is important that full turns are counted, not taking into account the consumption of wire (i.e. the second row of turns requires more wire, but the number of turns is wound).

Do-it-yourself instructions for winding transformers

The choice of petrol saws is determined by several criteria. One of them is chainsaw chain pitch. This parameter determines the capabilities of the equipment, the speed of sawing materials and must correspond to the engine power, only in this case it will be possible to extend the life of the tool and reduce the specific consumption of fuel and lubricants.

With prolonged use of the chainsaw, its individual components may fail. Most often, the chainsaw oil pump needs to be repaired. This is due to the fact that during the sawing process a large amount of chips are formed, which can enter the working mechanism.

By the onset of winter, you can try to make a snow blower from a chainsaw with your own hands. This will save a man from monotonous work using a shovel and speed up the cleaning process several times.

How to wind a transformer: step by step instructions

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

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

Design

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

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

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

winder

Toroidal transformers can be of different types. This must be taken into account in the process of creating a contour. Wind the transformer 220/220. 12/220 or other varieties can be done with a special tool.

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

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

Other tools

To wind a 12/220 transformer, pulse, ferrite or other types of structures, you need to prepare a few more tools. Instead of the above design, you can use a phone inductor, a film rewinder, a thread spool machine. There are many options. They must ensure the smoothness, uniformity of the process.

You will also need to prepare a device for unwinding. By its principle, such equipment is similar to the devices presented above. However, with the reverse process, it is possible to rotate without a handle.

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

To understand how to wind a pulse transformer, you need to make calculations. If an existing coil is being rewound, you can simply remember the initial number of its turns and purchase a wire of identical cross section. In this case, calculations can be dispensed with.

But if you want to create a new transformer, you need to determine the amount and type of materials. For example, a device with a workload of 12 to 220 volts would require a 90 to 150 watt machine. You can take a magnetic drive, for example, from an old TV. The cross section of the conductor is determined in accordance with the power of the unit.

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

• P \u003d 12 x 50/10 \u003d 60 turns.
• B \u003d 220 x 50/10 \u003d 1100 turns.

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

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

Layer isolation

To wind a ferrite transformer or other kind of devices, you need to study one more nuance. Between certain layers of conductors, insulating materials should be installed. Most often, condensate or cable paper is used for this. All necessary materials can be purchased in specialized stores. The paper should have sufficient density, be even without gaps or holes.

Between the individual coils, the insulating layers are made of stronger materials. The most commonly used varnish. It is covered with paper on both sides. It is also necessary to level the surface before winding. If the varnished fabric could not be found, paper folded in several layers can be used instead.

Paper is cut into strips, the width of which should be greater than the outline. They should extend beyond the edges of the winding by 3-4 mm. Excess material will tuck up. This will protect the edges of the coil well.

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

For an O-shaped magnetic drive, 2 coils must be prepared. For a W-shaped core, one circuit is required. In the first variant, the round core must be covered with an insulating layer. Only after that they start winding.

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

Winding step by step instructions

Winding the transformer with your own hands will be quite simple. To do this, the spool of wire must be installed in the unwinding equipment. The old wire will be removed from it. The frame of the future transformer must be placed in the winding equipment. Then you can make rotational movements. They should be measured, without jerks.

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

All the necessary tools and equipment must be laid out on the table in advance. At hand should be insulating paper, scissors, sandpaper, soldering iron (plugged in), pen or pencil. With one hand, it is necessary to turn the handle of the winding device, and with the other hand, fix the conductor. It is necessary that the turns fit evenly, evenly.

Considering step-by-step instructions on how to wind a transformer. attention should be paid to subsequent operations. After laying the conductor, the frame will need to be insulated. Through its hole it is necessary to pass the end of the wire taken out of the circuit. The fix will be temporary.

Experienced radio amateurs recommend that you first practice before winding. When it turns out to apply the turns evenly, you can get to work. The tension angle and the wires must be constant. Each next layer does not need to be wound all the way. Otherwise, the conductor may slide out of its intended place.

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

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

Connection process

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

For wires up to 0.3 mm thick, it is necessary to clean the ends by 1.5 cm. Then they can simply be twisted and soldered using the appropriate tool. If the core is thick (more than 0.3 mm), you can solder the ends directly. Twisting in this case is not required.

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

Having studied the procedure for winding a transformer, a few more recommendations should be taken into account. The number of turns of a thin conductor can reach several thousand. In this case, it is better to use special counting equipment. The winding is protected from above with paper. For a thick conductor, external protection is not required.

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

Having considered the step-by-step instructions for winding a transformer, you can repair an old one or create a new one. With strict adherence to all its points, it is possible to create a reliable, durable unit.

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calculation and rewinding of the transformer

Rewinding a transformer with your own hands is a simple, but time-consuming task. If it is checked in operation and all its parameters are known, how to rewind the transformer - there are no problems. It’s more difficult when you find an old unit in the garage. How to calculate the winding of a transformer, you have to strain. You can also turn it on to the network: it will burn out - it’s dear to him there, you still have to do a new calculation and rewind the transformer with your own hands, although the wire could come in handy. Only first you need to ring the windings for an open and a short to the hardware, find the primary. It is wound first, and its conclusions are closer to the core.
If you don't want to risk it, let's start disassembling this old unit. Before dismantling, measure the area of ​​the window N s * s and a section (let's call it Qc) of the rod on which the windings sit. On Fig. 1 and 2 is the pivot Cm. Its cross-sectional area is equal to the product of the width of the plate and the thickness of all plates.

Let's determine the power of the transformer. I use the formulas that I once studied. They didn't let me down.
For armored transformer (Fig. 1) S 1br \u003d f (Q c / k) 2 ;
for rod type (Fig. 2) S 1st \u003d 2f (Q c / k) 2 ;
where S 1br and S 1st- total power of armored and rod transformers, respectively, VA; k- constant for air transformers (6-8), f— current frequency, Hz.
For clarity of calculations, I will take the "iron" from the bulldozer. For example, a rod type with a rod section Q c \u003d 2 * 4 \u003d 8 cm 2 .
Primary Power S 1st \u003d 2 * 50 (8/7) 2 \u003d 100 * 1.30 \u003d 130VA .
What will the secondary give? Taking into account the losses due to efficiency transformer ( Table 1.), we find the total power of the secondary winding S 2st \u003d S 1st * efficiency \u003d 130 * 0.91 \u003d 118VA .
This is the power from which we will squeeze all the juice. Let's make a charger for 12-volt batteries. The output voltage should be about 16V. Why not 14V, as charging requires? When the diode bridge is connected, 2 volts will be lost at the output, and in order not to hang a lot of electrolytic capacitors to compensate. better to be safe. According to the amateur radio formula, we determine the number of turns per 1V:
w o = 50/Qc; w o = 50/8 = 6.25 .
16V required 6,25*16 = 100 turns. Given the losses, it is recommended to increase the number of turns by 5-10%. We get the secondary winding w 2 = 100*1,1 = 111 turns.
Find the number of turns of the primary winding: w 1 = w o *220 = 6.25*220 = 1375 turns.
Choosing a wire for winding. If we want to take the maximum power from the device, let's see what current we get. At 16V, the limiting current of the secondary winding I 2 \u003d S 2st / U 2 \u003d 118/16 \u003d 7.3A .
To charge a 65 A * h battery, a current of 6.5A is needed, which means that our current of 7.3A can handle it.
Primary current I 1 \u003d S 1st / U 1 \u003d 130/220 \u003d 0.6A .
Determine the cross section of the wire of the primary winding: s 1 \u003d I 1 / sq. t. = 0.6 / 2.3 = 0.261mm 2 .
Cross-section of the wire of the secondary winding: s 2 \u003d I 2 / sq. m. = 7.3 / 2.3 = 3.17mm 2 .
sq.t.- current density from table 1. I took 2.3 because our transformer is more than 100W, but less than 250W.
By table 2. we select a wire for the primary winding with a diameter of 0.6 mm (with insulation 0.64 mm), for the secondary - 2 mm (with insulation 2.065 mm). Will we get into the window with our rewind?
window area N s * s in my transformer, according to rough estimates, it should be about 2000mm 2. The area occupied by the primary winding: (0.64mm) 2 * 1375 turns = 563mm 2; secondary: (2.065mm) 2 *111 turns = 473mm 2. The total area is 1036mm 2. It seems that we got in - we shake it.
Finally, a few tips:
1. The coils must be tight, without gaps or looseness. Otherwise, when they vibrate during operation, the lacquer insulation will be erased: an interturn circuit is inevitable. To guarantee the winding, you can bathe in a lacquer bath.
2. Before assembling the hardware, carefully clean the plates with sandpaper from the old varnish so that they fit snugly against each other to prevent the transformer from rattling.
3. How to rewind the transformer if there is no wire that matches the calculations? You can take a smaller one, but at the same time reduce the current of the secondary winding. The current of the existing wire is determined based on our formulas. For example, for a wire with a cross section of 0.159mm 2 I 2 \u003d 0.159 * sq. t. A winding with a thick wire may not fit in the window, calculate the filling area again. If there is not enough wire - add it, make the place of soldering not inside, but bring it out.
4. If the wire to the secondary is thin, but you want to take a large current, wind two identical secondary with this wire. Just do not confuse the beginning and end of the windings. connect the beginning with the beginning, the end with the end. You can immediately wind it with a double wire, but this is a piece of jewelry, because the turns must lie flat and tight so that the transformer buzzes less.
5. Isolate the primary winding from the secondary varnished cloth so that if the insulation is broken, you will not feel 220V.
6. When assembling the plates, if necessary, use only wooden tools.
7. If you want to know the number of turns of the primary or secondary in a working transformer, wind 10 wires over the windings of the turns, measure the voltage at its terminals. For example, on these 10 turns, the voltage is 2V. There are 5 turns per 1V. This means that 1100 turns are wound on 220V. And to get, for example, 24V, you need to wind: 5 vit. * 24V = 120 turns.
Now you know how to rewind the transformer with your own hands?

Table 1.

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

Selection of materials

We take the Russian wire, it has stronger insulation. From old coils, the wire is used if there is no damage to the insulation. Paper, FUM film is suitable for insulation. For insulation between the windings, it is better to use a lacquer cloth, several layers of insulation. Cable paper, lacquer fabric is suitable for surface outer insulation. You can also wind the transformer using PVC electrical tape.

The frame is made of fiberglass or similar material.

Calculations of the parameters of a homemade transformer

On a simple transformer, the primary has 440 turns for 220 volts. It turns out for every two turns of 1 volt. The formula for counting turns by voltage:

N \u003d 40-60 / S, where S is the cross-sectional area of ​​\u200b\u200bthe 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 of 53 mm in height and 19 mm in width. The frame will be textolite. Two cheeks at the bottom and at the top 53 - 1.5 x 2 = 50 mm, frame 19 - 1.5 = 17.5 mm, window size 50 x 17.5 mm.

We calculate the required diameter of the wires. Do-it-yourself transformer core power in size 170 watts. On the network winding, the current is 170 / 220 \u003d 0.78 amperes. The current density is 2 amperes per mm 2, the standard wire diameter according to the table is 0.72 mm. Factory winding from wire 0.5, the factory saved on this.

• The winding of a simple high voltage transformer is 2.18 x 450 = 981 turns.
• Low voltage for heating 2.18 x 5 \u003d 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 \u003d 115 turns per layer. Number of layers 981 / 115 = 8.5. It is not recommended to draw a conclusion from the middle of the layer to ensure reliability.

Calculate the height of the frame with windings. Primary of eight layers with wire 0.74 mm, insulation 0.1 mm: 8 x (0.74 + 0.1) = 6.7 mm. The high voltage winding is best shielded 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. The height of the windings together: 7.22 + 7 = 14.22 mm. 3 mm left for filament windings.

You can calculate the internal resistance of the 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 the specific resistance from the table for copper.

When calculating the resistance of the primary winding section, a difference of about 6 ohms is obtained. Such 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 load, the sections are equal in voltage.

Making a transformer coil frame with your own hands

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

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

Do-it-yourself transformer winding

We lay the insulation of the first layer. 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 it like this: the wound coil will not slip from the finger. The wire must not be stretched, as the insulation will be broken. It is recommended to impregnate the finished coil with paraffin so as not to spoil the wire. If the winding hums during the operation of the transformer, then the insulation of the wire is erased, the wire is bent and destroyed. For this reason, the tension of the wire during winding is of great importance.

During winding, we move the turns towards each other, 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, then the insulation may be broken. We impregnate the first layer, then the second and so on. Insulation between windings must be treated conscientiously. It must withstand up to 1000 volts. At the top of the insulation, it is recommended to sign the number of turns and the size of the wire, this will come in handy during repairs.

The layers of a homemade transformer must have the correct shape. As it winds, the bobbin will bend at the edges. To do this, the layers must be equalized during winding, without damaging the insulation.

Forced wire joints are better on the edge of the frame behind the core. Connect the wire with a twist 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 lacquer cloth. Soldering should be without sharp corners.

The output ends of the windings are made in different ways. The main thing is to be reliable and quality.

Finishing the manufacture of a transformer with your own hands

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

We measure the current of a home-made transformer idle, it should be minimal. Let's look at heating. If the core is heated, then the iron is incorrectly selected. If the windings are hot, then there is a short circuit. If it is normal, then we close the secondary winding for a short time, there should not be cod and strong buzz.

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 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 pick up a magnetic core. We select a W-shaped magnetic core, and a frame from an old transformer. To determine the power delivered by a simple transformer, it is necessary to make a preliminary calculation.

Calculation of the transformer

We calculate the diameter of the wire of the primary winding. Transformer power P 1 \u003d 108 W:

P 1 \u003d U 1 x I 1

where: I 1 - current in the primary winding;

then the current in the primary winding:

I 1 \u003d P 1 / U 1 \u003d 108 W / 220 V \u003d 0.49 A.

Take I 1 \u003d 0.5 amperes.

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

A homemade transformer with your own hands can be wound without a machine. It will take two or three hours, no more. Let's prepare strips of paper for laying it 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 more millimeters so that the paper lies tightly, the turns do not climb on top of each other along the edges.

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

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

Primary winding

Now we take the wire from the old coil, which has a wire with good, not cracked insulation. We insert the end of the wire into a flexible tube of insulation from the old used wire of the corresponding suitable diameter. We push the end of the winding into the hole of the coil frame (they are already in the old frame).

The coil is wound tightly, coil to coil. After winding 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 all the time 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. Ludim varnished wire, heating the end with a soldering iron on an aspirin tablet. At the same time, the varnish is well removed.

When the winding of the primary winding is completed, then we isolate the end of the wire into a tube and bring the coils out. Between the primary and secondary windings we make winding insulation. You can wind the transformer further.

Secondary winding

Calculate the diameter of the wire of the secondary winding of a homemade transformer. We take the power of the secondary winding:

P 2 \u003d 100 watts

P 2 \u003d U 2 x I 2

U 2 \u003d 18 volts;

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

I 2 \u003d P 2 / U 2 \u003d 100 W / 18 V \u003d 5.55 A.

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

We take the wire that we received when winding the old transformer. We wind the wire of the secondary winding according to the same principle as the primary winding. The secondary winding wire is much stiffer, therefore, in order for it to lay flat when winding, it must be periodically upset by hammer blows through a wooden block so as not to damage the insulation. We got 3 layers of the secondary winding. It turned out a ready-made wound frame of a simple transformer.

Do-it-yourself transformer assembly

To speed up the assembly, we take two W-shaped plates. We insert them inside the frame alternately from two sides, two pieces each.

We haven't installed the cover plates yet. They will be installed later. If you insert all the plates at once with the whole package, then gaps appear between the plates and the inductance of the entire core drops. After assembling the W-shaped plates of a home-made transformer, we insert the overlapping plates, also two each.

After assembling the core, gently tap its planes with a hammer to align the plates. With the help of racks and studs, we will tighten the core. According to the rules, paper sleeves are put on the studs to reduce core losses.

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

Write comments, additions to the article, maybe I missed something. Take a look at , I will be glad if you find something else useful on mine.

!
This article will discuss how to properly wind a pulse transformer.

The author of the YouTube channel "Open Frime TV" Roman, not so long ago assembled a switching power supply on the IR2153 chip, and now he will tell you how to independently wind a pulse transformer for a homemade power supply.

It just so happened that the first transformer wound by the author was on a ferrite ring, and after that he could no longer wind on w-shaped ones, and there are several reasons for this. The first is a relatively small place for winding w-shaped cores, while for toroidal ones it can be stretched over the entire ring. And from here the second problem appears, if many turns are wound, then it is difficult to close the halves of the core.

Yes, you can say that the reverse side of the coin will be the prevalence of such cores in computer power supplies, but you first try to disassemble the core normally without breaking it. Although it has already been experimentally proven that a broken core after gluing works in the same way as a new one, the soul is calmer when solid ferrite is used.

Another, with the same dimensions, the ferrite ring has more power than the w-shaped core. Here are some hearts for example. A W-shaped one can deliver 150-180W of power, and a roughly the same size toroid can deliver 250W.

For comparison, here is another toroid that is only 1 cm larger than the previous one, and this one can already deliver 600W of power.

The author hopes that the arguments given by him were very weighty, and advises switching to winding transformers on toroidal cores. Well, now let's move on to the winding. For this we need a core. They are of different types. Here are those, still made in the USSR and here are those made in China:

You can use either one or the other. Cores made in the Soviet Union should be marked 2000NM, and when choosing Chinese ones, it is necessary to monitor the permeability, it should be in the region of 2000-2200.

With that figured out, let's move on. As you can see, the Chinese cores are already covered with paint and, in fact, can be wound directly onto the core without insulation.

But then the wire will slide over the surface. If you, like the author, are not satisfied with this, then for insulation you can use this yellow high-voltage Mylar tape:

Or you can use this thermal tape:

It is highly undesirable to use classic blue electrical tape in this case, since when heated, it greatly retains heat. Before making a transformer, you already know what voltage and power it should give out. So the author came up with the following technical task for himself: it is necessary to wind a transformer for 24V, with a power of 80W for a future soldering station project.

The following program will help us with the calculations:

The author left a link to it in the description under the video (link SOURCE at the end of the article). We enter the required value in the program. If you are making a switching power supply according to the author’s scheme, then simply repeat the steps as on the screen (this is shown in more detail in the author’s video at the bottom of the page).

The differences will be in several parameters. The first is frequency.

It depends on the value of this resistor:

You can calculate it with an online calculator. Here it is enough to score the value of the capacitor and resistor. The output is the frequency.

You will also have your own output voltages and wire diameters.

When we figured out the data, we proceed to the choice of the core. If you have cores available, then measure their size with a ruler or caliper, and then look for the same size in the program. When you have indicated your core, the program will show the overall power, and you already understand whether it fits or you need to look for a new one.

If there are no cores available, then just start sorting through different sizes. Thus, we find the desired core, and then it remains only to buy it in the store. I hope you understand the principle of choosing cores. The author had cores with a minimum power of 250W available, they can be safely used. Yes, there will be a slight overrun of material, but it's not scary, more power is better than less.

The author decided to use a core with obviously higher power, because the winding process will be more clearly visible on it. When we have entered all the data into the program, we press the "calculate" button, and we get the necessary parameters for winding.

As you remember, we need to get a voltage of 24V at the output, but according to the calculations, 26V is obtained. In this case, you can change the frequency and look for a value at which the output will have the desired voltage. Along with the change in frequency, the parameters of the winding also change. For example, we found a frequency of 38 kHz, at which the output voltage is exactly 24V. We go to the online calculator, and changing the value of the resistor, we find the value at which the desired frequency will be 38 kHz, and then directly when the resistor is soldered to the board, we set the desired value on it.

You can proceed to winding. Isolate the core.

Now you can wind the primary winding, but it will be difficult to evenly distribute it by eye, so let's make a markup. We need a leaf and a protractor. We make 2 diameters: inner and outer. We set a starting point and, using a protractor, divide our markup by the number of turns needed. Then we cut it out, and with the help of adhesive tape we glue it onto the core.

Next, you need to unwind the required length of wire for winding. This can be done by knowing the length of one turn, as well as the number of turns. We measure one turn and multiply by the quantity, and also add 5% due to the fact that the wire does not lay down a turn to a turn, but is slightly stretched, and conclusions must also be drawn.

When we found out the length of the wire, we unwind it, cut it off and you can wind it. To do this, the author uses the following device:

A wire is wound on it and then, calmly threading it into the core, winding is carried out strictly according to the markup. You can use superglue to attach the coils.

Now it remains to solder the stranded wire to the primary and insulate it with the same thermal tape.

That's all - the primary is ready, we proceed to the manufacture of the secondary. The winding direction of the primary and secondary may not coincide - it does not matter. The procedure for winding the secondary is practically the same as winding the primary winding, the same markings, though there are fewer turns, but the process is identical.

And now the most important thing. This is where most people get confused, this is how to make the middle point. So, now the author will demonstrate this as clearly as possible. Here we wound one half of the secondary - this will be the middle point.

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

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

Design

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

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

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

winder

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

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

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

Other tools

To wind the transformer 12/220, pulse, ferrite or other types of designs, you need to prepare a few more tools. Instead of the above design, you can use a phone inductor, a film rewinder, a thread spool machine. There are many options. They must ensure the smoothness, uniformity of the process.

You will also need to prepare a device for unwinding. By its principle, such equipment is similar to the devices presented above. However, with the reverse process, it is possible to rotate without a handle.

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

Calculations

To understand how to wind a pulse transformer, calculations need to be made. If an existing coil is being rewound, you can simply remember the initial number of its turns and purchase a wire of identical cross section. In this case, calculations can be dispensed with.

But if you want to create a new transformer, you need to determine the amount and type of materials. For example, a device with a workload of 12 to 220 volts would require an apparatus of 90 to 100 watts. You can take a magnetic drive, for example, from an old TV. The cross section of the conductor is determined in accordance with the power of the unit.

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

• P \u003d 12 x 50/10 \u003d 60 turns.
• B \u003d 220 x 50/10 \u003d 1100 turns.

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

• Tp \u003d 150: 12 \u003d 12.5 A.
• TV \u003d 150: 220 \u003d 0.7 A.

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

Layer isolation

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

Between the individual coils, the insulating layers are made of stronger materials. The most commonly used varnish. It is covered with paper on both sides. It is also necessary to level the surface before winding. If the varnished fabric could not be found, paper folded in several layers can be used instead.

Paper is cut into strips, the width of which should be greater than the outline. They should extend beyond the edges of the winding by 3-4 mm. Excess material will tuck up. This will protect the edges of the coil well.

frame

To understand how to wind a transformer attention should be paid to every detail of this process. Having prepared the insulation, wire and tool, you should make a frame. To do this, you can take cardboard. The inside of the frame should be larger than the core rod.

For an O-shaped magnetic drive, 2 coils must be prepared. For a W-shaped core, one circuit is required. In the first variant, the round core must be covered with an insulating layer. Only after that they start winding.

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

Winding step by step instructions

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

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

All the necessary tools and equipment must be laid out on the table in advance. At hand should be insulating paper, scissors, sandpaper, soldering iron (plugged in), pen or pencil. With one hand, it is necessary to turn the handle of the winding device, and with the other hand, fix the conductor. It is necessary that the turns fit evenly, evenly.

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

Experienced radio amateurs recommend that you first practice before winding. When it turns out to apply the turns evenly, you can get to work. The tension angle and the wires must be constant. Each next layer does not need to be wound all the way. Otherwise, the conductor may slide out of its intended place.

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

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

Connection process

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

For wires up to 0.3 mm thick, it is necessary to clean the ends by 1.5 cm. Then they can simply be twisted and soldered using the appropriate tool. If the core is thick (more than 0.3 mm), you can solder the ends directly. Twisting in this case is not required.

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

Trial

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

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

Having considered the step-by-step instructions for winding a transformer, you can repair an old one or create a new one. With strict adherence to all its points, it is possible to create a reliable, durable unit.