Winding a transformer with your own hands is not a difficult task if you prepare for it in advance. People who make various radio equipment or power tools have a need for transformers for specific needs. Since it is not always possible to purchase certain products, craftsmen often wind toroidal transformers themselves. Those who try to carry out winding for the first time encounter difficulties: they cannot determine the correctness of the calculations or select the appropriate parts and technology. It is important to understand that different types are wound differently.
Also toroidal devices are radically different. The calculation of a toroidal transformer and its winding will be special. Since radio amateurs and craftsmen create parts for power equipment, but do not always have sufficient knowledge and experience to manufacture them, this material will help this category of people understand the nuances.
Preparing for winding
Necessary materials
Winding materials require careful selection, every detail is important. In particular, you will need:
- Transformer frame. It is used to insulate the core from the windings and also holds the winding coils. It is made from strong and thin dielectric materials so as not to take up too much space in the intervals (“windows”) of the core. You can use cardboard, microfiber, textolite. The thickness of the material should not be more than 2 mm. The frame is glued together using ordinary carpentry glue (nitro glue). Its shape and dimensions depend entirely on the core, its height is slightly greater than that of the plate (winding height).
- Core. This role is usually performed by magnetic circuits. The best solution will be the use of plates from disassembled transformers, since they are made from suitable alloys and are designed for a certain number of turns. Magnetic cores have a variety of shapes, but most often there are products in the form of the letter “W”. In addition, they can be cut from various blanks that are available. To determine the exact dimensions, the wires of the windings are pre-wound.
- Wires. Here you need to use two types: for winding and for leads. The optimal solution for transforming devices is copper wires with enamel insulation (PEL or PE type). They are enough even for power transformers. Wide choose sections allows you to choose the most suitable option. PV wires are also often used. For the output, it is best to take wires with multi-colored insulation so as not to get confused when connecting.
- Insulation pads. Helps increase the insulation of the winding wire. As a rule, thin and thick paper is used (tracing paper is perfect), which should be laid between the rows. But the paper must be intact, there should be no tears or punctures, even the most insignificant ones.
How to speed up your workflow
Many radio amateurs have in their arsenal simple special units, with the help of which the winding is made. In many cases, we are talking about simple structures in the form of a small table or table stand, on which several bars with a rotating longitudinal axis are installed. The length of the axis itself must exceed the length of the winding frame by 2 times. A handle is attached to one of the exits from the bars, allowing you to rotate the device.
Reel frames are placed on the axles, which are locked on both sides with limiting pins (they prevent the frame from moving along the axis).
If you are interested in making welding machine or a voltage stabilizer, then you definitely need to know what toroidal transformers are. But the most important thing is how they work and what subtleties they have in manufacturing. In addition, such transformers, due to their design, are capable of delivering greater power compared to those wound on an W-shaped core. Consequently, such devices are ideal for powering very powerful equipment - for example, low-frequency amplifiers.
Basic data
So, before you start making a transformer, you need to study the hardware. First, you need to decide on the type of wire to use. Secondly, you need to calculate the number of turns (from this it follows that you will know how many meters of wire you need). Thirdly, you must choose the wire cross-section. The output current, and therefore the power of the toroidal transformer, depends on this parameter.
It is also necessary to take into account that with a small number of turns in the primary winding, heating will occur. A similar situation arises if the power of consumers connected to the secondary winding exceeds the value that the transformer can deliver. The consequence of overheating is a decrease in reliability. Moreover, overheating can even cause the transformer to ignite.
What is required for production
So, you start making a transformer. You need to get tools and materials. Of course, you may even need a sewing needle or matches, but surely everyone has such accessories. The most important thing is the iron from which toroidal transformers are made. You will need a lot of transformer steel, it should be in the shape of a torus. Next, of course, is the wire in varnish insulation. Be sure to have masking tape and PVA glue. Fabric-based insulating tape is also needed to separate the windings. And several pieces of wire to connect the ends of the windings. Moreover, the wire must be used in silicone or rubber insulation.
Transformer steel
Getting such an accessory may seem very difficult. But in any house, barn, even at metal collection points today you can find unusable voltage stabilizers. In the Soviet years, they were very popular, they were used together in black and white televisions, so as not to damage the picture tubes. It doesn’t matter to you whether this stabilizer works or is burnt out. The most important thing is the toroidal transformers that are used in it. They will be the basis of your design. But before that you need to get rid of the old winding, which is made of aluminum wire. And then - preparation of the core. Please note that it has right angles. You don't need this, as you can damage the varnish insulation when winding. Try to round the corners as much as possible by filing them. Then lay fabric-based electrical tape over the transformer steel. Only one layer is needed.
Windings
And now a little about how a toroidal transformer is calculated. You can, of course, use simple programs, of which there are a great many. You can use a ruler and a calculator to make the calculation. Of course, it will have an error, since many more factors that exist in nature are not taken into account. You should adhere to one rule when calculating - the power in the secondary coil should not be greater than the same value in the primary winding.
As for such a process as winding a toroidal transformer, it is very labor-intensive. It is good if it is possible to disassemble the magnetic circuit and, after winding, assemble it together. But if this is not possible, then you can use a kind of spindle. You wind a certain amount of wire around it. Then, passing this spindle through the torus, you lay out the turns of the windings. This will take a lot of time, so if you are not confident in your abilities, it is better to purchase a ready-made power supply.
Calculation example
The process is best described as specific example. The primary winding, as a rule, is powered by an alternating voltage network of 220 V. Let's say you need two secondary windings so that each produces 12 V. And you also use a wire with a cross-section of 0.6 mm in the primary winding. Therefore, the cross-sectional area will be approximately 0.23 square meters. mm. But this is not all the calculations; toroidal transformers need careful adjustment of all parameters. And now again, a little math - you need to divide 220 (V) by the sum of the voltages of the secondary circuits. As a result, you get a certain coefficient of 3.9. It means that the cross-section of the wire used in the secondary winding should be exactly 3.9 times larger than in the primary. To calculate the number of turns for the primary winding, you will need to use a simple formula: multiply the coefficient “40” by the voltage (in the primary circuit it is 220 V), then divide this product by the cross-sectional area of the magnetic circuit. It is worth noting that its efficiency and service life depend on how accurately the toroidal transformer is calculated. Therefore it's better once again repeat each step of the calculation.
When building a receiver, amplifier or other radio equipment, a radio amateur has to deal with the work of remaking an old one or making a new transformer.
Radio amateurs who are starting such work for the first time often do not have a clear idea of 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 most do the work relying on your own ingenuity, or resort to the help and advice of a more experienced friend.
Taking this into account, the author of this brochure has made an attempt to provide in a systematic form the necessary instructions for the manufacture of low-power transformers and teach practical techniques for winding them at home or in a radio circle.
Winding devices
In factories with mass serial or continuous production, transformers are usually wound on special, often automated machines. It is, of course, difficult for radio amateurs to rely on a special winding machine, and therefore they usually wind transformers either directly by hand, or using simple winding devices.
Let's look at how you can use scrap materials and ordinary tools manufacture simple devices for winding.
The simplest such device is shown in Fig. 1. It consists of two racks 1 (or metal bracket), mounted on a board 2, and an axis 3 made of a thick (8-10 mm in diameter) metal rod, threaded through the holes in the racks and bent at one end in the form of a handle.
To wind the wire onto 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 to fit it onto the axle.
The frame is put on a block, which is then placed on the axle and secured there with a pin 6. To prevent the frame from dangling and moving off the block, a sealing wedge 7 made of hard cardboard or thin plywood must be inserted between them.
To avoid axial play when winding, which is very important for even laying of the turns, on the free sections of the axis between the block and the racks it is necessary to put on pieces of tubes 8, which can be made from metal sheets, wrapping them around axis 3.
Fig. 1. The simplest winding device. 1 - racks; 2 - board; 3 - axis; 4 - coil frame; 5 - block; 6 - pin 7-wedge; 5-tubes.
Fig. 2. Winding device from a drill. 1 - drill; 2- vice; 3 - rod; 4 - nuts.
To remove the wound frame, you need to remove the pin 6 and pull out the axis 3.
A more convenient and reliable winding device is made from hand drill/ (Fig. 2), which must be clamped in a vice 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, onto 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 PCB with holes in the center.
It is also convenient to use a ready-made machine for textile bobbins, a winder for rewinding film, a telephone inductor, etc. as a winding device.
The film winder is especially convenient (after a little modification), as it is made firmly and has a soft, play-free motion. Its alteration consists in replacing the short roller with a lock for film reels with a long axis with threads and wings for securing various frames.
No less important for winding work than the winding machine itself is the unwinding device, on which a coil of wire or the frame of an old transformer is placed, the wire of which is used for new winding. To prevent the insulation of the unwinding wire from deteriorating, and also to avoid shocks (which is important when laying turns in a row), the wire must run completely evenly.
The simplest device for unwinding wire is shown in Fig. 3. This is an ordinary metal rod 1, threaded through the holes wooden racks 2, mounted on a board 3.
Making a wooden block for the frame of the unwinding coil 4 is not necessary in this case. To prevent it from hitting or jumping when unwinding, you can roll up a tube 5 of the required diameter from thick cardboard or paper, pass a rod through it and insert it tightly enough into the window of the frame.
Fig. 3. The simplest device for unwinding wire, 1 - rod; 2- racks; 3- board; 4 - coil with wire; 5 - tube.
Fig. 4. Machine for unwinding wire. 1 - bracket; 2 - board; 3-bolts; 4- hairpin; 5 - nuts (wings); 6 - cheeks.
It is better, however, to make a special unwinding device, shown in Fig. 4. Made from mild steel strip or other suitable material bracket 1 is bent and attached to board 2 (or table).
IN vertical racks The staples 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. A pin 4, cut along the entire length, is made from a metal rod with a diameter of 5-6 mm, shallow holes (3-4 mm) are drilled at the ends.
The cones and the pin are equipped with corresponding nuts (preferably wings) 5 and jaws 6 for clamping the coil or frame with the wire.
Very important in the winding process is the ability to accurately count the number of turns. Simple but demanding special attention The method is to verbally count each revolution (or every other 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.
Fig. 5. Connection of the thread counter with the winding device. a - using a flexible roller; b - using gears.
In a machine with a gear transmission, the gear ratio is taken into account, which should always be remembered.
Much better application a mechanical meter, which can be used as a bicycle speedometer or a counting mechanism from an electric meter, water meter, etc.
The meter can be connected to the machine using a flexible roller (a piece of thick-walled rubber tube) connecting the meter axis to the axis of the machine (Fig. 5a). In this case, each time you install a new frame, you have to disconnect the axle joint by removing the flexible roller, and after installing the new frame, put it on again.
A more convenient, but also more complex method of articulation is that the counter is connected to the machine through a pair of identical gears (Fig. 5,6). With this method, the counter is coupled to the machine all the time.
Frame for transformer
The transformer frame (or inductor) is needed to isolate the windings from the core and to keep the windings, insulating gaskets and terminals in order. Therefore, it must be made of sufficiently durable 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.
Typically, the material for the frame is thick cardboard (pressboard), fiber, textolite, getinaks, etc. Depending on the size of the transformer or inductor, the thickness sheet material for the frame, take from 0.5 to 2.0 mm.
To glue the cardboard frame, you can use office universal glue or regular wood glue. The best glue nitro glue (enamel, rolled oats) should be considered to have good moisture resistance. Getinax or textolite frames are usually not glued together, but assembled “into a lock”.
Fig. 6. Proportionality of the frame and core plates. a - for split plates; b - for plates with a perforation of the middle core.
Based on the dimensions of the core, the shape and dimensions of the frame are determined, after which its parts are drawn and then cut. If transformer plates with a middle core cut are used, then the height of the frame is made several 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 drawn on paper with the dimensions of individual parts of the frame. It is especially important to coordinate the individual parts of the frame when assembling it “into a castle.” Size ratios of frame and core plates for different types plates are given in Fig. 6.
Fig. 7. Cutting and gluing the frame for the transformer.
A regular frame for a transformer can be made like this. First, the cheeks of the frame are cut out and a sleeve with cuffs on the end sides is cut out according to Fig. 7. Having made cuts at the folds, the pattern is rolled into a box, with side 1 glued to side 5. After that, both cheeks are put on the sleeve.
Then you need to bend the flaps of the sleeve and, spreading the cheeks to the edges of the sleeve, glue the flaps to the outer planes of the cheeks. You can glue pieces of the same cardboard from which the frame sleeve was made into the corners on the outside of the cheeks. If the glue is strong and reliable enough, then the sleeve can be made without flaps, gluing the cheeks directly to the edges of the sleeve.
Fig. 8. Details of the prefabricated frame for the transformer. a is the width of the core plate, plus the gap, plus the thickness of the material of parts 3; b - the thickness of the set of core plates plus the thickness of parts 2; in is the thickness of the material.
The prefabricated frame is more difficult to manufacture, but it has great strength and does not require gluing. Details of the prefabricated frame are shown in Fig. 8.
They are manufactured as follows. 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 using a file. In cheeks 1, after drilling several holes in them, windows are cut out.
Fig. 9. Assembling the frame for the transformer coils into a lock.
After this, having laid out the parts on the table, they adjust sides 2 and 3 of the sleeve so that when assembling the frame, all the cuts and protrusions of the “lock” come together. When marking and manufacturing parts 2, the “key” part of one of them can be made significantly large sizes(the contours are shown by dotted lines in Fig.
8) for placing contacts or petals on it for soldering the winding leads. To avoid confusion of parts, they should be numbered before assembly. The order of assembly of the frame is clear from Fig. 9.
Immediately after making the cheeks, it is better to pre-drill holes for the leads in them “as a reserve”. When assembling the frame or gluing the cheeks, it is necessary to take into account which side of the transformer (or both) and which side of the cheeks the leads will be made in order to correctly position the sides of the cheeks that have 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 covered by the core plates.
The finished glued or assembled frame must be prepared for winding, for which you should round off the corners of the sleeve and cheeks with a file, and also remove burrs. It is useful (but not necessary) to coat or impregnate the frame with shellac, bakelite, etc.
Insulation pads
In some cases, a large voltage is generated between adjacent rows of transformer windings, and then the insulation strength of the wire itself is insufficient. In such cases, it is necessary to place thin insulating gaskets between the rows of turns. thick paper, tracing paper, cable, condenser or tissue paper. The paper should be smooth and, when viewed against the light, there should be no visible pores or punctures.
The insulation between windings in a transformer must be even better than between rows of turns, and the higher the voltage, the better. Better insulation- varnished fabric, but in addition to it, you also need thick cable or wrapping paper, which are also laid to level the surface for the convenience of winding the next winding on top. One layer of varnished cloth is always desirable, but two or three layers of tracing paper or cable paper can be substituted.
Having measured the distance between the cheeks of the finished frame, you can begin preparing the insulating strips of paper. To ensure that the outer turns of the winding do not fall between the edges of the strips and the cheeks, the paper is cut into slightly 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 folded.
When winding, notched or folded strips cover the outermost turns of the winding. The length of the strips should ensure that the winding perimeter overlaps with the ends overlapping by 2-4 cm.
To insulate leads, solder points and winding taps, pieces of cambric or vinyl chloride tubes and pieces of varnished fabric are used.
To tighten and secure the beginning and end of thick windings (incandescent and output), pieces (10-15 cm) of keeper tape or strips, cut from varnished fabric and folded three or four times for strength, are prepared.
If the outer row of the winding is close to the core, then rectangular plates are cut out of a thin sheet of PCB or cardboard, which are inserted between the winding and the core after assembling the transformer.
Winding and output wires
The windings of transformers that a radio amateur has to deal with are most often made of PE or PEL enamel insulated wire.
In power transformers, exclusively PE wire is used for the network and step-up windings, and for the incandescent windings of lamps, the same wire or, if large diameter(1.5-2.5 mm), wire with double paper insulation brand PBB.
The terminals of the ends and taps from windings made with 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 output from them.
Leads from overstitching made with thick wire can be made with the same wire. Pieces of thin-walled insulating tubes must be placed on the ends or taps of these windings. The lead conductors must be of such length that they can be freely connected to the circuit elements or to the joint strip (comb).
Winding
A reel with a wire intended for the next winding is clamped between the removable cheeks of the threaded pin of the unwinding device. A pin with a 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 break when unwinding, since the success and ease of laying the wire turn to turn depends on this. The unwinding device is located in front winding machine no closer than 1 m (further is better).
The prepared transformer frame is clamped between two cheeks loosely mounted on a pin.
Fig. 10. Location of transformer winding elements and winder arms.
The pin is then inserted into a drill chuck or clamped onto the shaft of a winding machine. The frame, as well as the coil with the wire, must be well centered so that it rotates evenly when winding and does not hit. The clamping brushes must be positioned in such a way that they do not cover the holes for the leads in the frame.
The coil with wire must be installed 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 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 conductors, an insulating tube for the leads, a sheet of paper and a pencil for making marks when counting turns if you don’t have a counter, scissors for trimming the gaskets, a piece of fine sandpaper for stripping the insulation and a heated soldering iron for soldering of leads. You yourself need to sit freely against the table (workbench) and practice hand interactions.
With your right hand you need to rotate the winding machine so that the wire rests on the frame from above, and with your left hand you need to hold and pull the wire, directing its movement so that it lies evenly turn to turn (to do this, place your left hand on the table under the axis of the machine or device, pulling it forward as far as possible). The farther the wire is directed from the frame, the more accurately and easily the wire is laid.
Fig. 11. Termination of output wires of the transformer winding. a-regular termination of the output wire; b - winding during normal wire termination; c - lead wire blank with wide laying; g - winding when terminating a wire with a wide laying; d - termination of the last winding terminal; e - blank loop output wire.
The frame, verified and secured to a machine or drill, is wrapped in a thin paper strip. To keep the strip in place, you can lightly glue it.
The lead conductor or the end of the winding wire itself can be secured in two ways.
If the wire is thin, then the output is made with another, flexible wire. Such a lead should be long enough so that, after passing it through the hole in the frame, it is possible to wrap it (in one turn) around the frame sleeve.
Solder the stripped end of the wound wire to the tip of the output conductor, which has been previously stripped and tinned by 2-3 mm, and, having insulated the soldering point with a piece of paper or varnished cloth folded in half, winding begins (Fig. 11a). The insulating pad is pressed when winding with subsequent turns (Fig. 11.6).
The lead threaded into the hole in the frame must be somewhat disassembled around the axis (pin) of the winding machine or tied to it so that during further winding it does not pull out of the frame. For greater reliability, the leads can be tied to the sleeve with several turns of strong thread.
Another method is that the lead wire, after passing it through the holes in the cheek of the frame, is captured by a strip of release paper, the edge of which is folded under the wire (Fig. 11c). Then a strip, which should be the width of the frame, is wrapped around the sleeve and presses the lead wire.
In this case, under the strip (at the end of the output wire) you need to place an insulating pad, which will then cover the junction of the output and wound wires.
To the tinned end of the output 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 will be pressed 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 turn to turn with some tension. In the process of winding this row, the left hand should be moved evenly behind the laying of the turns, trying to maintain the angle of tension. 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 through the cheek. This is especially important when winding high-voltage windings (for example, step-up windings in power or anode windings in output transformers).
Before starting winding (when the first terminal is tucked in and soldered), the revolution counter must be set to zero or its readings must be recorded. In the absence of a counter, the revolutions are counted silently or out loud, and every hundred revolutions is marked on paper with a stick.
After winding each row, the wire must be left taut so that when applying the paper gasket, 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 clothes clip. The gasket must cover the entire row of windings. It is glued together or temporarily (until it is held in place by the turns of the next row) pressed against the winding with a rubber ring, which can be made from a thin elastic cord.
The last output of the winding can be done in the same way as the first. Before winding the last complete or incomplete row, this output conductor, together with a paper gasket (Fig. 11, c), must be laid on the frame and, wrapping the frame with a strip of gasket, press the conductor with a rubber ring.
After winding the last row, the wound wire is cut and, after stripping, soldered to the tinned tip of the output conductor (Fig. 11e). 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 is laid on the frame in the same way as a regular output conductor.
Branches from 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. In this case, the loop is passed through the hole of a folded paper strip, which is tightened after pressing it to the winding with subsequent turns (Fig. 12.6).
You can do 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 conductor, which is soldered to the wire, as shown in Fig. 12, c.
Fig. 12. Taps from the transformer winding, methods of fastening. a - loop branch; b - sealing the loop branch; c - outlet from a separate wire.
Fig. 13. Fastening the ends of the transformer winding from thick wire. a - fastening the first winding terminal; b - fastening the last winding terminal; c - fastening two terminals with double-sided tightening.
The beginning and end of the thick wire windings are led out directly (without separate lead wires) through holes in the cheeks of the frame. You only need to put flexible insulating tubes on the ends coming out of the frame. The ends of the winding are secured using 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 wrapping 6-8 turns tightly around it, tighten the loop (Fig. 13a). The second output end of the winding is also secured.
In this case, without finishing 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, passing the end of the winding into the loop, the loop is tightened (Fig. 13.6).
If the winding of thick wire contains a small number of turns (no more than 10), then the lead ends can be secured with tape by tightening on both sides, 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 in the case 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 are cleaned by 10-15 mm with sandpaper, carefully twisted and soldered. The junction of the wires is then insulated with a piece of release 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 the wires in this case is considered reliable if a small ball forms at the end of the twist.
Windings of thin wire with a number of turns of several thousand can be wound not turn by turn, but “in bulk.” However, the turns should be laid evenly so that the winding does not have bumps or dips. Approximately every millimeter of thickness of such winding, paper gaskets must be made.
To symmetry two windings or halves of windings, frames are often used, partitioned in the middle with a cheek. First, one half of the winding is wound, and then the frame is turned 180 degrees and the other half is wound.
Since the turns of each half of the winding will be wound in different directions, when connecting the halves in series, you need to connect their beginnings or ends. In this case, it is more convenient to make conclusions from the windings on opposite sides of the frame.
The windings of a transformer or inductor can be made without a frame. Winding is done basically in the same way as with the frame, but the spacers between the windings (or rows) are made very wide (three times wider than the winding).
Upon completion of 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, the wound section is closed (Fig. 14). The end sides of the wound windings must then be filled with resin (from dry cells and batteries).
Fig. 14. Frameless winding of the transformer coil.
From the outside, if the top row of turns of the last winding is wound with thick wire and done fairly neatly, the coil does not need to be wrapped in anything. If the upper winding is made of thin wire, and is not wound turn to turn, then the coil should be wrapped in paper or leatherette.
In order to easily understand the leads and taps when installing the transformer, it is advisable to use multi-colored lead conductors. For example, make the terminals of the transformer network winding 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 output conductors, but then you need to put a cardboard tag with the appropriate designation on each output.
Core assembly and terminal installation
Having finished winding the transformer, they begin to assemble its core. If the winding leads are made on one side of the cheek of the frame, then it is placed on the table with the leads 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 terminals 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, a). This is especially important when the core plates are shaped with notches on the middle core.
The power transformer core plates are assembled without a gap into a ceiling (alternately left and right), as shown in Fig. 15, b. The cores of output transformers or filter chokes are often assembled with an air gap, inserting plates only on one side (Fig. 15, c).
To ensure that this gap remains unchanged, a strip of paper or cardboard is inserted into the joint between the plates and the core pads. In plates with a notch on the middle core, the thickness of the gap is determined by the thickness of the notch.
Fig. 15. Assembling the core for the transformer. a - preparation of the frame with windings for filling it with plates; 6 - assembly of the core plates into a “overlap”; c - assembly of the core plates at the joint with the gap; d - assembly of the core from plates with a perforation of the middle core.
If the frame is not very strong, then you need to fill it with plates (especially at the end of assembly) very carefully, since otherwise you can cut the sleeve with the sharp edge of the middle core and damage the winding. To prevent this, it is advisable to insert and bend a protective strip of mild steel into the frame window (Fig. 15, b).
When assembling a core from plates with a perforation of the middle core, you need to use an auxiliary guide plate (Fig. 15, d), cutting it, for example, from one core plate.
Frame window can be filled a large number plates If the transformer has been disassembled and rewound, then when reassembling it, you must use all the previously removed plates. During the assembly process, the core should be pressed several times by inserting a ruler or rod into the frame window.
The last plates, if they fit tightly, can be driven in with a hammer, lightly hitting them through a wooden lining. After this, turning the transformer in different directions and placing it on flat surface, it is necessary to straighten the core with light blows of a hammer through a wooden lining.
The core, after its assembly, must be well tightened. If there are holes in the plates, then it is tightened with bolts through overhead strips or angles (Fig. 16, a and b).
Along with this, you can also install a shield with petals for soldering the output ends of the windings.
Core small size, assembled from plates without holes, can be tightened with one common bracket cut from thin mild steel (Fig. 16, c).
It is very convenient to use the chassis on which the transformer is to be installed to fasten the transformer and tighten its core. 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 tightened with bolts through a common overhead frame (Fig. 16, d).
The output ends are connected to the corresponding sections of the circuit either directly or through a shield with contact petals installed on the chassis.
Fig. 16. Transformer assembly. a and 6 - transformers with contact shields, fastened with bolts using strips and squares; c - transformer, tightened with a bracket (clip); d - transformer, bolted between the bar and the chassis.
The simplest tests
The transformer, after its winding and assembly, must be tested. Power transformers are tested by connecting the primary (mains) winding to the electrical network.
To check the absence of short circuits in the transformer windings, we can recommend the following simple method. The network is connected in series with the primary winding of the transformer being tested electric lamp L (Fig. 17), designed for the corresponding network voltage.
For transformers with a power of 50-100 W, take a lamp of 15-25 W, and for transformers of 200-300 W, a lamp of 50-75 W. If the transformer is working properly, the lamp should burn at approximately “quarter incandescence.”
If you short-circuit any of the windings of the transformer, the lamp will burn almost fully incandescent. 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 this, making sure that the winding terminals are not shorted, the primary winding of the transformer must be connected directly to the network for one to two hours (by closing lamp L with the Vk switch). At this time, you can use a voltmeter to measure the voltage on all windings of the transformer and make sure that their values correspond to the calculated ones.
Fig. 17. Scheme for testing transformer windings.
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 II must alternately touch each of the outputs of the network winding 1.
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, by touching the output end of step-up winding II to the output ends of other windings, the insulation of these windings is tested. The absence of a spark or weak sparking (due to the capacitance between the windings) indicates the adequacy of the insulation between the windings of the transformer.
The transformer must be tested carefully, being careful not to come under the high voltage of the step-up winding.
Other types of transformers (output transformers, 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, the transformation ratio can be determined.
Having verified as a result of the test that the manufactured transformer is in good working order, the latter can be considered ready for installation and installation.
Lookup tables
Table 1. Characteristics of copper enameled wires PEL and PShO.
Table 2. Number of turns per centimeter of continuous winding length.
Table 3. Output transformer data from some radio receivers.
I'm already tired of assembling low-frequency amplifiers on microcircuits, my hands are itching, and I wanted to solder something serious. I decided to solder a transistor amplifier with bipolar power supply. The power source will be a linear power supply with a toroidal transformer, the winding of which I will talk about in this article.
First we need to decide on the power of the amplifier, the number of channels and load resistance.
I will have two channels, the output power will be approximately 100W per channel, the load resistance will be 4 Ohms.
You don’t have to bother and take a 300W transformer, but this is extra size and weight. Fortunately, if a class AB amplifier has an efficiency of approximately 50%, then in order to get 100W at the output, you need to consume 200W. If two channels are 100W each, then the consumption will be 400W. This is all approximate, and with the condition that the input signal will be a sinusoid with a constant amplitude. I don’t think that among reasonable people there are fans of listening to terrible squeaking in speakers.
The music we listen to has a sine wave waveform that varies in both frequency and amplitude. This signal will not always have a maximum amplitude; at such moments the electrolytic capacitor of the power source will be charged, and discharged at maximum amplitudes, thereby saving on transformer power. Again, if you are not a fan of listening to squeaking in the speaker system.
Let's calculate the power and voltage of our future transformer. Download and run the program.
We fill in all the fields at the top of the program, set the quiescent current to 10mA, the preamplifier current to 0mA, select the purpose and type of signal according to the taste of the music you are listening to. Click “Apply”.
The program calculated the voltage idle move power source, as well as capacitor capacity, these ratings are advisory in nature and are given for one arm.
Next, fill in the two lower windows in accordance with the recommended values and click “Calculate”. We got the output voltage of the transformer windings, I have 34.5V on each arm, the current of the secondary windings is 1.7A, diode parameters and connection diagram.
We have decided on the transformer parameters, now we download and run the program. We will calculate the winding data.
My core is toroidal and has dimensions of 130*80*25. Fill in the fields of the program.
We set the induction amplitude to 1.2 T, or maybe one and a half (as in my case), this is for strip cores, and for plate cores we set it to 1 T. This parameter depends on the hardware.
Current density for class AB is from 3.5-4 A/mm2, for class A 2.5 A/mm2.
We set the currents and voltage of the secondary windings, click calculate.
So, we got the number of turns of the primary and secondary windings, as well as the diameters of the wires.
You can do without calculations, wind approximately 900 turns, and periodically connect the winding to a 220V network in series through an incandescent lamp with a rated voltage of 220V.
If the lamp stays on, even at half heat, then we move on, checking periodically. As soon as the lamp stops glowing, it is necessary to measure the no-load current (but without the lamp, we connect the winding directly to the network), which should be 10-100 mA.
If the no-load current is less than 10mA, then this is not very good. Due to the high resistance, the transformer will heat up under the load. If the current exceeds 100mA, the transformer will heat up at idle. Although there are transformers with no-load current and 300mA, they heat up without load and hum terribly.
You can start winding the transformer itself. I need to wind 1291 turns of the primary winding with a wire whose diameter is 0.6 mm. Notice the diameter, not the cross-section! I have a 0.63mm wire.
I wrap it with rag tape. Once I wrapped the core with one lavsan tape, without electrical tape (or cardboard), and after winding several layers a breakdown occurred. Apparently the lower layers of the wire were crushed, and the varnish was damaged by the sharp edge of the core. Now, when winding toroidal transformers, I always wind the core with rag tape.
Mylar tape can be bought in the store, in the form of a baking sleeve, which is cut into ribbons using a razor blade and a metal ruler.
We take a 40cm wooden ruler, saw through both edges so that the wire can be wound around it. We reel in a large number of wires (I had to wind 1300 turns several times).
I wind all the windings clockwise, as in the picture.
We secure the free end of the wire with tape, or thread, and wind the winding layer turn to turn.
Solder the wires of the primary winding. We isolate the areas of soldering and stripping of varnish.
I'll give you one little advice. When soldering wires to the terminals of the primary winding, choose high-quality and durable wires, or do not solder them, but place them in dielectric tubes (heat shrink, cambric). While I was winding the secondary windings, my leads broke off due to repeated bending. I took the wires from the PC power supply.
We overlap 4-5 layers of lavsan tape taken from the baking sleeve.
Don’t forget to write down the number of turns in each layer on a piece of paper so you don’t forget. After all, winding a transformer can last not 1-2 days, but a month or several months, when there is no time, and you can forget everything.
We wind the remaining layers of wire in the same direction, between which we place layers of lavsan tape insulation.
The connection points must be soldered and insulated with heat shrink tubing.
When you reel it in required amount turns of the primary winding of a toroidal transformer, you need to connect the winding in series through a 220V lamp to the network, as mentioned above. The lamp should not glow. If it lights up, it means you have a small number of turns, or a short circuit between layers or turns (if the wire is bad).
My no-load current is 11mA.
Solder the tap. We isolate the primary winding from the secondary well, maybe 6-8 layers of Mylar tape.
The secondary winding can be wound according to the calculations made above, or using the following method.
We take a thin wire and wind two or three dozen turns over the “primary”. Next, we connect the primary winding to the network and measure the voltage on our experimental winding. I got 18 turns of 2.6V.
Dividing 2.6V into 18 turns, I calculated that one turn is equal to 0.144V. The more turns on the experimental winding are wound, the more accurate the calculation. Next, I take the voltage I need on one of the secondary windings (I have 35V) and divide by 0.144V, I get the number of turns of the secondary winding equal to 243.
Winding the “secondary” is no different. We wind it in the same direction, with the same shuttle, only we take the diameter of the wire from the calculations above. My wire diameter is 1.25mm (I didn’t have a smaller one).
A transformer is a unit designed to transmit electricity with changed parameters through the network to the end consumer. This equipment has a specific design. Transformers can step down or step up voltage.
Over time, the core may need to be rewinded. In this case, the radio amateur is faced with the question of how to wind a transformer. This process takes a lot of time and requires concentration. However, there is nothing complicated about rewinding a circuit. There are step-by-step instructions for this.
Design
The transformer operates on the principle of electromagnetic induction. He may have different design 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, you must initially consider the design of its coil.
Toroidal devices convert AC voltage one power to another. There are single-phase and three-phase designs. They consist of several elements. The structure includes a ferromagnetic steel core. There is a rubber gasket, primary and secondary winding, as well as insulation between them.
The winding has a screen. covered and core. A fuse and fasteners are also used. To connect the windings into a single system, a magnetic drive is used.
Winding device
Toroidal transformers can be different types. This must be taken into account during the contour creation process. 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 device. It consists of which are fastened together with a metal rod. It has the shape of a handle. This skewer will help you quickly wind the outlines. The twig should be no thicker than 1 cm. It will pierce the frame right through. Using a drill will make this process easier.
The drill is mounted on the surface of the table. It will be parallel. The handle should rotate freely. The rod is inserted into the drill chuck. Before this, you need to put a block with the frame of the future transformer on the metal pin. The rod may have a thread. This option is considered preferable. The block can be clamped on both sides using 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 design presented above, you can use an inductor from a telephone, a device for rewinding film, or a machine for a bobbin with thread. There are many options. They must ensure a smooth, uniform process.
You will also need to prepare the device for unwinding. In principle, such equipment is similar to the devices presented above. However, in the reverse process, rotation can be performed 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. An ordinary water meter or bicycle speedometer may be suitable for these purposes. Using a flexible roller, the selected metering device is connected to the winding equipment. You can count the number of turns of a coil orally.
Calculations
To understand how to wind a pulse transformer, calculations need to be made. If you are rewinding an existing coil, you can simply remember the original number of turns and purchase a wire of identical cross-section. In this case, you can do without calculations.
But if you need to create a new transformer, you need to determine the quantity and type of materials. For example, for a device with a working load of 12 to 220 V, a device with a power of 90 V will be required. You can take a magnetic drive, for example, from an old TV. The conductor cross-section is determined in accordance with the power of the unit.
The number of turns of the coils is determined for 1V. This figure is equivalent to 50 Hz. The primary (P) and secondary (B) windings are calculated as follows:
- P = 12 x 50/10 = 60 turns.
- B = 220 x 50/10 = 1100 turns.
To determine the currents in them, the following formula is used:
- Tp = 150: 12 = 12.5 A.
- TV = 150: 220 = 0.7 A.
The obtained result must be taken into account when choosing materials for creating a new device.
Layer insulation
To wind ferrite transformer or another type of device, it is necessary to study one more nuance. Conductors should be installed between certain layers. Most often, condensate or cable paper is used for this. All necessary materials can be purchased in specialized stores. The paper must have sufficient density and be smooth without gaps or holes.
Between the individual coils, insulating layers are created from stronger materials. Lacquered fabric is most often used. It is covered with paper on both sides. This is also necessary to level the surface before winding. If you couldn’t find varnished fabric, you can use paper folded in several layers instead.
The 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 be folded up. This will keep the edges of the reel well protected.
Frame
To understand how to wind a transformer correctly, attention should be paid to every detail of this process. Having prepared the insulation, wire and tools, you should make a frame. You can use cardboard for this. Interior the frame must be larger than the core rod.
For an O-shaped magnetic drive, you need to prepare 2 coils. For core W-shape one circuit is required. In the first option, the round core must be covered with an insulating layer. Only after this do they begin winding.
If the magnetic drive is W-shaped, the frame is cut out from the sleeve. Brushes are cut out of cardboard. In this case, the coil will need to be wrapped in a compact box. The brushes are put on the sleeves. Having prepared the frame, you can begin winding the conductor.
Step-by-step winding instructions
It will be quite simple. To do this, a reel of wire should 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 jerking.
During this procedure, the wire from the old coil will be moved to the new frame. The distance between the wire and the table surface should be at least 20 cm. This will allow you to place your hand and fix the cable.
Everything needs to be laid out on the table in advance. necessary tools and equipment. You should have insulating paper, scissors, sandpaper, soldering iron (plugged into the mains), pen or pencil. With one hand you need to turn the handle of the winding device, and with the other hand you need to fix the conductor. It is necessary that the turns are laid evenly and evenly.
Considering 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 removed from the circuit. The fixation will be temporary.
Experienced radio amateurs recommend practicing first before winding. When you can apply the turns evenly, you can start working. The tension angle and wires must be constant. Each subsequent layer does not need to be wound all the way. Otherwise, the conductor may slip from its intended place.
During the winding process, 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. At the same time, 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 performed. This procedure may also be required if you initially plan to create a circuit from several separate pieces of wire. Soldering is performed in accordance with the thickness of the wire.
For wire up to 0.3 mm thick, the ends need to be cleared to 1.5 cm. They can then simply be twisted and soldered using the appropriate tool. If the wire is thick (more than 0.3 mm), you can solder the ends directly. In this case, twisting is not required.
If the wire is very thin (less than 0.2 mm), it can be welded. They are twisted without undergoing a stripping procedure. The connection point is brought into the flame of a lighter or alcohol lamp. An influx of metal should appear at the junction. The junction of the wires must be insulated with varnished cloth or paper.
Trial
Having studied 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 thick conductor external protection not required.
To assess the reliability of the insulation, it is necessary to touch each output of the network circuits with the lead-out conductor in turn. The verification procedure must be performed very carefully. Avoid the possibility of electric shock.
After reviewing the step-by-step instructions for winding a transformer, you can repair an old one or create a new device. If all its points are strictly followed, it is possible to create a reliable, durable unit.
