Winding a transformer with your own hands is a simple task if you prepare for it in advance. People who make various radio equipment or power tools have a need for transformers for specific needs. Since it is far from always possible to purchase certain products, craftsmen often wind toroidal transformers on their own. Those who are trying to wind for the first time face difficulties: they cannot determine the correctness of the calculations, select the appropriate parts and technology. It must be understood that different types are wound in different ways.
Also fundamentally different toroidal devices. The calculation of the toroidal transformer and its winding will be special. Since radio amateurs and craftsmen create parts for power equipment, but do not always have sufficient knowledge and experience to manufacture them, this material will help this category of people deal with the nuances.
Preparation for winding
Necessary materials
Winding materials require careful selection Every detail matters. In particular, you will need:
- Transformer frame. It is used to isolate the core from the windings and also holds the winding coils. It is made of strong and thin dielectric materials so as not to take up too much space in the intervals (“windows”) of the core. You can use cardboard, microfiber, textolite. The thickness of the material should not exceed 2 mm. The frame is glued using ordinary joinery glue (nitro glue). Its shape and dimensions are completely dependent on the core, the height is slightly greater than that of the plate (winding height).
- Core. This role, as a rule, is performed by magnetic cores. 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 circuits have a variety of shapes, but most often there are products in the form of the letter "Ш". In addition, they can be cut from various blanks that are available. To determine the exact dimensions, the winding wires are pre-wound.
- Wires. Here you need to use two types: for winding and for conclusions. The optimal solution for transforming devices is copper wires with enamel insulation (PEL or PE type). They are enough even for power transformers. Wide choose sections allows you to choose the most suitable option. PV wires are also often used. For output, it is best to take wires with multi-colored insulation so as not to get confused when connecting.
- Insulating pads. Help to increase the insulation of the winding wire. As a rule, thin and thick paper is used (tracing paper is perfect), which should be laid between the rows. But the paper must be intact, tears and punctures, even the most insignificant ones, must be absent.
How to speed up your workflow
Many radio amateurs have in their arsenal simple special units, with which the winding is done. In many cases, we are talking about simple structures in the form of a small table or table stand, on which several bars with a rotating longitudinal axis are installed. The length of the axis itself must exceed the length of the winding frame by 2 times. A handle is attached to one of the exits from the bars, allowing you to rotate the device.
Coil frames are put on the axis, which are stopped on both sides by pins-limiters (they prevent the frame from moving along the axis).
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 more power in comparison with those wound on an E-shaped core. Therefore, 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 materiel. First, you need to decide on the type of wire you are using. Secondly, you need to calculate the number of turns (it follows that you will know how many meters of wire you need in total). Thirdly, it is necessary to choose the wire 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 also occurs if the power of consumers connected to the secondary winding exceeds the value that the transformer can give. The consequence of overheating is a decrease in reliability. Moreover, overheating can even lead to ignition of the transformer.
What is required for the manufacture
So, you start making a transformer. You need to acquire tools and materials. Of course, even a sewing needle or matches may be required, but for sure everyone has such supplies. 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. Further, of course, the wire in lacquer insulation. Be sure to have masking tape and PVA glue. Also, fabric-based electrical tape is needed to separate the windings. And a few 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, as it may seem, is very difficult. But in any house, shed, 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 TVs so as not to plant picture tubes. It doesn't matter to you whether this stabilizer works or it's burned out. The most important thing is the toroidal transformers that it uses. 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 - the preparation of the core. Note that it has right angles. You do not need this, as you can damage the lacquer insulation when winding. Try to round the corners as much as possible by filing them with a file. Then, on top of the transformer steel, lay the electrical tape based on the fabric. Only one layer is needed.
windings
And now a little about how the calculation of a toroidal transformer is carried out. You can of course use simple programs, of which there are many. You can use a ruler and a calculator to calculate. Of course, it will have an error, since many more factors that exist in general in nature are not taken into account. You should follow one rule when calculating - the power in the secondary coil should not be more than the same value in the primary winding.
As for such a process as winding a toroidal transformer, it is very laborious. 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 on it. Then, passing this spindle through the torus, you lay the turns of the windings. It 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 in specific example. The primary winding is usually powered by 220 V AC. Let's say you need two secondary windings so that each gives out 12 V. And you also use 0.6 mm wire in the primary winding. Therefore, the cross-sectional area will be approximately 0.23 square meters. mm. But this is not all 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 must be exactly 3.9 times larger than in the primary. To calculate the number of turns for the primary winding, you need to use a simple formula: multiply the coefficient "40" by the voltage (in the primary circuit it is 220 V), after which this product is divided by the cross-sectional area of \u200b\u200bthe magnetic circuit. It should be noted that its efficiency and service life depend on how accurately the calculation of the toroidal transformer is carried out. Therefore, it is better to repeat each step of the calculation once again.
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 journal articles and books, is usually insufficient, and the radio amateur has to most do the work, relying on your ingenuity, or resort to the help and advice of a more experienced comrade.
With this in mind, the author of this brochure has made an attempt to give in a systematic way the necessary instructions for the manufacture of low-power transformers and teach practical methods of winding them at home or in a radio club.
Winding accessories
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 they usually wind transformers either directly by hand or using simple winding devices.
Let's consider how it is possible from improvised materials and with the help of conventional tools make simple fixtures for winding.
The simplest such device is shown in Fig. 1. It consists of two racks 1 (or a metal bracket) mounted on a board 2, and an axis 3 made 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 6. 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 the 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.
Fig. 1. The simplest winding device. 1 - racks; 2 - board; 3 - axis; 4 - coil frame; 5 - block; 6 - hairpin 7-wedge; 5-tube.
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 axle 3.
A more convenient and reliable winding device is made of 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 winder for rewinding film, a telephone inductor, etc.
The film winder (after a slight alteration) is especially convenient, as it is made firmly and has a soft, backlash-free course. 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 coils in a row), the wire must go completely evenly.
The simplest device for unwinding wire is shown in Fig. 3. This is an ordinary metal bar 1 threaded through holes wooden racks 2 fixed on board 3.
The manufacture of a wooden block for the frame of the unwound reel 4 is optional in this case. In order for it not to beat or jump during unwinding, it is possible to roll a 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.
Fig. 3. The simplest device for unwinding a wire, 1 - a bar; 2- racks; 3- board; 4 - coil with wire; 5 - tube.
Fig. 4. Machine for unwinding the wire. 1 - bracket; 2 - board; 3-bolts; 4- hairpin; 5 - nuts (lambs); 6 - cheeks.
It is better, however, to make a special unwinding device, shown in Fig. 4. From mild steel strip or other suitable material bracket 1 is bent, which is attached to board 2 (or table).
IN uprights the brackets make holes (5-6 mm in diameter) with threads (thread M-5 or M-6), into which bolts 3 sharpened from the ends to a cone are screwed in. A stud 4 cut along the entire length is made from a metal rod with a diameter of 5-6 mm, 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. Simple but demanding special attention method - this is an oral count of each revolution (or through one revolution) of the handle of the machine. 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. Articulation of the counter of turns with the winding device. a - using a flexible roller; b - with the help of 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 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 performed using a flexible roller (a piece of thick-walled rubber tube) connecting the axis of the counter with the axis of the flock (Fig. 5a). In this case, each 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. 5.6). With this method, the counter is linked to the machine all the time.
Frame for transformer
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, getinax, etc. Depending on the size of the transformer or inductor, the thickness sheet material for the frame, from 0.5 to 2.0 mm is taken.
For gluing the cardboard frame, you can use office universal glue or ordinary carpentry glue. The best glue, with good moisture resistance, should be considered nitroglue (enamelite, hercules). Getinax or textolite frames are usually not glued, but are assembled “in a castle”.
Fig. 6. Proportionality of the frame and core plates. a - for split plates; b - for inserts with middle core punching.
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 ratio of the dimensions of the frame and core plates for different type plates are given in Fig. 6.
Fig. 7. Pattern and gluing of the frame for the transformer.
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 1 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.
Fig. 8. Details of the prefabricated frame for the transformer. a - the width of the core plate, plus the gap, plus the thickness of the material of parts 3; b - thickness of a set of core plates plus the thickness of parts 2; c is the thickness of the material.
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 1, after drilling several holes in them, windows are cut out.
Fig. 9. Assembling the frame for the transformer coils into the lock.
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 significantly large sizes(the contours are shown in 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. 9.
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 pads
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 gaskets 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 windings in a transformer must be even better than between rows of turns, and the better the higher the voltage. Better insulation- Lakotkan, but besides it, you also need thick cable or wrapping paper, 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 (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 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 lead 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 circuit elements 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 winding machine no closer than 1 m (further - better).
The prepared transformer frame is clamped between two cheeks loosely mounted on a stud.
Fig. 10. Location of transformer winding elements and winder hands.
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 beat. Clamping brushes must be positioned in such a way that they do not block 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 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 solder pins. 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.
Fig. 11. Termination of the output wires of the transformer winding. a-usual termination of the output wire; b - winding with normal termination of the wire; c - a lead wire blank with a wide gasket; g - winding when terminating a wire with a wide gasket; d - termination of the last output of the winding; e - blank loop lead wire.
The frame, verified and fixed on a machine or drill, is wrapped with a thin paper strip. To hold the strip, 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 somewhat disassembled 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 output wire), you need to put an insulating "overlay, which then covers the place of soldering 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, the stripped tip of the wound wire is soldered and winding is performed. 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).
The 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, and each hundred revolutions is 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, c), 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 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 wire, which is soldered to the wire, as shown in Fig. 12, c.
Fig. 12. Taps from the transformer winding, mounting methods. a - loop outlet; b - termination of the loop outlet; c - tap from a separate wire.
Fig. 13. Fastening the ends of the transformer winding from a thick wire. a - fastening of the first output of the winding; b - fastening of the last output of the winding; c - fastening of two conclusions with a double-sided tightening.
The beginning and end of the thick wire windings are led out directly (without separate lead 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 looped tape 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 180 degrees 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). The end sides of the wound windings must then be filled with tar (from dry cells and batteries).
Fig. 14. Frameless winding of the transformer coil.
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 output conductors, but then it is necessary to put on a cardboard tag with the appropriate designation for each output.
Core Assembly and Lead Mounting
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, a). 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, b. The cores of output transformers or filter chokes are often assembled with an air gap, inserting plates from one side only (Fig. 15, c).
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.
Fig. 15. Assembly of the core for the transformer. a - preparation of a frame with windings for filling it with plates; 6 - assembly of the core plates into a "overlap"; c - assembly of the core plates in a joint with a gap; d - assembly of the core from plates with a middle core 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 a 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, b).
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.
Frame window fills possible a large number plates. 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 shield with petals for soldering the output ends of the windings.
Core small size, 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.
Fig. 16. Assembly of the transformer. a and 6 - transformers with contact shields, tightened with bolts using strips and squares; c - transformer, tightened with a bracket (clip); g - transformer, bolted between the bar and the chassis.
The simplest 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. The network is connected in series with the primary winding / of the tested transformer electric lamp L (Fig. 17), 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 glow”.
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, 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.
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 in turn 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, touching the output end of the step-up winding II 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.
Reference tables
Table 1. Characteristics of copper enameled wires PEL and PSHO.
Table 2. The number of turns per centimeter of the length of a continuous winding.
Table 3. Data of output transformers from some radio receivers.
I'm already tired of assembling low-frequency amplifiers on microcircuits, my hands itch, and I wanted to solder something serious. I decided to solder a transistor amplifier with a bipolar 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 determine the power of the amplifier, the number of channels and the load resistance.
I will have two channels, the output power will be approximately 100W per channel, the load resistance will be 4 ohms.
You can not bother and take a 300W transformer, but these are extra dimensions and weight. On a good note, if an AB class amplifier has an efficiency of approximately 50%, then in order to get 100W at the output, it is necessary 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 a terrible squeak in the speakers.
The music we listen to has a sinusoidal waveform that varies in both frequency and amplitude. This signal will not always have the maximum amplitude, at such moments the electrolytic capacitor of the power source will be charged, and discharged at maximum amplitudes, thereby saving on the power of the transformer. Again, if you are not a fan of listening to a squeak 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 in the upper part 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 listen to. Click "Apply".
The program calculated the voltage idle move power supply, as well as the capacitance of capacitors, 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 for each arm, the current of the secondary windings is 1.7A, the parameters of the diodes and the connection diagram.
We have decided on the parameters of the transformer, now we download and run the program. We will calculate winding data.
My core is toroidal and has dimensions of 130 * 80 * 25. We fill in the fields of the program.
We set the induction amplitude to 1.2 T, it can be one and a half (as in my case), this is for tape cores, and for lamellar cores we set 1 T. This parameter depends on the iron.
Current density for class AB 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 about 900 turns, and periodically connect the winding to the 220V network in series through an incandescent lamp, with a rated voltage of 220V.
If the lamp burns, even at the glowing floor, then we wind it further, periodically checking. As soon as the lamp stops glowing, it is necessary to measure the no-load current (but without a lamp, we connect the winding directly to the network), which should be 10-100mA.
If the idle current is less than 10mA, then this is not very good. Due to the high resistance, the transformer will heat up at the load. If the current exceeds 100mA, then 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 section! I have a 0.63mm wire.
I wrap it with duct tape. Once I wrapped the core with one lavsan tape, without electrical tape (or cardboard), after winding several layers, a breakdown occurred. Apparently, the lower layers of the wire were crushed, and the varnish was damaged on the sharp edge of the core. Now, always when winding toroidal transformers, I wind the core with rag tape.
Lavsan tape can be bought at 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 40 cm wooden ruler, saw through both edges so that the wire can be wound around it. We wind a large number of wires (I had to wind 1300 turns several times).
I wind all the windings clockwise, as in the picture.
We fix with adhesive tape, it is possible with a thread, the free end of the wire and wind the coil to coil of the winding layer.
Solder the wires of the primary winding. We isolate the places of soldering and stripping the varnish.
I will give you one little advice. When soldering wires, choose high-quality and durable wires to the terminals of the primary winding, or do not solder, but lay 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 obtained from a baking sleeve.
Do not forget to write down on a piece of paper the number of turns in each layer, so as not to forget. After all, the winding of 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 insulation of mylar tape.
Connection points must be soldered and insulated with heat shrink tubing.
When you wind required amount turns of the primary winding of the 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 glows, then you have a small number of turns, or a short circuit between layers or turns (if the wire is bad).
My idle current is 11mA.
We solder the outlet. We isolate the primary winding from the secondary thoroughly, you can layer 6-8 lavsan tape.
The secondary winding can be wound according to the calculations made above, or by the following method.
We take a thin wire and wind a dozen two or three turns over the “primary”. Next, we turn on the primary winding in the network and measure the voltage on our experimental winding. I got 18 turns of 2.6V.
Dividing 2.6V by 18 turns, I calculated that one turn is equal to 0.144V. The more turns on the experimental winding will be 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 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 less).
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. 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, it is necessary to 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 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 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. Inner part the frame must be larger than the core rod.
For an O-shaped magnetic drive, 2 coils must be prepared. For the core W-shape 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.
Everything must be laid out on the table necessary tools and equipment. 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 thick conductor outdoor protection 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.
