Winding electric wires

Appointment winding electrical wires   consists in their use in the manufacture of windings of transformers, apparatuses, electrical machines and devices. In these windings of electrical devices, there are usually a huge number of turns of wire.

Winding wires, in contrast to the installation and installation wires are characterized by the diameter of the cores, and not by the area of ​​their cross-section. Therefore, many brands winding wires  have veins of very small diameter, and the thickness of the insulating layer is negligible.

Wires of very small diameter number about 100 marks and all this thanks to the development of technology for the production of extra-fine wire and the creation of progressive electrical insulating materials.

For a long time veins of winding wires were made only of copper. But today aluminum is used for these purposes, as well as alloys with a significant electrical resistivity. The use of aluminum makes it possible to save copper - a scarce material, and the use of alloys with a high specific resistance makes it possible to increase the heat resistance of winding wires.

The winding wires are classified according to the type of insulation , taking into account the material from which the conductive wires are made:

With enamel, fiberglass or fibrous insulation;
   - with enamel-fibrous (combined) insulation;
   - with film insulation.

When manufacturing winding wires, varnishes (for insulation of veins) and lavsan, cotton, silk threads (for insulation of veins and in production of braids and windings) are used.

The winding wires are labeled in the same way as the mounting wires - the letters indicate the material from which the vein or insulation is made.

  Let's talk about the basic letters used to indicate the brand of winding wires. First of all, determine the material from which the veins of the winding wires are made. In the first place put the letter P in the stamps of all copper wires  and at the same time designate: "wire", its veins are made of copper. In order to distinguish copper wires with enamel insulation from aluminum, put the letter A at the end of the mark, for example: PEV - wire with copper conductors; PEVA is a wire with aluminum conductors.
   In the marking of wires made of alloys with high specific resistivity, the letters: HX - nichrome, K - constantan, M - manganin; if it is necessary to designate that the wire is soft (annealed), then, following the letter M or K, put the letter M; to determine that the wire is solid, put the letter T. For example: PEMM-wire, its vein is made of soft manganin wire; PEMT is a wire, its vein is made of solid manganin wire; in the arrangement of these wires there are no other differences.

Letters for marking the type of insulation of winding wires:

EV - enamel high-strength on a polyvinyl acetate base;
   EL - enamel on an oil basis;
   EM - enamel high-strength on a polyvinyl-base;
   ELR - high-strength enamel on a polyamide-resole base;
   Ш - natural silk;
   L - lavsan;
   C - glass fiber;
   О - one layer of winding;
   B - cotton yarn;
   D - two layers of winding;
   ShK - kapron.

In the existing designation, the second letter П, the film insulation is marked, for example: PPF - the wire insulated with a film of PTFE.

When specifying that the marks of the wires are made of combined insulation, the letters are determined in the order of the layers of insulation from the inner layer to the outer one, for example: PELSHO - copper wire, with insulation from enamel on an oil base and one layer of a winding made from natural silk.

Examples (as the brands of winding wires are deciphered):

PETR - copper wire with insulation from high-strength enamel on a polyamide-based base; PEVKM - a wire made of soft constantan wire with insulation from high-strength enamel on a polyvinyl acetate base;

Winding wires are wires used for making windings of electrical machines, apparatuses and devices. A significant number of winding wires are also used in the manufacture of devices, in various radio engineering devices, in television sets, in aeronautical and space technology, and so on.
Winding wires can be classified:
  on applied conductor materials: copper, aluminum and alloys of resistance. An insignificant part of the wires is produced with conductors made of bimetals, precious metals and special alloys, in particular superconductors;
  by types of insulation: winding wires with enamel insulation, or enameled wires; winding wires with fibrous or combined enamel fibrous insulation, including fiberglass and paper; Winding wires with plastic insulation, including film. In addition, in limited quantities, winding wires with solid glass and glass-enamel insulation are produced;
by the value of the operating temperature (class of heat resistance). The most common group of winding wires are enameled wires with significant advantages: thinner insulation allows increasing the filling factor of the groove in electrical machines and apparatus, increasing their power or reducing the overall dimensions of electrical devices while maintaining the existing parameters. Also, in terms of production conditions, enameled wires are less labor-intensive than wires whose insulation is superimposed on the wire, for example, by winding. Therefore, when switching to the production of enameled wires, labor productivity at cable plants increases. An important trend in the production of enameled wires is the predominant growth in the output of the thinnest wires, caused by the desire for microminiaturization of radio electronic equipment and computers. At the same time, the production of enameled wires for special purposes, in particular, wires with an additional adhesive layer, used for winding the coils of deflecting television sets, as well as in the winding of electric motors without the use of solvents, is expanding. An important point is also the transition to the use of enamel varnishes with less toxic solvents and the introduction of enamelling technology from melt resin without the use of solvents. The modern production of winding wires requires the profes- sional knowledge in the field of equipment and technology, test methods, conductive and insulating materials to be used by cable plant specialists. The efficiency of winding wires in the composition of products is largely determined by the correctness of their choice in terms of conditions and modes of operation, product design, and also depends on the technology of making the product itself. The service life of the same wire in the composition of different products can differ several times, even if the operating temperatures are close. The main conductor material used for the production of winding wires is copper. In terms of electrical conductivity, copper is superior to all other materials, with the exception of silver, which makes it possible to ensure the minimum overall dimensions of the windings of electrical machines, apparatus and instruments. In accordance with GOST 859-78, copper by chemical composition is divided into several grades. In the cable industry only copper of increased purity of grades not lower than Ml, M00k, M0k, M0ku, M0ob, M0b, M1k, M1b, M1y is used. Do not apply copper grade M1f with an increased content of phosphorus (0.012 ... 0.06%), which reduces the electrical conductivity. In addition, in the production of winding wires, copper grade M1p, deoxidized with phosphorus and containing it in an amount of 0.002 ... 0.012%, can not be used, although such copper can be used for some other types of cable products, for example tapes. The content of copper along with silver in these grades of copper is 99.9 ... 99.99%. The indices for grades have the following values: k, ku - cathode copper, b - anoxic, y - katodnaya re-melted, p and ф - deoxidized. Figures 00.0 and 1 determine the copper content, with the highest content of copper being of M00k and M006. Impurities adversely affect mechanical and
electrical properties of copper, so copper with an impurity content of more than 0.1% in cable production is not used at all. Oxygen-free copper, almost free of oxygen, has the best parameters in terms of application in the production of winding wires, and primarily enameled wires. It surpasses the usual in terms of ductility and provides a wire with a better surface quality.
Appointment and classification of varnishes.
Electrical insulating varnishes used for enameling wires are solutions of high-molecular-weight film-forming compounds or low-molecular reactive oligomers of volatile volatile liquids. When the enamel of the enamel is heated in the enamel of the furnace, the molecular mass of the film-forming substances increases even more, and the solvent evaporates, as a result of which a solid enamel film forms on the wire. Various synthetic resins are used as film-forming agents, as well as some vegetable oils. Solutions of film-forming in a particular solvent may have a different concentration, depending on the solubility of the lacquer base. Enamel varnishes can have a synthetic or oily resin base. Synthetic varnishes form on the wire more durable and heat-resistant enamel films, so they practically displace the production of oil-resin-based varnish-based varnishes, which also use scarce vegetable oils. So, now more than 95% of all enameled wires are made using synthetic varnishes.
General requirements for enamel lacquers
Another representative of polyvinyl acetal lacquers used in domestic practice is varnish VL 941, or metalvin. Lacquer metalvin is a solution of polyvinylformate and phenol-formaldehyde resins in a weight ratio of 2: 1 with the addition of a stabilizer - triethanolamine. The resulting film, in its electrical insulating and mechanical properties, does not differ from the viniflex varnish film, but exceeds the latter in resistance to organic solvents and water. Abroad varnishes for the enameling of wire based on polyvinylformate resins are known under the name of formox, formavar, formadur, etc. These varnishes differ from those of the domestic composition of the modifying agents, and also partly by the methods of preparation and composition of the basic resin.
Varnishes for wires with a temperature index of 105 ºС
As coatings of enameled wires, coatings based on polyvinyl acetal varnishes are most widely used. Polyvinyl acetals are the reaction products of polyvinyl alcohol with various aldehydes (formaldehyde, acetaldehyde, oil aldehyde, etc.). Depending on the type of aldehyde used, polyvinyl acetals are called polyvinylformals, polyvinylethylals, polyvinyl butyral, etc. Polyvinyl acetals are used as film-forming enamel varnishes. The most common in the domestic practice of polyvinyl acetate left varnish is a varnish VL 931, or viniflex. It is a solution of polyvinylformaldehyde and resole phenol-formaldehyde resins in a mixture of technical chlorobenzene and ethyl cellosolve in a ratio of 1: 1. The vinylflex varnish film does not melt or soften when heated (thermosetting polymer), but at the same time it is flexible and flexible, resistance to abrasion.
Varnishes for wires with a temperature index of 120 ºС
Polyurethane varnishes are used for enameling wires with a temperature index of 120 ° C. Polyurethanes are the reaction product of diisocyanates with compounds containing two or more hydroxide groups. Domestic varnish UR 973 is produced by the interaction of monophenylurethane, phenolic and polyester resin with additives of polyvinyl acetal resin. Small additives of polyvinylformalital improve the spreadability of the varnish and improve the quality of the wire surface. Recently developed for the enameling of small-diameter wires, polyurethane lacquer grade UP 9119 has a number of advantages over varnish UR 973. The additional introduction of 0.3% zinc naphthenate in the lacquer accelerates the curing process during the heat treatment of the coating on the wire. Coatings based on varnish UR 9119 have increased resistance against sticking.
Varnishes for wires with a temperature index of 130 ... 180 ºС
For the production of enameled wires with TI 130, 155 and 180, varnishes are used on polyester, polyesterimide, polyester cyanurateimide and polyetheramidimide base. This group of varnishes is currently the main one both in our country and abroad. In domestic practice, two polyester varnishes differing in the production process are used, PE 943A and PE 939. Despite the relatively high heat resistance, insulation based on polyester varnishes has a specific disadvantage - reduced resistance to thermal shock, which consists in the fact that when stretching or bending wires to a certain extent, a sudden short-term exposure to high temperatures can lead to cracking of the insulation. In order to improve the resistance of enameled wires with polyester insulation to thermal shocks, while simultaneously increasing the heat resistance, modified polyester varnishes are used. Modified polyester varnishes have been developed to improve the heat resistance of enameled wire insulation, its mechanical resistance to abrasion, resistance to heat shock and some solvents. For the modification of polyester resins, isocyanuric acid derivatives are used. The heat resistance of insulation based on polyester cyanuric varnishes is 155 ... 180 ºС. The main types of modified polyester lacquers are polyetherimide and polyether cyanuratimide. Polyetherimides are heat-resistant polymers containing imide, ether groups and aromatic rings. In domestic practice, polyesterimide lacquer has the brand PE 955 and is a product obtained from dimethyl terephthalate, ethylene glycol, glycerol, trimellitic anhydride and diaminodiphenylmethane. Polyestercyanuratimide varnish grade PE 999 is a solution of polyester cyanurateimide resin based on dimethyl terephthalate, ethylene glycol, TGEIC, trimellitic anhydride and 4.4 diaminodiphenylmethane in a mixture of tricresol and xylene. Domestic varnish ID 9142 differs from varnish PE 999 with an increased content of the imide part. Covering on the basis of lacquer ID 9142 has increased resistance to abrasion, adhesion, punching temperature of insulation, resistance to heat shock. For the production of enamel wires PEVTL 155, a polyurethane lacquer UR 155K is proposed, containing up to 28 ... 32% non-volatile part, in the composition of cresol, solvent, xylene, with a viscosity of 25 ... 50 VZ. The heat resistance class H uses 180A PFA varnishes and PI 180FB, the chemical basis of which is polyimide alicyclic structure. The breakdown voltage is 8000/10000 V. Cresol, solvent, xylene are used as solvents for these varnishes. Their viscosity according to ВЗ 246 at 20 ºС: 120 ... 106 s (for the PI 180FA) and 35 ... 45 s (for the PI 180FB). PET wire 180 refers to freon-resistant wires. Intensification of the process of making enameled wires using high-speed enamel aggregates required the development of new enamel varnishes with specific properties: good spreadability, low content of low molecular weight film-forming resin fragments that burn out at elevated enameling temperatures, etc. ZAO Elektroizolit was developed for high-speed enameling of lacquers Elizvan 155 (155T) and PI 180 FM for enameling wires on enamel aggregates with VD\u003e 50. In the usual way, the floor The polyimides of an alicyclic structure is polycondensation, when, as a result of the interaction of dianhydrides and diamines, a polyamidoacid is first formed from which a film is formed, which then is thermally converted to polyimide, the temperature regime of the thermoforming of prepolymers rather rigid - from 80 ... 100 to 300 .. .350 ºС. It is known that among polyethylene film materials polyimide film occupies a special place due to high thermal, physical and mechanical properties, dielectric characteristics, chemical resistance.
Varnishes for wires with temperature index 200 ... 240 ºС
For wires that are used for a long time at a temperature of 200 ... 220 ºС, poliamide-based varnishes are used. Polyamidimides are polymers which, in addition to amide groups, contain imide aromatic rings. Domestic polyamideimide varnish AD 9113 is a solution of polyamideimide in a mixture of N methyl 2 pyrrolidone with a coal tar solvent in the ratio of 9: 1; in the varnishes PAI 200A, PAI 200B a solvent composition N methylpyrrolidone, xylene is used. In addition to high heat resistance, polyamide imide varnishes provide coatings with mechanical strength exceeding even the strength of coatings based on polyvinyl acetal resin. Polyimide varnishes are used to insulate wires that are continuously operated at 220 ... 240 ° C. During storage at room temperature, the viscosity of polyimide varnishes decreases. At elevated temperatures, on the contrary, gelatinization is possible due to cyclization and a strong increase in viscosity. The production of polyimide varnishes is associated with the use of expensive and scarce materials. The productivity of labor with enameling with polyimide varnishes decreases, which also leads to a rise in the cost of the wire. Therefore, the use of wires with polyimide insulation is limited. In addition, it should be taken into account that the polyimide-based enamel film has less mechanical abrasion resistance than, in particular, a polyester-based film.

The principle of operation of most electric machines is based on the interaction of magnetic fields, which are created with coil windings. Coils are an indispensable part of generators and transformers, almost all electronic devices.

To create them, use a winding wire. Let's talk about its types and brands, features and application of different types.

What is needed for knowledge of the features of wires for winding

Many make repairs with their own hands, or they build self-made structures. Frequently burnt out electric motors rewind themselves, reel electromagnets (solenoids) transformers, magnetic antennas and inductance coils for radio electronic devices. In this case, only the diameter of the wire and the number of turns are taken into account (these characteristics can be found in reference books, repair manuals or calculated).

• But often not only they are important, but also the type of wire - and it may not be indicated. For example, the required number of turns due to the fact that they chose a brand with a thicker layer of insulation may simply not fit into the dimensions of the coil.
• An important type of wire is both for the reliability of the device, and even for its safety, if it is chosen with insufficient insulation resistance or unintended for operation at such a temperature, an interturn closure or breakdown may occur.
• If the first will only lead to the failure of the device, the second, if the safety measures (grounding, zeroing, etc.) are not observed, can be life-threatening.

In addition to the above, the price of wires with the same electrical characteristics, but different types, can vary significantly. Knowing this, you can save on the material.

Why overpay for a wire designed to work at elevated temperature and humidity for a transformer in which the well-known brand PEV can work perfectly.

Classification of wires

Classify the wires according to several criteria.

Conductor material

It:

1. Copper  - most widely distributed.
2. Aluminum  - because of the greater than copper resistivity is used less often. But, lately, their use is expanding, as aluminum is cheaper.
3. Of alloys of resistance (nichrome and the like)  - used for some devices.

Section geometry

Wire cross-sections are round and rectangular. The latter are used, if necessary, to pass through the conductor a large current, for conductors with a large cross-sectional area. For cold coils, use a hollow wire.

Insulation material

Various materials are used - from paper and natural fibers, to glass. Often apply several layers, for example: paper and enamel.

For insulation, not only dielectric properties are important, but also mechanical strength, as well as thickness. The smaller it is, the more turns can be laid in the coil for a given wire diameter.

Wire marking

They are marked with several letters and numbers, after the mark, usually denote the diameter of the section.

Attention. The diameter of the wire cross section is determined by copper, so if you want to know it by measuring, for example, a micrometer, remove the insulation first.

The copper wires are first followed by the letter P (wire), aluminum is designated AP, for alloys of resistance there are signs. Then comes the designation of isolation, usually according to the initial letters of the materials of its components and the number of layers. For rectangular wires, the letter P (rectangular) is put at the end, then a figure that differentiates types can follow further through the hyphen.

For example PELSHKO - Wire Enamel Lacquer Silk Kapron Single, copper wire coated with varnish enamel, and additionally insulated with one layer of kapron silk. If there were two layers, then there would be a letter D (double).

Attention. We give the marking, which is generally accepted in our country. The imported wire may differ, up to the point that each company has its own system of designations. Therefore, buying material from foreign manufacturers, you need to study the passport characteristics, and select the analogs for the operating conditions.

Paper insulation

Such wires, because of low dielectric properties, are usually used in low-voltage devices, combined with other materials. Paper for their production is used special: cable or telephone.

Widely used winding wire  in paper insulation for oil-filled transformers. In them, oil not only cools the windings, but increases resistance to breakdown. Example of marking АПБ - aluminum winding wires in paper insulation.

Attention. Letter B can denote not only paper but also cotton yarn, very similar to it in terms of characteristics.

Fiber and film insulation

For it, various fibers and films are used: both natural (cotton, silk), and synthetic. They withstand greater mechanical loads than winding wires with paper insulation, but lose them in thickness.

They are produced more often by multilayer winding of fibers on the conductor. A variant is possible and when the threads are interlaced, this method is used for large diameters. The film is applied by passing through a bath with a liquid insulating material. To improve the properties, this insulation is combined with enamel, or the same paper.

The designations of winding materials are as follows:

• asbestos - A;
• arimide-Ar;
• cotton - B;
• lavsan-L;
• kapron-K;
• trilobal - Kn;
• plastic - P;
• glass - C;
• glass with polyester - Сл;
• fluoroplastic (Teflon) -F;
• natural silk - Sh.

Example: wires PBBO - winding wires with paper insulation, the layer of which is reinforced with a layer of coiled cotton yarn.

Enamel

These wires are used most often. Virtually all windings of transformers and inductors in electronic devices are wound around them. The photo at the beginning of the article shows the coils of these factory-assembled wires.

They are used in widely used electromechanical devices. Almost every standard engine, generator, or contactor we meet, which is not designed to work under special conditions, will most likely have coils that use winding wires with enamel insulation.

The advantage of this type of insulation is the low thickness of the protective layer and the ease of application. Enough to dip the wire in the enamel. Indicate the insulation material with the letter E, followed by the following type of enamel.

1. Polyamide - An.
2. Viniflex - V.
3. Polyamido fluoroplastic - I.
4. L is an oil-based varnish-based enamel. The most common type. This is not a reservation, we mean the resistance to the impact of the electrotechnical lacquer, more precisely the solvents included in its composition. The fact is that the coils are impregnated with lacquer for additional protection and mechanical fixation of the conductors after winding. Enamel should not lose its properties after carrying out this operation.
5. Polyestercyanurateimide resistant to freons - F. Winding wires with enamel insulation of this type are used for windings cooled by freons.
6. Polyester - E.
7. Polyetherimide - EI.

Also distinguish the wires at the maximum temperatures that can withstand their coating without losing their properties. Divide them into groups (index) - 105, 120, 130, 155, 180, 200, 220 and above, respectively.

What other features of insulation can be indicated in the marking

In addition to the type of material for insulation and the number of its layers, the following additional markings may be indicated:

1. The fact that it is reinforced - U.
2. Refined - I.
3. Covered with a layer of additional varnish on the surface - L.

Winding wire for high frequencies

• In addition to standard single-core wires for coils operating at high frequencies, special wires are used - litzendras.
• The fact is that high-frequency currents pass only along the surface of the conductor. The resistance in this case depends not on the area of ​​the conductor, but on the length of its perimeter.
• In order to maximize it, the winding wire is made multifilament - from a beam of thin, diameter in a fraction of a millimeter, conductors. The transfusion is also carried out in a special way. Denote such wires by L.

We list the most common brands of such wires:

1. LEP and LEL  - a bundle of conductors has no additional general insulation.
2. LASHO and LESHD  - wrapped in silk in one and two layers respectively.
3. LEPCO  - with a fibrous nylon coating.

Attention. Remove the insulation from such wires mechanically, because of thin veins is difficult, therefore, before they are tin-plated, special etching compositions are used for desoldering. Only power lines and LEPCO can be soldered at once - their insulation is removed when heated by a soldering iron tip.

How to choose a wire for a winding or a coil

By the way, manual winding is of special quality (with the appropriate qualifications of employees).

The cross-section and mark of the wire in the windings is usually indicated in the product's passport, often the data is written on the device itself. If the document is lost, then there are several ways to find out the data.

1. For electric motors, contactors, inductors and chokes, it is easy to find the characteristics in the directories - only if a copy of a foreign production is not caught, or with an erased marking.
2. If the voltages on the transformer windings and its power are known, then there are simple calculation methods. The instruction how to do this is simple - you need to measure the cross section of the core, and calculate a few formulas. Even easier, calculate the electromagnets and coils of inductance and choke.
3. If it is impossible to apply the previous two methods, then simply, when disassembling a burned or broken winding, we measure the diameter and count the number of turns. Of course, it takes a long time for a large number of turns, but you can use a winding device with a counter.

Knowing the cross-section and the number of turns, we select the wire, with the necessary insulation taking into account all factors. The desired marking can be determined approximately by visually recognizing the insulation.

But it is necessary to take into account other factors. So, for fast-rotating windings, there are no wires with enamel insulation - its dielectric properties are lost at a temperature of more than 180 degrees Celsius, and it just melts.

If the device is operating under conditions of high humidity, then do not use fibrous winding because of its hygroscopicity. The operating conditions of the wires are detailed in the passports.

Council. If there is a problem with the purchase of the wire of the desired diameter, it is possible to wind the winding of two three connected in parallel, the main thing is that the sum of the areas of their cross-section (can be found in the reference books) was equal to the required value. Well, it's natural to fit in the dimensions of the coil.

We will be glad if our article helped you in the repair of various devices or in their own design and assembly. Not bad even if we just deepened our knowledge of electrical engineering and now you know what distinguishes winding wires with paper insulation from the type of PEV.