Winding wires. Types and markings. isolation and application. Winding wires for transformers. Modern requirements for the quality of wires Copper wires for transformers

and many other mechanisms.

The winding wire, unlike other types of conductors, has as its main parameter the diameter of the conductive core, and not its cross section. There is a very thin wire for windings, and having a negligible layer of insulation. The thinnest winding conductors are made according to a special production technology for especially thin conductors and electrical insulation materials.

For a long time, winding wires were made exclusively of copper. Today, aluminum and other alloys with significant resistance are often used for them. Aluminum saves expensive and scarce copper.

Classification

Winding wires are classified according to the material of insulation, according to the shape of the section and the material of the core.

Insulation material

The winding wire is manufactured with the following types of insulation:

• Fibrous.
• Enamel.
• Combined.

fibrous

Wires with fibrous insulation have increased mechanical strength. The thickness of the fibrous insulation is quite large, and can reach up to 0.4 mm per side. Chemical resistance and moisture resistance of such wires is low.

Fibrous insulation of wires used for the rewinding of electric motors and the production of oil coils may include paper, cotton fabric, glass, as well as asbestos fibers, lavsan, silk. These fibers and fabrics are superimposed in several layers in the likeness of a braided stocking.

enamel insulation

The enameled insulation material is vinylflex, metalvin, organosilicon base, polyether terephthalic acid, polyurethane.

Winding wire coated with a special enamel has electrical strength, resistance to moisture, aggressive chemicals. A feature of enamel winding wires is a very small thickness of the insulated layer (the largest thickness is 0.09 mm). The strength of the enamel of the PEL wire is small, such a wire is used only for windings of coils operating in a stationary state.

High-strength enamel wire PETV, as well as PET-155, is used for windings of electric motors with a power of up to 100 kilowatts. PET-155 enameled wire is used for the production of a new series of electric motors, the strength of its insulation makes it possible to wind the wire on automatic machines. Enamel wires also have high heat resistance, and are able to withstand temperatures up to 155 degrees.

Combined

Winding wire with combined insulation in its parameters is in an intermediate position between the two types of wires considered. The combined type of insulation includes several layers. The outer coating usually consists of fibrous material, while the inner coating is enamel. For example, PELSHO wire means: copper winding wire with silk and lacquer enamel insulation.

If the conductor is impregnated with heat-resistant varnish and covered with fiberglass, then its marking contains the letter "K". This type of wire has become popular due to its high reliability, and is used for electric motors of hoisting and transport mechanisms, including shipbuilding cranes.

Section shape

Winding wires come in two cross-sectional shapes:

1. Round.
2. Rectangular.

The round section of the wire is used in various fields. Such a wire has high strength and electrical characteristics.

The sizes of rectangular sections of wires are standardized. Such a wire is often used for transformer windings. The thickness of rectangular reins reaches up to 5.9 mm, and the width is up to 14.5 mm.

The ratio of these sizes may vary. There are some disadvantages expressed in the use of winding wires of flat section. When it is wound on a coil, there is a high probability of damaging the insulation, and also, with very small wire sections, it is visually difficult to distinguish the smaller side of the section from the larger one.

In any winding, an important element is the coil of the conductor around the core. According to the current power, the required wire cross-section is selected. Round wire is usually used for light loads, while rectangular wire is used for higher loads.

Conductor material

Most winding wires are made from the following materials:

• Copper.
• Aluminum.

Copper winding wires make up the majority of all wires produced. They have low resistivity, significant weight. The cost of copper wires is high.

Recently, instead of copper wires for windings, aluminum wire has been used, which is much lighter in weight, has a lower cost, but has a higher resistivity than a copper conductor.

Marking

To designate a wire, it is marked, which means the material of the core and insulation.

• At the beginning of the designation is the letter "P" for copper wire, and means "wire".
• To distinguish between aluminum and copper wires, there is an “A” at the end of the marking, for example, PEVA.
• If the core is made of an alloy with a high resistivity, then there are additional letters in the designation, for example, HX - nichrome, M - manganin, K - constantan.
• To designate a soft conductor, the symbol "M" is put, for a hard one - "T". For example, PEMT wire is hard wire copper wire, and PEMM wire is soft wire.

Letters for isolation

• EM - high-strength polyvinyl enamel.
• EL - oil base.
• EV - high-strength polyvinyl acetate enamel.
• L - lavsan.
• Sh - natural silk.
• B - cotton yarn.
• Oh, one layer.
• C - fiberglass.
• ShK - capron.
• D - two layers.

If the marking is the 2nd letter "P", this means that the insulation is in the form of a film. The PPF wire is equipped with insulation in the form of a fluoroplastic film.

For marking combined insulation, the symbols are in the order of the layers, starting from the inner one. PELSHO - copper wire, oil-based enamel and a single-layer silk braid.

Requirements

• The winding wire is covered with uniform insulation. Allowed at some thickening points according to the brand and size of the wire.
• The wire is transported in coils, drums and bobbins, depending on the size and brand. The conductor in such packages must be wound evenly and tightly, without confusion of turns. The number of pieces of wire in the coil or coil must correspond to the size and brand of the wire.
• Packages must be packed with paper capable of protecting the wire insulation from damage during transport. The maximum weight of the box with wire must not exceed 80 kg.
• A label is attached to the drum and reel with the designation of the manufacturer, weight, standard size and brand of the wire, as well as other parameters.

How to choose winding wires for the motor

The selection of the necessary wire for rewinding electric motors is carried out taking into account the heat resistance class, the allowable insulation layer and other requirements.

Enamel winding wires have the minimum thickness of the insulation layer. They are used with an increased percentage of groove filling during winding. The smooth surface of the insulation facilitates their installation in the grooves, and its small thickness with increased heat transfer provides protection against overheating.

The use of enamelled wires should be consistent with the specific types of lacquers and solvents used in a particular facility, or with those brands of lacquers that the facility is able to supply. There are solvents and varnishes that can destroy the enamel. And also, when heated to 170 degrees, this insulation becomes plastic, which does not allow it to be used for windings of rotors rotating at high angular speed.

The maximum thickness of the insulated layer has a winding wire with a combined and fibrous layer. Its use is prohibited for windings in an aggressive or humid environment. For such purposes, it is advisable to use winding wires equipped with glass insulation, but the low strength of the insulation imposes certain restrictions on the use of such wires. Although, in terms of heat resistance, glass-insulated wires are suitable for such classes of windings. When purchasing a winding wire, it is necessary to take into account that the cost of a wire of one standard size depends on the brand. When repairing low-voltage electrical machines, the price of the wire will make up a large part of the financial costs of the total cost of the repair. In this regard, it is necessary to take into account the technical and economic factors of choice, that is, the price and technical parameters.

In the process of repairing and rewinding electric motors, one cannot do without a winding wire with a round or rectangular cross section. The brand of wire depends on the material of the current-carrying core and the type of insulation used. The most commonly used products are made of copper wire.

Any brand has the letter P (wire) in its name. Next comes the insulation marking code. There is fibrous, enamel and combined insulation.
Fibrous insulation are made from natural and artificial silk, cotton fiber, nylon, fiberglass and lavsan. Such wires are mainly used for the manufacture of oil transformer windings.
enamel insulation is a mixture of synthetic varnishes, which, when heated, forms a strong thin layer on the wire. It is used for winding electrical machines and devices that do not have strict restrictions on the thickness of the wire insulation.
Fiber insulation

• Natural silk - Sh
• Cotton yarn - B
• Kapron - K
• Artificial silk - ISH
• Asbestos fiber - A
• Fiberglass - C

The letter code O or D indicates the number of layers of insulation used, one or two, respectively.
enamel insulation

• Viniflex (high-strength enamel) – EV
• Heat-resistant polyester enamel - ET
• Varnish-resistant enamel - EL
• Polyamide resol enamel - ELR
• Polyurethane enamel - EVTL

Combined insulation consists of several layers, the inner coating is made of enamel, and the outer one is made of fibrous material. For example, the PELSHO marking stands for copper winding wire insulated with a layer of natural silk and varnish-resistant enamel.
If the winding wire is impregnated in a heat-resistant varnish and insulated with fiberglass, the letter K will be present in the marking. Such a wire is quite common due to its high reliability indicators, it is used for windings of electric motors for cranes, including shipbuilding ones.
aluminum wires have an additional letter A in the marking.
Examples of marking winding wires:

• PETV - Winding wire Enameled Heat-resistant with Enamel insulation, is a copper core-wire;
• PETV2 - where "2" - the number of layers of varnish on the wire;
• PELSHO - copper winding wire insulated with varnish-resistant enamel and a layer of natural silk;
• PB - winding copper wire, insulated with paper in several layers;
• PBO - copper winding wire, insulator - one layer of cotton yarn;
• APB - aluminum wire of round or rectangular cross section, insulated with cable paper in several layers;
• APSD - aluminum winding wire, insulated with two layers of fiberglass winding impregnated with heat-resistant glyptal varnish;
• PETSO is a wire insulated with high strength Vinyflex enamel and one layer of glass yarn winding.

PETV

Wire section types

The cross-sectional size of a rectangular wire has standard values. For the square wire used in most transformers, the thickness is 1.35 - 5.9 mm, the width is 3.8 - 14.5 mm.


The ratio of thickness and width may be different, but this value must comply with the standards of GOST 6324 - 52. There are inconveniences in using square wires, since when winding it on coils, there is a high probability of damage to the coil insulation. In addition, it is almost impossible to distinguish by eye the smaller side of such a wire from the larger one.
An important part of the winding is the coil of the winding wire around the core of the magnetic circuit. Depending on the rated power of the load current, the desired section of the coil is also selected. Round wire is suitable for small currents, for large currents, rectangular wire should be selected. In the manufacture of windings, it is possible to use several parallel wires to increase the cross section of the wire.
The number of turns of the winding depends on the magnitude of the voltage. The winding turns are assembled into coils, an electrical device may consist of several windings or coils (transformers, motors), less often one (chokes, electromagnets). In the process of winding the coil, the turns are superimposed next to each other (serial winding), or one on top of the other (layers). The winding method determines the type of winding resulting.

The subtleties of choosing a winding wire

When choosing a product brand, the following criteria should be considered

1. Required heat resistance class. Enamel-insulated wires are not suitable for high-speed windings, as temperatures above 160 - 170 degrees Celsius can melt the protective layer.
2. Permissible thickness of the insulating layer. Combined and fibrous insulation have the largest thickness of wire insulation. However, their use in conditions of high humidity is undesirable.
3. Requirements for the required level of mechanical strength, moisture resistance, frost resistance and protection from chemicals.

Winding wire quality criteria

Depending on the size and brand, the wires are produced in coils, drums and coils. The winding of the wire must be even, twisting of the turns is unacceptable. The insulation layer must be uniform, no thickening of the layer is allowed. Winding rows should be uniform and dense, without gaps and ribbing. Permissible enamel flows at specific points of the wire are strictly regulated in the accompanying documentation.
Paper is wrapped around drums and spools of wire. To pack the bays, matting or burlap is used. Coils are additionally placed in boxes, the permissible weight of which should not exceed 80 kg.

Each coil, reel or drum must be accompanied by a label with information about the brand of wire, manufacturer, weight and diameter of the winding wire. It is necessary to store the wire in closed rooms with a low level of humidity.

Winding wires with enamel insulation are indicated by an alphanumeric code, which indicates: the type of insulation, the shape of the wire section, the type of insulation and through a hyphen - design, temperature index, wire material. The symbol of the wire includes the wire brand with the addition (at intervals) of the nominal diameter of the round wire or the dimensions of the sides of the rectangular wire (for a rectangular wire) and the designation of the standard or specifications for wires of specific brands. Winding wires with enamel insulation (PE) are classified according to various criteria

• enamel insulation: polyvinyl acetate; wineflex (B); metalvin (M); polyurethane (U); polyester (E); polyimide (I); polyamide (AI); polyetheririmide (EI); polyether cyanura atimide freon-resistant (F).
• section shape: round; rectangular (P).
• insulation thickness: type 1; type 2.
• insulation design: single-layer; two-layer (D); three-layer (T); four-layer (H); with a thermoplastic coating that sticks together under the influence of temperature (K).
• temperature index (heat resistance), °С: 105, 120, 130, 155, 180, 200, 220 and above.
• wire material: copper; iron-free copper (BZh); copper nickel-plated (MN); aluminum soft (A); aluminum solid (AT); bimetallic: soft aluminum-copper (AM), steel-copper (CM); alloys: soft manganin (MM), hard manganin (MT), stabilized manganin (MS), soft constantan (KM), hard constantan (CT), nickelcobalt (NC); precious metals; nickel; nichrome (NH).

Winding wires with enamel-fibrous, fibrous, plastic and film insulation are divided into:

• by type of insulation: fibrous: cotton (B), natural silk (Sh), nylon (K), polyester (lavsan) (L), trilobal (Kp), oxalon (Od), arimid (Ar); paper (B); fiberglass (C); glass polyester (SL); plastic (P); film: fluoroplastic (F), polyamide-fluoroplastic (I), fluoroplastic with polyimide-fluoroplastic (FI); combined.
• according to the number of windings: single-layer (O); two-layer (D).
• by type of impregnation: glyptal, polyester and other bases (130 °C); organosilicon (155 and 180 °C); organosilicate composition (over 180 °C).
• by type of insulation: normal; refined (T); reinforced (U); additional surface varnishing (L).
• by distinctive features: transposed wire (t); subdivided wire (P); the number of elementary conductors (indicated by a number); thickness of the overall paper insulation (denominator of the fraction).
• operating temperature: 60, 80, 90, 120, 180, 200 °C; impregnated heat resistance into classes: U (90°C), A (105°C), E (120°C), B (130°C), D (155°C), H (180°C), C (over 180°C).
• wire material: copper; iron-free copper (BZh); copper nickel-plated (MN); aluminum (A); manganin soft (MM); manganin solid (MT); constantan soft (KM); constantan solid (CT); nichrome (NH).
• alloys: copper-based (BrMgTsr); plated with a word of nickel or iron and nickel plated by electroplating and alloy based on other materials.
• according to the design of the core: round (single-wire, multi-wire); rectangular; hollow.

Main characteristics of winding wires

The main parameters of winding wires of round cross section for transformers

Our company sells various brands of aluminum winding wires from warehouses located throughout Russia, or under an order for production. Cable.RF specialists know everything about this product, so they will competently advise you in choosing the necessary wire, taking into account technical requirements, help you make timely delivery and select the appropriate type of transport.

Aluminum winding wire is used for the manufacture of windings of various high and low voltage electrical installations operating on direct and alternating current. First of all, these are electrical machines - oil and dry-type transformers, electric motors (in most cases, high-voltage versions), generators, welding equipment (transformers). In addition, various starting equipment is made using aluminum wire.

The product is allowed for operation on land in all macroclimatic regions (tropical, cold and temperate). Quite often, the wire can be operated in an insulating oil environment, for example, in oil-filled power transformers. We add that for some versions of wires, prolonged overheating of the core and mechanical impact during operation are allowed - for example, in electric motors operating in difficult conditions (frequent mechanical overloads on the shaft). The wire is intended for fixed installation in specially designed for this purpose units of machines and assemblies.

For the manufacture of this wire, a core made of aluminum monolithic wire of the AT and AM brand for round sections and the PAM brand for a rectangular section is used. Conductors are insulated with enamel, fibrous, glass-fiber and paper insulation. Enamel is, as a rule, two layers of various electrical insulating varnishes (synthetic, polyamideimide polyurethane, as well as varnish based on polyester resins for heat-resistant performance). Fibrous insulation is based on one or more layers of fibrous materials (natural or synthetic silk, cotton yarn, lavsan fiber). The winding direction of each layer is opposite. For fiberglass insulation, glass fiber winding is used, followed by impregnation with a heat-resistant varnish or compound. Paper insulation is a winding of a core with tapes of telephone or cable paper in several layers.

Main advantages:

• the presence of a heat-resistant version of the wire;
• various versions of the wire according to the insulation material;
• long service life;
• lower cost of manufacturing wire compared to copper version.

Winding aluminum wire: price

You can buy aluminum winding wire from us at a bargain price, for this you need to leave an application for the calculation of the cost to the company manager.

A. P. Kashkarov, St. Petersburg

For the manufacture of transformers and chokes, special winding wires are used. The main types of such wires of domestic and foreign production are described in this article.

Domestic winding wires

Winding wires in enamel insulation based on high-strength synthetic varnishes with a temperature index (TI) in the range of 105 ... 200 are most widely used. TI is understood as the temperature of the wire at which its useful life is at least 20,000 hours.

Copper enameled wires with insulation based on oil varnishes (PEL) are produced with a core diameter of 0.002 ... 2.5 mm. Such wires have high electrical insulation characteristics, which are practically independent of the external influence of elevated temperatures and humidity.

PEL-type wires are characterized by a greater dependence on the external influence of solvents, compared to wires with insulation based on synthetic varnishes. The PEL winding wire can be distinguished from others even by its external sign - the enamel coating is close to black in color.

Copper wires of types PEV-1 and PEV-2 (produced with a core diameter of 0.02 ... 2.5 mm) have polyvinyl acetate insulation and are distinguished by a golden color. Copper wires of types PEM-1 and PEM-2 (with the same diameter as PEV) and rectangular copper conductors PEMP (section 1.4 ... 20 mm2) have varnished insulation on polyvinylformal varnish. Index "2" in the corresponding designation of PEV and PEM wires characterizes two-layer insulation (increased thickness).

PEVT-1 and PEVT-2 are enameled wires with a temperature index of 120 (diameter 0.05 ... 1.6 mm), they have insulation based on polyurethane varnish. These wires are easy to install. When soldering, it is not necessary to strip the varnished insulation and apply fluxes. Enough ordinary solder brand POS-61 (or similar) and rosin.

Enamelled wires with insulation based on polyesteramide PET-155 have a TI equal to 155. They are produced with conductors not only of a round cross section (diameter), but also of a rectangular (PETP) type with a conductor diameter of 1.6-1 1.2 mm2. In terms of their parameters, PET wires are close to the PEVT type wires discussed above, but have a higher resistance to heat and thermal shock. Therefore, winding wires of types PEVT and PET, PETP can be especially often found in powerful transformers, including transformers for welding.

Domestic high-frequency winding wires

At high frequencies, stranded enameled winding wires (litz wires) of the LESHO type in silk single-layer insulation or LESHD - fv double silk insulation are used. Such wires consist of a bundle of copper enameled wires with a diameter of 0.05 ... 0.1 mm and are used for inductors (and chokes). In high-frequency wires of LESHO, LESHD, PELO, LELD, DEP, LEPKO types, the cores are twisted from separate enameled wires to reduce losses from the surface effect (proximity effect). Table No. 1 shows the diameters of widely used high-frequency winding wires of domestic production. For odd numbers, the wire diameter is approximately equal to half the sum of the diameters of two adjacent (even) numbers.


Designation of popular foreign winding wires

In the US and UK, the designation of the diameters of the winding wires is written with the words wire size (wire size).

For example, in the USA the system

American Wire Gauge (AWG). Also sometimes in the USA they use the B&S system, and in the UK they use the Standard Wire Gauge (SWG). Table 2 and Table 3 show the diameters of widely used types of winding wires according to AWG and SWG standards.
Permissible load on conductors


The maximum allowable current that can be passed through the wires without worrying about fire or contact failure is determined in accordance with Table 4. The maximum heating of rubber or plastic (as well as their combinations or derivatives) insulation of wires should not exceed +50 degrees. The duration of safe exposure depends on this temperature parameter.
on the conductor of the maximum allowable current (I max A in Table 4)
Magazine "Electrician"