Branching of copper conductors of wires and cables. Methods for connecting current-carrying conductors of wires and cables to the terminals of electrical appliances and equipment

The termination and connection of aluminum and copper conductors of insulated wires and cables is carried out by crimping, welding, soldering and mechanical compression. The choice of method is determined by the reliability of the contact, the simplicity of technology, economy, etc. Therefore, all methods are divided into three groups: should be used, recommended and allowed.

Should be applied - the best method, which should be used in the first place; recommended - one of the best ways, but not required; allowed - a satisfactory way, and in some cases forced. The last group includes methods that are now rarely used: benzo- and acetylene-oxygen welding, contact heating welding, electric arc welding with a carbon electrode.

The most productive methods are crimping, propane-oxygen (propane-air) and argon-arc welding, thermite welding, and in some cases soldering and mechanical connections using clamps. For electric welding of contact joints, electricity is required, for gas - special equipment, and for thermite - only simple devices.

Connections and terminations by soldering are now rarely used, since this method, which provides a reliable connection, is laborious, requires the consumption of non-ferrous metals and is less economical. The choice of the method of connection, branching and termination depends on the material of the cores, their cross section, voltage.

Crimping.

This method is used to connect and terminate both copper and aluminum conductors of wires, but the crimping of aluminum conductors has some peculiarities compared to copper ones. The presence of an oxide film on the cores, the inner surface of the sleeves in the cylindrical part of the tips complicates the process of preparing and creating a contact.

To obtain a reliable electrical contact, it is necessary to carefully clean the connected elements from the oxide film and use special means of protection against further oxidation of aluminum both during the creation of the contact and during its operation. Such a protective agent is quartz-vaseline paste, composed of technical petroleum jelly and quartz sand of special grinding.
Protected surfaces are coated with a paste to prevent further oxidation. When pressed, quartz destroys the oxide film, contributes to the creation of reliable point contacts, and vaseline prevents their oxidation during operation.

The length of the aluminum sleeve and the cylindrical part of the aluminum tip is greater than the length of the copper sleeve and the tip (increased indentation area and number of indentations). When pressing aluminum conductors by local indentation, two holes are formed on the tubular part of the tip, and four holes are formed on the sleeve (two indentations of each core inserted into the sleeve). For copper conductors, crimping is carried out with one indentation for the tip and two indentations for the connecting sleeves. When using a two-pronged instrument, two indentations are performed in one step, four - in two steps.
The general requirements for connecting and terminating wire cores by crimping are: cleanliness of the contact surface; compliance with the norm of contact pressure; ensuring the depth of pressing set according to the instructions; correct selection of dies, punches, tips or connecting sleeves; the correct location of the holes formed in the places of indentation.

The cleanliness of the contact surface is ensured by removing insulation residues from the cores, cleaning the sleeves and tips from dirt and cleaning the inside to a metallic sheen.

Compliance with the norm of contact pressure is achieved by choosing the right tool for crimping (punches and dies) in accordance with the cross section and brand of the core, as well as measuring the depth of indentation after crimping and checking according to a special table. Tips or connecting sleeves are selected in accordance with the cross section and type of core. The location of the holes formed in the places of indentation, and the distances between them are defined in the tables. The connection and branching of single-wire aluminum wires with cores with a cross section of 2.5 to 10 mm2 is carried out in sleeves of the GAO series. The maximum total cross section of the cores of the connected wires in the GAO sleeves is 32.5 mm2. The crimping of the sleeves is carried out with one indentation for one-sided filling of the cores and two indentations for two-sided filling. To connect and terminate wires with a cross section of more than 10 mm2, GA sleeves and TA and TAM lugs are used.

Sealed tubular lugs are used to terminate aluminum conductors of cables. Leakage of the cable impregnating composition through the slot in the blade of the tip is prevented by two-sided counter indentation of semicircular grooves in its flat part.

Single-wire sector conductors are rounded off with a special tool before being inserted into the tip or sleeve. After that, the ends of the cores are cleaned, lubricated with quartz-vaseline paste, and the connection or termination is made in the usual manner.

AT recent times apply new way crimping of single-wire conductors - pressing out the tips. At the end of the sector core, in a PPO powder action press, a terminal with a hole is stamped in one shot, which receives the necessary contact surface in the shape of the tip. When terminating a single-wire core by pressing out the tip, the same methods of sealing the place of the cut of the core insulation are used as with conventional tips.

Welding. The connection and termination of aluminum conductors is carried out by electric, thermite and gas welding. The general requirements for their connection and termination by the specified welding are as follows: protection from overburning of individual wires; insulation protection against overheating and damage; prevention of aluminum spreading; protection of insulation from the direct action of the flame; protection of aluminum from oxidation during welding; protection of the junction and termination from corrosion.

For this purpose, welding is carried out only from the ends of the cores in a vertical or slightly inclined position. To remove heat, special coolers are used with a set of replaceable copper or bronze bushings installed on bare sections of the cores. Welding in all cases is performed in special forms; in order to avoid spreading of aluminum, the exits of the core from the mold are sealed with corded asbestos. In gas and thermite welding, disk steel screens are used to protect the insulation from the direct action of the flame. The lateral surfaces of individual wires must be free of traces of melting, burns and shells and enter into the monolithic part of the joints without reducing their cross section.

To protect aluminum from oxidation during welding and to remove the aluminum oxide film from the surface of the wires to be welded, VAMI fluxes (potassium chloride 50%, sodium chloride 30%, cryolite 20%) and Af-4a are used. The joints and terminations are cleaned of flux and slag residues, washed with gasoline, coated with a moisture-resistant varnish and insulated with tape or a plastic cap.

The connection and branching of single-wire aluminum conductors with a cross section of up to 12.5 mm2 by electric welding with contact heating is performed using tongs and a carbon electrode without the use of flux or with it. In the first case, the ends of the cores are fused into a monolithic rod in a cage heated by carbon electrodes; in the second case, the ends of the cores, pre-cleaned, rounded and coated with flux, are melted directly with a carbon electrode without a cage until a ball of molten metal is formed at the ends. In both cases, a 0.5 kV-A transformer with a secondary winding of 9-12 V serves as a source of electricity for welding. -1 with a welding gun (no flux). The device provides for the termination of welding at the moment of melting the wires to a predetermined length. Its productivity is one to three welds per minute.

Electric welding of joints and terminations of stranded wires by contact heating is performed with a carbon electrode from a welding transformer with a voltage of 6-12 V (arcless welding). The connection of stranded aluminum conductors is carried out in two steps: fusion of the ends of the connected conductors into a monolithic rod and welding them into open form. When terminating, the end of the core is inserted into the sleeve of the tip and fused into a common monolithic rod with the upper protruding part of the sleeve.

Electric contact heating is used mainly for connections and branches of aluminum wires of small sections, especially on technological lines for the preparation of lighting electrical wiring. When terminating aluminum conductors of wires and cables directly on the installation, the method of contact heating is almost never used due to low productivity.

Termination of cores of wires and cables with a cross section of 16 to 240 mm2 with plastic or rubber insulation with tips is carried out by argon-arc welding using a semiautomatic device or a non-consumable tungsten electrode. For welding, a PRM-4 semiautomatic device is used with a single-station power source PS G-500, VDG-301 or another source direct current with tough external characteristics.
Schemes of arc and argon-arc welding, technological methods and their sequence are covered in detail in other teaching aids and special instructions.

Thermite welding, which is the most reliable way to connect aluminum conductors of wires and cables, has its advantages: high reliability connections; simplicity of technology; small overall dimensions and mass of devices; independence from energy sources.

Thermite welding is carried out due to the heat released during the combustion of the thermite mass. It requires thermite cartridges and matches, filler rods made of aluminum wire, flux, acetone, sheet and cord asbestos, as well as devices produced in a separate kit.

For welding, the ends of wires or cables are cut at a certain length, the oil-rosin composition is removed from the cores (for cables). At the ends of the veins, after removing the burrs from them (remaining after cutting), apply thin layer flux and put on aluminum caps, which isolate the surface of the cores from the walls of the molds, which, when the thermite mixture burns, are heated to 100 ° C or more. Then a thermite cartridge is put on the ends of the veins. The inner surface of the cartridge mold is covered with chalk. The cartridges are sealed from the ends by winding the asbestos cord.

Coolers are put on the bare areas of the cores, which are mounted on a tripod. The core to be welded is fenced off from other cable cores with asbestos sheet screens at least 4 mm thick, and then the cartridge is set on fire with a thermite match held by a special holder. After ignition, the match is brought closer to the end of the cartridge until it comes into contact with it. As soon as the cartridge begins to burn, a filler aluminum rod coated with flux is introduced into it.

After the end of the burning of the thermite cartridge, the melting of the cores and the filling of the gate tube, the liquid metal is mixed. When the metal hardens, the cartridge is chipped off and the mold is removed. Gating profit is sawn off with a file. The entire connection is cleaned with a cardolent brush, covered with asphalt or other moisture-resistant varnish and insulated in the usual way. The outer layer of wire insulation is also coated with asphalt varnish, and the connection of the cable cores is processed, depending on what type of sleeve is installed on the cable. When welding cores of cables with a cross section of 70 mm2 and above with plastic insulation, it is necessary to apply windings from a moistened asbestos cord or felt with a thickness of at least 10 mm in sections of 80 mm.

When thermite welding, the requirements must be strictly observed, the violation of which worsens its quality. These include: careful sealing of the molds with an asbestos cord to avoid melting of the cores when leaving the mold or metal leakage; the introduction of the additive into the weld pool simultaneously with the start of the muffle burning (delay with the introduction of the additive causes the mold to burn); coating the inner surface of the molds with chalk to prevent aluminum from sticking to the mold; thorough cleaning of the filler wire from oxide (so that the latter gets into the welding of the joints to a lesser extent); correct ignition of the thermite cartridge with a match (the ignited match is brought close to the muffle and the end face is rubbed with the side surface of the burning match).

When performing thermite welding, the safety precautions set out in the instructions must be observed. The burning temperature of a thermite cartridge is more than 2500 °C, and matches - 1500 °C, so careless handling of them can lead to severe burns. Thermal matches used to ignite thermite cartridges (when welding cores of wires and cables) have a short and thin wooden rod, often with transverse lamination. This shortcoming does not provide safety conditions when working with thermal matches, since when rubbed against a grater, the match rods break and the burning heads fly off to the side. Heat burning match head also causes a risk of burns to the hand of the person working with the match.

Given the increased danger of thermite welding, it should be used mainly in the absence of electricity, for example in the field.

Gas welding of aluminum wires is carried out in the flame of various combustible gases - acetylene, oxy-benzo mixture, propane-butane. Most often, propane-butane mixtures are used, which have the ability to liquefy at low pressures. A small internal pressure and a small volume of a liquefied mixture of propane and butane make it possible to store them and transport them in small-sized thin-walled cylinders.
For propane-air and propane-oxygen welding, as well as for propane-air soldering, special equipment is produced in the form of NSP sets, which include cylinders, containers with a set of welding accessories, gas-air burners GPVM with flame stabilization, etc. Welding gas burner perform in two steps; the ends of the stranded wires are fused into a monolithic rod and the monolithic wires are welded together. Melt when finished upper part tip sleeves together with the end face of the aluminum core.

For welding twists of aluminum wires with a cross section of up to 10 mm2 in boxes during the installation of electrical wiring, a propane-butane torch is used, which, using a VAMI flux, creates a reliable high-quality connection. This connection method is more economical and productive compared to other methods. Continuation of welding from 10 to 50 s depending on the number of wires and their cross section.

When working with propane-butane, safety regulations must be observed with particular care. Propane-butane gas is in pressurized cylinders and, if there is a malfunction in their fittings or hose, an explosive mixture is formed in the air.

Propane-butane has a sharp unpleasant odor that causes irritation and inflammation of the mucous membrane of the nasopharynx and eyes, as well as headache. Therefore, working with propane-butane should be well aware of the protection measures against harmful effects gas on the human body: do not stay in gassed rooms, work with a propane-butane burner with the ventilation turned on, work in cable tunnels and wells in the presence of an observing person, etc.

Liquefied propane-butane, getting on the skin of a person, causes frostbite. Therefore, it must be quickly washed off with water.

Soldering.

The method of connection by soldering, which is the most time-consuming, is used when connecting and terminating copper conductors and less often when connecting aluminum. Soldering is performed with a propane-butane torch or a gasoline blowtorch using solder A, TsO-18 and TsA-15 for aluminum conductors and POS for copper. As a flux, rosin, stearin and soldering fat are used.

Connections and branches of single-wire conductors of aluminum wires with a cross section of 2.5-102 mm are performed by soldering a double twist with a groove, stranded conductors with a cross section of 16 to 150 mm2 by direct fusion of solder in a detachable form or by pouring pre-molten solder.

Bolt and screw clamps. Connections, branches and connections of aluminum conductors of wires and cables, including branches from continuous lines, are also performed mechanically using clamps.

For connection copper wires luminaires with aluminum wires of the network use chandelier clamps. In clamps with a detachable plastic housing, branches are carried out from the main network without cutting it.

For the production of connections, terminations and branches of aluminum and copper cores of insulated wires and cables, basic and auxiliary materials are used. The main materials include:

• propane, gaseous compressed oxygen for propane combustion;
• solders A, TsO-12, TsA-15, POS-40;
• VAMI fluxes for dissolving aluminum oxide film when welding wire cores, as well as for terminating and branching wire and cable cores, and AF-4a for dissolving aluminum oxide film when welding cable cores in couplings;
• quartz-vaseline paste;
• thermite cartridges PAN, PAT, PA complete with aluminum sector sleeves and aluminum sleeves, as well as thermite matches;
• copper tips of the T and P series, copper-aluminum TAM and ShP series (pin), aluminum TA series;
• copper sleeves of the GM series, aluminum series GA and GAO (for single-wire conductors) and branch clamps in a plastic case;
• rosin and a solution of rosin in alcohol;
• welding wire SvAK5;
• welding coals.

Auxiliary materials are:

• aviation or unleaded gasoline;
• technical vaseline;
• acetone;
• technical dichloroethane;
• asbestos cardboard 2-4 mm thick and asbestos cord;
• sandpaper;
• cleaning rags, chalk, insulating tape and plastic caps;
• varnish and paint.

Cutting wires and cables

Cutting wires and cables is carried out in the following order:

l using reference books, determine the dimensions of the cut, depending on the design of the conductor and the type of connecting or end device;

b mark the cut using cable rulers or templates;

l stepwise impose several turns of fixing bandages made of galvanized steel or copper wire, twisted twine, cord or nylon thread, harsh threads, as well as cotton or plastic tape;

b make an annular transverse and linear longitudinal incision of the shells to be removed (armored, lead, aluminum, plastic shells and monolithic insulation);

b remove or wind up the covers to be removed;

b bred the ends of the cores of stranded conductors, i.e. give them a shape and location that are convenient for the next operation;

l treat the bare end sections of the conductive conductors, i.e., they are cleaned to a metallic sheen, tinned, covered with fluxes, quartz-vaseline paste or conductive glue, and the stranded conductors are caught into a monolith.

Note that the need for the above operations is determined by the design of the conductors. AT in full they are carried out for power cables with paper insulation, and for the simplest conductors, the cutting technology is reduced to removing PVC insulation and processing the core.

Connecting and terminating wires

Wire - one uninsulated and one or more insulated cores, on top of which, depending on the conditions of installation and operation, there may be a non-metallic sheath, winding or braid with fibrous materials or wire.

In structure symbol installation wires, the first letter characterizes the material of the conductive core (A - aluminum, copper - the letter is omitted); the second letter P - wire or PP - flat wire 2- or 3-core; the third letter characterizes the insulation material (V - PVC; P - polyethylene; R - rubber; N - nayrite).

For example: APV - aluminum wire with PVC insulation.

Cable - one or more insulated cores (conductors), enclosed, as a rule, in a metal or non-metallic sheath, on top of which, depending on the laying and operation conditions, there may be an appropriate protective cover, which may include armor.

Cord - two or more insulated flexible and highly flexible conductors with a cross section of up to 1.5 mm2, twisted or laid in parallel, over which, depending on the operating conditions, non-metallic sheaths and protective coatings. The cord is designed to connect electrical household appliances to the electrical network.

Connections of conductors of wires between themselves and with electrical installation devices (sockets, sockets, etc.) must have the necessary mechanical strength and low electrical resistance throughout the entire period of operation.

Heating and cooling under the action of the load current, temperature and humidity of the environment, chemically active particles in the air have an adverse effect on the contact connections. In addition, an oxide film forms on the surface of the conductors, which affects the quality of the connection.

The connection of aluminum or copper conductors is best done by crimping or welding, but at home it is unlikely that anyone will do this. Connection of conductors by soldering is also allowed.

When soldering aluminum wires with a cross section of 4-10 mm2, the insulation is removed from the ends of the cores, they are cleaned with a knife, steel brush or sandpaper to a shine and twisted. The joint is heated with a burner flame or blowtorch and tinned with special solders of type A, B and cadmium. Flux is not needed. When using soft solders of the AVIA-1 and AVIA-2 types (melting point 200 °C), the AF-44 flux is used. Soldering points must be cleaned of flux residues, wiped with gasoline, covered with moisture-proof (asphalt) varnish, and then with insulating tape, which is also varnished.

Copper single-wire and stranded wires with a cross section of up to 10 mm2 are connected by twisting, followed by soldering the junction with POS-30 solders (30% tin and 70% lead) or POS-40 and rosin as a flux.

Do not use acid or ammonia when soldering. Twisted connections must be at least 10-15 outer diameters of the wires to be connected.

The termination of the wires under the screw terminal is carried out in the form of a ring, and under the flat terminal - in the form of a rod.

With a wire cross section of up to 4 mm2 inclusive, the termination in the form of a ring is performed as follows: the insulation is removed from the end of the wire for a length sufficient to make the ring. The core of the hard wire is twisted into a ring clockwise, and the flexible wire is twisted into a rod, and then into a ring and tinned.

When terminating the wire in the form of a rod, the insulation is removed from the end of the wire, the twisted rod of the flexible wire is tinned.

The transition between the tubular part of the cable lug and the wire insulation is insulated with a PVC tube or electrical tape.

Connecting more than two wires to one terminal is prohibited. The terminals must be suitable for the rated voltage and current. The clamping screws are designed for connecting wires of the following sections: in clamps up to 10 A - two wires with a cross section of up to 4 mm2 without lugs, in clamps up to 25 A - two wires with a cross section of up to 6 mm2 without lugs, in clamps up to 60 A - two wires up to 6 mm2 without ferrules and one wire with a cross section of 10 or 16 mm2 with a ferrule.

The screw clamp to which the aluminum conductors are connected must have a device that limits the possibility of unwinding the ring and does not allow the weakening of the contact pressure due to the fluidity of aluminum. A ring of aluminum single-wire wire is cleaned before being put into contact and, if possible, lubricated with quartz-vaseline and zinc-vaseline paste.

Connection of wires to devices having contact petals is carried out by soldering. Soldered mounting connections must ensure the reliability of electrical contact and the necessary mechanical strength. The main material for soldering is solder POS-40, and for critical equipment - POS-61. Solder is recommended to be used in the form of tubes filled with rosin or wire with a diameter of 1-3 mm. The flux is a solution of rosin in alcohol or pine rosin of the highest or first grade.

Wiring requirements. The connection of the cores to each other and their connection to electrical installation devices must have the necessary mechanical strength, low electrical resistance and retain these properties for the entire period of operation. Contact connections are subject to the action of the load current, cyclically heated and cooled. Changes in temperature and humidity, vibration, the presence of chemically active particles in the air also have an adverse effect on contact connections.

Physical and Chemical properties aluminum, from which wire cores are mainly made, complicate the implementation of a reliable connection. Aluminum has (compared to copper) increased fluidity and high oxidizability, while a non-conductive oxide film is formed, which creates a large transition resistance on the contact surfaces. This film must be carefully removed from the contact surfaces before the connection is made and measures must be taken to prevent its recurrence. All this creates some difficulties when connecting aluminum wires.

Copper conductors also form an oxide film, but unlike aluminum, it is easily removed and does not significantly affect the quality. electrical connection.

The large difference in the coefficients of thermal linear expansion of aluminum compared to other metals also leads to contact failure. Given this property, aluminum wires cannot be pressed into copper lugs.

During long-term operation under pressure, aluminum acquires the property of fluidity, thereby breaking the electrical contact, therefore, the mechanical contact connections of aluminum wires cannot be pinched, and during operation it is necessary to periodically tighten threaded connection contact. Contacts of aluminum conductors with other metals on outdoors exposed to atmospheric influences.

Under the influence of moisture, a water film with electrolyte properties is formed on the contact surfaces, as a result of electrolysis, shells form on the metal. The intensity of the formation of shells increases when an electric current passes through the place of contact.

Particularly unfavorable in this respect are aluminum compounds with copper and copper-based alloys. Therefore, such contacts must be protected from moisture or coated with a third metal - tin or solder.

Connection and termination of copper wires

Connection, branching of copper wires with a cross section of up to 10 mm2 is recommended to be performed by twisting followed by soldering, and single-wire copper wires with a cross section of up to 6 mm2, as well as stranded wires with small areas sections are soldered by twisting. Cores with a cross-sectional area of ​​​​6-10 mm2 are connected by bandage soldering, and stranded wires - by twisting with a preliminary unwinding of the wires.

The length of the joints by twisting or bandage soldering should be at least 10-15 outer diameters of the connected cores. They are soldered with lead-tin solder using a rosin-based flux. It is not allowed to use acid and ammonia when soldering copper wires, since these substances gradually destroy the soldering points.

Compression connection. Crimping copper wire connections are widely used. The ends of the wires are stripped by 25-30 mm, then wrapped with copper foil and crimped with special tongs such as PC.

Connection and termination of aluminum wires

Aluminum cores of wires are connected by welding, soldering and mechanically.

Aluminum wires are welded on a special mold using carbon electrodes powered by a welding transformer.

For soldering, aluminum wires are twisted, and then the place of twisting is heated in a blowtorch flame and soldered with solders of the following compositions.

Solder A, melting point 400 - 425 degrees, composition: zinc - 58-58.5%; tin - 40%; copper 1.5 - 2%.

TsO-12 Mosenergo, melting point 500 - 550 degrees; composition: zinc - 73%; tin - 12%; aluminum - 15%.

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General information about the connection and termination of conductive conductors of wires and cables

Connecting and terminating the conductive cores of wires and cables is a very important operation, from correct execution which to a large extent depends on the reliability of electrical installations. Contact connections are divided into detachable and one-piece. The former are carried out with the help of screws, bolts, wedges and clamps, the latter are carried out by welding, soldering and crimping.
For reliable operation, the contact connection must: have a low electrical resistance, not exceeding the resistance of the entire section of the same length. (Increased contact resistance leads to increased local heating, which can cause destruction of the connection. According to the standards, short-term heating of the wires during a short circuit is allowed up to 150 ° C with rubber and plastic insulation and up to 200 ° C with paper insulation. It is clear that the contact connection must withstand the same temperatures and, in addition, work reliably with repeated heating and cooling.):
have high mechanical strength (especially if the connection must withstand significant mechanical forces - the connection of tires, wires of overhead lines, etc.);
be resistant to corrosive vapors and gases, changes in temperature and humidity, possible vibrations and shocks that may occur during operation of the equipment.
In electrical practice, copper and aluminum conductive parts are used. When mounting connections, pairs of "copper - copper", "aluminum - aluminum" and "copper - aluminum" are possible. In copper, an oxide film forms slowly, has little effect on the quality of the contact connection, and is well removed. Therefore, the connection of copper conductive parts has the best electrical and mechanical properties. Aluminum also oxidizes in air, but its oxide film forms very quickly, it has great hardness and. high electrical resistance. In addition, the melting point of this film is about 2000 ° C, so it prevents the soldering and welding of aluminum wires by conventional methods.
In the connection of copper with aluminum, a galvanic couple is formed, as a result of which the connection is quickly destroyed by electrochemical corrosion.

Screw connections

The main type of contact connection of copper and aluminum conductors of small cross section to electrical machines, devices and devices is a screw connection. It is used for wires with a cross section of up to 10 mm2.
To connect copper conductors of small cross sections, they are bent in the form of a ring, which, in the case of a stranded conductor, is soldered. Screw connections of aluminum conductors make it somewhat more difficult. The fact is that aluminum under pressure begins to “flow” into an area with less pressure. Therefore, if the aluminum connection is excessively tightened with a screw, then over time the contact connection will weaken, since some of the metal will “leak out” from under the washer. This process occurs especially rapidly during periodic heating and cooling of the compound. To prevent this phenomenon, the screw clamp must have a device that prevents the aluminum ring from unwinding and compensates for the weakening of the contact due to the fluidity of aluminum.
To lock the ring, a star washer or a rectangular washer with sides is used, and spring washers are used to compensate for pressure. Before tightening the screw, the contact surfaces are cleaned to a shine and lubricated with quartz-vaseline paste.

Crimp connection

Rice. 1. Pressing tongs PK-2M in GAO-type sleeves
When connecting by crimping, the ends of the wires to be connected are inserted into the connecting sleeve (a piece of pure copper or aluminum tube) and squeezed with a special tool. Great importance for the quality of the connection, the contact surfaces are clean, therefore, with any method of crimping, dirt, insulation residues and oxide films must be removed from the cores and sleeves. The oxide film is removed from copper wires during the crimping process, when the metal surface stretches and “flows”, so no special treatment, except for stripping, is required for copper wires. As for aluminum, to destroy the strong film of its oxide, a paste is applied to the cleaned contact surfaces, consisting of petroleum jelly with the addition of hard grains of quartz sand or zinc oxide. During crimping, solid particles destroy the film, and Vaseline prevents the contacts from re-oxidizing.
Crimping of aluminum wires with a cross section of up to 10 mm2 is carried out with a diameter of up to 9. mm) using PK-2M press tongs (Fig. 1). They have handles with latch 5, which limits the degree of indentation, one of which is connected to the stop bracket 3, and the second to the pusher 4. A matrix 1 is fixed on the bracket, and a punch 2 with a tooth is fixed on the pusher.


Rice. 2. Pressing tongs PK-1M

Rice. 3. Crimping of wires in GAO sleeves:
a - in a shortened sleeve, b - in an elongated sleeve, c - installation of the sleeve in the press, d - sleeves after crimping, e - sleeve insulation
Pressing tongs PK.-1M (Fig. 2) due to the large length of the handles create pressure sufficient for crimping sleeves with a diameter of up to 14 mm. In hydraulic mounting tongs GKM, the working movement of the pusher with the punch occurs due to the pressure in the hydraulic cylinder, which occurs when the handle is pressed.

The technological process of crimping is shown in fig. 3. Preparation of aluminum wires for connection consists in their stripping and coating with paste. After that, a shortened GAO sleeve is put on the ends of the wires (with one-sided crimping, Fig. 3, a) or an elongated sleeve of the same brand (with double-sided crimping, Fig. 3, b) and one or two indentations are made with a press or tongs (Fig. 35 , c, d). The punch is pressed into the sleeve until the lock-limiter is activated or until the punch touches the die (if the pressing tongs do not have a lock). The pressed contact connection is cleaned of paste residues and insulated with polyethylene caps or insulating tape (Fig. 3, e).

Rice. 4. Crimping tool:
a - RMP-7M mechanical press, b - RGP-7M hydraulic press

For crimping aluminum wires and cable cores with a cross section of 16 ... 240 mm2, sleeves of the GA type are used. As a crimping tool, presses are used to create large indentation forces. On fig. 4 shows a manual mechanical press RMP-7M and a manual hydraulic press RGP-7M. The first of them works on the same principle as press tongs, the work of the second is similar to the operation of hydraulic tongs GKM. The pressing force of these pliers is up to 69 kN (7 t).
Crimping of wires of large cross-sections is carried out in the following order. After removing the insulation, cleaning and processing with paste, the wires are inserted into the sleeve so that the joint of the cores is in its center (Fig. 4.5, a). The sector core of the cable must be rounded so that it fits into the sleeve without large gaps.
This operation on stranded conductors is performed with universal pliers, and on single-wire conductors - with the help of special crimps, which are temporarily installed for this purpose in a press instead of a matrix and a punch (Fig. 5, b). During crimping, four indentations are made on the sleeve - two on each half (Fig. 5, c).

4.5. Crimping connection technology:
a - core preparation, 6 - core rounding, c - sleeve after crimping
To speed up and improve the quality of crimping, you can use a two-tooth matrix by installing it in an electro-hydraulic press PGEL-2.
Crimping of copper wires is carried out in the same way and with the same tools in sleeves of the GM brand. Copper stranded conductors with a cross section of up to 2.5 mm2 can be connected by crimping without sleeves (Fig. 6).

Rice. 6. Connection of copper conductors with a cross section of up to 2.5 mm2:
a - the location of the cores, 6 - the imposition of a copper or brass tape, c - sealing the tape, d - crimping, e - finished connection
The stripped sections of the cores 20 ... 25 mm long are tightly pressed against each other and wrapped in several layers with copper or brass tape (foil) 18 ... 20 mm wide, 0.2 ... 0.3 mm thick. Then, a comb matrix and a punch are installed in PK-2M tongs, with the help of which crimping is performed.

Conductive cores of wires and cables during installation and repair are connected in the following ways: welding, soldering and crimping. For a threaded contact connection, metal (copper, aluminum) lugs are used to terminate the current-carrying wires.

Electric welding of cores

For welding of cores, non-arc welding is used by the contact heating method, semi-automatic arc welding in argon with a consumable electrode, and manual arc welding in argon with a non-consumable electrode. Arc welding is used for high heat capacity of conductors - for stranded conductors of large cross sections (aluminum conductors up to 1500 mm² and copper conductors up to 300 mm²), as well as for monolithic aluminum conductors with a cross section of up to 240 mm².

For welding joints and branches of single-wire conductors with a cross section of up to 10 mm², welding with electrodes or the VKZ-1 apparatus is used.

Welding at the ends of stranded conductors with a cross section of up to 240 mm² is carried out in steel or coal forms, using previously produced complete installations of the U SAP series or transformers with a power of about 2 kW, carbon electrodes and coolers to protect the insulation from overheating. The secondary voltage of the transformers must be within 8-12 V.

To improve the quality of welding, it is necessary to reliably remove oxides from the surface of the metals being welded. This is especially true for aluminum conductors. Oxides are removed with fluxes, for example, AF-4a and VAMI (when welding aluminum conductors). The welded joint is protected with waterproof varnishes.

Welded joints are considered unsuitable if there are: burns of the outer layer, violations of the integrity of the weld metal when the joint is bent, or shrinkage cavities with a depth of more than one third of the core diameter.

Gas welding of cores

Propane-air and propane-oxygen gas welding have found the greatest application in assembly practice. All methods of gas welding have common technological features.

The gas welding flame strongly dissipates heat. In this regard, there is a risk of damage to the insulation. Therefore, when welding, protective screens made of sheet asbestos are widely used. The impact of a concentrated gas welding flame on individual wire strands often leads to their burnout. Therefore, when welding, welding solid or collapsible steel, as well as coal molds are used, which are put on the cores of wires and are indirect heaters of the cores: flames are directed not at the cores, but at the surface of the molds. The core material is heated by heat radiation from the inner surfaces of the molds.

Strong heating during welding can cause overheating of the insulation. Therefore, massive steel coolers are used, which are tightly installed on bare cores near the welding zone.

The use of fluxes is undesirable, since it is difficult to remove flux residues from stranded wires after welding. Remaining on the wires, fluxes contribute to corrosion and destruction of the connection. For getting good quality welded metal slags are removed with a steel rod - a stirrer.

Thermite welding of cores

Thermite welding is based on high calorific value a special combustible composition - thermite (by weight Fe 2 O 3 - 72.5%, Al - 18%, Mg - 4.5% and 40% ferromanganese - 5%). Thick-walled hollow cylinders are pressed from thermite - muffles, which form the basis of thermal cartridges. To ignite the thermocartridge muffle, special thermite matches are used, which create a temperature of about 1000 ° C. The thermite cartridge burns at a temperature of about 2800 ° C.

Rice. 32. Thermite cartridges PA ( a), PAT ( b), PAS ( in), M ( G):
1 - muffle; 2 - vein; 3 - bushing for monolithic sector cores; 4 - chill mold; 5 - additives; 6 - cap; 7 - seal; 8 - steel mold; 9 - aluminum insert; 10 - copper mold; 11 - liner made of copper-phosphorus solder.

Thermite welding provides high productivity and good quality of the resulting joints. Thermal chucks are used for thermite welding. various designs: PA (Fig. 32, a) - for butt joints of aluminum conductors with a cross section of 16-800 mm² and welding of tips to conductors with a cross section of 300 - 800 mm²; PAT (Fig. 32.6) - for butt welding of stranded aluminum conductors with a total cross section of up to 240 mm² and for welding tips to conductors with a cross section of 70 - 240 mm²; ATO for welding on the ends of stranded conductors with a total cross section of 5 - 32 mm², twisted together.

For welding non-insulated aluminum and steel-aluminum wires of overhead lines with sections of 16-240 mm², PAS thermochucks are used (Fig. 32, c). copper wires VL with sections of 25 - 150 mm² are welded with thermochucks M (Fig. 32, d).

For sector cores, adapter bushings are made with a cylindrical outer surface and a sector-shaped opening (Fig. 32, a, h). Thermite welding is performed using fluxes AF-4a, VAMI.

Rice. 33. Device for welding aluminum conductors:
1 - coolers; 2 - folding screws; 3 - connecting bar; 4 - screw for fastening the connecting plate to the tripod; 5 - tripod; 6 - retractable rack; 7 - screen; 8 - replaceable split sleeve.

Butt thermite welding of aluminum conductors of cables is carried out in the following order:

soldering lived

Soldering is used when connecting copper conductors with a cross section of 16-185 mm². It is characterized by simplicity of technology, but high labor intensity.

Solders A, TsO-12, TsA-15 are widely used for soldering aluminum conductors in steel removable forms. In the remaining copper sleeves, aluminum conductors, previously tinned with solder A, are connected with POS-30 and POS-61 solders. The same solders are used when soldering copper wires. When soldering copper wires, rosin or its alcohol solution KSp is used as a flux.

Rice. 35. Connection of cores by direct solder fusion:
a - applying solder, b - rubbing the solder with a steel brush, c - soldering in the form.
1 - burner; 2 - solder; 3 - steel brush; 4 - asbestos yarn; 5 - heat shield; 6 - shape: 7 - cable core.

The connection and branching of the cores by direct solder reflow (Fig. 35) is carried out in removable forms or in connecting sleeves. Split molds are supplied by the industry and are used repeatedly. One-piece forms are bent from roofing steel for single use.

Aluminum stranded conductors with a cross section of 16 - 240 mm² are cut, degreased and cleaned. The ends of the veins 7 are tinned (Fig. 35, i, b), periodically destroying the oxides with the end of the steel brush 3. At the junction of the veins, the border of the form is marked, from which asbestos yarn 4 is wound up to a length of 10-12 mm inside the junction. Then form 6 is installed on the veins and secure it with bandages. The form is protected from both sides with thermal screens 5 (Fig. 35, c), heated by the flame of the burner 1 to the melting temperature of the solder and filled with solder 2 to the top. While heating the mold, thoroughly mix the liquid solder with a stirrer, removing slags from the surface. Then the compound is cooled. During solidification, the solder is protected from impacts and shocks: all solders for aluminum are especially brittle at temperatures from 250 ° to the melting point. Next, the form, screens and coolers are removed, the remnants of asbestos yarn are removed, the joint is cleaned and filed. The finished connection is isolated.

Crimping of conductors

The most widely used are three methods of crimping: local indentation, continuous crimping and combined crimping.

The method of local indentation is characterized by relatively small pressing forces, however, the connection contacts are less stable, and the geometric shape of the conductive wires is distorted. At voltages of 6-10 kV, the distortion of the shape of the cores leads to the creation of an inhomogeneous electric field, which is dangerous for insulation. Using local indentation, aluminum conductors with a cross section of 16 - 95 mm² are connected at voltage cable lines up to 10 kV inclusive, with a cross section of more than 95 mm² at a voltage of up to 1 kV.

The methods of continuous and combined compression are associated with the use of more powerful and expensive presses with drives. By these methods, contact connections are obtained more than High Quality than with local indentation.

Rice. 36. Press tongs PK-3:
1 - pusher; 2, 5 - screws; 3 - block punch; 4 - block matrix; 6 - yoke; 7, 10 - handles; 8 - thrust; 9 - blocking device.

Crimping tools that directly affect the metal of the joint are sets of punches and dies and are interchangeable in mechanisms (presses). AT last years crimping tools have been modernized and are available as NISO kits for crimping aluminum wires with a cross section of 16 - 240 mm² and NIOM for crimping copper wires of the same cross sections.

Rice. 37. Crimping mechanisms PGE-20 with electric drive (a), RMP-7 (b), PGR-20M1 (c), hydraulic tongs GKM (d):
1 - yoke; 2 - hydraulic cylinder; 3 - pump; 4 - drive; 5 - handle; 6 - folding bracket; 7 - body; 8 - drum; 9 - matrix; 10 - punch; 11 - piston; 12 - handle-reservoir.

To create the forces necessary for crimping, a variety of mechanisms are used (Fig. 36 - 38). The most convenient in the practice of repair work are the PGR-20M1 and PGE-20 mechanisms, in which seats for the tool are unified (Fig. 37). This allows the use of mechanisms both with a set of NISO and with a set of NIOM, i.e., to crimp aluminum and copper conductors.

The connection and branching of single-wire aluminum conductors with a cross section of 2.5-10 mm² is performed in GAO sleeves. The connection of aluminum and copper conductors with a cross section of more than 10 mm² is carried out in aluminum tubular sleeves, and the termination is in TA and TAM lugs. To connect and terminate copper conductors, copper tubular sleeves and tips T are used.

Rice. 38. Powder press PPO-95M:
1 - trunk; 2 - shock absorber; 3 - protective cover; 4 - body; 5 - screw; 6 - matrix; 7 - punch; 8 - shock absorber nut; 9 - retaining spring; 10 - extractor; 11 - shutter; 12 - mainspring; 13 - drummer; 14 - button.

In addition to tubular products, pin copper-aluminum tips ShP and ring copper tips P (pistons) are used for crimping. Tips ShP are produced for stranded aluminum conductors with a cross section of 16 - 240 mm², and caps P - for copper conductors with a cross section of 1.0; 1.5 and 2.5 mm².

There are some differences in the technology of crimping aluminum and copper conductors. An oxide film is formed on the surface of aluminum conductors, which has a high electrical resistance. Therefore, to avoid the formation of this film, when preparing aluminum conductors for crimping, quartz-vaseline paste is used. It is applied to a surface previously cleaned with steel brushes and ruffs, then the dirty paste is removed with a rag and applied new layer pastes. The sequence of termination and crimping of aluminum conductors with a cross section of 16-240 mm is shown in fig. 39.

Rice. 39. The sequence of crimping aluminum conductors with a cross section of 16 - 240 mm²:
a - the ends of the wires after removing the insulation; b - stripping of veins; c - cleaning the inner surface of the sleeve; g - lubrication of the inner surface of the sleeve with quartz-vaseline paste; e - lubrication of the cores with quartz-vaseline paste; e - connection prepared for crimping; g - crimping lived; h - pressed connection.

Choose a tool, a mechanism and a tip (sleeve) for a given type and section of the core. From the core section equal to the length of the tip sleeve or half the length of the sleeve, remove the insulation (Fig. 39, a), clean the core (Fig. 39, 6), inner surface sleeve (Fig. 39, c) or tip and lubricate with quartz-vaseline paste (Fig. 39, d, e). The tip is put on until it stops, the cores are inserted into the sleeve until the joint (Fig. 39, e) (the joint should be in the middle of the sleeve length). The assembled connection is installed in the crimping mechanism; previously, the punch is retracted from the die to the extreme position (Fig. 39, g). Carry out crimping. The end of the crimping process is determined by the moment the punch washer rests against the die end. The crimping of the tips is carried out by two indentations with a single-toothed tool or by one indentation with a two-toothed tool. Two indentations are made on the sleeve on each side (Fig. 39, h). The best crimping results are achieved by using the NUSA set with a stepped punch.

Excess paste is removed from the pressed connection or tip, the sharp edges on the connection are blunted and degreased. One layer of cable paper is applied to the connection of cable cores with a voltage of 6-10 kV with the overlap of all holes, pre-filled with MP cable mass. The finished connection is isolated.

Rice. 40. Connection of wires VL:
a - the sequence of crimping in two connectors with a shunt and using welding; b, c - the order of compression (shown in numbers) of monometallic and steel-aluminum wires; d, e - connection by twisting without the use and with the use of welding.

Crimping and crimping of uninsulated wires VL (Fig. 40) is carried out in the case when high requirements are not imposed on the connection as an electrical contact.

Connections are made in connectors, which are sections of pipes of oval, round or shaped sections.

Crimping of wires using welding is carried out in two connectors with a shunt, in elongated connectors with a shunt and in connectors with a loop, where the welded joint is located. The first and third options allow you to completely unload the welded joint from mechanical loads.

Connections in two oval connectors are made in the following order: they are cleaned, washed in a solvent and wiped dry oval connectors 1 (Fig. 40, a), after which they are put on wires 3. Prepare the ends of the wires for welding and carry out thermite welding of the cores 2. Cut off from the shunt wire 4 with a length equal to three connector lengths. They mark, clean from dirt, wash in a solvent, wipe dry the places where the connectors are installed on the wires and on the shunt, cover them with neutral technical vaseline. The assembled connection is crimped with tongs designed for crimping wires. The quality of the compression is controlled by inspection and measurement of the depth of indentations. If a defect is found, the connection is cut out and performed again.

In connections with a loop (a loop is performed, as in a twist connection - Fig. 40.6), the wires are passed through the connector so that their free ends are at least three-quarters of the length of the connector. Crimping or crimping is carried out according to general scheme. The ends of the wires are bent in a loop, joined and welded by thermite welding.

Compression of aluminum wires is carried out with tongs, for example MI-19A, according to the risks on the connector (Fig. 40.6, c). First, the cores of the cores are pressed, introducing them inside the steel connection (in this case, the main connector must be pushed onto one of the wires). After crimping the steel core, the main connector is placed symmetrically on top of it and crimped on the aluminum layers of wires.

Twisting connections in oval connectors (Fig. 40, d, e) for wires with a cross section of 10-185 mm² are made in a fixture with a fixed clamp and a rotating faceplate. The wires with the connector are rigidly fixed in the clamp and the faceplate. Then the faceplate is rotated 3 - 4.5 turns (in proportion to the cross section of the cores). If necessary, perform welding in the loop (Fig. 40.6).

If there are cracks on the surface of the connector, mechanical damage or signs of significant corrosion, if the curvature of the molded connector is more than 3% of its length, the molded contact joints are rejected.

Rice. 41. Means and methods of quality control of crimping:
a, b - with local indentation with a special meter; c, d - with local indentation with a caliper with a nozzle; e - with combined compression with a caliper.

The method of measuring residual thicknesses with the help of calipers or line instruments adapted for this purpose is widely used for quality control of pressed joints (Fig. 41). The measured residual thicknesses h, h 1 and h 2 must comply with the regulations. 3-5% of connections are subjected to control by crimping cable cores and 5-10% of VL connectors.

Wire connection methods

Contact connections of conductors are a very important element of the electrical circuit, therefore, when performing electrical work, you must always remember that the reliability of any electrical system is largely determined by the quality of electrical connections.

All contact connections are subject to certain technical requirements. But first of all, these connections must be resistant to mechanical factors, be reliable and safe.

With a small area of ​​contact in the contact zone, a rather significant resistance can occur for the passage of current. The resistance at the point where the current passes from one contact surface to another is called transient contact resistance, which is always greater than the resistance of a solid conductor of the same size and shape. During operation, the properties of the contact connection under the influence of various external and internal factors can deteriorate so much that an increase in its contact resistance can cause overheating of the wires and create an emergency. The transient contact resistance largely depends on the temperature, with an increase in which (as a result of the passage of current) an increase in the contact resistance occurs. Heating of the contact is of particular importance in connection with its influence on the process of oxidation of the contact surfaces. In this case, the oxidation of the contact surface is the more intense, the higher the contact temperature. The appearance of an oxide film, in turn, causes a very strong increase in contact resistance.

This is an element of an electrical circuit where the electrical and mechanical connection of two or more individual conductors is carried out. At the point of contact of the conductors, an electrical contact is formed - a conductive connection through which current flows from one part to another.

A simple overlay or slight twisting of the contact surfaces of the connected conductors does not provide good contact, because due to microroughness, the actual contact does not occur over the entire surface of the conductors, but only at a few points, which leads to a significant increase in contact resistance.

At the point of contact between two conductors, a contact resistance of an electrical contact always arises, the value of which depends on physical properties materials in contact, their condition, compression force at the point of contact, temperature and actual area of ​​contact.

From the point of view of the reliability of electrical contact aluminum wire cannot compete with copper. After a few seconds of exposure to air, the pre-cleaned aluminum surface is covered with a thin hard and refractory oxide film with high electrical resistance, which leads to increased transient resistance and strong heating of the contact zone, resulting in an even greater increase in electrical resistance. Another feature of aluminum is its low yield strength. A strongly tightened connection of aluminum wires weakens over time, which leads to a decrease in the reliability of the contact. In addition, aluminum has the worst conductivity. That is why the use of aluminum wires in household electrical systems is not only inconvenient, but also dangerous.

Copper oxidizes in air at normal residential temperatures (about 20 °C). The resulting oxide film does not have great strength and is easily destroyed by compression. Particularly intense oxidation of copper begins at temperatures above 70 °C. The oxide film on the copper surface itself has negligible resistance and has little effect on the value of the transient resistance.

The state of the contact surfaces has a decisive influence on the growth of the contact resistance. To obtain a stable and durable contact connection, high-quality cleaning and surface treatment of the connected conductors must be performed. The insulation from the cores is removed to the desired length with a specialized tool or knife. Then the bare parts of the veins are cleaned with an emery cloth and treated with acetone or white spirit. The length of the cut depends on the characteristics of the particular method of connection, branch or termination.

The transient contact resistance decreases to a large extent with an increase in the compression force of the two conductors, since the actual contact area depends on it. Thus, to reduce the transition resistance in the connection of two conductors, it is necessary to ensure their sufficient compression, but without destructive plastic deformations.

There are several ways to make an electrical connection. The highest quality of them will always be the one that provides, under specific conditions, the lowest value of the transient contact resistance for as long as possible.

According to the "Electrical Installation Rules" (clause 2.1.21), the connection, branching and termination of the cores of wires and cables must be carried out by welding, soldering, crimping or clamping (screw, bolt, etc.) in accordance with applicable instructions. In such connections, it is always possible to achieve a consistently low contact resistance. In this case, it is necessary to connect the wires in compliance with the technology and using appropriate materials and tools.

This is an important and responsible operation. It can be performed different ways: using terminal blocks, soldering and welding, crimping, and often ordinary twisting. All of these methods have certain advantages and disadvantages. It is necessary to choose a connection method before starting installation, as this also involves the selection of appropriate materials, tools and equipment.

At wire connection the same color of neutral, phase and ground wires should be observed. Usually the phase wire is brown or red, the zero worker is blue, the protective earth wire is yellow-green.

Very often, electricians have to connect a wire to an existing line. In other words, you need to create a branch wire. Such connections are made using special branch clamps, terminal blocks and piercing clamps.

In direct contact, copper and aluminum form a galvanic pair, and an electrochemical process occurs at the point of contact, as a result of which aluminum is destroyed. Therefore, to connect copper and aluminum wires, special terminal or bolted connections must be used.

Wires connected to various devices, often need special tips that help ensure reliable contact and reduce contact resistance. Such lugs can be attached to the wire by soldering or crimping.

There are the most various kinds. For example, for copper stranded conductors, lugs are produced from seamless copper pipe, flattened and drilled for a bolt on one side.

Welding. Connection of wires by welding.

It gives a solid and reliable contact, so it is widely used in electrical work.

Welding is performed at the ends of previously stripped and twisted conductors with a carbon electrode using welding machines with a power of about 500 W (for a twist section of up to 25 mm2). The current on the welding machine is set from 60 to 120 A, depending on the cross section and the number of wires to be welded.

Due to the relatively low currents and low (compared to steel) melting temperature, the process occurs without a large blinding arc, without deep heating and splashing of the metal, which makes it possible to use goggles instead of a mask. In this case, other security measures can be simplified. At the end of welding and the wire cooling, the bare end is insulated with electrical tape or heat shrink tubing. After a little training with the help of welding, you can quickly and efficiently make connections. electrical wires and cables in the power supply system.

When welding, the electrode is brought to the wire to be welded until it touches, then it is retracted to a short distance (OD-1 mm). The resulting welding arc melts the twisted wires until a characteristic ball is formed. Touching the electrode should be short-term to create the desired melting zone without damaging the wire insulation. Greater length arcs cannot be made, since the welding site is porous due to oxidation in the air.

At present, it is convenient to perform welding work on connecting electrical wires with an inverter welding machine, since it has a small volume and weight, which allows the electrician to work on a ladder, for example, under the ceiling, hanging the welding inverter apparatus on your shoulder. For welding electrical wires, a graphite electrode coated with copper is used.

In a joint obtained by welding, electricity flows through a monolithic metal of the same type. Of course, the resistance of such compounds is record low. In addition, such a connection has excellent mechanical strength.

Of all the known methods of connecting wires, none of them can be compared with welding in terms of durability and conductivity of the contact. Even soldering is destroyed over time, since a third, more fusible and loose metal (solder) is present in the connection, and at the boundary different materials there is always additional contact resistance and destructive chemical reactions are possible.

Soldering. Connecting wires by soldering.

Soldering is a method of joining metals using another, more fusible metal. Compared to welding, soldering is easier and more affordable. It does not require expensive equipment, is less flammable, and the skills to perform a good quality soldering will require more modest than when making a welded joint. It should be noted that the metal surface in air is usually quickly covered with an oxide film, so it must be cleaned before soldering. But the cleaned surface can quickly oxidize again. To avoid this, chemicals are applied to the treated areas - fluxes that increase the fluidity of the molten solder. Thanks to this, the soldering is stronger.

Soldering is also the best way terminations of copper stranded conductors into the ring - the soldered ring is evenly covered with solder. In this case, all wires must completely enter the monolithic part of the ring, and its diameter must correspond to the diameter of the screw clamp.

The process of soldering wires and cable cores consists in coating the heated ends of the connected cores with molten tin-lead solder, which after hardening provides mechanical strength and high electrical conductivity of the permanent connection. The soldering should be smooth, without pores, dirt, sagging, sharp solder bulges, foreign inclusions.

For soldering copper conductors of small cross sections, solder tubes filled with rosin are used, or a solution of rosin in alcohol, which is applied to the junction before soldering.

To create a high-quality soldered contact connection, the cores of wires (cables) must be carefully tinned, and then twisted and crimped. The quality of the soldered contact largely depends on the correct twisting.

After soldering, the contact connection is protected by several layers of insulating tape or heat shrink tubing. Instead of an insulating tape, the soldered contact connection can be protected with an insulating cap (PPE). Before this, it is desirable to cover the finished joint with a moisture-resistant varnish.

Parts and solder are heated with a special tool called a soldering iron. A prerequisite for creating a reliable connection by soldering is the same temperature of the soldered surfaces. Of great importance for the quality of soldering is the ratio of the temperature of the soldering tip and the melting temperature. Naturally, this can only be achieved with the right tool.

Soldering irons vary in design and power. To perform household electrical work, a conventional electric soldering iron with a power of 20-40 W is quite sufficient. It is desirable that it be equipped with a temperature controller (with a temperature sensor) or at least a power controller.

Experienced electricians often use soldering original way. A hole with a diameter of 6-7 mm and a depth of 25-30 mm is drilled in the working rod of a powerful soldering iron (at least 100 W) and filled with solder. When heated, such a soldering iron is a small tin bath, which allows you to quickly and efficiently solder several stranded connections. Before soldering, a small amount of rosin is thrown into the bath, which prevents the appearance of an oxide film on the surface of the conductor. The further soldering process consists in lowering the twisted joint into such an impromptu bath.

One common way to create a contact is to use screw terminals. In them, reliable contact is ensured by tightening the screw or bolt. In this case, it is recommended to attach no more than two conductors to each screw or bolt. When using stranded wires in such connections, the ends of the wires require preliminary tinning or the use of special lugs. The advantage of such connections is their reliability and collapsibility.

By appointment, terminal blocks can be through and connecting.

Designed to connect wires to each other. They are commonly used for switching wires in junction boxes and switchboards.

Feed-through terminal blocks are used, as a rule, for connecting various devices to the network (chandeliers, lamps, etc.), as well as for splicing wires.

When connecting wires with stranded wires using screw terminals, their ends need to be pre-soldered or crimped with special lugs.

When working with aluminum wires, the use of screw terminals is not recommended, since aluminum conductors, when tightened with screws, are prone to plastic deformation, which leads to a decrease in the reliability of the connection.

Recently, a very popular device for connecting wires and cable cores has become self-clamping terminal blocks type WAGO. They are designed to connect wires with a cross section of up to 2.5 mm2 and are designed for an operating current of up to 24 A, which allows you to connect a load of up to 5 kW to the wires connected by them. Up to eight wires can be connected in such terminal blocks, which greatly speeds up the wiring as a whole. True, compared to twisting, they take up more space in soldered boxes, which is not always convenient.

The screwless terminal block is fundamentally different in that its installation does not require any tools and skills. The wire, stripped to a certain length, is inserted into its place with little effort and is securely pressed by a spring. The design of a screwless terminal connection was developed by the German company WAGO back in 1951. There are other manufacturers of this type of electrical products.

In spring-loaded self-clamping terminal blocks, as a rule, the effective contact surface area is too small. At high currents, this leads to heating and release of the springs, resulting in a loss of their elasticity. Therefore, such devices should be used only on eyeliners that are not subjected to heavy loads.

WAGO manufactures terminal blocks for both DIN rail mounting and for screwing to a flat surface, but building terminal blocks are used for installation as part of home wiring. These terminal blocks are available in three types: for junction boxes, for fixture fittings and universal.

Terminal blocks WAGO for junction boxes, they allow connecting from one to eight conductors with a cross section of 1.0-2.5 mm2 or three conductors with a cross section of 2.5-4.0 mm2. And terminal blocks for fixtures connect 2-3 conductors with a cross section of 0.5-2.5 mm2.

The technology for connecting wires using self-clamping terminal blocks is very simple and does not require special tools and special skills.

There are also terminal blocks in which the conductor is fixed using a lever. Such devices allow you to achieve good pressure, reliable contact and at the same time are easily disassembled.

One of the connecting products popular among electricians is. Such a clamp is a plastic case, inside of which there is an anodized conical spring. To connect the wires, they are stripped to a length of about 10-15 mm and folded into a common bundle. After that, PPE is wound on it, turning clockwise until it stops. In this case, the spring compresses the wires, creating the necessary contact. Of course, all this happens only when the PPE cap is correctly matched to its face value. Using this clamp, it is possible to connect several single wires with a total area of ​​2.5-20 mm2. Naturally, the caps in these cases are of different sizes.

Depending on the size, PPE have certain numbers and are selected according to the total area cross section twisted cores, which is always indicated on the packaging. When choosing PPE caps, one should be guided not only by their number, but also by the total cross section of the wires for which they are designed. The color of the product has no practical value, but can be used for marking phase and neutral conductors and ground wires.

PPE clamps greatly speed up installation, and due to the insulated housing, they do not require additional insulation. True, their connection quality is somewhat lower than that of screw terminal blocks. Therefore, ceteris paribus, preference should still be given to the latter.

Twisting. Twisted wire connection.

Twisting bare wires as a connection method in the "Electrical Installation Rules" (PUE) is not included. But despite this, many experienced electricians consider a correctly performed twist as a completely reliable and high-quality connection, arguing that the contact resistance in it practically does not differ from the resistance in the whole conductor. Be that as it may, a good twist can be considered one of the stages of connecting wires by soldering, welding or PPE caps. Therefore, high-quality twisting is the key to the reliability of all electrical wiring.

If the wires are connected according to the “how it happened” principle, a large contact resistance can occur at the point of their contact, with all the negative consequences.

Depending on the type of connection, twisting can be performed in several ways, which, with a small transient resistance, can provide a completely reliable connection.

First, the insulation is carefully removed without damaging the wire core. Sections of veins exposed to a length of at least 3-4 cm are treated with acetone or white spirit, cleaned with sandpaper to a metallic sheen and tightly twisted with pliers.

Crimping method widely used to make reliable connections in junction boxes. In this case, the ends of the wires are stripped, combined into appropriate bundles and pressed in. The connection after crimping is protected with electrical tape or heat shrink tubing. It is non-detachable and does not require maintenance.

Crimping considered one of the most reliable ways to connect wires. Such connections are made using sleeves by continuous compression or local indentation with special tools (press tongs), into which interchangeable dies and punches are inserted. In this case, the indentation (or compression) of the sleeve wall into the cable cores occurs with the formation of a reliable electrical contact. Crimping can be done by local indentation or continuous compression. A solid crimp is usually made in the form of a hexagon.

It is recommended to treat copper wires with a thick lubricant containing technical petroleum jelly before crimping. This lubrication reduces friction and reduces the risk of damage to the core. A non-conductive lubricant does not increase the contact resistance of the connection, since, if the technology is followed, the lubricant is completely displaced from the contact point, remaining only in the voids.

For crimping, manual press tongs are most often used. In the most common case, the working bodies of these tools are dies and punches. In the general case, the punch is a movable element that produces a local indentation on the sleeve, and the matrix is ​​​​a figured fixed bracket that perceives the pressure of the sleeve. Matrices and punches can be replaceable or adjustable (designed for different sections).

When installing ordinary home wiring, as a rule, small crimping pliers with curly jaws are used.

As a crimping sleeve, you can, of course, use any copper tube, but it is better to use special sleeves made of electrical copper, the length of which corresponds to the conditions for the reliability of the connection.

When crimping, the wires can be inserted into the sleeve both from opposite sides until mutual contact is strictly in the middle, and from one side. But in any case, the total cross section of the wires must correspond to the inner diameter of the sleeve.