The most important task when connecting any electrical contacts is to ensure their minimum resistance. With poor contact, the resistance between the copper wires increases significantly, as a result of which the cable heats up. There are many ways to connect contacts, but the most reliable and effective is considered to be the welding of copper wire. This technology allows you to monolithically connect all the strands of the wire, thereby achieving the lowest possible electrical resistance. As a result, heating of the wires is eliminated, therefore, the level of fire safety is significantly increased.
Wiring connection methods
Copper is the main conductor material. Due to the physical and chemical properties of this material (high plasticity, lack of elasticity), working with it has its own characteristics. The rules for the installation of electrical installations state that operations for connecting, branching and terminating the cores of cables and wires canperformed by soldering, welding, crimping or clamping (bolted, screw, etc.). Each of them has its own characteristics, which will be discussed below.
Connecting wires by twisting
Simple twisting of wires is prohibited by the PUE, as this is the most inefficient, short-lived and fire hazardous connection. Despite this, home craftsmen never stop using this method, although the consequences of such "needlework" can be the most fusible.
Twisting has one important drawback: copper connections deform and weaken over time, eventually finally breaking down due to high transient resistance.
It should be remembered that the twisting method can only be used in exceptional cases, if it is urgent to restore power supply, and other methods are not available in a particular situation. At the same time, it is very important to take care of the quality, security and reliability of the connection.
Strictly prohibited:
- Connect wires made of different materials (aluminum and copper);
- Connect a single-core copper wire with a stranded one.
The twisting process is as follows:
- Peel the wires from the insulation at a distance of 6-8 cm from the edge;
- Lay one wire on the other crosswise and twist as tightly as possible. If the cross section of the copper wire is more than 1 sq. mm, this operation is performed with pliers.
- Cut off the remaining ends of the wires with wire cutters.
- Isolatetwisting with special insulating materials (PVC or heat shrink tubes, caps) or several layers of insulating tape. The insulation must necessarily capture the insulating layer of the wires.
Crimping
This method is a process of connecting wires by crimping them with a special tubular sleeve or tip. These devices are used if the cross section of the copper wire is 2.5-240 square meters. mm. The indisputable advantages of the crimping technology are the speed and accuracy of the work, as well as the subsequent durability and safety of the connections.
For crimping, a special tool is used - mechanical, hydraulic or electric pliers or professional crimping presses. The selection of sleeves is carried out taking into account the cross section and the number of connected wires.
After removing the insulation and stripping the cores, quartz-vaseline paste is applied to them, a sleeve is put on and crimped. Pressed sleeves are insulated.
Crimps and terminals
The use of various crimps and terminal blocks is quite widely practiced when connecting electrical outlets, switches, lighting fixtures, as well as when installing switchboards. These devices allow you to accurately and quickly connect a copper single-core wire, however, a stranded wire cannot be clamped into a screw clamp without prior soldering or crimping with a tubular lug.
KThe indisputable advantages of screw terminals include the possibility of connecting aluminum wires with copper wires, as well as the absence of the need for subsequent insulation of contacts.
However, this type of connection is not without drawbacks. It needs periodic maintenance, which consists in tightening the clamping elements. Copper is a very soft material that tends to "leak" under load. Even if connections are made using rigidly spring-loaded self-clamping terminal blocks, due to the too small area of the contact surfaces, under heavy load, the spring elements heat up and release, as a result of which their elasticity decreases along with the quality of the connection.
VS-weld soldering
To ensure good contact, soldering or welding copper wires is most often used. Which is the best of these methods? Definitely welding. The fact is that soldering is a rather laborious and lengthy process, especially if you want to connect a copper stranded cable. Plus, solder joints are destroyed over time due to the presence of a third, more loose and fusible metal - solder. The presence of transient resistance at the joints of different alloys contributes to the appearance of destructive chemical reactions and other negative processes.
When the copper wire is welded, the concept of “contact” disappears altogether, since the connection turns out to be monolithic from the same type of metal. Naturally, such connections are characterized by record low resistance, due to which heat is practically not released.
Soldering
Immediately followsNote that this operation requires certain knowledge and experience. As paradoxical as it sounds, high-quality twisting is better than poor soldering, remember this.
The soldering process begins with preliminary cleaning of the ends of the wires from insulation and oxides. Then they are twisted, coated with a special substance - flux, and then soldered. You can solder not only copper wires, but also aluminum wires, the main thing is to choose the right flux and solder. The use of active acid flux is not recommended, as it will definitely remain on the wires, as a result of which the connection will quickly collapse.
One soldering takes a long time, but if done correctly, such a connection will be reliable and durable. After the wires have cooled, they must be carefully insulated.
Welding
The highest quality and safest connection is the welding of copper wire. The resistance at the point of contact of the wires does not exceed their standard resistance. This method does not require much time and is considered relatively simple. With minimal skills and knowledge, welding copper wires at home is quite doable.
When carrying out welding work, all fire and electrical safety rules must be strictly observed. To avoid burns and eye injuries, it is imperative to use personal protective equipment - special protective clothing andgloves, welding mask or goggles.
Welding equipment
The connection of wires by welding is carried out by various types of devices. It is most convenient to use an inverter machine for welding copper wires, since devices of this type are characterized by small dimensions and weight, economical energy consumption and a wide range of welding current adjustments. Their advantages include the ability to ensure stable burning of an electric arc.
If a significant amount of electrical work is planned, then the purchase of an inverter-type welding machine will be quite expedient and justified. In addition, this equipment will certainly not lie "dead weight" in the future.
Features of the process of welding copper wires
Welding of copper wire can be carried out with both alternating and direct current at a voltage of 15-30 V. It is very good if the device has the ability to adjust the current.
For example, to weld two copper wires with a cross section of 1.5 square meters. mm, 70 A is enough. To weld three wires with the same cross section, the current must be increased to 90 A. The connection of three wires with a cross section of 2.5 square meters. mm will require from 80 to 100 A, and for welding five similar wires - 120 A. If the optimal welding current is selected, the electrode does not “stick”, and the arc burns quite steadily. copper "pencils" (electrodes). If there are none, then it is possible to use carbon rods from finger-type batteries.
Technologywelding
The ends of the wires 5-6 cm long are cleaned of the insulating coating and twisted, starting from the insulation cuts, leaving 5-6 mm at the end of the twist in an untwisted form. These tips must be straightened, folded in parallel and pressed against each other. When twisting three or more wires, you still need to leave only two free ends at the end, and cut off the rest in the place of the last twist of the twist. If the welding machine is not powerful enough, such twisting will make it easier to form a ball of melt. If there is enough welding current in the machine, simple twisting can be done.
Next, the twist is clamped with a welding clamp. If this device is not available, you can use the usual old pliers.
The prepared joint is welded with a carbon electrode. In the process of welding copper wires, the ends left untwisted are melted until a ball of melt is formed. To ensure reliable mechanical and electrical contact of the wires, the melting zone must reach the twist.
The duration of welding should not exceed 2-3 seconds, otherwise the insulation of the wires will melt. After the connection has completely cooled down, it is isolated using several layers of electrical tape or special caps, PVC or heat shrink tubing.
