Cables are an integral part of any electrical device. No matter whether they are used for internal connections or power supply, they are responsible for transmitting power and signal in electrical engineering. We shall make a simple classification of cables which have no connectors. Cables with connectors have to a large extent been designed for a specific purpose, whereas cables „per meter“, although specified by type, still have versatile functions.
The simplest example of a cable is a single-core insulated cable, which in this case is called a conductor. It may be solid, with a hard copper (Cu) core, aluminum (Al) or an alloy of the two metals, but it can also be a stranded conductor with a core that comprises a plenty of thin wires, each with a thin lacquer coating. When a conductor has a solid core, sometimes the wire is tin-plated along its entire length in order to be easily soldered, and it looks as if it is made of white metal, but when stripped by a knife, the copper appears underneath.
The conductor can be thermostable and if it has silicon insulation, it is called SIF. It may also be shielded, with a metal braid over the basic insulation. A main parameter of each conductor is its section, which is indicated in square millimeters. This is not its diameter, but the surface of the cross-section of the wire, i.e. if we have a stranded single-core conductor with cross-section 2.5 mm2, this means that the sum of the surfaces of all wires in the cable is 2.5mm2. Some conductors are manufactured stranded because in this way they are more flexible and you can handle them more easily.
They are used for cabling of machines and equipment, building electrical installations and implementation of wiring diagrams. They are produced in a very wide range of colors as the color shows the function of each wire. Most often wires a mono-colored with one important exception – yellow-green. A yellow-green wire is used as neutral or grounding, in the latter case a blue wire is used as neutral.
Another type of conductor is the high-voltage conductor. Its more common name is a high-voltage cable, although it is single core. It has much thicker silicone insulation, which sometimes has two or three layers. A basic parameter of this cable is the voltage it can take. This voltage may be 7.5kV, 15kV, 30kV and so on.
There are special conductors, used for the winding of coils on electrical machinery and devices. Their core is made of soft constantan. This is a metal alloy of 40% Ni and 60% Cu, enameled with thin insulation of natural silk.
The conductor’s resistance remains constant with the temperature rise. Another important feature is that it can work without problems in a very wide temperature range – from -60°C to + 105°C. The Russian name of this conductor is ПЭШОКМ.
There are cases where it is more convenient for some installations to use two or three twisted around each other conductors with hard solid cores.
One of the most used cables for building electrical installations is a solid flat cable with two, three or four copper cores with color insulation of each core and common white insulation. Its well-known name is a bridge cable.
This cable is flat on purpose. Its design intends its easier application directly under plaster, i.e. such cables are embedded in walls. In this way, oxygen has no access to the cable and this significantly delays the aging of the PVC insulation. Another way of placing a bridge cable is on the wooden surfaces of shacks, huts, summer-houses, etc., where in the space between the two conductors, the cable is fixed to the wooden surface through nails.
Another type of installation cables are CBT cables. This is a power cable for voltages up to 1000V with a frequency of 50Hz. It is resistant to atmospheric changes and solar radiation. It can function continuously at core heating temperature up to 70°C and in case of short circuit – for about 5 seconds up to 160°C with coated cores and common insulation of PVC compound. During installation this cable can be placed in a corrugated pipe or can be mounted directly into the ground.
These are cables that power industrial or household electrical appliances and machinery, and movable electrical equipment. They are flexible, stranded, with colored PVC insulation:
Cables H05VVH2 – they are flexible, with individually insulated copper cores and a common shell;
Cables HO1N2-D – a stranded single-core cable with rubber insulation used in arc welding;
Cables HO5RR-F – a flexible multi-core cable, rubber insulated, used for powering electric machines at high mechanical loads; the cable can contact hot surfaces;
Power cables for solar systems – they resist high overheating, UV radiation and various weather conditions. The special insulation of cross-structured polymer, produced by new technology with electronic radiation, provides the cable with over 25 years of life under intense UV radiation.
Cables for data transmission
These cables carry analog or digital signals with low voltage. They are also called communication cables or cables for control and management. Among them are:
computer network cables (LAN cables) – FTP and UTP;
telephone cables type ShTPR;
information cables LIYY, LIYCY, OPVC, TRC, J-Y(L)Y;
Ribbon flat cables – they have different number of wires, different sections and different grid; they can be shielded or rubber. These cables have wires which are arranged side by side and glued into a thin strip. They are used in electronics, computer industry, etc.
Audio video cables
As their name suggests, these cables are used in audio and video technology. Here the quality is very important because in case of impurities in the copper (Cu), the quality of the picture and sound transmitted by these cables gets worse. In some of the cables each core is individually shielded to protect the signal from high-frequency interference. When these shielded cables have two cores, they are called cinch cables, because of the connectors with which they are used.
The single-core cables for audio systems with silicone insulation and a relatively large section are used in car sound systems to connect powerful bass-cases. The finest among them are produced in oxygen-free environment and are made of pure copper (Cu), to achieve the best possible transmission of audio and video signal.
This category also includes two-core cables for speakers that are used for carrying out the electrical connection between the speakers and the amplifiers. The two parallel constructively placed wires are electrically identical but they are marked so that they can be easily distinguished in order to keep the polarity because they are designed to carry a DC signal and if the polarity is wrong, the speaker may burn out.
The so called coaxial cables also belong to this category. RF coaxial cables are designed to transmit signals and are used in high-frequency control and measuring equipment, in high-frequency information systems, to connect radio and TV antennas with radio and television receivers, security cameras, etc. In the middle of the cable there is a solid copper core, around which there is PVC insulation, over which there is screening foil and aluminum or, in better cables – copper braid, over which again there is PVC insulation.
Heating cables are used for heating the surrounding space or the surface, near which they are placed. They can be sold per certain size with certain power consumption, for example: 57m, 1000W as a finished product with outlets and special insulation, intended for dry and wet premises. The heating element is the conductor itself, composed of metals and alloys with anti-corrosion coat and increased electrical resistance. The insulation and the outer protective covering of the conductors are of high quality PVC compound with high thermal resistance and mechanical strength. The cables designed for wet premises have a protective conductor- screen of copper braid for protection against electric shock.
There are also heating conductors that are sold per meter, with specially marked places where to cut them. They are used for protection against freezing of water pipes, gutters and containers, as well as for maintaining technological temperature in certain industrial processes.
There are a lot of other specialized cables and conductors that haven’t found place in this classification because it was designed for the most commonly used cables and conductors for low voltage, except for high-voltage ones, in industry and households.