What is a unipolar cable?
A unipolar cable is a type of electrical cable that consists of a single insulated central conductor, that is, it only has a single "polarity" or "conducting wire" in its structure. This type of cable is used in applications where electrical current is required to be carried in only one direction, such as in direct current (DC) circuits or in some alternating current (AC) systems where only one active conductor is needed.
In contrast, bipolar or multi-wire cables have several insulated conductors in the same jacket and are used for circuits where both forward and return electrical current need to be carried, such as in most AC electrical systems.
Unipolar cables can be found in different sizes and gauges, and the insulation covering the center conductor can vary depending on the specific application. These cables are used in various situations, such as in the installation of solar energy systems, where direct current is transported from the solar panels to the inverters, or in electrical power applications in industrial machinery and control systems.
It is important to select the appropriate cable type, whether unipolar or bipolar, based on the electrical system needs and design specifications to ensure safe and efficient operation.
A unipolar electrical cable, like other types of cables, is an electrical conductor that is used to carry electrical current from a power source, such as an electricity generating plant, to a device or system that requires that electrical energy to operate. They are designed to safely transmit electricity from one point to another, whether in low voltage applications, such as in appliances and electronic devices, or in high voltage applications, such as in the transmission of electricity through long distances on high voltage lines.
Any electrical cables and therefore also single-pole cables are made up of several components:
- Conductor: It is the central part of the cable and is made of a conductive material, such as copper or aluminum. This conductor allows electric current to flow through it.
- Insulation: The conductor is covered with an insulating material, such as PVC (polyvinyl chloride), polyethylene, rubber, or rubber, which prevents electrical current from escaping and protects against short circuits and electric shock.
- Outer sheath: In some cases, electrical cables have an additional outer sheath to protect them from mechanical damage, moisture and other environmental elements, acids, oils, etc. Such as cables for photovoltaic use
Unipolar electrical conductors come in different sizes and types, depending on the specific application. For example, the cables used in a residential electrical installation will be different from the cables used in a high voltage transmission line. It is important to select the appropriate cable type for the desired application and comply with local electrical codes and regulations to ensure the safety and proper performance of the electrical system. Depending on whether the conductor is made up of a single strand or thread or more, we will say that the cable is unifilar or multifilar.
Single-core unipolar cables
A single-core cable refers to a type of electrical cable that consists of a single central conductor and a single conductive strand or filament. In other words, it is a cable that has a single insulated conducting wire inside. This central conductor is surrounded by an insulating material that protects it and prevents it from coming into contact with other conductors or components.
Single-core cables are rigid and are used in applications where a simple and direct electrical connection is needed. They are also known as rigid wire or wire. They are usually found in various sizes and calibers, depending on the amount of electrical current they must carry and the specifications of the system in which they are used.
It is important to note that this type of cable is not used for high voltage power transmission systems or for applications that require a more complex connection. Instead, they are used in situations where a single, simple conductor is needed, such as when connecting electronic components or making electrical connections in low-voltage circuits. They are also used in some other applications where a multi-core cable is not suitable due to its flexibility. For example, they are widely used in the connections of prototyping boards also called breadboards and in wrapping connection techniques.
In summary, a single core single core cable is an electrical cable consisting of a single, individually insulated central conductor, and is used in applications where a simple and direct electrical connection is required.
Unipolar multi-core cables
A stranded cable is a type of electrical cable that consists of several individual conductive strands or strands grouped together into a single assembly. These conductive wires or filaments can be made of copper, aluminum or other conductive material and are insulated from each other. Multi-core cables are used in a variety of applications where greater flexibility and handling capacity is required compared to single-core cables.
The advantages of multi-core cables include:
Flexibility: Because they are made up of multiple conductive strands, multi-core cables are more flexible and less likely to break when bent or handled. This makes them ideal for applications where greater mobility is required or where cables must withstand repeated bending.
Fatigue resistance: Multi-core cables are less prone to mechanical fatigue and constant bending rupture compared to single-core cables, making them more durable in applications where continuous movement is required.
More secure connections: Multi-strand cables are suitable for applications where secure connections are needed, such as in plug and connector terminals, as the multiple strands provide a greater electrical contact area.
These cables are common in the electrical industry and are used in a variety of applications, from installing electrical systems in buildings and automobiles to manufacturing extension cords and flexible cables for electrical and electronic devices. Their flexibility and handling capacity make them especially useful in situations where high mobility and durability are required.
How important is the section of the individual strands in a multi-core cable?
The cross section of the individual strands in a multi-core cable is of great importance and can have several implications on the performance and functionality of the cable. The cross section refers to the area of each of the individual conductor wires that make up the multi-core cable. The following highlights some of the key considerations regarding the importance of individual strand section in a multi-core cable:
Current capacity: The cross section of the strands determines the current capacity that the cable can carry. The larger the cross-sectional area, the greater the amount of current the cable can safely carry without overheating. This is especially important in applications where high current capacity is required, such as in power cables.
Electrical resistance: The electrical resistance of a cable is inversely related to the cross-sectional area of the strands. The larger the area, the lower the electrical resistance and therefore the lower the energy loss due to heating. This is especially relevant in electrical energy transmission applications, where energy losses are sought to be minimized.
Flexibility and durability: The cross section of the strands also affects the flexibility and durability of the cable. Thinner individual strands can provide greater flexibility to the cable, which is important in applications where constant movement or bending of the cable is required. However, it is also important that the strands are robust enough to resist mechanical fatigue and breakage.
Cable size: The cross section of the strands influences the overall size of the stranded cable. The larger the area of the strands, the larger the diameter of the cable as a whole. This can be a determining factor in selecting the right cable for a specific application, especially when there are space restrictions.
In summary, the cross section of the individual strands in a stranded cable is important because it affects the current capacity, electrical resistance, flexibility, durability, and overall cable size. Proper choice of cross section is critical to ensuring safe and efficient performance in a variety of electrical and electronic applications.
If what we want is a cable that is in continuous movement, such as the head of a 3D printer or connection wiring in an electronic laboratory, where we need cable mobility to work comfortably, we will use more flexible cables than those we will require for a fixed installation. The individual strands have a diameter of Ø 0.05 to Ø 0.07 mm, which already requires greater precision in manufacturing with the considerable increase in cost. To achieve the same section we will use a greater number of threads than if the conductor were made up of thicker strands. As an example, a 4.0mm² multi-wire test lead cable has the following characteristics:
|
Sección nominal
|
4,0 mm² |
| Conductor diameter |
Ø 3,0 mm |
| Number of threads |
1036 hilos de x Ø 0,07 mm
|
| External diameter |
Ø 4,8 mm |
| Rated voltage |
600 V |
| Rated current |
42 A |
As we can see, the number of wires is already very large even though the diameter of the cable is not so large. And although in this case the insulation is PVC, the cable is still very flexible, even more flexible than other cables with silicone insulation without such extremely fine strand or thread diameters.
