Cable Strands: What are the Common Types Available?

FACTS CHECKED BY  Jose George​

There are two types of conductors available, solid and stranded. However, stranded conductors are becoming quite popular in the electrical industry because they are flexible and easy to use in complex circuitries. However, to facilitate different applications, you need to choose different classes and different types of cable strands. Let us see some types of Cable strands arrangement and how they facilitate the electric power systems. 

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Facts about Stranded Conductors

  1. Stranded conductors have enough elasticity so that you can coil them easily for long-distance transportation, making them a good choice for such situations.
  2. Moreover greater the number of strands in a stranded conductor, the greater the flexibility of the wire.
  3. Also, it is possible to create stranded conductors by layering the strands and twisting them with each other.
  4. Each layer’s strands are spread out in a spiral pattern on top of the one before it. This practice is known as stranding.
  5. The standard procedure for each succeeding layer is to be stranded in a different direction from the previous layer. Moreover, when you wind one layer of wires clockwise, you have to set the strands of the following layer anticlockwise, and so on, where ‘x’ represents the number of layers in the wire.
  6. To calculate the total number of conductor strands, use the formulas of, i.e.,

             N=3×2-3x+1

            Here, several strands are represented by the number N.

       7. The formula for calculating the conductor’s diameter is as follows:

           D=(2x-1)d

           D is the conductor’s diameter, and ‘d’ is the strand’s diameter.

Cable Strands 1

Caption: Different Types of Stranded Wires

Stranding Classes

Following are the typical stranding classes used by the manufacturers.

Concentric Lay Conductor

  • Class-B for typical power cords.
  • Class-C for Power Cords that are more flexible than class B.
  • Class-D for Power Cables with extra flexibility.

Bunch Conductors and Rope Lay Strands

  • Class-G for portable use cables.
  • Class-H for extremely flexible cables.
  • Class-I for motor leads and apparatus wires.
  • Class-K for stationary service 30 AWG wire.
  • Class-M for Constant service 34 AWG copper wires.

Types of Strands

Bunched Strand

Bundles made from single wires or clustered multi-wires are known as “bunched strands.” It’s hard to tell which way the lay should be, although it may be either S or Z. The position of every single wire is not well specified in this strand. 

Moreover, the size and roundness of the external surface are not consistent, resulting in a sloppy appearance. Thin-walled insulation can’t be done with this type of strand. Thus, flexible cords, building cables, control cables, and other types of cables can all benefit from this group’s inclusion.

Concentric Strand

Concentric stranding uses a regular pattern of strands while laying out the strands. Each layer changes direction and has an increasing lay length as it progresses through the inner layer (the center strand is the longest). Thus, it has symmetric wire numbers like 1, 6, 12, 18, 24, and 30. Typically, these wires are available in 7-stranded, 19-stranded, 37, 61, or 91-stranded designs. 

There are two common concentric strands available, true concentric and inlay. 

  • True concentric types have different locations from the outer to the inner strand layer.
  • Inlay type, on the other hand, goes for the same, uniform direction for every layer.

Most designs go for concentric stranding as it has brilliant mechanical strength and crush resistance, among other characteristics. Moreover, all concentrically stranded wires have precise outer surfaces and diameters. Hence, you can use it for thin-wall installations where high-quality insulation is needed.

Equally

Equally, wire has the same stranding technique as the above. However, unlike concentric stranding, the strands in this method are uniform in length. Each layer has the same lay length.

Semi-concentric Strand 

Semi-concentric strand wires are similar to concentric wires. However, it does not follow an asymmetric number of wires. For example, a combination may call for 2, 8, 4, or 3, 9, or 16 stranded layers. 

Additionally, the external surface and outer layer are uniform around the core, making it a good option for thin-wall insulation.

Rope Strand 

Cable groupings of strands form by arranging them in a cabled pattern. Each group typically has seven, thirteen, nineteen, or twenty-seven strands since you may conveniently arrange those numbers in a circular arrangement. Rope lay stranding is by far the most flexible type and is present in cables with a diameter of 10 AWG or greater.

Sector Conductor

In some cases, the cross-section of the wire is about the form of one part of the circle. This is called “sector conductor.” If a cable has a lot of conductors, it has a smaller surface area than if the same cable had round conductors. Thus, it has become popular in the electrical industry.

Segmental Conductor

Some conductors consist of three or four sections that aren’t very close to each other. These sections are called “segments.” AC resistance is lower because there is more surface area and the skin effect, making it easier for electricity to flow through it.

Annular Conductor

Annular stranding is a ground conductor with a big core enough for the strands to be wrapped around it. Most of the time, the center consists of non-conducting material. Due to the skin effect, this design will have less total AC resistance for the same amount of conductor cross-sectional area.

Compact Strand

A compact stranding conductor is a sector or round conductor with all of its layers positioned in the same direction and rolled into the ideal shape for most applications. Furthermore, the finished conductor is very smooth on the outside and doesn’t have a lot of gaps or air spaces in the middle. Because of this, the diameter of the thing is smaller.

Compressed Strand

Compressed conductors are in the middle between compact and concentric conductors in terms of size.

Some of the space between the wires has been squeezed out by going through a roller. This is how each wire is made in a compact conductor. Moreover, manufacturers bend each wire into a trapezoid before stringing them together to make a finished conductor. This means leaving almost no space between strands.

Conclusion

Stranded wires tend to be more flexible than common solid wires. Thus, it is common to use in circuits where there are a lot of twists and turns. Moreover, the different types of stranding facilitate different applications. Here at Cloom, we offer wiring harnesses and cable assemblies. If you have any questions concerning them, please do not hesitate to contact us.

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