Back to Basics: Conductor Stranding
For our first Back to Basics lesson we learned about different conductor materials. We emphasized the importance of understanding the requirements of your application in order to pick a material that will best suit your temperature range, abrasion resistance level, and flexibility needs. This week’s blog discusses different conductor stranding configurations.
There are various stranding formations used in the wire and cable industry, and similar to conductor materials, it is crucial to understand the properties of each conductor stranding arrangement before choosing which accommodates your application best.
Solid Conductors: The cross-sectional area appears as a solid circle. This type of stranding is the most economical; however, it is stiff and prone to breakage.
Stranded Conductor: The cross-sectional area is not a solid circle, and as a result, the stranding is flexible and can withstand repeated bending. This version is more expensive than solid conductors and it is made up of various individual gauge sizes to create the finished AWG size.
Bunched: The individual strands are twisted together with no specific geometric configuration, thus causing the stranding to have a rough surface. All the strands have the same lay direction and lay length. These types of conductors are usually used in static cable designs, such as the Alpha Xtra-Guard® Series.
Unilay®: Conductors are twisted together with the same lay direction and cable lay length and have a well-defined geometric configuration and defined cross-section. This configuration, like the bunched configuration, is also common in static cable designs.
Unidirectional Concentric: The word “concentric” refers to the definition of the word, meaning having a common center. A concentric conductor is defined by a central strand surrounded by one or more layers of helically laid (think DNA) conductors. In this case, the helically laid conductors surround the central strand with the same direction or lay and an increased lay length. Concentric configurations allow for tight diameter tolerances and have smooth surfaces that are suitable for high performance torsional designs such as Robotics applications.
Concentric: Conductors that are surrounded by well-defined layers of helically laid conductors are considered to be true concentric. Each layer has a reversed lay direction and an increased lay length in each layer. Similar to Unidirectional Concentric stranding, this configuration is typically used in high performance torsional designs.
Equilay®: This includes central conductors that are surrounded by well-defined layers of helically laid conductors. Each layer has a reverse lay direction and increasing lay length. This configuration can also be used in torsional designs.
Rope: Several groups of either bunched or concentric strands combined into a circular pattern are considered a rope stranding. The most common number of conductor groups is usually 7 or 19. Rope stranding increases flexibility more than a simple bunched configuration, because it allows for a larger number of fine strands to be used while maintaining a tight diameter tolerance.
With the above in mind, you can now confidently choose the stranding you need for your next application.