Conductor Stranding: How important is it?

Conductor stranding can be a bit confusing. Wire and cable is manufactured in a variety of configurations, not all wire is the same. The conductors for wire (aside from solid core) are made of multiple strands of fine wire bunched or twisted together. Conductor stranding plays an important part of the flexibility and the performance life of the wire. The more individual wire strands in a wire, the more flexible, break-resistant and stronger the wire is. Hi flex applications where repetitive flexing is required use different stranding than wire used to wire a building or home. "Off the shelf wire normally is available in solid, 7 strand and 19 strand constructions which is fine for applications not requiring flexibility or repetitive movement.

Repetitive flexing can cause conductor strands to break over time which lowers the conductivity of the wire. Using higher strand wire helps eliminate this problem. High strand wire is used in medical handheld devices, robotics and even headphones.

Many custom wire and cable manufacturers offer high strand wire which you cannot obtain easily from distribution. For example, a 20AWG wire can be manufactured with a solid conductor or solid core all the way to 168 strands. Knowing which conductor stranding option will best suit your needs is important.

Identifying the conductor call out: A typical call out is XX (YY / ZZ). The "X" is the gauge of the wire, "Y" is the number of strands and "Z" is the gauge size of those strands. Once you understand what these numbers mean, identifying the conductor construction is simple. A wire gauge chart is a handy tool to view wire gauge stranding options

The more common conductor stranding configurations are concentric (true concentric, equilay concentric, unidirectional concentric, and unilay concentric), bunched and rope.

Rope stranding is conductor construction consisting of single strands assembled together into concentric or bunched configurations. Rope constructions consist of concentric or bunched members stranded together into the final concentric or bunched configuration. Rope stranding has the advantage of increasing flexibility by using a larger number of finer strands while maintaining a tighter diameter tolerance than a simple bunched construction. Ropes are more evident in the larger AWG sizes, such as 8 AWG and larger, but there are also many applications that require the flexibility of rope constructions in the smaller gauges. Constructions vary and can contain hundreds or thousands of strands.

Depending on the use, the type of conductor is important. Hi flex and load bearing applications would require conductors with higher tensile strength such as alloys. Copper conductors are normally for less rigorous flexing

Flexible wire is a term which can be interpreted in many ways from hi flex to the actual flexibility of the wire. Letting your cable manufacturer know what your expectation is for the flexibility of your wire or cable will help in choosing the right conductor stranding. Calmont has manufactured extremely flexible large gauge wire and cable as big as 4/0 which is limp and flops over the end of a table. Of course insulation and jacket material also plays an important role in making a flexible cable, but the conductor stranding is where you start