Conductor Strand Types

Concentric Strand

A concentric stranded conductor consists of a central wire or core surrounded by one or more layers of helically laid wires. Each layer after the first has six more wires than the preceding layer. Except in compact stranding, each layer is usually applied in a direction opposite to that of the layer under it.



Bunch Strand

The term bunch stranding is applied to a collection of strands twisted together in the same direction without regard to the geometric arrangement.


Rope Strand

A rope stranded conductor is a concentric stranded conductor each of whose component strands is itself stranded. A rope stranded conductor is described by giving the number of groups laid together to form the rope and the number of wires in each group.



Sector Conductor

A sector conductor is a stranded conductor whose cross-section is approximately the shape of a sector of a circle. A multiple conductor insulated cable with sector conductors has a smaller diameter than the corresponding cable with round conductors.



Segmental Conductor

A segmental conductor is a round, stranded conductor composed of three or four sectors slightly insulated from one another. This construction has the advantage of lower AC resistance due to increased surface area and skin effect.



Annular Conductor

An annular conductor is a round, stranded conductor whose strands are laid around a suitable core. The core is usually made wholly or mostly of nonconducting material. This construction has the advantage of lower total AC resistance for a given cross-sectional area of conducting material due to the skin effect.


Compact Strand

A compact stranded conductor is a round or sector conductor having all layers stranded in the same direction and rolled to a predetermined ideal shape. The finished conductor is smooth on the surface and contains practically no interstices or air spaces. This results in a smaller diameter.



Compressed Strand

Compressed conductors are intermediate in size between standard concentric conductors and compact conductors. A comparison is shown below:



In a concentric stranded conductor, each individual wire is round and considerable space exists between wires. In a compressed conductor, the conductor has been put through a die that "squeezes out" some of the space between wires. In a compact conductor each wire is preformed into a trapezoidal shape before the wires are stranded together into a finished conductor. This results in even less space between wires. A compact conductor is, therefore, the smallest in diameter (except for a solid conductor, of course).

source from : You are not allowed to view links. Register or Login


You are not allowed to view links. Register or Login

Conductor Strand Types in Electrical Cables

In electrical cables, conductors are made from strands of wire, typically copper or aluminum, which carry the electric current. The way these strands are configured can vary based on the application, flexibility requirements, and other factors like resistance and current carrying capacity. The most common types of conductor strands are solid conductors and stranded conductors.

---

1. Solid Conductor

A solid conductor is a single wire of a specific material, typically copper or aluminum, that carries the electrical current. It is one of the simplest and most common forms of conductors in electrical wiring.

Advantages:
- Lower Resistance: Solid conductors have lower resistance due to the continuous nature of the wire.
- Better for Short Runs: Ideal for shorter, less flexible cable runs, where the cable will not be moved frequently.
- Simplicity: Easier to manufacture, simpler design.

Disadvantages:
- Lack of Flexibility: Solid conductors are rigid and may break if bent frequently or over long periods.
- Limited Application: They are less suited for environments where cables are subjected to mechanical stress, like movable equipment.

---

2. Stranded Conductor

A stranded conductor consists of several smaller wires twisted or braided together to form a larger conductor. This design offers more flexibility and is ideal for applications where the cable may experience mechanical stress, such as in robotics, electric vehicles, or machinery.

Advantages:
- Flexibility: Stranded conductors are much more flexible compared to solid conductors, making them suitable for installations where cables are frequently moved or bent.
- Resilience: Better for environments where mechanical stresses (like vibrations) are common.
- Larger Surface Area: Stranded conductors typically have a larger surface area for current flow, though their resistance is slightly higher than solid conductors of the same diameter.

Disadvantages:
- Higher Resistance: Due to air gaps between strands and the fact that the conductor isn't a single continuous piece, stranded wires tend to have slightly higher resistance than solid wires.
- Manufacturing Complexity: Stranded wires are more complex and expensive to manufacture.

---

3. Types of Stranding

Within the category of stranded conductors, there are several configurations that can be used depending on the specific needs of the application:

a. Flexible Stranding: 
Fine wires twisted together to maximize flexibility. Ideal for applications requiring cables to bend or move regularly.

b. Compact Stranding: 
Strands are tightly packed, reducing air gaps between them. More efficient, reduces diameter, while maintaining flexibility.

c. Concentric Stranding: 
Conductors arranged concentrically, with the central conductor surrounded by a layer of concentric strands. Often used in power cables.

d. Bunched Stranding: 
Wires grouped together randomly without any specific direction of winding. Cost-effective for low-voltage applications.

e. Rope-Lay Stranding: 
Multiple layers of wires twisted in different directions to increase flexibility and strength. Used for larger cables in heavy machinery or industrial applications.

---

4. Common Applications of Stranded vs. Solid Conductors

Solid Conductors: 
- Ideal for fixed wiring, such as in electrical panels or buildings.
- Best for applications that don't involve frequent movement or bending.

Stranded Conductors: 
- Used for flexible cables like extension cords, machinery, and equipment exposed to movement or vibration.
- Common in power transmission and communication cables subjected to bending over long distances.

---

Summary

- Solid Conductors offer lower resistance and are ideal for fixed, short-range installations.
- Stranded Conductors are more flexible and resilient, making them suitable for environments with movement and mechanical stress.
- Stranding techniques like rope-lay, compact, and concentric provide different balances of flexibility, surface area, and cost efficiency based on requirements.

The choice between solid and stranded conductors depends on the specific application and factors such as flexibility, resistance, durability, and cost.