Why are Electrical Busbars Rectangular Instead of Circular?

Electrical Technology

Why is the Preferred Shape of Busbars Rectangular or Flat Rather than Circular or Round Shaped Cables?

What is an Electrical Busbar?

An electrical busbar is a metallic strip or bar that conducts electricity within a power distribution system. It serves as a centralized connection point for multiple electrical circuits, allowing for the safe and efficient distribution of high electrical currents.

Busbars are typically made from materials with excellent electrical conductivity, such as copper or aluminum, and are commonly designed in flat or rectangular shapes. They are used in various electrical equipment, including switchgear, busways, distribution boards, panels, load centers, and substations.

The primary purpose of busbars, or a bus system, is to safely and reliably collect incoming power and distribute it to various output load circuits. They are commonly used in industrial and commercial power systems, substations, and large buildings for distributing electrical power.

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Why are Busbars Flat or Rectangular?

Busbars are usually flat or rectangular rather than circular, like cables, because these shapes provide a larger surface area for efficient heat dissipation and electrical conductivity. The flat design offers ease of installation, reduces electrical losses, distributes current evenly, and enables the connection of multiple circuits without requiring individual wiring for each.

The following are key reasons for designing flat busbars instead of circular or other shapes:

1. Surface Area and Heat Dissipation

The rectangular shape offers a larger surface area compared to a circular cross-section of the same conductor size. This increased surface area allows for better heat dissipation, which is crucial for cooling in high-current applications.
Overheating can reduce the lifespan of the busbar and compromise safety. Effective heat management is essential, as busbars are often used in high-load environments, such as power distribution systems.

2. Current-Carrying Capacity

The skin effect is a phenomenon where AC current tends to flow more on the surface of a conductor, especially at higher frequencies, rather than uniformly throughout its cross-section. A rectangular busbar provides more surface area relative to its cross-sectional area, mitigating the effects of the skin effect and improving current distribution. This allows rectangular busbars to carry more current than circular cables with the same cross-sectional area.
For DC applications, where the skin effect doesn’t apply, the flat design still helps distribute the current more uniformly.

3. Efficient Space Utilization

Rectangular busbars are more space-efficient than circular conductors when installed in electrical panels, switchgear, or busbar trunks. Multiple flat busbars can be stacked or arranged closely together with insulation in between, maximizing space utilization, which is crucial in compact electrical enclosures.
This also makes them easier to manage and align in large-scale electrical distribution systems.

4. Mechanical Stability

Flat, rectangular busbars are more rigid and mechanically stable than circular cables. This rigidity helps reduce vibrations and movement under high-current conditions, ensuring more reliable operation over time.
Circular cables, on the other hand, are flexible and are used where movement or bending is required, such as in wiring systems.

5. Cost Efficiency

The manufacturing process for rectangular busbars can be more efficient in terms of material usage for specific applications. The shape allows manufacturers to optimize the use of copper or aluminum, reducing overall costs in large installations.
The overall manufacturing cost of flat busbars is lower due to the simpler techniques used for punching, cutting, and bending. In contrast, round conductors and cables require more complex processes like drawing, extrusion, and detailed calculations.

6. Ease of Connection and Installation

Flat surfaces on rectangular busbars make it easier to drill holes for connections to other conductors or equipment.
They are simpler to terminate and can be bolted or clamped into place without needing special busbar’s connectors or adapters, which round busbars may require for joints, bends, and tap connections.

Despite the advantages of rectangular busbars, different shapes may be used based on specific requirements and applications. For instance, circular busbars are sometimes used in cases involving extreme mechanical stresses, such as high-voltage direct current (HVDC) transmission systems.

However, rectangular busbars remain the preferred shape for high-power electrical systems due to their superior heat dissipation, current-carrying efficiency, space utilization, mechanical stability, and ease of installation.

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Why is Busbar Proffered over Cable?

Busbars are preferred over cables in many electrical systems due to their superior performance in high-current applications, space efficiency, and ease of maintenance. With a flat, wide design, busbars have a larger surface area, allowing for better heat dissipation, which reduces the risk of overheating compared to bundled cables.

A busbar chamber, unlike cables, provides a simpler method for distributing incoming power to multiple distribution boards and panels without the need for multiple joints. As a result, tapping and terminating busbars is easier than cables, especially in complex power distribution circuits.

They can carry higher currents with lower impedance, resulting in reduced voltage drop over long distances. Additionally, their rigid structure offers greater mechanical strength, making them more durable and resistant to environmental and physical stress.

Busbars also offer flexibility in design, allowing for modular expansion and easier installation, particularly in compact spaces like electrical switchgear and industrial power distribution systems. They can handle higher fault currents during short circuits, ensuring greater safety and reliability.

With these combined benefits, busbars provide a more efficient, scalable, and organized solution, making them the preferred choice for high-power applications over traditional cabling systems.