Busbars are often manufactured in a flat strip shape primarily to facilitate efficient heat dissipation.
When electrical current flows through any conductor, it generates heat due to resistance (known as Joule heating). Busbars are designed to carry very large currents, which means they generate significant heat. This heat must be effectively dissipated to prevent the busbar from overheating, which could damage the conductor, insulation, or surrounding components, and reduce system efficiency and lifespan.
A key reason for the flat shape is its large ratio of surface area to cross-section area.
The Importance of Heat Dissipation
- Busbars act as central conductors in electrical distribution systems, carrying high currents from power sources to various loads.
- Carrying these high currents generates heat within the busbar material (typically copper or aluminum).
- Effective cooling is crucial to maintain the busbar temperature within safe operating limits.
High Surface Area to Cross-Section Ratio
As highlighted by industry practice, shapes like flat strips and hollow tubes are common for busbars since these shapes can allow more heat dissipation of the large ratio of surface area to cross-section area.
- Cross-section area determines how much current the busbar can carry for a given current density limit. A larger cross-section allows for more current.
- Surface area is the external area exposed to the surrounding environment (usually air), where heat can be transferred away.
- A flat shape maximizes the surface area relative to its cross-sectional size compared to, for example, a solid round bar of the same material volume. Imagine flattening a round bar – its width increases significantly, exposing much more surface area.
This increased surface area allows for better convective and radiative cooling, meaning heat generated within the busbar can transfer more readily to the air, keeping the conductor cooler.
Benefits of the Flat Shape
The flat shape offers several advantages related to its thermal properties:
- Improved Cooling: The large surface area facilitates more efficient heat transfer away from the conductor.
- Higher Current Carrying Capacity: For a given amount of conductive material (and thus cross-section area), the enhanced cooling allows the busbar to safely carry higher currents without exceeding temperature limits compared to less efficient shapes.
- Space Efficiency: Flat bars can often be stacked or mounted edge-wise to fit within tighter spaces in electrical panels and switchgear.
While other shapes like hollow tubes are also used (often for similar reasons of surface area ratio and weight reduction), the flat strip is a widely adopted and effective form factor primarily because it balances electrical current carrying capacity with the critical need for efficient heat dissipation due to its favorable surface area to cross-section area ratio.
