Bending Copper Busbars for Switchgear & Control Panels

This blog explains why copper remains the preferred material for high-current distribution in switchgear and control panels. It also outlines best practice for bending and fabricating copper busbars correctly, highlighting how precision machinery such as Rittal's CW 120 system, combined with digital planning tools like Eplan, supports accurate and repeatable production in modern panel building environments.

Busbars are essentially the high current highways in switchgear and control panels, distributing power from an incoming source to various outgoing feeders.

They are typically made from copper, as opposed to lighter, lower-cost alternatives such as aluminium. Copper provides superior conductivity, thermal performance, and mechanical strength, with key benefits that include:

• Low resistivity. Copper has the highest electrical conductivity of any non-precious metal, which means less energy is lost as heat and allows for more compact switchgear designs.
• Lower thermal expansion. Copper expands and contracts less than aluminium under thermal cycles, preventing joints from loosening over time - a major cause of electrical fires.
• Greater corrosion resistance. Copper naturally forms a protective oxide layer. In harsh environments, it can be easily tinned or silver-plated to prevent oxidation entirely.
• Higher short-circuit strength. During a fault, busbars experience massive electromagnetic forces. Copper’s high tensile strength ensures the bars don't deform or "whip" under stress.

Installing Busbars in Electrical Systems

Busbars need to be bent and shaped for various reasons. For example, it means you can custom-fit them within electrical systems such as switchgear or control panels, plus it reduces the need for mechanical joints and connectors which can slow their performance.

However, bending a solid bar of copper has to be done with care and precision. Otherwise, there is a risk you will harden the metal, causing it to crack or thinning the outer edge of the bend. This can creates "hot spots" within narrower sections.

Key Stages for Bending a Copper Busbar:

1. Before applying any bend to a copper busbar, you first need to know how much material is required.

When bending the bar, the outside stretches and the inside compresses, so you must calculate the Neutral Axis.

A rule of thumb for a 90° bend is:

Developed Length = Internal length + External length + (0.5 × Thickness of bar).

2.  Choose your bend type. There are typically three to choose from:

1. Flatwise bend: bending the bar along its widest face. This is the commonest and easiest type of bend.
2. Edgewise bend (aka. hard bend): bending the bar along its narrow edge. This needs specialised hydraulic equipment to prevent the metal from buckling or tearing.
3. Offset (aka. Z-bend): where two parallel 45° or 90° bends shift the busbar into a different plane.

3. Use the right tools. Options include:

1. Hydraulic busbar benders: for smooth, consistent pressure.
2. Protractor/angle binder: accounts for spring-back (ie. the tendency of the metal to unbend slightly after pressure is released).
3. Radius mandrels: ensures the inside radius of the bend is at least equal to the thickness of the bar (R≥T) to prevent cracking.

All of these options are included within Rittal's CW 120 system.

We offer two different bending machines in the CW 120 System range:

• Rittal’s CW 120-S is two tabletop machines which can bend, punch holes and cut
• Rittal’s CW 120-is an all-in-one mobile unit on castors

The CW 120 machines can be combined with Rittal’s online configurator Eplan Cloud, or Eplan’s Pro Panel Copper Module, to create a complete packaged guide to bending the busbar.

4. Avoid any "orange peel" effect. A rough, pebble-like texture on the outside of the bend indicates that you have overstressed the copper. This is often as a result of bending it too quickly or using a radius that is too narrow. A smooth, mirror-like finish on the bend signifies the integrity of the grain structure within the metal. 

5. Understand the bend allowance. You need to account for the "stretch" to ensure your bolt holes line up perfectly after the bend is made. The bend allowance (BA) can be calculated using this formula:

Where:

• A = Bending angle (e.g., 90°)
• R = Inside radius
• T = Material thickness
• K = K-factor (typically 0.33 to 0.5 for copper)

In Summary

Switchgear and control panels have long life-cycles, often within environments where access is limited and performance needs to be guaranteed. If joints loosen or a bend is poorly calculated then you are effectively building in potential liabilities.

Copper’s stability under thermal cycling and fault conditions offer you a wider margin for error, but correct assembly is what ultimately will protect your installation.

As we’ve highlighted, alignment issues can be avoided if you calculate the bend allowances accurately and use the correct tooling. This in turn ensures contact resistance is minimised and commissioning is straightforward.

In other words, precision at the bending stage translates directly into reliability in service. When handled properly, copper busbars underpin systems that are safer and designed to endure.