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Copper Busbar

Similar to wiring systems, busbars, particularly copper busbars, distribute power and energy from a supply point to different output circuits. 

However, although busbars are sometimes initially more expensive than wiring harnesses, they are also more efficient and flexible while requiring minimal maintenance, hence reducing their overall costs.

Additionally, busbars allow for quick installation and are environmentally friendly.

Because of all this, factories, data centers, and libraries have all been turning towards busbars to satisfy their energy distribution needs.

What Is A Copper Busbar?

Busbars are metallic strips that ground as well as conduct electricity. They are coated with different materials that lead to varying conductivity limits and different lifespans.

Moreover, busbars also vary in shapes and sizes, providing different ampacity, which is the amount of current a busbar can carry.

Also, busbars can be made from different metals, such as copper, brass, or aluminum, yet the most popular material is copper.

Now, why are most busbars made of copper? What are its relative advantages?

Copper is one of the most abundant metals in the Earth’s crust, as well as one of the most conductive. 

Aside from its relative cheapness and high conductivity, copper busbars have several other advantages over other types of busbars.

For starters, copper has a relatively lower coefficient of linear expansion, which reduces the overall stress the busbar is exposed to as it heats up from the current.

Moreover, copper has a high modulus of elasticity, which not only makes it stiffer than other metals but also decreases the strain resulting from stress.

Additionally, when the surface of copper oxidizes, a thin layer of oxidation on its surface is still conductive.

For all these reasons, copper busbars have a longer lifespan than most other types of busbars.

Copper Busbar Properties

When assessing a busbar system, the main properties that should be looked at are as follows:

  • electrical conductivity and thermal properties.
  • mechanical properties.

The properties of copper, the main component in copper busbars, can differ according to the number of alloys or impurities that are present inside it. 

However, for the remainder of this article, we will be talking about C101, which contains more than 99 percent copper.

Electrical Conductivity and Thermal Properties

In any energy distribution system, a portion of the energy will be lost in the form of heat. 

This lost energy can be attributed to the resistance of the system, which is why it is preferable to use highly conductive material.

Otherwise, if the resistance of the busbar is too high, the amount of heat energy released may cause the busbar system to over-stress, reducing its lifespan. 

What’s more, the cost of the lost energy may end up exceeding the cost of installing the busbar system in the first place.

The good news is that C101 is 100 percent conductive in IACS units. For reference, the conductivity of aluminum is only 61 percent.

In more vivid terms, a factory would need an aluminum busbar with 1.6 times the cross-sectional area of a busbar made from copper just to generate the same level of conductivity.

Additionally, C101 has an electrical resistivity of 0.0171 Ω per mm² for every meter

Again, for reference, aluminum has a resistivity of 0.0279 Ω per mm² for every meter.

Another important factor to consider is the temperature coefficient of resistivity. This measures the change in resistance of a metal as its temperature changes.

As the metal heats up, its conductivity decreases, and its resistivity increases.

For C101, the temperature coefficient of resistivity is 0.0039 for every degree in Kelvin, which is almost the same as that of aluminum.

Mechanical Properties

The mechanical properties of copper busbars are important when designing the system.

To begin with, it’s necessary to take into consideration the tensile strength of the metal because it affects both the construction of the system and its ability to withstand the stresses produced by thermal expansion.

That said, the tensile strength of annealed C101 is 200 to 250 N per mm². In comparison, annealed aluminum has a tensile strength of 50 to 60 N per mm².

Another important factor is a metals’ proof strength, which is the stress that would cause permanent deformation.

For annealed C101, 50 to 55 N per mm² is enough to cause a plastic strain of 0.2 percent

Additionally, C101 has an elastic modulus of 116 to 130 kilonewtons per mm², while aluminum has an elastic modulus of 70 kilonewtons per mm².

Current Carrying Capacity of Copper Busbars

First and foremost, it is necessary to point out that busbars can transport both alternating currents and direct currents equally. 

The only variable that matters is the size of the current a busbar can allow, which is also known as its ampacity.

In other words, if a busbar can carry 200 amps, then it can transport 200 amps of AC or DC.

That said, it’s important to know the current-carrying capacity of copper busbars when designing the energy distribution system.

The general rule of thumb is that the current-carrying capacity of a copper strip can be estimated to be 1.2 times the cross-sectional area in mm², i.e. the product of the width and the thickness.

For example, if we have a strip that is 100 mm wide and 10 mm thick, then its capacity is equal to 1.2*100*10, which equals 1200 amps.

Why Are Copper Busbars Plated?

Even though copper resists rust better than most other materials used in busbars, the fact remains that copper will still oxidize after a long enough period, especially if the busbar is in an area with high moisture.

This rust can increase the resistivity of the copper, reducing its energy efficiency and increasing the heat generated as a result of energy loss. 

Moreover, extreme oxidation can cause the copper to flake and for parts of it to fall off.

Consequently, copper is plated, usually with either tin or silver, to preserve its positive qualities and to protect it from excessive rust for as long as possible.

Tin and Silver Plating

Tin and silver offer several benefits that make them ideal for plating copper busbars.

For starters, they are both soft metals, which means that they are easy to work with when it comes to plating. 

Moreover, they are conductive themselves, so they don’t add too much resistance to the surface of the busbars.

As for which is better, there is no consensus. 

While it takes 10 microns of tin to match or perhaps outperform a single micron of silver, the fact remains that silver is far more expensive, and its price is climbing consistently.

So, although silver is more effective, since it takes 10 times the amount of tin to perform the same job as silver, because of the discrepancy in price, tin remains more economical.

As a result, tin is usually the more preferable choice. 

Nevertheless, silver can be used on occasions where there will be moving busbar parts or if arcing could pose a serious problem.

Finally, regardless of which of these materials is used for plating, it is necessary to add on top an anti-tarnish so that the surface remains clean and conductive.

To Sum Up

Busbar systems are efficient, flexible, and versatile. 

While their initial cost may be higher than conventional wiring systems, they more than make up for it in savings down the line, including lower maintenance costs and higher efficiency in energy transmission.

Most busbar systems use copper as their main ingredient owing to the many benefits that the metal brings. 

Not only is copper highly conductive, but it also has excellent mechanical properties that facilitate the construction of different systems. 

Compared to aluminum, copper proves to be a more reliable option in almost every category.

Finally, almost any busbar system will be plated with either tin or silver to protect the surface against excessive rust.

About Bunty

Bunty has been servicing companies in the metal manufacturing sector for more than two decades. 

Over this time, the company has consistently delivered high-quality manufactured custom parts along with stellar customer service.

Throughout its history, Bunty has served countless industries, including aerospace, robotics, and energy. In fact, it is a supplier for world-renowned brands like BMW, P&G, and NASA.

And, to ensure that its service has been consistent over the years, Bunty has an AS9100D as well as an ISO 9001:2015 certified quality management system.

This excellent service history has made Bunty a premier US vendor, particularly when it comes to custom metal parts as well as product modifications. 

Additionally, Bunty can produce busbars according to the client’s specifications.

It is Bunty’s strong design capabilities that have enabled it to produce innovative product modifications that are designed, built, and delivered on-spec, on-budget, and on time.

So, to learn more about Bunty or to explore how the company can help service your metal manufacturing needs, get in touch with us today.

About us

From a contract manufacturing firm, BuntyLLC evolved into a full service custom machined, forged and cast metal parts fabrication enterprise. We supply global solutions from our headquarters in Greenville, South Carolina.

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