Copper is important in supporting renewable energy and electric vehicles (EVs). For example, approximately 5.5 tons of copper are used per megawatt (MW) of photovoltaic power, 183 pounds of copper are used in electric vehicles, and only 48 pounds of copper are used in internal combustion engine (IEC) cars. Not all copper is created equal; A wide variety of copper alloys are used in renewable energy and electric power (EV) applications.

Copper alloys are made using one or more metals other than copper. They offer a range of trade-offs in terms of electrical conductivity, mechanical strength and cost. Some applications, such as power harnesses in EV drivetrains, are not subject to much mechanical stress and benefit from maximum conductivity and lowest cost. On the other hand, slip ring connectors used in wind turbines must be able to withstand challenging mechanical conditions. Not surprisingly, the two applications use different copper alloys.



Electrical conductivity and tensile strength

In addition to cost, electrical conductivity and tensile strength are also basic parameters for wires and other connecting components. The International Annealed Copper Standard (IACS) was developed by the International Electrochemistry Commission. The conductivity of annealed copper is 5.8001 x 107 Siemens per meter (S/m), defined as 100% IACS at 20 °C.

Tensile strength is the maximum axial force that a material can withstand before breaking. Strength measurements can be made in ksi (kg pounds per square inch). The weight that the wire can bear can be determined by multiplying the ksi by the area of the wire cross section.


Electrolytic copper

Electrolytic copper has been refined by electrolysis. This type of refined copper can be more than 99.9% pure. Many metals can be added to copper to adjust the trade-off between cost, conductivity, and strength.


Copper alloy for connectors

Several copper alloys are particularly suitable for connectors. Copper zinc (brass) has good electrical properties but low yield strength. It is not usually used for contacts, especially for connectors that must withstand extremely multiple insertions. It is sometimes used for connector parts that are not mechanically demanding, such as welded pieces.

Beryllium copper can provide the best combination of strength and electrical conductivity, but it is relatively expensive. It is used in miniature connectors and demanding high-cycle applications.

Bronze is made up of copper and about 12% tin. Adding phosphorescence results in phosphor bronze being stronger than brass, but not as good as beryllium copper. Beryllium copper is suitable for micro-contact systems, while phosphor bronze is used for larger contact systems.

Copper-nickel-tin (about 9% nickel by weight) and tin (about 2% by weight) are other common copper alloys used in connectors. Its excellent relaxation properties make it ideal for the manufacture of contacts. Other characteristics that make it suitable for connectors are its high corrosion resistance, good weldability and high temperature stability.


Copper-nickel-silicon for wind turbines

Copper-nickel-silicon combines very high strength, excellent wear and corrosion resistance, and good electrical and thermal properties. Its high strength makes it particularly suitable for current-carrying applications such as slip rings in wind turbines, industrial squirrel-cage motors, short-circuited rings, and heavy-duty switchgear.

Other qualities that make it particularly suitable for applications such as slip rings include high wear resistance, good electrical and thermal conductivity, extremely low permeability, excellent corrosion resistance and very good low temperature mechanical properties. In addition, it has good machinability and dimensional stability.


Sum up

There is no single "best" copper alloy. A wide variety of alloys offer a variety of combinations of cost, electrical conductivity and mechanical strength. There are several copper alloys that are particularly suitable for connectors in applications such as electronic systems and EVs. Other alloys offer a better combination of mechanical strength and stability as well as electrical and thermal conductivity, making them suitable for rotary applications such as slip rings in wind turbines.