Silver’s high thermal and electrical conductivity make it an ideal contact material for contact applications—in fact, it has the highest electrical and thermal conductivity of all the metals. Pure silver, however, is susceptible to mechanical wear; it has a low softening temperature; it is susceptible to welding; and it can cause total failure in switching devices. Silver, therefore, is often mixed with other metals to create various silver-based contact materials. Different contact applications have different contact material requirements, and for that reason, there are a variety of different silver-based contact materials. Each silver-based contact material has its distinct advantages. Knowing the intended application of the silver-based contact materials will give you the opportunity to select the most advantageous one.
The selection of contact materials for your electrical contact assemblies is an incredibly important part of the planning process. It’s always advised that you discuss the application requirements with an engineer or other professional as early in the design process as possible. Of course, depending upon your specific needs, there could be multiple options available in terms of the materials to be used. Each contact material will obviously come with its own pros and cons, whether that’s a tendency toward welding or “sticking,” or simply affordability. There’s also the concern of whether or not you’ll require UL or IEC approval. To learn a bit more about the different materials used in manufacturing electrical contact assemblies, you can continue reading below.
Also known as AgW, silver tungsten is a popular material for use in both large air and oil circuit breakers. It’s known for having a high resistance to arc erosion. It’s also a common choice for re-closures, line disconnects, and both high current contactors and switches. Thanks to its resistance to welding, it can also serve as a good shorting contact. Composites of silver tungsten that contain more silver are used quite often in circuit breakers and in high current contactors.
Commonly known as CuW, copper tungsten is also a very popular contact material. It’s known for being heat-resistant, ablation-resistant, easy to machine, and it’s both highly thermally conductive and electrically conductive. Copper tungsten can serve as an excellent material for switches and contacts for oil-filled devices. Thus, copper tungsten is a material commonly found used in the fossil fuel industry, as well as related industrial and commercial fields. You may also find it used in some oil, gas, or even air circuit breakers.
Sometimes shown as AgC, silver graphite is popular for many electrically conductive applications. It’s also known for having the best anti-welding properties of all contact materials. Because it has the best protection against contact welding, it’s an excellent choice for closed contacts under short circuit conditions. It’s also known for having low contact resistance and low erosion. For industrial purposes, silver graphite is excellent for circuit breakers, but it’s also effective for residential circuit breakers.
This is by no means an exhaustive list. Putting together the best electrical contact assemblies always necessities identifying the appropriate materials, so it’s always recommended that you discuss your application requirements at length before making a final decision.