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Switching and interrupter contacts

Electrical switching contacts safeguard a reliable electrical connection of a large number of machines and devices. In this process, they have to have a mechanical and thermal stability which should be optimised if possible under diverse operating conditions and, moreover, they also have to have a high degree of resistance against external influences. In the selection of the contact materials the stresses arising during the processes of switching on and switching off as well as during current conduction whenever the contact pieces are closed have to be taken into account.

Switching and interrupter contacts can be found in household appliances, designed as light and protective switches, no-load switches, power circuit breakers and starters as well as as heavy-duty circuit breakers.

The most important basic material for the production of switching and interrupter contacts is silver. This element offers the highest possible electrical and thermal conductivity, is oxidation-resistant and easily malleable. A further crucial requirement is their arc load stability. Depending on the respective application and concrete requirements, alloys with copper, nickel or wolfram are used or ceramic materials, such as CdO, ZnO, SnO2 or tungsten carbide are mixed in. Carbon can also be found as a component in special switching and interrupter contacts.

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