3. Fixed and sliding electrical contacts

There are two main types of contact [20][21] :

• fixed contacts with separation perpendicular (opening contacts) or parallel (switches, circuit breakers) to the contact surface;

• sliding contacts :

  • in one case, the surfaces of the two elements in contact are reduced and permanently used (brushes on commutator and bushes),

  • in another case, a single surface is reduced and always rubbing against the surface of a virtually infinite element (rubbers), the surface in contact never being the same.

In these applications, the advantage of carbon and, more often, graphite is that they don't...