Significance of resistances of switching contacts for the temperature rise of LV circuit breakers

Inhalt:
In electro-mechanical switchgears switching contacts produce an additional resistance, which generate an additional and mostly significant heat source and influence the temperature profile of devices considerably. The variance of the resistance results, among others, from the actual contact points, so-called “a-spots”. These depend on, for example, material combination, contact force and production process. These contact points significantly influence the electrical as well as the thermal resistance of switching contacts. While the electrical resistance influences the total performance and therefore also the temperature of the terminals, the thermal resistance determines mostly the temperature of the hot spot inside the circuit breaker. This temperature is an important criterion for the choice of material for components close to the current path.