Editing Circuit breaker (section)

==Short circuit==
<!--"Ampere Interrupting Capacity" redirects here.-->
Circuit breakers are rated both by the normal current that they are expected to carry, and the maximum short-circuit current that they can safely interrupt. This latter figure is the '''ampere interrupting capacity''' ('''AIC''') of the breaker.

Under short-circuit conditions, the calculated or measured maximum [[prospective short-circuit current]] may be many times the normal, rated current of the circuit. When electrical contacts open to interrupt a large current, there is a tendency for an [[electric arc|arc]] to form between the opened contacts, which would allow the current to continue. This condition can create conductive ionized gases and molten or vaporized metal, which can cause the further continuation of the arc or create additional short circuits, potentially resulting in the explosion of the circuit breaker and the equipment that it is installed in. Therefore, circuit breakers incorporate various features to divide and extinguish the arcs.

The maximum short-circuit current that a breaker can interrupt is determined by testing. Application of a breaker in a circuit with a prospective short-circuit current higher than the breaker's interrupting capacity rating may result in failure of the breaker to safely interrupt a fault. In a worst-case scenario, a breaker may successfully interrupt a fault only to explode when reset.

Typical domestic panel circuit breakers are rated to interrupt {{val|6|ul=kA}} ({{val|6000|u=A}}) short-circuit current.<!--Other common values are 10 and 25 kA.-->

Miniature circuit breakers used to protect control circuits or small appliances may not have sufficient interrupting capacity to use at a panel board; these circuit breakers are called "supplemental circuit protectors" to distinguish them from distribution-type circuit breakers.