A circuit breaker is an electrical switch used to prevent damage to an electrical circuit due to overloads or short circuits. AIC, or ampere interrupting capacity, is an important factor to consider when choosing a circuit breaker.

## Definition

AIC is the rating of current flow that a circuit breaker can interrupt to protect a circuit. The typical ratings for circuit breakers range between 5,000 and 200,000 ampere interrupting capacity. An ampere is equivalent to 100 volts.

## Circuit Locations

Circuit breaker AIC ratings must be equal or greater to the current available, or that can be generated, at the location in the circuit where the breaker will be installed. Determining the available current is done by calculating the fault current, or amount of current that results in a short circuit.

## Fault Current

The fault current amount is determined by the transformer rating and transformer impedance, as well as any current generated by electric motors that may be connected to the circuit. Transformer impedance is the measure of opposition to the flow of an electric current between the transformer's conductors, which are responsible for transferring energy between circuits.