This example shows how to model a circuit breaker. The electromechanical breaker mechanism is approximated with a first-order time constant, and it is assumed that the mechanical force is proportional to load current. This simple representation is suitable for use in a larger model of a complete system. When the 20V supply is applied at one second, it results in a current that exceeds the circuit breaker current rating, and hence the breaker trips. The reset is then pressed at three seconds, and the voltage is ramped up. The breaker then trips just beyond the circuit breaker current rating.