Abstract: A limiting circuit breaker comprises two separable contacts 68, 70 and a mechanism 12 with energy storage 36 operated by an opening catch 30. The mechanism 12 drives a movable cage 58 between a closed position and an open position to perform opening of the contacts. One of the contacts is movable with respect to the cage 58 in the closed position and can thus take a separated position. A Thomson effect electromechanical actuator 100 is provided to drive the movable contact 68 to the separated position. A latch 80 enables the movable contact to be held in the separated position. In the event of a fault requiring a very high-speed response, separation of the contacts is obtained by means of the Thomson effect actuator and is then confirmed by opening of the mechanism. In other cases, only the mechanism operates to perform opening.