Abstract: This invention concerns a multi-pole circuit breaker with molded case and static tripping unit, comprising an electronic device to process the signals delivered by current transformers associated with each pole, which electronic processing device is part of a subassembly inserted in a compartment of the molded case and delivers a tipping signal to a tripping coil in the case of an overload or a short-circuit. A feature of the circuit breaker according to the invention is that the aforementioned compartment is sealed off from the rest of the inside of the molded case and is in open communication with the ambient atmosphere by means of ventilation holes provided in the outer walls protected from the circuit-breaking gases generated inside the casing and is cooled down by the air circulating through these ventilation holes, while the aforementioned current transformers are housed in the other separate part of the casing.