An alternator disconnector circuit-breaker of the invention includes a cylindrical cam (40) for optimizing the sequence for opening/closing the switch-over first switch (10), the circuit-breaker second switch (20), and the disconnector third switch (30). The cam (40) has a cylindrical wall in which three slots (42), and preferably three pairs of slots, of different shapes, are defined; an end element of an element driving a respective one of the switch contacts is mounted to slide in each slot.