An alternator disconnector circuit-breaker of the invention presents a resistance (30) in series with the circuit-breaker switch (20′); the resistance (30) is of fixed ohmic value that is about 104 times greater than the value of the resistance of the main circuit of the circuit-breaker. By means of this configuration, it is possible to use a vacuum chamber as the circuit-breaker switch (20′), and to dimension the main switch (10), which, de facto, breaks the current even for very high short-circuit currents, under more advantageous conditions.