A low-voltage power circuit breaker, comprising a vacuum chamber which contains at least one fixed contact and at least one moving contact which can be mutually coupled/uncoupled in correspondence of a closed/open condition of the circuit breaker, and actuation means which are operatively connected to the moving contact and provide the energy required to move the moving contact and to produce its coupling/uncoupling with respect to the fixed contact, said actuation means comprising an electromagnetic actuator.