Circuit breaker

A circuit breaker device for protecting an electrical low-voltage alternating current (AC) circuit, the circuit breaker device comprising:

• a housing with network-side connections and load-side connections for the electrical low-voltage AC circuit;
• an electronic interruption unit;
• a mechanical isolating contact unit having contacts and connected in series with said electronic interruption unit, wherein said mechanical isolating contact unit is assigned to said load-side connections and said electronic interruption unit is assigned to said network-side connections, said mechanical isolating contact unit being switched by means of opening of at least one of said contacts in order to avoid a current flow or closing of said at least one contact for the current flow in the electrical low-voltage AC circuit;
• said electronic interruption unit having semiconductor-based switching elements and being switched, by means of said semiconductor-based switching elements, to a high-impedance state of said semiconductor-based switching elements in order to avoid the current flow or a low-impedance state of said semiconductor switching elements for the current flow in the electrical low-voltage AC circuit;
• a current sensor for determining a level of a current of the electrical low-voltage AC circuit;
• a controller connected to said current sensor, said mechanical isolating contact unit and said electronic interruption unit, wherein avoidance of the current flow in the electrical low-voltage AC circuit is initiated if current limit values or/and current-time limit values are exceeded;
• said mechanical isolating contact unit having a position sensor for determining position information relating to a closed or open state of said at least one contact;
• said mechanical isolating contact unit further having a handle for manually opening and closing said at least one contact;
• and
• said mechanical isolating contact unit configured such that said at least one contact can be opened, but not closed, by said controller.