Circuit breaker and method

A circuit breaker for protecting an electric low-voltage circuit, the circuit breaker comprising:

• a housing having at least one grid-side connection and at least one load-side connection;
• an electronic interruption unit being associated with said at least one grid-side connection;
• a mechanical isolating contact unit connected in series with said electronic interruption unit, said mechanical isolating contact unit being associated with said at least one load-side connection;
• said mechanical isolating contact unit having contacts opening to prevent a current flow or closing to permit a current flow in the low-voltage circuit;
• said electronic interruption unit having semiconductor-based switch elements configured to be switched into a high-ohmic state to prevent a current flow or into a low-ohmic to permit a current flow in the low-voltage circuit;
• a current sensor unit for determining a current level in the low-voltage circuit;
• a control unit connected to said current sensor unit, to said mechanical isolating contact unit and to said electronic interruption unit, for initiating prevention of a current flow of the low-voltage circuit upon exceeding at least one of current or current/time limit values;
• and
• said electronic interruption unit being switched to a low-ohmic state for a first period of time to test functionality of the circuit breaker upon said contacts of said mechanical isolating contact unit being closed and said electronic interruption unit being switched to a high-ohmic state.

A method for operating a circuit breaker for protecting an electric low-voltage circuit, the method comprising:

• providing a housing having at least one grid-side connection and at least one load-side connection;
• providing an electronic interruption unit being associated with the at least one grid-side connection and having semiconductor-based switch elements;
• connecting a mechanical isolating contact unit in series with the electronic interruption unit, the mechanical isolating contact unit being associated with the at least one load-side connection and having contacts;
• switching the mechanical isolating contact unit by opening the contacts to prevent a current flow or by closing the contacts to allow a current flow in the low-voltage circuit;
• switching the semiconductor-based switch elements of the electronic interruption unit into a high-ohmic state to prevent a current flow or into a low-ohmic state to allow a current flow in the low-voltage circuit;
• determining a current level in the low-voltage circuit between the at least one grid-side phase conductor connection and the at least one load-side phase conductor connection;
• preventing a current flow in the low-voltage circuit upon exceeding at least one of current or current-time limit values;
• and
• switching the electronic interruption unit to a low-ohmic state for a first period of time for functional testing of the circuit breaker with the contacts of the mechanical isolating contact unit being closed and the electronic interruption unit being switched to a high-ohmic state.