Circuit breaker

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

• a housing having grid-side and load-side terminals for conductors of the low-voltage circuit;
• an electronic interruption unit connected to said load-side terminals, said electronic interruption unit having semiconductor-based switching elements;
• a mechanical isolating contact unit connected to said grid-side terminals and connected to said electronic interruption unit, said mechanical isolating contact unit having contacts and a handle for opening and closing said contacts;
• said contacts of said mechanical isolating contact unit being closed and said semiconductor-based switching elements of said electronic interruption unit having a low-resistance state, for enabling a current flow in the low-voltage circuit, or
• at least one of said contacts of said mechanical isolating contact unit being open, for enabling a galvanic isolation preventing current flow in the low-voltage circuit or said semiconductor-based switching elements having a high-resistance state, for preventing a current flow in the low-voltage circuit;
• a current sensor unit disposed in a conductor downstream of said mechanical isolating contact unit, for determining a current level in the low-voltage circuit;
• a control unit connected to said current sensor unit, to said electronic interruption unit and to said mechanical isolating contact unit, for initiating prevention of a current flow in the low-voltage circuit upon exceeding at least one of current limits or current-time limits;
• and
• a power supply unit for supplying power to the circuit breaker, said power supply unit connected to conductors of the low-voltage circuit between said mechanical isolating contact unit and said electronic interruption unit.

A method for operating a circuit breaker, the method comprising:

• providing a circuit breaker having a series circuit of a mechanical isolating contact unit and an electronic interruption unit, the mechanical isolating contact unit being disposed on a grid side, the electronic interruption unit being disposed on a load side, the mechanical isolating contact unit having contacts and a handle for opening and closing the contacts, and the electronic interruption unit having switching elements;
• determining a current level in the low-voltage circuit and, upon exceeding at least one of current limits or current-time limits, initiating prevention of a current flow in the low-voltage circuit;
• connecting a power supply unit for supplying power to the circuit breaker to conductors of the low-voltage circuit between the mechanical isolating contact unit and the electronic interruption unit;
• using the handle of the mechanical isolating contact unit to close the contacts during a power-on operation, and placing the switching elements in a high-resistance state;
• upon closure of the contacts, supplying power to the power supply unit, causing a checking function of the circuit breaker to be performed;
• and
• upon a positive result of the checking function, placing the electronic interruption unit in a low-resistance state for supplying load-side terminals of the circuit breaker with power.