switching unit of a circuit breaker so as to trip main contacts of main circuits of the circuit breaker in response to a detection of a current being above a predetermined level in at least one of the main circuits the tripping unit includes a fuse configured to be connected in series to a main circuit of the circuit breaker and a detection unit connected in parallel with the fuse and configured to generate the tripping signal for the switching unit in response to the fuse being blown application_number US 201113153548 A description an aspect of the present invention is to provide at tripping unit that overcomes the above drawbacks in an embodiment of the present invention a tripping unit for tripping the main contacts of main circuits of a circuit breaker by sending an electrical tripping signal to a switching unit of the circuit breaker when a current above a certain level is detected in at least one of the main circuits is characterized in that the tripping unit comprises at least one fuse which is connected in series to a main circuit of the circuit breaker and wherein a detection unit which is connected in parallel to the at least one fuse is adapted to generate the tripping signal.