Alternating current circuit breaker, comprising - a live line between a live supply connecting terminal (Lin) and a live load connecting terminal (Lout), and a neutral line between a neutral supply connecting terminal (Nin) and a neutral load connecting terminal (Nout) for connecting an alternating current load to a mains supply, - a first galvanic separation switch and a bypass switch in the live line, and a second galvanic separation switch in the neutral line, and - a semiconductor switch element (IGBT) connected parallel to the bypass switch, - a processing unit arranged to control the first and second galvanic separation switch (SW2, SW3), the bypass switch and the semiconductor switch element (IGBT), the alternating current circuit breaker further comprising - a short circuit and overcurrent detection unit connected to the processing unit for determining a short circuit situation or overcurrent situation, wherein the processing unit is further arranged for - tripping the alternating current circuit breaker by opening the bypass switch and semiconductor switch element (IGBT) after determination of a short circuit or overcurrent situation, and to - execute a reclosing attempt after a predetermined time period after tripping of the circuit breaker, wherein the predetermined time period is dependent on the type of situation causing the tripping of the circuit breaker, wherein a reclosing attempt comprises closing of the semiconductor switch element (IGBT) first, monitoring for a possible short circuit or overcurrent situation, and only if no short circuit or overcurrent situation exists, closing the bypass switch, characterized in that the processing unit is arranged to monitor the actual load current I and load current increasing speed dI/dt using the short circuit and overcurrent detection unit prior to tripping of the circuit breaker, and if the load current increasing speed dI/dt is below or equal to a preset threshold value, to select a first time period as predetermined time period, and if the load current increasing speed dI/dt is above the preset threshold value, to select a second time period as predetermined time period, the first time period being longer than the second time period. - a live line between a live supply connecting terminal (Lin) and a live load connecting terminal (Lout), and a neutral line between a neutral supply connecting terminal (Nin) and a neutral load connecting terminal (Nout) for connecting an alternating current load to a mains supply, - a first galvanic separation switch and a bypass switch in the live line, and a second galvanic separation switch in the neutral line, and - a semiconductor switch element (IGBT) connected parallel to the bypass switch, - a processing unit arranged to control the first and second galvanic separation switch (SW2, SW3), the bypass switch and the semiconductor switch element (IGBT), the alternating current circuit breaker further comprising - a short circuit and overcurrent detection unit connected to the processing unit for determining a short circuit situation or overcurrent situation, wherein the processing unit is further arranged for - tripping the alternating current circuit breaker by opening the bypass switch and semiconductor switch element (IGBT) after determination of a short circuit or overcurrent situation, and to - execute a reclosing attempt after a predetermined time period after tripping of the circuit breaker, wherein the predetermined time period is dependent on the type of situation causing the tripping of the circuit breaker, wherein a reclosing attempt comprises closing of the semiconductor switch element (IGBT) first, monitoring for a possible short circuit or overcurrent situation, and only if no short circuit or overcurrent situation exists, closing the bypass switch, characterized in that the processing unit is arranged to monitor the actual load current I and load current increasing speed dI/dt using the short circuit and overcurrent detection unit prior to tripping of the circuit breaker, and if the load current increasing speed dI/dt is below or equal to a preset threshold value, to select a first time period as predetermined time period, and if the load current increasing speed dI/dt is above the preset threshold value, to select a second time period as predetermined time period, the first time period being longer than the second time period.