Abstract: An alternating current circuit breaker has a series circuit of bipolar switching modules which are inserted in series into a phase line of an alternating current line. Each switching module has an energy storage device and actuatable power semiconductors that can be activated and deactivated. Each switching module can be driven such that a switching module voltage that corresponds to a positive or negative energy storage device voltage or a zero voltage can be generated at the poles of the switching module. A controller is configured to actuate the switching modules based on a polarity change of a phase current such that the switching module voltage switches polarity, wherein a switching module voltage opposite the phase voltage can be generated. A method for switching alternating currents is effected with the alternating current circuit breaker.