Air-magnetic circuit breakers are widely used for short-circuit protection in DC electric railways or industrial plants. The well-known drawbacks of these breakers are mainly a slow breaking action, a short lifetime and high maintenance costs due to the destructive effects of the arc. The use of power semiconductors in a full-static circuit breaker configuration allows to eliminate these disadvantages but is limited by excessive conduction losses. The paper will present a so called hybrid breaker, drawing its name from the combination of a high-speed mechanical switch and a bi-directional IGCT assembly connected in parallel.