Interchangeable tripping device for a circuit-breaker

An interchangeable three phase tripping device for a three pole molded case circuit-breaker, wherein the circuit-breaker comprises a casing, a current-passing conductor for each of the phases of the three pole circuit breaker, and a control mechanism operable by the tripping device to break the circuit of the current-passing [conductor] conductors of the three phases in unison ;

• said tripping device including insulating case, common tripping mechanism, and excess current detection means for each phase constituted as a magnetic circuit which, in operation, surrounds the respective current-passing conductor, the magnetic circuit being made of two separable parts, one of which is installed in said casing of the molded case circuit-breaker and the other separable part being [removable and integral with said interchangeable tripping device] fixed in said insulating case of the tripping device such that replacement of the interchangeable tripping device in the circuit-breaker can be made without disconnection of the current-passing [conductor] conductors of the circuit-breaker , said other separable part of said excess current detection means for each phase acting on said tripping mechanism which is common for the three poles whereby there is excess current in one phase all three poles of the circuit-breaker are opened.