An instantaneous trip mechanism for a mould cased
circuit breaker in a trip mechanism of a mould cased
circuit breaker, the instantaneous trip mechanism capable of easily adjusting a trip current sensitivity for initiating an instantaneous trip operation and of fabricating a reliable mould cased
circuit breaker by employing a simple construction for the adjusting unit and supporting a constant trip current sensitivity by products, the instantaneous trip mechanism for the mould cased circuit breaker comprising: a fixed
electromagnet for generating a magnetic force which is changed according to a current flowing on a circuit; an armature disposed to face the fixed
electromagnet and rotatable to a position for
tripping the mould cased circuit breaker by the magnetic force from the fixed
electromagnet when a great current exceeding a normal current flows on the circuit; a spring for elastically biasing the armature in a direction of being separated from the fixed electromagnet; an adjusting dial member having a
cam surface for adjusting a gap between the armature and the fixed electromagnet; and an adjusting bar having one end contacted with the
cam surface of the adjusting dial member and another end contacted with the armature, and rotatable to change the gap by pushing the armature according to a position of being contacted with the
cam surface of the adjusting dial member.