Abstract: A molded case circuit breaker having a contact on mechanism which can perform a trip operation and automatically rotates the handle to the on position or a position toward the on position if the handle is manipulated to move to the off (or reset) position in a state that the contacts are melt-adhered to each other, the contact on mechanism, including: a contact on plate which is vertically movable by being guided according to the operation of the switching mechanism, a trip bar that drives the restricting unit to a releasing position, a lever connected to the handle and that provides a pivot point of the handle, a lever pin fixed to the lever, for driving the restricting unit to the releasing position by pressing the trip bar, and thereby operating the switching mechanism to the trip position, and a trip spring providing an elastic driving force for enabling the switching mechanism to operate to the trip position when the restricting unit is moved to the releasing position.

Abstract: A molded case circuit breaker having a contact on mechanism which can perform a trip operation and automatically rotates the handle to the on position or a position toward the on position if the handle is manipulated to move to the off (or reset) position in a state that the contacts are melt-adhered to each other, the contact on mechanism, including: a contact on plate which is vertically movable by being guided according to the operation of the switching mechanism, a trip bar that drives the restricting unit to a releasing position, a lever connected to the handle and that provides a pivot point of the handle, a lever pin fixed to the lever, for driving the restricting unit to the releasing position by pressing the trip bar, and thereby operating the switching mechanism to the trip position, and a trip spring providing an elastic driving force for enabling the switching mechanism to operate to the trip position when the restricting unit is moved to the releasing position.

Abstract: 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 c