Abstract: A molded case circuit breaker having an instantaneous trip mechanism including main circuit units in a lower compartment of the molded case circuit breaker; a stationary contactor and a movable contactor; a switching mechanism in an upper compartment of the molded case circuit breaker and having an open position and a closed position; an instantaneous trip mechanism in the upper compartment and operating by an electromagnetic attraction in response to generation of a fault current, which triggers the switching mechanism to the open position; and an intermediate insulation barrier providing electrical insulation by partitioning the lower compartment and the upper compartment.

Abstract: Disclosed is a molded case circuit breaker having an instantaneous trip mechanism capable of instantaneously breaking a circuit upon occurrence of a fault current, the circuit breaker comprising: a main circuit unit present in a lower compartment of the molded case circuit breaker, and configured to open or close a circuit by having a stationary contactor and a movable contactor rotatable to contact with or separated from the stationary contactor; a switching mechanism present in an upper compartment of the molded case circuit breaker, and having an open position where the switching mechanism is connected to the main circuit unit to drive the main circuit unit to open a circuit, and a closing position where the switching mechanism drives the main circuit unit to close a circuit; an instantaneous trip mechanism present in the upper compartment, and operating by an electromagnetic attraction in response to generation of a fault current on a circuit so as to trigger the switching mechanism to the open position;