Molded case circuit breaker having instantaneous trip mechanism
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.
1. A molded case circuit breaker comprising:
a plurality of main circuit units located in a lower compartment of the molded case circuit breaker, wherein each of the plurality of main circuit units is configured to open or close a circuit via a stationary contactor and a movable contactor, wherein the movable contactor is rotatable to make contact with or separate from the stationary contactor;
a switching mechanism located in an upper compartment of the molded case circuit breaker, the switching mechanism connected to each of the plurality of main circuit units and having:
an open position in which the switching mechanism drives open a circuit, and
a closed position in which the switching mechanism drives each of the plurality of main circuit units to close the circuit;
an instantaneous trip mechanism located in the upper compartment and operated via electromagnetic attraction in response to generation of a fault current in the circuit, wherein the instantaneous trip mechanism causes the switching mechanism to be in the open position; and
an intermediate insulation barrier installed commonly for the plurality of main circuit units between the upper compartment and the lower compartment and configured to provide electrical insulation between the switching mechanism and instantaneous trip mechanism located in the upper compartment and the plurality of main circuit units located in the lower compartment by partitioning the lower compartment and the upper compartment, wherein the intermediate insulation barrier is a portion of and forms a single body with an upper outer casing of the molded case circuit breaker, and
wherein the intermediate insulation barrier is configured to substantially cover the entire area of the lower compartment.
2. The circuit breaker of claim 1 , further comprising:
an electric conductor located in each of the plurality of main circuit units with an interval between each of the plurality of main circuit units,
wherein the instantaneous trip mechanism comprises:
an armature installed to face each electric conductor and made of a strong magnetic substance such that the armature is rotatably attracted by each conductor when a fault current flows through the conductor; and
an instantaneous trip spring that is contactable with the armature to apply an elastic force to the armature in order to return the armature to an original position when a normal current flows through each conductor,
wherein the instantaneous trip spring applies a predetermined elastic force to the armature when the armature is rotated in response to an instantaneous trip current flowing, and
wherein the predetermined elastic force is smaller than a rotational force of the armature.
3. The circuit breaker of claim 2 , wherein the switching mechanism comprises:
a latch having a restricted position and a released position;
a latch holder rotatable between a first position for restricting the latch and a second position for releasing the latch; and
a nail configured to cause the latch holder to rotate to the second position,
wherein the instantaneous trip mechanism further comprises a cross bar that is rotatable upon being pressed by the armature and having an extension portion extending towards the nail in order to press and rotate the nail when the cross bar is rotated.