Mechanical trip device for a circuit breaker

摘要

In a power circuit breaker a trip mechanism is provided normally to oppose the large opening forces associated with the separable contacts of the breaker and to hold the contacts closed. The trip mechanism in response to overload current conditions collapses and trips open the breaker contacts. Forces related to the opening force of the breaker contacts are present throughout the trip mechanism when the contacts are closed. The trip mechanism provides two eccentric latch mechanisms in series each of which reduce the magnitude of the forces acting in the trip mechanism that are related to the opening force. The two latch mechanisms are each mounted to a pivot for rotation therewith. A force related to the opening force is applied against each latch mechanism. Because the pivot for each latch mechanism is eccentric to the line of force acting against the latch mechanism, the force translates into a rotational force that tends to rotate the latch mechanism and pivot. The rotational force is considerably smaller in magnitude than the force acting against the latch mechanism. By utilizing the two eccentric latch mechanisms connected in series, the trip mechanism becomes a relatively simple and inexpensive device.