| 摘要 |
A thermal-magnetic trip unit, suitable for use in a circuit breaker, for eliminating the requirement for latching surfaces while still providing the additional force and motion required to trip the breaker during a short circuit or an overcurrent trip event. The trip unit comprises a link that is biased based on the position of a trip bar. A spring biases the link in a first direction when the trip unit is in a reset condition and biases the link in a second direction when the trip bar is rotated about a pivot point. A trip unit further including an improved indication-of-trip system comprising a two-piece trip bar mechanism and flag system is described to discriminate between overcurrent and short circuit faults. In this embodiment of the invention, visual confirmation of the cause of the trip is provided. The case of the circuit breaker includes a window disposed therein in a location conducive to a user viewing an identification flag thus enabling the rapid determination of the type of trip which has occurred. To identify a trip caused by an overcurrent condition, a first flag is employed. To identify a trip caused by a short circuit condition, a second flag is employed. If an overcurrent event occurs then the first slide of the two piece trip bar mechanism moves to expose the first flag. If a short circuit event occurs, only the second slide of the two-piece trip bar system moves to expose the second flag.
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