Electricity: electrical systems and devices – Safety and protection of systems and devices – Circuit interruption by thermal sensing
Reexamination Certificate
1999-09-28
2001-11-27
Ballato, Josie (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
Circuit interruption by thermal sensing
C361S072000, C361S103000, C361S104000, C361S114000, C361S115000
Reexamination Certificate
active
06324043
ABSTRACT:
BACKGROUD OF THE INVENTION
This invention relates to residual current detectors for use with electric circuit breakers, and more particularly to such residual current detectors that include an electronic trip circuit.
Circuit breakers and similar electrical contactors provide protection against faults in electrical power systems, such as overcurrent, ground fault and short circuit protection. In order to provide protection against ground fault currents or other abnormal operating conditions, circuit breakers can be equipped with an electronic residual current detector, or ground fault detector, that senses an abnormal condition and trips the circuit breaker in response to the abnormal condition. U.S. Pat. No. 5,907,461 discloses a molded case circuit breaker with ground fault protection. A ground fault circuit mounted within the circuit breaker case activates a solenoid in the event of an abnormal condition. The solenoid, in turn, trips the circuit breaker.
Residual current detectors typically include an electronic circuit that is used to detect abnormal operating conditions and a device for tripping the associated circuit breaker in response to the abnormal conditions. The electronic circuit may be powered by a transformer that is coupled to a power conductor within the circuit breaker. The tripping device may include a manually operated reset switch such that once the abnormal condition has been removed, the residual current detector can be reset. However, under some abnormal conditions, the electronic circuit portion of the residual current detector may become damaged to the point where it is inoperable.
If the electronic circuit of the residual current detector is disabled, the residual current detector will be unable to sense an abnormal condition. Therefore, it is desirable to prevent manual resetting of the residual current detector if the electronic circuit is disabled.
SUMMARY OF THE INVENTION
This invention provides a residual current detector comprising a trip circuit; a magnetic lock assembly including a solenoid that operates in response to a signal from the trip circuit, causing movement of an operating member, with the magnetic lock further including a reset mechanism for resetting the residual current detector following a trip operation; and means for preventing reset of the magnetic lock by restraining movement of the solenoid when the trip circuit is disabled.
In the preferred embodiment, a plunger assembly is mounted adjacent to the solenoid of the magnetic lock assembly and fusible link is connected in series with the trip circuit and mounted to prevent movement of a plunger in the plunger assembly. When the trip circuit is subjected to excessive current, the fusible link will melt, thereby permitting the plunger to interfere with movement of the armature of the solenoid. This prevents rest of the magnetic lock assembly.
REFERENCES:
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patent: 4631624 (1986-12-01), Dvorak et al.
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patent: 5907461 (1999-05-01), Hartzel et al.
patent: 5920451 (1999-07-01), Fasano et al.
patent: 5936817 (1999-08-01), Matsko et al.
patent: 5956218 (1999-09-01), Berthold
patent: 6040967 (2000-03-01), DiSalvo
patent: 6040971 (2000-03-01), Martenson et al.
Ballato Josie
Eaton Corporation
Marquis Vaughn
Moran Martin J.
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