Importance

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Abstract

This invention prevents a circuit breaker from being re-set for a time sufficient to insure safe dissipation of ionized gases. Current monitors and rectifiers generate a reduced voltage direct current output which is fed into an auxiliary rectifier circuit. That direct current output is proportional to current in power conductors controlled by a circuit breaker. A holding circuit has an electrical power source derived from the power conductors and connected to a release coil for the main power contacts in the circuit breaker. A holding relay has a holding coil in the rectifier circuit, and normally closed holding contacts in the holding circuit. A time switch is connected in shunt with the holding coil. When the direct current output reaches a value corresponding to an overcurrent condition in the power conductors, it energizes the holding coil to open the holding contacts and cause the release coil to trip open the main contacts. Concurrently, the time switch activates; after a predetermined time (e.g., 3 minutes) the time switch closes and shorts out the holding coil enabling the holding contacts to close. This re-energizes the release coil enabling the main power contacts to be re-set. A rectifier in the holding circuit holds the holding coil energized while the holding contacts are open.

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First Claim