Circuit protection device with half cycle self test
AssigneePass & Seymour, Inc.
InventorBruce F. Macbeth
Life of this patent
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Abstract
A circuit protection device connected between two lines of an AC power source self checks for an introduced simulated ground fault every half cycle during a period when a trip SCR cannot conduct. If the self check fails, the device is tripped on the next half cycle of different phase. Possible responses to the self check failure include lighting an indicator lamp and locking out the device reset mechanism.
Claims29
A protection device connected between two lines of an AC power line, comprising:
- means for introducing a simulated ground fault current between said two lines during a first predetermined half-cycle of said AC power;
- detection means for detecting said introduced ground fault during said first predetermined half-cycle of said AC power;
- and
- response means, responsive to said detection means, for responding to an absence of detection of said introduced ground fault.
A self testing protection device connected between two lines of an AC power source, comprising:
- a resonant tank;
- a ground fault sensor,
- a rectified ground fault sensor bypass current sourced from a first polarity of said AC power source and used to energize said ground fault sensor;
- a first detector activated by said ground fault sensor, wherein said activated first detector causes said resonant tank to resonate, thereby indicating that all ground fault detection components in said device are operational;
- and
- a second detector, wherein said second detector responds to an absence of resonation in said resonant tank.
A method for self-testing a protection device connected between two lines of an AC power line, comprising the steps of:
- introducing a simulated ground fault between said lines during a first predetermined half cycle of said AC power;
- detecting said introduced simulated ground fault during said first predetermined half cycle;
- and
- responding to an absence of detecting said introduced simulated ground fault.
Dependencies are inferred from the claim text.