Circuit protection device with half cycle self test
First Claim
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1. 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.
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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.
108 Citations
29 Claims
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1. A protection device connected between two lines of an AC power line, comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
said two lines are a hot line and a neutral line; and
said means for introducing a ground fault includes a first predetermined half-cycle bypass connected between said hot and neutral lines.
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9. A protection device according to claim 1, wherein said detection means includes:
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a capacitor placed across a series string consisting of a solenoid and a parallel combination of an SCR and a snubber circuit, wherein said capacitor charges on a second predetermined half cycle of said AC power;
a blocking diode between said capacitor and said hot line; and
a checking circuit connected to said snubber circuit, wherein said checking circuit produces an output which triggers said response means when said introduced ground fault is not properly detected by said detection means.
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10. A protection device according to claim 9, wherein said checking circuit operates from a power supply independent from a remaining portion of said protection device.
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11. A protection device according to claim 1, wherein said detection means includes:
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a capacitor placed across a series string consisting of a solenoid and a parallel combination of an SCR and a diode, wherein said capacitor charges on a second predetermined half cycle of said AC power;
a blocking diode between said capacitor and said hot line; and
a checking circuit connected to said capacitor, wherein said checking circuit produces an output which triggers said response means when said introduced ground fault is not properly detected by said detection means.
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12. A protection device according to claim 11, wherein said checking circuit operates from a power supply independent from a remaining portion of said protection device.
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13. A protection device according to claim 1, wherein said detection means includes;
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a capacitor placed across a series string consisting of a solenoid and a parallel combination of an SCR and a diode, wherein said capacitor charges on a second predetermined half cycle of said AC power;
a blocking diode between said capacitor and said hot line; and
a secondary transformer in operative cooperation with said solenoid;
a checking circuit connected to said secondary transformer, wherein said checking circuit produces an output which triggers said response means when said introduced ground fault is not properly detected by said detection means.
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14. A protection device according to claim 13, wherein said checking circuit operates from a power supply independent from a remaining portion of said protection device.
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15. A protection device according to claim 1, wherein said detection means includes:
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a capacitor placed across a series string consisting of a solenoid and a parallel combination of an SCR and a resistor-capacitor-diode network;
a blocking diode between said capacitor and said hot line; and
a checking circuit connected to said network, wherein said checking circuit produces an output which triggers said response means when said introduced ground fault is not properly detected by said detection means.
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16. A protection device according to claim 15, wherein said checking circuit operates from a power supply independent from a remaining portion of said protection device.
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17. A protection device according to claim 1, wherein said protection device is one of a GFCI device, a GFEP device, and an AFCI device.
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18. A self testing protection device connected between two lines of an AC power source, comprising:
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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. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. A method for self-testing a protection device connected between two lines of an AC power line, comprising the steps of:
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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.
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Specification
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Current AssigneePass & Seymour Incorporated (Legrand SA)
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Original AssigneePass & Seymour Incorporated (Legrand SA)
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InventorsMacbeth, Bruce F.
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Primary Examiner(s)Deb, Anjan K.
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Application NumberUS09/725,525Publication NumberTime in Patent Office1,133 DaysField of Search324/509, 324/523, 324/525, 324/524, 324/424, 324/527, 324/423, 361/5, 361/45, 361/42, 361/115US Class Current324/509CPC Class CodesH02H 3/331 responsive to earthing of t...H02H 3/335 the main function being sel...
