초록 ▼

Arc faults in ac electric power systems including aircraft 400 Hz and other such ac electrical systems are detected by an arc fault detector generating a time attenuated cumulative sum of amounts by which the current in each most recent cyclic interval of current, preferably each half cycle, exceeds

Arc faults in ac electric power systems including aircraft 400 Hz and other such ac electrical systems are detected by an arc fault detector generating a time attenuated cumulative sum of amounts by which the current in each most recent cyclic interval of current, preferably each half cycle, exceeds the magnitude of the current in the immediately preceding cyclic interval in absolute magnitude after a first cyclic interval in which the current exceeds a selected arming magnitude. Preferably, the magnitude detected by a peak detector is used, but alternatively differences in the average magnitude or the rms magnitude between half cycles can be accumulated. When the cumulative sum reaches a preset value, an arc fault indication is generated. The time cumulative sum is cleared if it decreases to a preset value and the selected arming current must be exceeded again to reinitiate generation of the time attenuated cumulative sum.

대표청구항 ▼

Arc faults in ac electric power systems including aircraft 400 Hz and other such ac electrical systems are detected by an arc fault detector generating a time attenuated cumulative sum of amounts by which the current in each most recent cyclic interval of current, preferably each half cycle, exceeds

Arc faults in ac electric power systems including aircraft 400 Hz and other such ac electrical systems are detected by an arc fault detector generating a time attenuated cumulative sum of amounts by which the current in each most recent cyclic interval of current, preferably each half cycle, exceeds the magnitude of the current in the immediately preceding cyclic interval in absolute magnitude after a first cyclic interval in which the current exceeds a selected arming magnitude. Preferably, the magnitude detected by a peak detector is used, but alternatively differences in the average magnitude or the rms magnitude between half cycles can be accumulated. When the cumulative sum reaches a preset value, an arc fault indication is generated. The time cumulative sum is cleared if it decreases to a preset value and the selected arming current must be exceeded again to reinitiate generation of the time attenuated cumulative sum. usting a first optical distance in conjunction with at least one other optical distance between said first reflective surface and said at least one additional partly reflective surface and wherein said at least one other tuned optical distance is defined as that value wherein said light source imaged onto said selected target surface forms a minimum radius spot size upon said selected target surface. 16. The system of claim 15, wherein said second reflective surface has a reflectivity between about 10% and about 100%. 17. The system of claim 15, wherein said first reflective surface has a reflectivity in the range from about 7% to about 98%. 18. The system of claim 17, wherein said first reflective surface has a reflectivity from about 50% to about 98%. 19. The system of claim 15, wherein said at least one additional partly reflective surface has a reflectivity from about 10% to about 98%. 20. The system of claim 19, wherein said first reflective surface has a reflectivity in the range from about 7%