Electrical switching apparatus with digital trip unit and automatic frequency selection
US5428495A · kind A · utility
20Cited by
10References
9Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Sep 30, 1992 |
| Grant date | Jun 27, 1995 |
| Priority date | — |
| Expiry date | Sep 30, 2012 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02H3/093
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A microprocessor based switch such as a circuit breaker generates digital rms representations of analog load currents from n samples of the analog currents per cycle synchronized to the line frequency, where n is an odd integer equal to a selected highest order harmonic to be detected plus 2. A routine determines whether the power system is 50 or 60 Hz, and automatically sets the sampling interval to provide exactly n samples per cycle for the connected source. Terminals for rapidly resetting an analog memory for calibration and field testing of a long delay trip are hidden behind a removable rating plug.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.