Portable ground fault detector
US5363047A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 30, 1992 |
| Grant date | Nov 8, 1994 |
| Priority date | — |
| Expiry date | Oct 30, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01R31/52
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Disclosed is a ground fault detection apparatus for an operating, normally ungrounded supply system, the apparatus having a periodically grounded center tap of a test impedance that is connected across conductors of the system, and detector circuitry including a charge balance circuit having low gain and wide dynamic range that measures the amplified voltage output of a Hall effect current sensor. A preferred implementation of the circuit has a charge transfer variable oscillator. A pair of microprocessor-controlled counters that are responsive to the oscillator precisely measure the average frequency of the oscillator over intervals that are automatically maintained at approximately one second in duration, the microprocessor calculating the fault current as the difference between current measurements taken with and without the center tap grounded. The apparatus has sufficient dynamic range for directly measuring system currents on the order of 100 A, while reliably detecting leakage currents in the milliampere range.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.