Ground fault circuit interrupter
US4258403A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 31, 1979 |
| Grant date | Mar 24, 1981 |
| Priority date | — |
| Expiry date | May 31, 1999 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02H3/105
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A ground fault detecting circuit interrupter is taught. A ground fault is sensed by utilizing a summing transformer interconnected with the three-phase current transformers for normal fault detection. The turns ratio between the primary winding and the secondary winding of the summing transformer is kept purposely high so that the excitation current for the current transformers is made relatively small when compared to the normal secondary current of the current transformers. This has the effect of improving the accuracy of the normal fault detecting portion of the circuit breaker. The relatively high turns ratio between the primary and second of the summing transformer usually supplies insufficient current to directly actuate the trip coil of the circuit interrupter on the occurrence of a ground fault. However, this latter current is utilized to charge a capacitive storage element after a ground fault has been sensed. When the capacitive storage element is fully charged, it is switched into a circuit disposition suitable for discharge through the trip coil of the circuit interrupter with sufficient current flow to open the separable main contacts of the circuit interrupter.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.