Phase breakdown- and null current-detector, especially for an electronic motor protection relay possessing current-dependent triggering
US3988641A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 30, 1975 |
| Grant date | Oct 26, 1976 |
| Priority date | — |
| Expiry date | Sep 30, 1995 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02H6/00
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A phase breakdown- and null current detector, especially in or for an electronic motor protection relay with current-dependent response or triggering, which is controlled by detection alternating-current voltages proportional to current values in the motor outer conductors and contains an electrical motor simulator representative of the thermal or heating behavior of the motor due to the charging operation of a capacitive storage. The motor simulator can be adjusted by a controlled switching device to different time-constants corresponding to the operating conditions of the motor. At the input side of a voltage comparator-circuit arrangement there are electrically connected circuit elements for comparison of the mean or average value of a measurement voltage obtained by rectification of the detection alternating-current voltages with at least one comparison voltage in such a manner that in the presence of an asymmetry of the detection alternating-current voltages greater than a predetermined asymmetry of such detection alternating-current voltages there is delivered by the voltage comparator-circuit arrangement an output signal as a phase breakdown-reporting or indicator signal and…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.