Circuit for providing phase loss and phase imbalance protection
US5502611A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 14, 1994 |
| Grant date | Mar 26, 1996 |
| Priority date | — |
| Expiry date | Oct 14, 2014 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02H7/09
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A circuit for detecting phase imbalance in a three phase electrical system. The circuit includes a three phase current transformer or three separate current transformers for monitoring the current flowing in each phase of a three phase electrical system. The current transformers provide an induced current proportional to the monitored current. The induced current passes through a full-wave bridge rectifier which produces a voltage output proportional to the induced current. This voltage signal is passed to a two pole Sallen-Key filter which allows a desired signal having a particular frequency range to pass through and blocks the passage of an undesired signal having a particular frequency range. A scaling circuit then receives a portion of the desired signal and produces a scaled average signal which is of a preselected magnitude lower than the desired signal. The scaled average signal and a portion of the desired signal are passed to a comparator/timer which produces an output signal based on a comparison of the desired signal and the scaled average signal. The output signal from the comparator/timer is only produced when the desired signal is lower in value than the scaled avera…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.