Current ratio device
US4841236A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 22, 1988 |
| Grant date | Jun 20, 1989 |
| Priority date | — |
| Expiry date | Mar 22, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01R1/20
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A current ratio device for use in constructing a current transformer comprises a first magnetic core, a second magnetic core, a measuring winding electromagnetically coupled with the first core but not with the second core, and a compensating winding electromagnetically coupled with both cores. An externally powered amplifier has its input connected to receive the voltage waveform across the measuring winding. Its output provides a compensating current through the compensating winding equal to a magnetizing current required to magnetize the second core. The amplifier output also provides a measuring current through the measuring winding in the direction opposite that of the compensating current and equal to the compensating current multiplied by the ratio of turns in the compensating and measuring windings. This device is a self-contained article of commerce that, when electromagnetically coupled (without electrical connection) to conventional primary and secondary windings and a burden, provides a current transformer with improved qualities. In particular, the magnetizing current needed by the transformer is provided by the separate current ratio device, thus avoiding the error in…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.