Detector apparatus
US4071875A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 29, 1975 |
| Grant date | Jan 31, 1978 |
| Priority date | — |
| Expiry date | Dec 29, 1995 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02H7/0852
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A circuit is shown useful to protect dynamoelectric machines from overtemperature conditions. The circuit comprises first and second tuned circuits coupled to the power lines of the dynamoelectric machine along with an oscillator for injecting a selected frequency signal in the line and a detector for detecting the signal when the tuned circuits are resonant. A thermally responsive switch comprising an electromechanical bimetal switch or a solid state PTC or NTC switch is adapted to be disposed in heat conductive relation with the dynamoelectric machine and is electrically coupled to one of the tuned circuits so that the temperatures below a selected level the switch will be in one state, e.g. a low impedance state, precluding resonance while at temperatures above the selected level the switch will be in an opposite state, e.g. a high impedance state, permitting resonance. A detector particularly useful for detecting the above-mentioned signal is shown to comprise a three legged E-I transformer core on one leg of which is disposed a shunt winding. The shunt winding is coupled to a frequency selective device such as a capacitor. A sensing winding is disposed on the center leg and a …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.