Positive temperature coefficient transition sensor
US5493101A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 15, 1993 |
| Grant date | Feb 20, 1996 |
| Priority date | — |
| Expiry date | Dec 15, 2013 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02H9/026
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A transition sensor is responsive to transition of a positive temperature coefficient resistive element from a nominal low resistance state to a protective high resistance state. A positive temperature coefficient (PTC) element is placed in a power distribution circuit between a power source and a load. Excessive load current in the event of a high current fault heats the PTC element to a threshold temperature at which the PTC element transitions into a protective state of high resistance, limiting current flow to the load. The LED of an optoisolator is coupled in parallel with the PTC element, preferably with a resistor in series with the LED. Under nominal current conditions the voltage across the LED is less than its forward bias voltage. During a high current fault, the LED becomes forward biased and switches on the optoisolator phototransistor to operate an alerting device such as an audible alarm and/or a light. A relay can be coupled to the phototransistor for decoupling the load and the PTC element from the power source, and preferably is arranged to latch in the protective position when tripped. The invention is applicable to direct current or alternating current and singl…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.