Protective element
US6396383B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 10, 1998 |
| Grant date | May 28, 2002 |
| Priority date | — |
| Expiry date | Dec 10, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01C7/027
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A protective element for protecting in particular an electric motor against overload currents includes in a polymer matrix, preferably ETFE, for example 40% (by volume) of a first powdered filler of a conductive material, preferably TiB2, so that, as in the case of a PTC element, the resistance increases abruptly at a switching temperature corresponding to the melting temperature of the polymer. Also added are 20% (by volume) of a second powdered filler, a phase transition material which, at a critical temperature below the switching temperature, undergoes a phase transition in which it absorbs heat of transformation. As a result, the response time (T) of the protective element is notably extended in a range of the overload current factor (F) corresponding to higher permissible motor starting currents. Examples of materials which come into consideration for the second filler are those with a solid-solid phase transition such as pentaerythritol, NaNO2, NaNO3 or else with a solid-liquid phase transition such as UHMWPE, quinol or, in particular, microencapsulated metals, alloys and salts.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.