Patent Number: 6,396,383

Title: Protective element

Abstract: A protective element for protecting in particular an electric motor againstoverload currents includes in a polymer matrix, preferably ETFE, forexample 40% (by volume) of a first powdered filler of a conductivematerial, preferably TiB.sub.2, so that, as in the case of a PTC element,the resistance increases abruptly at a switching temperature correspondingto the melting temperature of the polymer. Also added are 20% (by volume)of a second powdered filler, a phase transition material which, at acritical temperature below the switching temperature, undergoes a phasetransition in which it absorbs heat of transformation. As a result, theresponse time (T) of the protective element is notably extended in a rangeof the overload current factor (F) corresponding to higher permissiblemotor starting currents. Examples of materials which come intoconsideration for the second filler are those with a solid-solid phasetransition such as pentaerythritol, NaNO.sub.2, NaNO.sub.3 or else with asolid-liquid phase transition such as UHMWPE, quinol or, in particular,microencapsulated metals, alloys and salts.

Inventors: Glatz-Reichenbach; Joachim (Baden-Dattwil, CH), Greuter; Felix (Baden-Rutihof, CH), Loitzl-Jelenic; Ruzica (Kirchdorf, CH), Skindhoj; Jorgen (Frederiksberg, DK), Strumpler; Ralf (Gebenstorf, CH)

Assignee:

International Classification: H01C 7/13 (20060101); H01C 7/02 (20060101); H01C 007/10 ()

Expiration Date: 05/28/2014