Norbert Mitlmeier

Increase of lifetime of electromagnetically actuated contactors by avoiding self-synchronization

This work deals with the unequal contact erosion frequently observed in electromagnetically controlled three-phase contactors. This effect of uneven erosion is caused by the non-uniform distribution of the switching angles, due to the synchronization between the electromagnetic drive and the three load contacts and is referred to as self-synchronization. This is initially investigated and analyzed by the means of a specially conceived test rig whereby both make and break operation have been considered. The main focus of This work is on the here-specified self-synchronization, which occurs due to interaction of the armature system of the contactor and the three-phase system. Following the analysis, advice is given as to how synchronization can be avoided and thus lifetime of the contactor can be significantly extended.