Experimental investigation on parameters of switches contacts

The important demand in the sense of safety and reliability in the area of domestic applications requires, for the improvement of switch devices, deeper knowledge on switches contacts characteristics and on their behavior during their lifetime. The most important problems are excessive wear and erosion or other harmful effect occurring in normal use, because of presence of electrical arc during making and braking operations. The reliability of low voltage switches is verified by endurance tests. Tests are done for a-c switches with a rate voltage (250V) and with AgNi contacts. Switches are tested with inductive and capacitive loads and are subjected up to 5000 operations with capacitive load and up to 30000 with an inductive one. The subject of this work is to find parameters that characterize electrical contacts or have a relation with the number of opening-closing operations. Parameters studied are peak arc current value and contacts capacitance. The first result shows that the peak arc current value increases with the number of operations for capacitive load. But for inductive one it is stabilized. The second result shows that the capacitance of contacts (for inductive or capacitive loads) keeps approximately a stable value witch is different for closed contacts and opened ones.