Experimental Research On Electrical Performance Of DC Contactor In Salt-fog Environment

In coastal areas,sea water is attacked by wind waves and evaporation to form a salt-fog environment.Salt fog corrodes the contact surface of low voltage electrical appliances,which makes the contact more seriously corroded by arc in on-load operation.In this paper,the characteristics of switching arc and the electrical performance of contacts during the making and breaking operation of DC contactor in coastal salt-fog environment are studied.The mass changes and surface morphology of contact anode and cathode before and after the experiment are also studied.This research is of great significance to the reliability and safety of low voltage electrical apparatus in salt-fog environment.First,according to the requirements of national standards for special experiments,an experimental platform for DC contactor electrical performance in salt-fog environment was built.Then,according to the distance between the area and the seashore,salt-fog experiments were carried out for AgCdO contacts with 30% silver content in 1%,3%,5% and 7% NaCl solution.According to the national standard of salt-fog test and the investigation of salt-fog concentration in coastal areas by national standard for classification of environmental conditions,salt-fog experiments were carried out on different contact pairs of AgCdO contacts with silver content of 30%,50% and 85% respectively in salt-fog environment of 5% NaCl solution.Finally,the voltage and current data of arc under different salt-fog concentration conditions were obtained.The arc duration time,arc energy and contact resistance were analyzed with the increase of operation times.The mass changes of contact anode and cathode before and after the experiment were weighed by electronic balance.The surface morphology were observed by metallurgical microscope.The erosion mechanism of arc on contact and the mass changes of DC contactor in salt-fog environment are analyzed.The results show that the erosion degree of DC contactor is enhanced under the closing and breaking operation of DC contactor in salt-fog environment.Under symmetrical contact pairing,the higher the silver content of contacts,the worse the arc resistance and corrosion resistance of contacts after several experimental operations.The arc resistance and corrosion resistance of contacts under asymmetrical contact pairing are worse than that under symmetrical contact pairing,and there is deterioration effect,which can provide a basis for the study of the corrosion resistance and matching mode of contact materials in salt-fog environment.