Experimental Study On Electrical Contact Characteristics Of Silver Metal Oxide Contact Materials

Contacts are the direct execution components of various switching appliances?contactors,relays,circuit breakers,etc.?to complete signal conduction and current interruption.Nowadays,various alloys and composite contact materials have been commonly used in contacts.The electrical contact performance of contact materials affects the reliability of various power distribution and control systems.In order to evaluate the electrical contact performances of silver metal oxide contact material more accurately,and improve the preference of contact materials.Three contact materials:Ag Sn O₂,Ag Cd O,and Ag Ni are used as research objects in this paper,and a new type of automatic electrical contact simulation test system is designed.The electrical contact simulation test method is used to obtain and analyze the sensitive degradation parameters of the electrical properties of contacts,and then the electrical properties degradation process and life prediction process of the three materials under different experimental conditions are studied,the dynamic welding phenomenon of the contacts,the bonding characteristics and the physical mechanism of failure are also analyzed based on this system.Firstly,a new type of single-station contact test and analysis system for electrical contact characteristics is designed and developed.The system can simulate the opening/closing action process of dynamic and static contacts in real switching appliances.It can adjust mechanical parameters such as contact magnetic gap,contact opening distance,idle distance and overtravel,and can easily change the dynamic and static contact materials.The main circuit of the developed hardware test realizes the real-time synchronous measurement of electrical parameters and dynamic forces of the contacts.The host computer system based on Lab VIEW realizes the calculation,display and storage of contact resistance,static pressure,arc energy,rebound energy and related time parameters.Secondly,the degradation processes of the contact resistance,static pressure,arcing energy,and rebound energy of the three materials are experimentally compared and studied under the same resistive load level,then the failure physical mechanism of its sensitive degradation parameters are analyzed.The life of Ag Sn O₂contacts is predicted and evaluated by analyzing the contact resistance degradation parameters.Finally,the characteristics of important degradation parameters of Ag Sn O₂contacts under different load levels and different contact opening distances are studied experimentally.The electron microscope is used to observe the microscopic surface morphology of Ag Sn O₂after failure,and the dynamic fusion welding characteristics and bonding characteristics of Ag Sn O₂contacts and their failure mechanism are analyzed.What's more,the effects of contact pressure and load conditions on the bonding properties are investigated through experiments.The experimental results show that the data obtained by the electric contact simulation method is more intuitive and accurate than the traditional electrical simulation method.Combined with the comparison and analysis of the example waveforms,it is concluded that Ag Cd O has the best comprehensive electrical performance.The degree of fusion welding increased with the increase of load grade level and increased with the decrease of contact opening distance during the Ag Sn O₂electrical contact simulation test.The research results in this paper can provide a certain reference for the scientific evaluation of electrical properties of contact materials and component optimization and improvement,and provide a certain theoretical basis for the design of electrical appliances with contacts such as relays.