Experimental Study On Electrical Characterisics Of Silver Tin Oxide Type Contacts Under Surge Current Load

Contact is the direct executing part of signal conduction in switch,the accelerated degradation and dynamic welding problem of which under surge load has become the key to improve life and reliability of low-voltage electrical appliances.As the most widely used functional material,the electrical characteristics of silver tin oxide type contacts under surge load have attracted much attention.Based on the two-station simulation experiment system of contact materials,this paper experimentally studies the features and degradation process of electrical characteristics and the mechanism of dynamic welding failure on silver tin oxide type contacts under surge load.Firstly,a novel test equipment for real-time measurement of electrical characteristics on contact materials is developed.Its main functions include: with five-degree-freedom adjusting mechanism,the variable mechanical parameters,such as over travel,free travel and contact gap are easily adjustable;the action of contact can be completed by the electromagnet;the designed test units can achieve synchronous and real-time measurement of contact force and electrical parameters;with the help of LabVIEW programing environment,the characteristic parameters of electrical properties,such as bounce time,bounce energy,arc energy,can be calculated,displayed and stored.Secondly,combined with the typical waveforms of contact voltage and contact current under capacitive load,the experiment circuit and typical waveforms are analyzed in theory.The mathematical model for transient process of contact action is proposed.Besides,the influence of peak value and duration of surge current on the electrical characteristics during the process of contact action is analyzed.Then,experimentally study the degradation process of electrical parameters of silver tin oxide type contacts in the surge durability test.The degradation features of sensitive parameters are summarized to analyze causes and physical mechanism of degradation.Finally,by changing the type of load,the value of load capacitance and the contact gap,experiments are conducted to study the dynamic failure phenomenon of silver tin oxide type contacts.Through summary the features of sensitive parameters and surface micro-topography of welding contact,this paper describes the process of contact welding and analyzes its failure mechanism.The research not only provides experimental means for scientific evaluation and optimization improvement of contact materials,but also has practical value for long life design and contact failure analysis of low voltage electrical apparatus.