| Electrical appliances are the basic components used in circuits to achieve switching,control and other functions.As the main executive part of the electrical appliance,the contact is responsible for the function of making and breaking current.The direct consequence of arc discharge during the switching process of the contacts is the ablation of the contact surface,which will lead to failure of electrical functions in severe cases.Aiming at the shortcoming that the arc erosion process of contact materials cannot be directly observed in the electrical life test,this paper analyzes the arc erosion characteristics,evolution law,physical mechanism and influencing factors in the process of silver-based contact materials electrical life experiment through the in-situ observation experimental system and the corresponding arc erosion image processing methodsFirstly,a new type of in-situ observation experimental system for arc erosion of contact materials is designed.The experimental system uses the electric sliding table as the actuator to simulate the contact arc ablation,and designs the contact surface image observation unit and the microscopic physical characteristic test unit.The measurement and control system can measure electrical performance parameters such as arcing energy and contact resistance.The human-computer interaction interface of the developed experimental system can automatically acquire,display and store the image of the contact surface.Secondly,according to the characteristics of the ablation zone in the center of the contact,a method for identifying and extracting features of the arc erosion image is proposed.Based on the maximum between-class variance segmentation algorithm and the morphological calculation method,the automatic acquisition of the central ablation area area is realized,and the registration method on the laser confocal microscope data result and the arc erosion image is further proposed,and the central ablation image of the arc erosion image is obtained.The evolution process and physical mechanism of the characteristic parameters of the arc erosion of Ag Sn O2 contact materials are experimentally studied.The experimental results show that the area of the ablation zone in the center of the electro-erosion image increases exponentially with the increase in the number of actions.Combined with the trend analysis of the non-optical characteristic parameters of the electro-erosion,it is determined that the contact electro-erosion process has a dynamic change stage of the surface structure,the area of ablation zone expansion stage,and the depth of ablation zone expansion stage.The analysis of the contact state between dynamic and static contacts reveals the dominant competitive relationship between the ablation area of the contact material and the height of the rough peak at the micro-scale during the arc erosion process.Finally,a mathematical model of the cumulative characteristics of the arc erosion image of the contact material is established.The influence of the contact material preparation process,load voltage,and load current on the arc erosion characteristics is studied experimentally,and the negative correlation between the area growth rate of the central ablation zone and the reduction rate of the rough peak height at the micro scale is determined.The mathematical models of the central ablation zone area of AgSnO2 contacts and Ag Ni contacts under the influence of load voltage and load current with the number of actions are established by regression analysis.This study can provide an experimental method for the evaluation of the electrical corrosion resistance of contact materials,and can also provide research ideas for the prediction of the remaining electrical life of the contact materials and the analysis of the failure mechanism. |
