Research On Three-dimensional Synchronous Test Technology For Electric Contact And Arc&Motion Characteristics Of Arc Root

During the action process of the electrical apparatus,the arc will appear in the contact gap.The high temperature of arc and arc force make contact material vaporization and liquid splashing,which eventually lead to contact erosion or welding,seriously affect the life and reliability of electrical appliances.Due to the arc root with large current density and high temperature,if the arc is burned in a certain place during the whole combustion,even in a short arcing time,it also will cause significant harm,so it is necessary to study the movement of arc root.At present,most of the research on the visualization of arc root adopts the method of two-dimensional test.As the arc combustion process is affected by the action mechanism,load conditions or external magnetic field,there are non-uniformity and uncertainties in all directions.Therefore,carrying out the research of three-dimensional synchronous test for motion process of electrical action mechanism and the arc combustion process as well as arc root movement characteristics are helpful to understand the influence of the operating mechanism and the external conditions on the motion of the arc root.It will provide the basis for the optimization design of electrical products,and has theoretical and practical significance for improving the life and reliability of electrical products.Combined with the optical measurement technique,a three-dimensional synchronous test system for electric contact and arc root motion characteristics is established based on virtual binocular vision theory in this paper.The system consists of four parts:planar mirror imaging system,lighting system,fixture and image acquisition system.The internal and external parameters of the image acquisition system based on high-speed camera are obtained by Zhang Zhengyou's calibration method.And the accuracy of the test system is verified by testing and 3D reconstruction of the object with known size.The three-dimensional synchronous test system is used to test the contact moving process and the arc combustion process,and take the images of the contact and the arc during the breaking process of the contactor.Finally arc images are carried out the pre-processing,image enhancement,Gaussian filtering,edge detection,arc root extraction by the MATLAB software,and the three-dimensional curves of the contact and arc root is obtained by three-dimensional reconstruction based on binocular vision principle.The three-dimensional model of the contact is established and the trajectory of the arc root is drawn on the surface of the contact,and the three-dimensional movement of the contact and the arc root is visually displayed.The three-dimensional synchronous test system is applied for the test on the breaking arc of the contactor under the different conditions such as the initial breaking speed of the contact,load and external magnetic field.Three dimensional motion characteristics of contact system,arc root movement characteristics and variations of the arc diameter with time are analyzed under different conditions.The results show that increasing the initial breaking speed of the contact helps to promote the movement of the arc root and reduce the arcing time.Under the conditions of the same power but different resistive load,with the voltage increasing,larger contact gap is required in order to extinguish the arc.External magnetic field can make the arc move away rapidly from the contact surface,and greatly reduce the arc duration,so that the erosion of the arc on the contact is reduced.