An Experimental Investigation of Dynamic Welding Mechanism of Contacts Used in Low Current Switching Devices

Dynamic welding failure mechanisms of silver metal oxide composite contact are hot topics in the area of low current switching devices and electrical contact materials. What is the root reason for contact dynamic welding in electrical endurance tests? Is it the degradation of the physical properties of the material or the variations of mechanical operation characteristics or the changes in contact surface morphology? In this paper, a series of electrical endurance tests (including resistive load and capacitive load) are conducted by using our designed model switch. The typical waveforms of dynamic force during contact break are recorded, and then the extraction method for occurred welding force value is presented. Further, the variations in contact gap, arc energy, bounce arc energy, and static contact force as a function of operation cycles are analyzed explicitly. Particularly, the distribution of welding force are counted and explained with the change of collected parameters. Finally, the possible dynamic welding failure mechanisms of contact materials is proposed.