Experimental Investigation of Contact Welding Characteristics of Electromechanical Relays

Contact dynamic welding failure problems seriously limit the electrical lifetime of electromechanical relay. However, the welding behavior occurred in contact making and breaking process and relevant influencing factors are still unknown. In this article, a series of experiments are carried out in make only, break only, and make & break (M&B) operation modes individually to differentiate the effects of making and breaking processes on contact dynamic welding. The typical dynamic force and electrical waveforms of contact making and breaking processes are obtained and the statistical results of welding force are presented. The roles of bounce arc and molten bridge in welding force are interpreted explicitly by using the variations in electrical parameters such as bounce energy, contact resistance, molten bridge energy, break arc energy, and surface substructure morphologies. It is determined that the bounce arc plays a crucial role in the formation of weld nugget and strength, and the strongest welding occurs in the M&B operation mode.