ABSTRACT
In this chapter, consideration is given to the events occurring when switching low current, typically up to 30 A, at voltages below 300 V. Switching devices used in this range are normally mass produced and are generally optimized for a low number of component parts. It has been shown in the previous chapters that the phenomena associated with switching contacts and stationary contacts can be both complex and difficult to predict. The weakness and potential for failure of the electrical contact interface stems from the extreme operating conditions implicit with the interface. Some of the major mechanisms leading to failure are chemical corrosion owing to the environment, arc erosion, material transfer in the plasma developed between the contacts at opening and closing, and mechanical wear owing to sliding, rolling, and fretting motions. Often the overall wear can be a complex interaction of these processes, the study of which has necessitated an interdisciplinary approach. In addition to the electrical contact phenomena, a switching device will also be influenced by the mechanical action of the mechanism used. The mechanism used in a low-current device can often appear to be simple; however, in-depth studies reveal complex mechanical dynamic characteristics during switching.
