THE EVALUATION OF ARC EROSION ON ELECTRICAL CONTACTS USING 3-DIMENSIONAL SURFACE PROFILES

Three-dimensional surface profiling is a useful technique for the eval uation of electrical contact erosion. A review is given of the various methods by which a 3-D surface profile can be measured, and numerical techniques are described which can be used to analyze electrical cont acts to define erosion in terms of volume and height changes. Experime ntal data on the rate of change of mass of Ag-CdO contacts are used to compare with volume and height changes over a number of switching cyc les. Emphasis is given to the evaluation of 3-D surface profile in the I;articular condition where the change of mass of the contacts is nea rly zero after a large number of break only switching cycles, and it i s shown that in this condition the contacts exhibit volume changes bot h above and below the datum surface of a new contact.