The evaluation of arc erosion on electrical contacts using three-dimensional surface profiles

Three-dimensional surface profiling is a useful technique for the evaluation 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 contacts to define erosion in terms of volume and height changes. Experimental 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 cycles. Emphasis is given to the evaluation of 3-D surface profile in the particular condition where the change of mass of the contacts is nearly zero after a large number of break only switching cycles, and it is shown that in this condition the contacts exhibit volume changes both above and below the datum surface of a new contact.