Investigation of Material Transfer by 3D Precision Alignment of Topographical Data of Electrical Contact Surfaces

Material transfer in low-power direct-current switchgear is commonly known to cause contact failures to open due to mechanical interlocking, which is determined by (i) the shape of the material transfer pip-and-crater formation and (ii) the relative movement of the contact pieces during contact separation. A novel method is presented, which allows examining the shapes and relative positions of the material transfer pip and crater: first, the topographies of the two contacts are recorded by means of 3D optical profilometry; in this paper a confocal white light microscope was used. The two datasets of the topographies are then aligned and subsequently subtracted, using a custom developed software. As a result, the spatially resolved gap between the corresponding material transfer shapes on cathode and anode is obtained. The tendency towards interlocking can be expressed by combining the spatial assembly in the contact area and the relative movement of the contact pieces. First applications of this method for various contact materials are presented.