Assessment of anodic aluminium oxide coatings towards an alternative solution to spark erosion damage of bearings

This thesis is based on a cost effective solution for an on going issue; Bearing failure due to electrical leakage [1] in variable speed AC motors. Due to current leakage across the bearing rings there would be a high intensity sparks generated at the contact points and we will notice a premature bearing failure, if it’s a small motor the whole motor should be discarded. The actually problem of this issue is not the issue but the cost of the present available solutions which makes the bearing so expensive that practically it’s not economical to be used in small motors and could be viable to be used only where the cost is not a criterion. In this thesis we are replicating a concept of the available solution, but implementing in a new way. One of the available solution is, aluminium oxide is plasma coated on the outer ring of the bearing to provide a high insulating layer to cut off the current that were leaking across the bearing rings. Hence terminate the possibility of sparks at contact point. Our concept is indeed anodizing an aluminium sheet metal pressed in the form of cap which covers the outer ring of the bearing during installation into the motor housing. This thesis is mainly focused on the characterisation of the mechanical properties of the aluminium oxides to suite the plasma coating aluminium oxides hardness [1.3.1]. Hence we drive different combination of aluminium anodized samples to achieve the most optimistic sample. Further, we are not determining any electric properties of the oxides, but we made a sincere attempt to give a short preview on the methods used to determine the electrical properties of the anodized aluminium oxide and the parameters affecting it. The over all main aim of the thesis is to provide a cost effective solution for the issue that is derived in the Chapter 1.