An innovative jig to test mechanical bearings exposed to high voltage electrical current discharges

Abstract

Premature bearing failures due to Electrical Current Discharge (ECD) has been recognised for almost a century. The purpose of this paper is to present an innovative jig that may be used to expose mechanical bearings to ECD, in order to clarify its associated effects on the bearing that need to be understood before any mitigating techniques can be proposed. An experimental design is used in this study. A method is presented using an ignition coil wiring harness of a vehicle to safely induce ECD across a specific bearing. Three samples were used and analysed with an optical and electron scanning microscope. The used ball bearing exposed to ECD showed micro-cratering, a result of electric current passage. Micro arching marks on the raceway surface of this bearing was also visible, and especially near the groove of the synthetic rubber seal and steel plate slinger. Surface pits were observed which were produced by electrical arching. A few deep scratches and indentations were observed on the raceway surface. This is due to abrasive wear particles embedded in the raceway surface sliding between the major bearing components. The aspect of electrical pitting wear and debris found in the lubricating oil are unknown and deserve further research from a tribological point of view. A recommendation is made to use this innovative jig to test the impact of ECD on bearings from other suppliers.