Effect of lubrication conditions in rolling element bearings of electric machines

Abstract

This aim of this literature is the investigation of the effects of lubrication conditions on the dynamics of rolling element bearings using MATLAB and the specialised RoBeDyn toolbox for computational simulations. Bearings cause about 40-50% of electric motor failures, with insufficient lubrication being the cause of about 80% of said failures. Three different scenarios, under-lubricated, well-lubricated, and over-lubricated were compared using the rotor model with the Hertzian contact of ball bearing parts as base for its stiffness. Using the Hamrock-Dowson model of EHL film thickness to evaluate six viscosity levels of mineral oil, from ISO VG 10 to ISO VG 150. Insufficient lubrication increases stiffness and raises critical speeds. Over-lubrication reduces efficient stiffness thus reducing critical speeds and raising viscous energy losses. The main finding of this literature is the trade-off between controlling vibrations and saving energy. ISO VG 46-68 mineral oil is best suited for general-purpose electric motor bearing use. Investigations with more experiments and lubrication-dynamics interaction models would validate findings on this investigation.