Steady-state Thermal Analysis of the Contact in Bearings Exposed to Electrical Currents

Electrical bearing currents, e.g. in inverted-fed electrical machines, may disturb the performance of the bearings. In this paper the steady-state temperature of the bearing surface at the electrical contact point between the balls and the raceway is derived in the mixed lubrication state. The thermal analysis is presented based on the Holm's electric contact model, namely the a-spot. The contact model of Andreason is presented as well for comparison. The results are extended to predict the instantaneous contact surface temperature in an axial bearing (type 51208) at 500 rpm with 1 A average bearing current and with an axial bearing force of 800 N. Moreover the average of the contact surface temperature is obtained for the same bearing in a range of operating points, i.e. a rotating speed from 0 rpm to 3000 rpm, a bearing average current from 0.25 A to 3 A, at an axial bearing force 800 N. The results can be utilized to predict the contact temperature on the bearing surface for any given bearing from the measured bearing voltage.