Electric damage of bearing under AC shaft voltage at different rotation speeds

The breakdown characteristics and the electric damage of bearing were studied at different rotation speeds. The breakdown voltage of bearing could be defined as the instantaneous voltage corresponding to the zero point of the first derivative of equivalent resistance. Under the combined effect of frictional heat and electric heat, the breakdown voltage decreased with the rotation speed. The relationship between lubrication leakage rate and bearing temperature was consistent with the Arrhenius formulation. After breakdown, electric erosion began to form on the raceway and roller. The enrichment of carbide was observed beneath the breakdown surface, indicating a tempering effect of martensite. The hardness analysis suggested that there was a competition be-tween friction-induced hardening and current-induced softening on the bearing surface.