Effect of Voltage Frequency on the Formation of Electric Damage on Bearing Outer Race

Abstracts: Electrical erosion in high-frequency alternating current (AC) electric fields is the main failure mode of traction motor bearings in fields such as new-energy vehicles. The electrical damage on the outer race of bearings was produced from direct current (DC) to 1 MHz AC condition. The average friction coefficient increased from 0.019 to 0.097 and then decreased to 0.052. The equivalent contact resistance decreased to its minimum at 0.99 Ω then rose to 2.6 Ω. Three electric erosion morphologies were observed: pitting under DC and low frequency, fluting under resonance frequency (1 kHz) and frosting under high frequency. It was speculated that the frequency may affect the number of charge-discharge cycles of the bearing capacitance. This further affected the energy density of the bearing breakdown together with the current density, ultimately affecting the morphology of electrical corrosion.