Modeling the Probability of Oil Film EDM Breakdown in High Power Inverter Motor Bearings

doi:10.3901/JME.2025.17.137

Abstract

Abstract: With the wide application of pulse width modulation technology and the rapid increase of bus voltage of variable frequency motor, the shaft current damage of high power variable frequency motor has become the dominant factor of bearing failure in wind turbine, rail transit traction motor and other fields. Aiming at the problem of evaluating the micro-damage probability of bearing current in high-power variable frequency motor, considering the influence of micro-roughness of bearing raceway, the calculation method of oil film partial pressure and withstand voltage is proposed, and the EDM breakdown probability model of bearing oil film in variable frequency motor is constructed. The oil film breakdown probability and shaft current density of the non-drive end bearing of 190 kW traction motor are calculated analytically. The modeling results are similar to the shaft current damage in the actual service of the bearing, which verifies the validity and reliability of the model. The results show that the shaft current damage is usually concentrated at the maximum load ball in the Hertz contact area of the inner ring or the outer ring of the bearing, and the possibility of breakdown discharge of the oil film is the highest. The insulating bearing can effectively suppress the breakdown probability of the oil film and the shaft current density by relying on the small capacitance partial pressure and large resistance blocking characteristics of the coating.

Key words: shaft current damage, minimum oil film thickness, breakdown probability, insulated bearing

CLC Number:

TH133

LI Xuejun, LIAO Haize, TANG Hujiao, ZHOU Xianwen. Modeling the Probability of Oil Film EDM Breakdown in High Power Inverter Motor Bearings[J]. Journal of Mechanical Engineering, 2025, 61(17): 137-149.

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