Method for Probing Plasma Bearing Currents

Abstract

In electric machines, electric currents that significantly reduce the service life of the bearings can occur. Bearing currents are electric currents that occur in rolling or plain bearings of electric machines. The invention relates to a method for the early detection of the development of damage in a bearing, in particular crater formation, owing to bearing currents as a result of a lack of heat dissipation in the case of a short discharge time, plasma formation being detected on the basis of the evaluation of an electromagnetic spectrum of the field strength that arises during the discharge. The solution is based on the following basic concepts: The discharges due to the bearing currents must be considered as a chronologically dynamic process. A discharge must occur within a short time, e.g., in the three-digit picosecond range, in order to produce craters that lead to groove formation. If the discharge occurs slowly, only melting and solidification with crater formation and low material removal occur. Said craters do not lead to groove formation. In contrast, if a faster discharge occurs, the heat dissipation is less.

Description

technical field [0001] Currents (bearing currents, English: Bearing Currents) that greatly reduce the service life of the bearings may appear in the motor. Bearing currents are currents that occur in the rolling or plain bearings of the motor. [0002] The bearing current is caused by a voltage (bearing voltage) generated by an electrical or magnetic leakage field inside the machine or by an externally applied current flowing through the machine. This current is generated once the bearing voltage exceeds the breakdown voltage (ablation voltage) of the lubricating oil film. [0003] Negative effects of bearing currents are, for example: [0004] - burns grease (reduces residual lubricity); [0005] - formation of pits (Kraterbildung) in raceways and rolling elements; [0006] - and in extreme cases: corrugations in the raceways. [0007] The corrugations are here transverse to the raceway. [0008] These bearing currents have been a well-known phenomenon for more than ten...

AI Technical Summary

Problems solved by technology

In between there is a large gray area including a large part of the drive system in which no conclusions can currently be drawn

[0011] Remedial measures for this bearing current are often very expensive and based on this large gray area it is difficult to assess whether this expenditure is sufficient

Nonetheless, these costly approaches have in the past partially failed to achieve the desired goals

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