Statistical approach to discharge bearing currents

Abstract

Purpose

The purpose of this paper is to propose a statistical approach, which enables the prediction of the risk of the appearance of discharge bearing currents in a given drive that can damage the motor bearings. Using such an approach, the drives for the decisive but expensive, long‐term destructive investigations can be selected. A comparative analysis is presented to show the applicability of the presented statistical model.

Design/methodology/approach

In the paper, a statistical approach to large data sets of measured bearing currents is presented. Weibull distribution has been chosen to describe the amplitudes of bearing currents, whereas exponential distribution is used for the approximation of the awaiting times to puncture. In order to check the hypothesis that these distributions are independent two tests has been conducted: F‐Snedecor, to check equality of mean values and Bartlett's to check variance equality. On this basis, joint distribution is expressed as the product of independent marginal distributions.

Findings

The comparative analyses show that special caution is required for a proper selection of EMI filters. The additional inductance of the filter in a common mode (CM) current path decreases the damping factor of the circuit and significantly increases the risk of bearing damage caused by electric discharge machining currents. The CM transformer is a cheap and effective solution that reduces CM current without increasing the rate and the amplitudes of bearing currents.

Originality/value

This paper presents a new approach to bearing currents that allows prediction of the risk of bearing damage in a given drive.

Citation

Smolenski, R., Kempski, A. and Bojarski, J. (2010), "Statistical approach to discharge bearing currents", COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, Vol. 29 No. 3, pp. 647-666. https://doi.org/10.1108/03321641011028233