Bearing voltages and associated bearing currents in electric machines driven by pulsewidth modulation converters with high switching frequencies and high dv/dt can cause premature bearing failures. This article proposes a new modeling approach for the prediction of steady-state and transient bearing voltages based on two-dimensional (2-D) electromagnetic finite element analysis with coupled external circuits using measured bearing capacitance values. The distributed-element external circuit was employed mainly to take into account the influence of wire distribution and frequency dependency, which are typically neglected by traditional equivalent circuits. The developed model was then used to simulate bearing voltages for various scenarios and evaluate the effectiveness of several easy-to-implement bearing voltage reduction methods from the perspective of machine design and manufacturing, such as using the insulated shaft and/or bearings, introducing additional insulation in the rotor, and changing the material of machine components. Experimental measurements are also provided to facilitate the analysis and validate the proposed approach.

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Published in IEEE Transactions on Industry Applications, v. 57, issue 5.

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The document available for download is the authors’ manuscript version accepted for publication. The final published version is copyrighted by IEEE and is available as: P. Han, G. Heins, D. Patterson, M. Thiele, and D.M. Ionel, “Modeling of bearing
voltage in electric machines based on electromagnetic FEA and measured bearing capacitance,” in IEEE Transactions on Industry Applications, doi: 10.1109/TIA.2021.3092700.

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The support of Regal Beloit Corporation, University of Kentucky, the L. Stanley Pigman endowment, and Ansys, Inc. is gratefully acknowledged.