Electrostatic shielding for bearings discharge currents attenuation: Analysis of its effectiveness, losses and impact on the motor performance-a study for design guidelines

Abstract

The authors deal with the use of electrostatic shielding to mitigate the electric discharge machining (EDM) currents on the induction machine bearings. Employing 2D and 3D models, several finite element analysis (FEA) simulations were thoroughly made addressing the shielding effectiveness to attenuate the shaft-to-frame voltage and the associated eddy current losses for different shield widths, thicknesses and materials. The obtained results provide very good guidelines for the practical design of the shielding device. In addition, comparisons between frequency-and time-domain models highlight the importance of considering factors such as the saturation of the iron core, the rotor movement and non-sinusoidal sources to compute the eddy current losses in the shield. Besides, the authors present a comprehensive theoretical review of the EDM currents, where the main influencing factors and action mechanisms are compiled in a clear and didactic approach, for the purpose of broad comprehension.