On the Application of Extended Grounded Slot Electrodes to Reduce Noncirculating Bearing Currents

Abstract

Power-electronic-converter-induced motor bearing currents are a widespread problem in the field of electrical drives. Parasitic capacitances between the electrical machine's parts provide a path for leakage currents, which finally harm metallic ball bearings. Remembering that end-windings have a significant contribution in building up stray capacitances, a countermeasure affecting both the lamination stack and end winding areas is needed. This paper focuses on a countermeasure against the non-circulating bearing currents in the cluster of solutions at the motor side. Electrostatic shielding approach, which is a known principle to reduce capacitive couplings, is applied in electrical machines every now and then. In this work, the principle of slot-embedded grounded electrodes is extended to cover also the end-windings. Thus, the electrodes provide a better shaft-to-ground voltage mitigating effect compared to the case where electrodes are applied only in the lamination stack area. The feasibility and effectiveness of such a countermeasure are investigated. Different options in terms of scaling of both the machine size and diameter of the electrodes were analyzed and corresponding conclusions were pointed out.

Formation of Corrugated Damage on Bearing Race under Different AC Shaft Voltages

“…Many researchers have observed that an electric field between the inner and outer rings can lead to electrical erosion of the bearing surfaces [1]. Electrical damage to bearings has become a critical problem that affects the safe operation of electric motor systems [2][3][4]. Therefore, the mechanism of the electrical erosion of bearings has been extensively studied.…”

Novel Stator Slot Opening to Reduce Electrical Machine Bearing Currents

“…For the same target, Vostrov et. all suggested an extended ground electrodes to mitigate their circulation [15]. Alternatively, authors in [16] analysed the Daniele De Gaetano, Wenjun Zhu, Xiangyu Sun, Xiao Chen, Antonio Griffo and Geraint W Jewell are within the Department of Electronic and Electrical Engineering, The University of Sheffield, Sheffield, U.K..…”

Modelling and suppression of bearing voltage of wind turbine permanent magnet synchronous generators

“…This proportion is gradually increasing with the higher levels of power semiconductor devices and switching frequency [3]. Several factors can contribute to bearing failure, but the most significant one is bearing voltage [4][5][6]. The reason is the highfrequency common mode voltage produced by pulse-width modulation converter.…”

“…In addition to that, the maintenance costs are high. Electrostatic shielding by electrodes in slots is studied and the results indicate bearing voltage is mitigated effectively [5]. However, the method is suspected to be used in practical engineering.…”