HF near-field probe for magnitude measurements of EDM bearing currents

Different kinds of bearing currents occur in modern electric motors fed by variable-speed drives. Meanwhile, knowledge of the bearing impedance behavior and its effects on various types of bearing currents is accumulating, which leads to a conclusion that an approximation-based approach to determine the aging impact of bearing currents is challenging. A further issue is the stepwise aging mechanism that also necessitates continuous online monitoring. In this paper, a novel magnetic-near-field probe to measure the magnitude of bearing currents is designed and tested. It is found that the nonintrusive probe is a key element in order to design a feasible, nonintrusive, low-cost online monitoring system for bearing current magnitude measurements.