On radio-frequency based detection of high-frequency circulating bearing current flow

The possibility of bearing damage caused by inverter-induced bearing currents in modern variable-speed drive systems has been well recognized today. Further research is needed to develop appropriate nonintrusive methods for detection and monitoring of such currents. A radio-frequency-based nondestructive method has been applied to detect discharge bearing currents. The method is understood to work on the energy that is radiated in the electric field during the bearing discharge event. We show that the method is also applicable to high-frequency circulating bearing currents that have so far been associated with ohmic bearing characteristics and no discharges occurring. The analysis and understanding of the applicability of the method to detect such currents also contributes to further understanding of the electric characteristics of the bearing, notably the moment the current conduction begins.