On the role of the shaft end and the influence of frame size and load coupling on the RF emission characteristics of induction motors

A novel nonintrusive radio-frequency-based method to detect discharge bearing currents occurring in variable-speed drives has been presented previously. Further understanding of the emission characteristics of the discharge and of the electric machine in which it occurs will extend its areas of application. To this aim, this paper addresses the modeling of the machine as an antenna, identifying the shaft ends to play a key role in RF pulse transmissions. Experimental and theoretical studies are carried out for squirrel-cage induction machines of different shaft heights, with the lengths of shafts and loads connected through different forms of coupling.