Suppression for Discharging Bearing Current in Variable-Frequency Motors Based on Electromagnetic Shielding Slot Wedge

High-frequency current in the bearings of variable-frequency motors coupled with their shafts is a common issue that will shorten the bearings lifetime ultimately. A new method, which could be used to suppress high-frequency discharge bearing current, was proposed in this paper. In this method, an electromagnetic shielding slot wedge (ESLW) was used to reduce the capacitive coupling between the stator windings and the rotor. The electromagnetic coupling resulted from the common-mode voltage could be blocked by this electromagnetic shield layer. In addition, the mathematical model of the suppression method was given and the high-frequency electromagnetism performance of the motor was analyzed. Finally, an experimental platform was setup and a motor was modified to evaluate the suppressing effectiveness. The shaft voltage, bearing currents, and the general features of the modified motors, with and without ESLW, were measured and compared.