Investigation of Electrostatic Shieldings in Traction Motors to Mitigate Capacitive Bearing Currents

Electrostatic shieldings in electrical machines have the capability to mitigate harmful capacitive bearing currents. By employing Finite Element (FE)-simulations, the shieldings' effectiveness, influence on parasitic capacitances, and the associated eddy current losses are investigated. The study includes various shielding designs for both, the stator and end-winding part of a motor. Based on the knowledge gained by the Finite Element Analysis (FEA), motorettes with slot-shieldings and stators with overhang shieldings were built. Finally, the study presents the validation of the slot-shieldings' effectiveness by impedance measurements. The measurements confirm a reduction of the winding-rotor capacitance up to approx. 84 %. A large focus is given to the development of an appropriate design regarding its suitability in series production.