Influence of teeth and cooling ducts on the high-frequency common mode flux of inverter-fed AC machines

Inverted-fed asynchronous machines suffer from high-frequent common mode current components generating circumferential fluxes in the stator, rising a voltage drop along the shaft and possibly leading to endangering circulating bearing currents. The common mode current distribution in the stator laminations can be described by a 2D axisymmetric eddy-current model, which, however, neglects azimuthal asymmetries such as stator slots. In this paper, this model is extended to better reflect the geometry of the laminations. Furthermore, a finite-element model incorporating all cross-sectional details is constructed. A comparison of the extended models to the original one indicates that stator slots and cooling ducts housing can significantly influence the magnitude of the common mode flux.