Mitigating noncirculating bearing currents by a correct stator magnetic circuit and winding design

Abstract

Different mechanisms by which bearing currents flow inside the electrical machine are well studied. In contrast, investigation and development of different techniques to mitigate these currents remain a field for improvement, and the final common solution to the problem has not been provided yet. In pursuit of addressing the problem, this paper deals with noncirculating (or capacitive) bearing currents. The circuit mechanism of capacitive currents is explained in brief, and an approach for their mitigation is introduced. The paper studies the influence of the stator winding and the slot geometry and presents different geometries to modify the motor to reduce the capacitive bearing currents. The effectiveness of the proposed mitigation technique is shown by finite element-based modeling and verified by laboratory tests with different induction motor designs, where the winding and magnetic circuit geometries are varied. The technique can be used, in particular, for the mitigation of noncirculating currents, but it also offers potential for further research.