Impact of Motor Stator Winding Faults on Motor Differential-mode Impedance and Mode Transformation

Motor impedance and mode transformation have significant effects on the electromagnetic interference (EMI) generated in motor drive systems. Stator winding faults commonly cause motor failure; however, in their early stages, they may not affect the short-term operation of the motor. To date, EMI noise under the influence of premature stator winding faults has not been adequately studied, particularly the differential-mode (DM) noise due to the common-mode (CM)-to-DM transformation. This study investigates and quantifies the influence of stator winding faults on the motor DM impedance and mode transformation. First, the transmission line model of an induction motor is described based on the scattering (S) parameter measurements of each phase of the motor. It offers the flexibility to emulate different types of stator winding faults at specific locations and various severities, such that the impacts of the faults on the motor DM impedance can be easily estimated. Second, a test setup is proposed to quantify the CM-to-DM transformation due to the stator winding faults. The findings of this study reveal that even the early stages of stator winding faults can result in significant changes in the DM noise.