Prediction of common-mode current reduction using ferrites in systems with cable harnesses

Bulk ferrite chokes are widely used to reduce common-mode (CM) currents on system harnesses. The impact of the ferrite on the CM currents depends on a variety of factors and is difficult to predict. A simple closed-form analytical model of the CM impedance of the ferrite that allows efficient evaluation of the impact of the ferrite is considered. In order to apply this model to a real active power system with cable harnesses, information about the system's CM loop impedance is measured using the minimally-invasive dual current clamp method. The predicted impact of the ferrite on the CM loop impedance of the system and the CM currents on the harness showed reasonable agreement with measurements in both a simple passive test setup and in a real active system.