Evaluation of ferrite core EMI suppression under realistic working conditions

A novel measurement method is proposed to evaluate the performance of a ferrite core on a power cord under actual operating condition. The proposed method allows the common-mode impedance of a ferrite core under in-circuit condition to be measured so that it provides a more realistic assessment of the noise suppression capability of the ferrite core. With a pre-measurement characterization process, possible error due to parasitic effects of the measurement setup can be determined and eliminated. Hence, good accuracy is achieved for the proposed measurement method.