Unexpected Common Mode Choke Saturation

This paper presents an analysis of common mode choke (CMC) saturation. Next to a phenomenon of CMC saturation due to leakage inductance, a saturation caused by unbalanced impedance leading to mode conversion is discussed. A measurement setup mimicking the unbalanced condition, evaluating the saturation of the CMC under the dc bias is presented. Several CMCs made with nanocrystalline and ferrite cores, of various core sizes and a number of turns have been evaluated.