Common-mode DC-bus filter design for variable-speed drive system via transfer ratio measurements

Filters used in electromagnetic interference suppression are often described in literature on drive systems and have become a standard solution in industry. The effect of the commercial off-the-shelf filter depends significantly on how it is installed. A model that includes the installation parameters is made first and then the parameters of the model are extracted by transfer ratio measurements. One possibility is to include the filter on the dc-bus inside the converter. The differential mode dc-bus filter is well known, but the common-mode dc-bus filter has received little attention. Our model is used to show that the common-mode dc-bus filter can achieve the same or even better suppression of common-mode noise by careful design. The transfer ratio is used to evaluate the performance of filter design.