Different EMI filters have been designed for an industrial power electronic converter system and a study on the performance of these different input filter topologies has been performed. Based on one filter topology a study on the influence of the orientation and direction of the windings on the CM chokes and the resulting coupling between two CM chokes as well as with the X capacitors has been performed. This study has shown a large dependency of the filter effectiveness on the CM chokes winding orientation and direction, both for DM and CM noise. This dependency is due to the varying inductive coupling between the two CM chokes as well as between the CM chokes and the ESL of the X capacitors. Also a study of one filter employing an LC band-rejection network to filter the resonant converter switching frequency has been performed.