Evaluation of EMI filter performance for uninterruptible power systems

When designing an uninterruptible power system, it is important to be able to predict the performance of the EMI filter accurately. In this paper, the effects of parasitic elements of the filter components and the noise impedance on the filter performance are evaluated. Methods to determine the values of the parasitic elements and the noise impedance are described. Based on the insertion loss, three situations are compared using two different filter topologies. It is shown that our approach can significantly reduce the discrepancy between the theoretical prediction and the measurement and thus is useful for the design of EMI filters