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Using Ruggedized EMI Filters To Pass The CS101 Requirement Of MIL-STD-461D-F

by Kevin Seaton and Leonard Leslie, VPT, Blacksburg, Va, How2Power Today, May 15 2014

Focus:
Power systems designed for military applications that require compliance to MIL-STD-461D-F must use an input EMI filter (ahead of the dc-dc converter) that contains adequate damping to meet the conducted susceptibility requirements of CS101. The risk of failing the CS101 test is often highest in the mid-frequency range, which includes the EMI filter cutoff frequency where some filters exhibit peaking in their responses. Put another way, an input filter without adequate damping may enable the power system (i.e. the EMI filter plus dc-dc converter combination) to pass conducted emission requirements, but may amplify input power bus ripple at the filter cutoff frequency to the point where the power system fails the conducted susceptibility requirements of CS101. In this article, the CS101 requirements are examined and their implications for the design of the power system are discussed. While this material is aimed more at those who will specify rather than design an input EMI filter, there are practical details here that may be helpful for those building their own filters. The article concludes by discussing testing precautions that designers should observe.

What you’ll learn:

How to meet the CS101 conducted susceptibility requirement of MIL-STD-461D-F by employing an input EMI filter with adequate damping
How to perform the CS101 conducted susceptibility test required of MIL-STD-461D-F on a power system

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