High-Density EMI Filter Design for Dc-Fed Motor Drives

This paper presents various strategies in a systematic way to reduce both differential mode (DM) and common mode (CM) noise using passive filter in a dc-fed motor drive. The type of grounding and components used is the key to a good design in order to optimize filter size and performance. Grounding schemes, materials comparison (ferrite vs. nanocrystalline core) and a new integrated filter structure are addressed. The latter maximizes the window area of the ferrite core and increases its leakage inductance by integrating on the same core both CM and DM inductances. Small- and large-signal experiments are conducted to verify the validity of the structure showing an effective size reduction and a good improvement at low and high frequency.