How Active EMI Filter ICs Reduce Common-Mode Emissions In Single- And Three-Phase Applications (Part 3): Modeling Nanocrystalline Chokes

Focus:

Part 2 discussed impedance characterization of a ferrite choke using a behavioral mode as an essential step in EMI filter design. This task becomes more challenging when the core material is nanocrystalline due to its frequency-dependent and nonlinear magnetic permeability. This part 3 article examines comprehensive simulation models for nanocrystalline-cored chokes for use in passive and active filter circuits. Following a review of complex permeability and its impact on the impedance behavior of ferrite and nanocrystalline chokes, this article describes a SPICE-compatible behavioral model for a nanocrystalline CM choke using an intuitive ladder circuit structure. Using an extraction procedure of model parameters from measured impedance data, the synthetized behavioral model for the choke impedance can accommodate single- and three-phase chokes. The article concludes with a practical example, applying the modeling procedure to a three-phase four- winding nanocrystalline choke used in an EMI filter for an automotive onboard charger application.

What you’ll learn:

• How to generate a SPICE-compatible model for nanocrystalline-core common-mode chokes in EMI filters
• How to design active EMI filter circuits

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Author & Publication:

Timothy Hegarty, Texas Instruments, Phoenix, Ariz., How2Power Today, Mar 15 2024

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