Performance Study of Split Ferrite Cores Designed for EMI Suppression on Cables

Abstract

The ideal procedure to start designing an electronic device is to consider the electromagnetic compatibility (EMC) from the beginning. Even so, EMC problems can appear afterward, especially when the designed system is interconnected with external devices. Thereby, electromagnetic interferences (EMIs) could be transmitted to our device from power cables that interconnect it with an external power source or are connected to another system to establish wired communication. The application of an EMI suppressor such as a sleeve core that encircles the cables is a widely used technique to attenuate EM disturbances. This contribution is focused on the characterization of a variation of this cable filtering solution based on openable core clamp or snap ferrites. This component is manufactured by two split parts pressed together by a snap-on mechanism which turns this into a quick, easy to install solution for reducing post-cable assembly EMI problems. The performance of three different materials, including two polycrystalline (MnZn and NiZn) materials and nanocrystalline (NC) solution, are analyzed in terms of effectiveness when the solid sleeve cores are split. The possibility of splitting an NC core implies an innovative technique due to the brittleness of this material. Thus, the results obtained from this research make it possible to evaluate this sample’s effectiveness compared to the polycrystalline ones. This characterization is carried out by the introduction of different gaps between the different split-cores and analyzing their behavior in terms of relative permeability and impedance. The results obtained experimentally are corroborated with the results obtained by a finite element method (FEM) simulation model with the aim of determining the performance of each material when it is used as an openable core clamp.

Characterization of Nanocrystalline Cores for EMI Suppression in Cables

“…The intended (DM) current is not affected by the presence of the cable ferrite because the DM current travels in opposite directions and is transmitted through the signal and returns. Thus, the current of the two conductors is opposing, meaning they cancel out and the cable ferrite has no effect [10,11]. In the case of wanting to filter the DM currents, it would be necessary to use a sleeve core in each of the cable's conductors.…”

“…This treatment modifies the magnetic properties and the amorphous structure forms ultrafine crystals with a typical size of 7-20 nm, obtaining the nanocrystalline material. The last stage of this procedure corresponds to applying a protective coating or a plastic housing that protects the obtained cores due to the brittle nature of the tape [11,18,28].…”

Analysis of Compromising Video Disturbances through Power Line

“…There are studies that provide the calculation of geometric dimensions for these ferrite rings [ 32 , 33 , 34 , 35 ], but a good starting point for people not specialized in this field are the ferrites rings applied on the video cables for the VGA interface.…”

Methods of Assessing the Effectiveness of Filter Elements in Power Electronics

“…The most common materials that absorb electromagnetic waves in filters are ferrites. The advantages of ferrites are profitability, excellent magnetic losses, and work stability [6].…”