Effectiveness Assessment of a Nanocrystalline Sleeve Ferrite Core Compared with Ceramic Cores for Reducing Conducted EMI

Abstract

The interconnection of different electronic devices or systems through cables is becoming more difficult due to the hard restrictions related to electromagnetic compatibility (EMC) in order to comply with requirements. Therefore, the use of EMC components is a good solution to manage the problems associated with the filtering of electromagnetic interference (EMI) in cables and to pass the compliance test. In this sense, sleeve ferrite cores become a very interesting solution since they can be set around a wire and, hence, they provide an effective solution against EMI without having to redesign the electronic circuit. This contribution is focused on the characterization of the performance of a sleeve ferrite core based on a novel nanocrystalline (NC) novel material for EMI suppression and comparing it to the most conventional ceramic ferrite cores such as MnZn and NiZn. The research highlights the suitability of an NC novel component in terms of its magnetic properties to reduce EMI within the conducted emissions range. This range is generally defined by the International Special Committee on Radio Interference (CISPR) test standards frequency band that covers from 150 kHz up to 30 MHz (108 MHz in the case of CISPR 25). First, this study presents a description of the main parameters that define the behavior of NC and ceramic cores and, secondly, by analyzing the data obtained from experimental procedures, it is possible to directly determine the insertion loss parameter. Hence, this characterization procedure is used to obtain the performance of NC material compared to the conventional sleeve ferrite core compositions employed to filter the interferences in this problematic frequency range. As can be deduced from the results obtained, an NC sleeve ferrite core provides the best performance in terms of EMI filtering within a significant frequency range between 100 kHz and 100 MHz.Electronics 2019, 8, 800 2 of 21 circuit. The most common sources of these interferences include natural ones (such as atmospheric electrical phenomena), power lines, auto ignition or radio frequency (RF) interference.In terms of the kind of disturbance that is transmitted, EMI is divided into two categories: conducted and radiated emissions; regarding the way the electromagnetic field is propagated. In the case of radiated EMI, it is caused by induction whereas conducted EMI is generated by physical contact of conductors. Thus, in the low frequency range EMI is generally emitted via conduction and, in the high frequency region via radiation. Likewise, conducted EMI can be classified into two kind of currents in terms of different directions of leading: differential mode (DM) and common mode (CM) [3]. In the correct working of a circuit, a differential current is designed to flow in order to obtain a clear signal. When opposing currents are created and flow in the same direction as the intended current, the differential intended currents are canceled. In CM, currents flow in both conductors in the same direction and are not suppressed as ...

Characterization of Nanocrystalline Cores for EMI Suppression in Cables

“…In these photographs, it is possible to observe the internal structure and the grain size of MnZn (a) and NiZn (b) ceramic materials. The results presented in [19,20] highlighted the great suitability of NC EMI suppressors to filter electromagnetic interference throughout the frequency band from 100 kHz to 100 MHz. Furthermore, data obtained from its magnetic properties indicate that this EMC solution could also provide good performance in terms of EMI suppression at higher frequencies.…”

“…Nanocrystalline sleeve core represents an innovative and increasingly used solution for EMI suppression in cables. This solution has demonstrated excellent suitability to reduce interferences from the low-frequency region to the mid-frequency range [19,20]. In this sense, some researchers have investigated the use of NC structure compositions to make EMC components because this kind of core can reduce its volume by 50-80% and yield greater magnetic properties and insertion losses than conventional ceramic components [21][22][23][24].…”

“…Thereby, MnZn materials can provide a significant performance for EMI suppression applications, covering the range of frequency from hundreds of kHz to some MHz. In contrast, NiZn materials are intended for a higher frequency operation than MnZn, covering from tens of MHz to several hundreds of MHz [16,19,20,27].…”

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

“…One of the main advantages of MnZn and NiZn materials is the possibility of creating cores with many different shapes and the possibility of halving them without modifying their internal structure [17,18]. Preliminary studies have shown that NC sleeve ferrite cores provide a significant effectiveness when used as an EMI suppressor [17,19,20]. Nevertheless, the internal structure and manufacturing process have traditionally made it complicated to obtain a split-core sample that can be used as a snap ferrite, keeping its effectiveness.…”

“…This analysis is performed through an experimental measurement setup that is compared with the results obtained through a finite element method (FEM) simulation model. The simulation model helps to determine the study's accuracy, specifically in the high-frequency range where parasitic elements may affect the experimental results [20]. Likewise, the stability of three solid (not split) and split cable ferrites based on different compositions are characterized in order to determine the influence of DC currents on the impedance response provided.…”