Determination of Core Size Dependency on the EMI Suppression in Cable Ferrites

Electromagnetic Compatibility (EMC) engineering should be approached via the systems approach, considering EMC throughout the design to anticipate possible electromagnetic interferences (EMI) problems. Nevertheless, an EMI source may appear when the designed device is supplied via an external power system or it is connected to another device to communicate to it. In these both cases, the cables or interfaces that interconnect the systems could represent the EMI source. Thereby, one of the most common techniques for reducing EMI in cables is the application of an EMI suppressor such as sleeve ferrite cores to them. The advantage of this solution is that it does not involve redesign the electronics and, generally, the mechanical redesign. This is an interesting point since the analysis at this time to find which of the possible interference path combinations are contributing to the problem may not be simple. However, this solution involves the addition of an extra component whose drawbacks result in increasing the size and weight of the product besides the cost of the filtering component and its installation. This contribution focuses on characterizing the performance of different cable ferrites based on the same material composition with the aim of determining the core size dependency in terms of the EMI suppression. The results presented show the relation between core inductance, dimensions and impedance as well as how to determine the optimum core size.