In many transformer designs ferrites are used as the core material. This article will address the properties of the ferrite materials and core geometries which are of concern in the design of low power broadband transformers. Broadband transformers are wound magnetic devices that are designed to transfer energy over a wide frequency range. Most applications for broadband transformers are in telecommunication equipment where they are extensively used at a low power level.
The high-Q achievable by self-resonant structures increases the range and efficiency of wireless power transfer (WPT). However, to date implementations of this structure have been thick, which limits their practical implementations. In the attached paper, they explore the design of thin self-resonant structures. Looking into a computationally efficient 2-D optimization algorithm is proposed to design thin resonant structures and illustrate the trade-offs in the design, and a new magnetic core shape is proposed which shapes the magnetic field lines to be parallel to the conductive layers and reduces current crowding.
Our past article (see “How to Choose Ferrite Components for EMI Suppression,” Conformity, June 2002) was intended to help design engineers optimize the performance of ferrite materials by analyzing the effects of frequency, field strength, temperature and core geometry. In our ideal world, safety (including effect on environment), quality and performance are paramount.
This presentation was given at APEC 2016 on Low Loss 67 Material by our Vice President Rachael Parker. Click on the presentation to view.
Fair-Rite presents this information from the March/April 2022 issue of On the Air with express written permission from ARRL. No further distribution is permitted.
How to Choose Ferrite Components for EMI Suppression.pdf
The following pages will focus on Soft Ferrites used in the application of electromagnetic interference (EMI) suppression. Although the end use is an important issue and some applications are mentioned, this technical section is not intended to be a design manual, but rather, an aid to the designer in understanding and choosing the optimum ferrite material and component for their particular application. Ferrite suppressor cores are simple to use, in either initial designs or retrofits, and are comparatively economical in both price and space. Ferrite suppressors have been successfully employed for attenuating EMI in computers and related products, switching power supplies, electronic automotive ignition systems, and garage doors openers, to name just a few
The range and efficiency of wireless power transfer systems are limited by the quality factor of the transmit and receive coils used. Multi-layer self-resonant structures have been proposed as a low-cost method for creating high-Q coils for high frequency wireless power transfer. In these structures thin foil layers are separated by a dielectric material in order to form a capacitance that resonates with the inductance of the structure, while also forcing equal current sharing between conductors. In order to reduce winding loss, these structures are made with foil layers much thinner than a skin depth, which makes the layers of the structure extremely difficult to handle. In this paper, we present a modified self-resonant structure in which the layered conductors are made from standard PCB substrates with no vias. The PCB substrates provide an inexpensive way to handle thin conductive layers, and the modified self-resonant structure ensures that the poor dielectric properties of the PCB substrates do not impact the quality factor of the structure. The modified self-resonant structure makes it feasible to achieve advantages similar to litz wire, but at multi-MHz frequencies where effective litz wire is not commercially available. Experimental results show that the structure has a quality factor of 1177 at 7.08 MHz, despite only being 6.6 cm in diameter. The quality factor normalized by the diameter is more than 6.5x larger than other coils presented in the literature.
Construct an easy-to-build choke balun for use on the amateur radio bands that covers 160 through 10 meters and uses a Fair-Rite Products FR31 core.
Ferrites are offered in a wide variety of material grades and geometries to suit different applications. Often, a particular geometry may be offered in multiple material grades. In order to find a suitable replacement; Sometimes it is necessary to evaluate a ferrite core to determine what type of material it was made out of. There are many distinguishing characteristics separating different ferrite material grades but, the main material characteristic is initial permeability. This paper explains how to evaluate a core for initial permeability along with a simplistic surface resistance test. These two characteristics can give a good estimation for the material grade and type of a ferrite.
Design Considerations for High Frequency Magnetic Materials.pdf
In a developing market where miniaturization of designs has become critical, operating frequencies of magnetics have been increasing in order to minimize their size. As a result, engineers have a lot to consider when selecting magnetic components for their designs. Join us with John Lynch, Director of Engineering at Fair-Rite, as he discusses the role of ferrites in power supplies. John’s presentation will address the advantages of ferrites in power supply designs, the important parameters of ferrite materials, the impact of these parameters on performance, guidelines to select your ferrite material, and optimizing configuration based on design limitations.
