Technical Papers and Flyers

July 30, 2015
By Rachael Parker, Vice President of Fair-Rite Products Corp.
75-material for Low-Frequency EMI Suppression Demystified

Ferrites are ceramic components that can be used to suppress electromagnetic interference (EMI) in certain applications. This paper will discuss the basic properties of solid round ferrite cores, the impact an air-gap can have on the performance of these cores, and special considerations. In particular, this paper focuses on the use of 75-material in low-frequency suppression applications since its permeability is relatively high compared to other soft ferrites used for this purpose, making the effect of an air-gap much greater.

February 17, 2016
Fair-Rite Products Corp.
Automotive Flyer

Electronics are profoundly changing the automotive industry as the Internet of Things (IoT) and mobile connectivity become more prominent in our vehicles. Electronic content in cars has steadily increased, and this trend is only expected to accelerate. However, with the adoption of technology comes an increase in EMC, power and signal integrity issues. Coupled with growing concerns over robustness and safety, automakers are forced to strike a balance between cost, performance, and quality.

March 07, 2014
By Henry Ott Consultants
Ferrite Cores For Low-Frequency EMI Cable Suppression

Ferrite cores (chokes) provide an inexpensive, and effective, way of coupling high-frequency resistance into a cable in order to reduce the  common-mode current, and hence the radiation (or pickup) from the cable. They are commonly used  on mouse, keyboard, video, and other peripheral cables connected to personal computers, as well as on power supply cables when a device is powered from an external transformer (wall-wart) or power supply. The ferrite core acts as a one-turn common-mode choke, and can be effective in reducing the conducted and/or radiated emission from the cable, as well as suppressing high-frequency pick-up in the cable. Basically ferrites can be thought of as high-frequency resistors, with little or no impedance at low-frequencies or dc. Ferrite cores are most effective in providing attenuation of  unwanted noise signals above 10 MHz. The figure below shows a ferrite choke on a USB cable.

ch05fg32

For low-frequency cable emission problems, typically below 10 MHz, ferrite chokes have not been very useful, since their impedance is too low, at these frequencies, to be effective. I have always wished  for a similar, simple low-frequency solution to cable emission/susceptibility problems. My wish finally has been granted.

Recently Fair-Rite Products Corp. introduced a new low-frequency, Type 75, ferrite material optimized for EMI suppression in the 200 kHz to 30 MHz frequency range. This material has an impedance peak in the 1 to 2 MHz range. Information on the new Type 75 ferrite cores is included in Fair-Rite’s  17th edition catalog.

For example,  part number 2675540002 (9/16″ OD,  1/4″ ID , and 1-1/8″ long core) has a peak impedance of  160 Ω at about 1.6 MHz as shown below.

2675540002-1

Type 75 ferrite cores can be especially useful in reducing emission problems in the 500 kHz to 10 MHz frequency range, across which the impedance of the above ferrite is greater than 80 Ω..

The impedance of  ferrite cores can be further increased by using multiple turns. However, this also increases the inter-winding capacitance and degrades the high-frequency performance of the choke. Since the Type 75 material is intended for low-frequency use, this increase in capacitance is less of an issue, and two to five turns can be used with very little, if any, detrimental effect. The same 2675540002 core discussed above has an impedance of 1,400 Ω at 1.3 MHz when three turns are used, and an impedance of almost 4,000 Ω when five turns are used, see below. A three turn choke using this core will have an impedance greater than 500 Ω from 300 kHz to 20 MHz.

2675540002-2

Even at 150 kHz, the low-end of the FCC/CISPR conducted emission measurement range, the three turn configuration has an impedance of approximately 250 Ω, and the five turn configuration has an impedance of approximately 700 Ω. Therefore, by using multiple turns high impedances can now be obtained at these low-frequencies.

Both smaller and larger cores are available from Fair-Rite. Type 75 cores ranging from 3/8″ to 1-1/4″ OD (7/32″ to 3/4″ ID) are listed in the Fair-Rite catalog. At present only solid cores are available, but snap-on split cores should also be available later this year. Snap-on cores are convenient for troubleshooting, and can be easily applied as an after-the-fact fix to cables. Since the manganese-zinc (MnZn) Type 75 cores are slightly conductive (resistivity, ρ = 3×10^2 Ω-cm), care should be taken that they do not touch any live electrical terminals.

Give the new Fair-Rite Type 75 material a try for your low-frequency emission/susceptibility cable problems. You might be pleasantly suppressed with the results.

February 07, 2015
Fair-Rite Products Corp.
Cable Cores for EMI Suppression

With an assortment of materials to suppress frequencies from 100 kHz into the GHz range, Fair-Rite has the spectrum covered.

January 02, 2015
Fair-Rite Products Corp.
75 Material Snap-Its

Once again, Fair-Rite Products Corp. is the first to introduce an innovative solution to the electronics industry! Our new 75 material is now available in Snap-It form so you can quickly find a solution to your low-frequency noise issues. Providing enhanced impedance between 150 kHz and 10 MHz, this material is superior to any other product available on the market and delivers twice the impedance at 1 MHz.

August 01, 2007
By Carole Parker, President of Fair-Rite Products
Specifying a Ferrite for EMI Suppression

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.

 

August 01, 2002
By Fair-Rite Products Corp.
How to Choose Ferrite Components for EMI Suppression

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

January 08, 2011
Fair-Rite Products Corp.
Use of Ferrites in Broadband Transformers

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 levels.

 

February 12, 2015
Fair-Rite Products Corp
Flexible Ferrite Sheets

Fair-Rite’s Flexible Ferrite Sheets provide the benefits of soft-magnetic materials, while freeing you from their mechanical constraints! These materials are composed of NiZn to provide high-volume resistivity and high insertion-loss over a broad frequency range. Available in six material grades and four standard thicknesses as thin as 0.13mm, these RoHS compliant sheets come “scored” in a 2mm x 2mm rectangular grid.