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Ferrite:
EMI Suppressor materials
Steward's nickel-zinc ferrite parts are used extensively in the suppression
of electromagnetic interference, commonly known as EMI. Suppression of
EMI has become a major concern in the transmission, reception, and processing
of electronic intelligence. Ferrite materials exhibit varying magnetic
properties depending on the frequency at which they are excited. In electronic
applications, the relation of the magnetic loss to frequency is utilized
to attenuate high frequency interference where the material's losses are
high, yet pass lower band where data is carried. By changing the ferrite
composition, it is possible to enhance attenuation in selected frequency
ranges. Steward offers a family of ferrites with varying compositions to
allow the user to select the optimal type for the application.
Ferrite:
Wide Band Transformers & Filter Cores
Steward's manganese-zinc and nickel zinc ferrite toroids range in initial
permeabilities from 16 to 10,000. These products are used primarily in
pulse transformers, isolation transformers, dataline and power filters,
and ground fault interrupters. Parts are available bare or coated.
Ferrite:
Copier Developer Materials
Steward is the custom manufacturer of carrier bead ferrite materials
for dual-component xerographic applications. A wide range of particle distributions
and properties is available. Our carrier bead powders are supplied to coy
machine manufacturers around the world.
Ferrite:
Fine Loading Powders
Steward produces a wide selection of sintered fine particle ferrite
powders with particle sizes ranging down to sub-micron. These energy attenuating
powders may be loaded into injection molded, extruded, coated, rollcompacted
or multi-layer laminated products. Other uses include inductive filters,
pigments, fibers and microwave heating coatings.
Iron Silicide:
Microwave Absorbing Materials
Steward's iron silicide powder provides solutions for may problems
experienced with standard microwave absorbing materials, and has characteristics
suitable for metallurgical uses as well. This patented alloy, available
in numerous particle sizes, is rust resistant, corrosion resistant, erosion
resistant, chemical resistant, and less dense than iron. Iron silicide
provides excellent survivability with low maintenance.
Ferrites:
The EMI Solution
Some electronic designers in the industry were already familiar with
similar EMI regulations of Germany and the U.S. military. They immediately
applied their knowledge of ferrite components to design new products that
produced much lower levels of EMI. As demand grew for suppression components,
Steward drew upon its four decades of expertise in ferrite materials to
develop an EMI suppression component design and manufacturing facility.
The Simple Secret of Ferrites
While many electronic circuits found in computers and consumer electronics
may be designed to operate at a single fundamental frequency, they may
actually generate significant energy, and thus potential EMI, at up to
ten times their basic operating frequency. For example, a personal computer
with a processor operating at 40 MHz could produce measurable EMI up to
400 MHz. When used strategically, ferrites can suppress and dissipate (as
minute quantities of heat) these higher frequency "noise" components
while leaving the intended signals and operation of a circuit undisturbed.
EMI suppression ferries are often used as two-terminal circuit elements. Even in this simple configuration, EMI and design engineers give pause when asked to explain exactly what makes ferrites such indispensable noise eliminators. In concise terms, EMI suppression ferries provide broadband, current operated low Q and high frequency series impedance with both reactive (inductive) and lossy (resistive) elements. For EMI suppression above 30 MHz, Steward's high frequency/low permeability ferrites can provide over one hundred ohms of lossy impedance over a bandwidth of several hundred MHz. Due to this broadband lossy behavior, many engineers prefer to consider ferrites as frequency dependent resistors. While this view is essentially correct at higher frequencies, the inductive reactance of EMI ferries provides additional attenuation at lower frequencies. Finally, designers should not neglect the effects of a ferrite's differential inductance on intended signals when used in high speed broadband applications such as video or networking circuitry.
Product Line
While many potential EMI problems can be prevented through meticulous
design practice, unforeseen noise issues often arise soon after a new design
is build and tested. To provide EMI suppression for both initial design
and retrofit applications, Steward offers a comprehensive product line:
Coatings
Steward can supply cylindrical cable beads polyurethane coated.
Coatings are usually applied to ferrites to prevent chipping or to change
the appearance of the part. Electrical insulation is not normally a concern,
due to the inherently high resistivity of most EMI ferrites. Polyurethane
coatings typically exhibit dielectric strengths of 400-500 volts per mil
and are applied in thicknesses of 1 to 2 mils.
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New
Century NORTHWEST LLC