The inventers and first producers of early non-ideal CuZn ferrites Born out of research done in by Dr. Yogoro Kato and Dr. Takeshi Takei. Also traded by Amidon! Amidon Inc.
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The World Is Flat 3. Jump to Page. Search inside document. Their permeability range is from one to 35 mu they can offer excellent 'Q' factors up to more than Miz. They are widely used for broadband inductors, especially in higher pover applications.
This group will have somevhat lover 'Q' and they are mainly used for EMI filters, low frequency chokes, and input and output filters for switched node pover supplies. Toroidal cores are self shielding and it is not necessary to isolate or shield a them to prevent cross talk or feedback.
Turns for a desired inductance may be calculated by using the given Ay, value and the forma below. Available in toroidal form only. Inductance vs. Available in both toroidal form and shielded coil fora. Available in both toroidal and shielded coil forms. Available in toroidal and shielded coil forms. Available in toroidal core form and shielded coil fora.
Offers good 'Q' and high stability for frequencies 40 Mhz to Miz. Available in both toroidal form and shielded coil form. Available in all shielded coil forms. Has highest permeability of all of the iron powder materials. The 26 material is very similar to the older fl material but provides an extended frequency range. Available in all toroidal core sizes. Note: 12 material vill eventually be superseded by the 17 material. The 26 Iron Powder material is ideally suited for these applications since it combines low "Q!
Since the DC flux does not generate core loss, our primary concern becomes saturation and copper loss. The DC saturation characteristics of the 26 material are shown in Fig. In 60 Hz. The connon-node noise is in relation to earth ground and is comon to both Lines. Differential mode noise is the noise between the tvo lines. Tron Powder cores are not recomended for Conmon-mode noise filters. This allovs the 60 Hz. The AC saturation characteristics of the 26 material Fig. B and core loss information Fig.
C can be seen below. Notice how the permeability initially increases with AC excitation. This effect allows greater energy storage in 60 Hz. Wire size based on Max. This is a question often asked, but unfortunately there is no simple answer. Now the question becomes ' How large a core must I have to prevent overheating at a given frequency and power level'? Operating frequency 1s one of the most important factors concerning pover capability above 1 Miz.
A core working well at 2 MHz may burn up at 30 Miz. Overheating can be caused by both wire and core material losses. Wire heating is affected by both DC and AC currents, while core heating is affected only by the AC content of the signal. With a normal sinewave signal above Kilz, both the Tron Powder and Ferrite type cores will first be affected by overheating caused by core losses, rather than by saturation.
Figures may vary slightly according to material used. AC Flux Density: gauss gauss 57 gauss 42 gauss 36 gauss 30 gauss Iron Powder cores low permeability are superior to the Ferrite material cores for high power inductors for this reason: Fever turns will be required by the Ferrite type core for a given inductance. When the same voltage drop is applied across a decreased number of turns, the flux density will increase accordingly. To prevent the flux density fron increasing when fever turns are used, the flux drive will have to be decreased.
Ferrite cores vill require fever turns and vill couple better, whereas the Iron Powder cores will require more turns and not couple as well but will tolerate more power and are more stable. The equation for Bag and a sample calculation are shown below: The sample calevlation is based on a frequency of 7 Miz, a peak voltage of 25 volts, a primary winding of 15 turns, and a cross-sect.
This is vell within the above guidelines to prevent overheating. Core saturation is affected by both AC and DC signals. Saturation will decrease the permeability of the core causing it to have impaired performance or to becone inoperative. The safe operating total flux density for most Ferrites is typically gauss, vhile the Iron Powders can tolerate up to gauss. Both wire heating and magnetic action within the core will contribute to the temperature rise of the coil. Core losses are lover at low Frequencies and lov power levels, but increase rapidly as either 1s increased.
Maximum flux density can be calculated with the Faraday Lav and Aaperes Lav, both of which are shown below: vs. Frequency range: 0. J1xt0 ixio? When placed on to a current carrying conductor it will act as an RF choke. It offers a convenient, inexpensive, yet a very effective means of RF shielding, parasitic suppression and RF decoupling.
Adjacent leads and unshielded conductors can also provide a convenient path for the transfer of energy from one circuit to another. A few ferrite beads of the appropriate material placed on these leads can greatly reduce or completely eliminate the problem. Best of all, they can be added to most any existing electronic circuit. The amount of inpedance is a function of both the material and the frequency, well as the size of the bead.
As the frequency increases, the permeability vill decline causing the losses to rise to a peak. With a rise in frequency the bead will present a series resistance with very little reactance.
Since reactance is Jow there is little chance of resonance vhich could destroy the attenuation effect. Impedance is directly proportional to the length of the bead, therefore impedance will be additive as each similar bead is slipped onto the conductor.
Since the magnetic field is totally contained within, it does not matter if the beads are touching or separated. We recommend the 73 or the 77 ferrite bead material for the attenuation of RFI resulting from transmissions in the anateur band. The 43 naterial vill provide best RFI attenuation from 30 to Miz, and the 64 material is most effective above Miz.
The 75 material is recomended for RFI fron 1 to 20 Miz, but they can also be very effective even below the AM broadcast band. Ferrite beads are usually quite small and as a result only one pass, or a small nunber of turns are possible. On the other hand, a toroidal core usually has a much larger ID and will accept a greater number of turns. If a large amount of impedance is required the ferrite core can be used to advantage, since the impedance increases as to the number of turns squared.
To physically complete one turn it would be necessary to cause the wires to meet fon the outside of the device, however the bead or core does not care about the termination of each end of the wire and considers each pass through the center hole as one turn. Each type of winding will produce very different results. The impedance figures for the six-hole bead in our chart is based on the current industry standard, which is two and one half turns threaded through the holes, criss-crossing from one side to the other.
Tenpefature rise above the Curie point vill cause the bead to becone non- nagnetic, rendering it useless as a noise attenuating device. Other lover permeability materials with higher resistivity are non- conductive and this precaution 1s not necessary. When dealing with any noise problem it is helpful to know the frequency of the interference. This is valuable when trying to determine the correct material as well as the maximum turns count.
RFI emanating from such sources as computers, flashing signs, switching devices, diathermy machines, ete. For this type of interference, the 43 material is probably the best choice since it has very good attenuation in the 20 Miz to Miz. Some noise problems may require additional filtering with hi-pass or lo-pass filters. If the noise is of the differential-mode type, fan AG line filter may be required.
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