Magnetic beads main raw material is the ferrite. Ferrite is a cubic lattice structure of ferrite magnetic material. Ferrite material for magnesium alloy iron or iron nickel alloy, its manufacturing process and mechanical properties similar with the ceramics, color is black. One of the most frequently used types of magnetic cores in electromagnetic interference filters is ferrite materials, and many of the manufacturers provided special ferrite materials for electromagnetic interference suppression. The characteristics of this kind of material is have the high frequency loss, has very high magnetic permeability, he can between the inductance of the coil winding in high frequency and high resistance minimum capacitance. For the suppression electromagnetic interference of ferrite, the most important performance parameters for magnetic permeability μ and saturated flux density Bs. Magnetic permeability μ
can be expressed as a complex number, real part constituting the inductor, imaginary parts represent the loss, increase with increasing of frequency. Therefore, its equivalent circuit on the grounds of series circuit composed of inductance L and resistance R, L and R is a function of frequency. When the conducting wire passes through the ferrite core, the inductance impedance in the form of increased with the increase of frequency, but the mechanism is quite different at different frequencies.
In the low frequency band, impedance is composed of inductance reactance, R is small when low frequency, high permeability of magnetic core, so inductance larger and L play main role, the electromagnetic interference is suppressed by the reflection, and at this time the magnetic core loss is small, the whole device is a low loss, high Q characteristics of inductance, the inductance easily lead to resonance in the low frequency band, and sometimes may appear to the phenomenon of use ferrite bead after interference enhancement.
At high frequency, impedance consists of resistive component, with the increase of frequency, permeability of the core decreased, lead to reduce the inductance of the inductor, and the inductive component decreases, however, at this time the loss of the core increases, the resistance component increases, resulting in the total impedance increases, when the high frequency signal through the ferrite, the electromagnetic interference is absorbed and in the form of converted into heat energy dissipation.
Ferrite inhibitory components widely used in printed circuit board, power supply line and a data line. Such as on a printed board power cable inlet end and ferrite suppression components, you can filter high-frequency interference. Ferrite ring or bead is special to restrain the signal line, the power line high frequency interference and interference peak, it also has the ability to absorption electrostatic discharge pulse interference.
Proportional to the length of the two components of the numerical size and magnetic beads, the longer the better effect of the inhibition beads, magnetic length of the inhibitory effect is better.
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