Assembly of the effective permeability of magnetic ring me and inductance is calculated as: me = DL/4N2S/109

Where: d is a core diameter (cm), l is the inductance (), n is the winding turns, s is the core of effective sectional area (cm2).

(1). iron powder cores

Iron powder cores commonly used is made up of carbon-based ferromagnetic powder and resin carbon-based ferromagnetic powder composition. In the core price

(3). sendust powder core (Kool Mm Cores)

Sendust powder core consists of 9%Al, 5%Si, 85? powder composition. Mainly instead of iron powder cores, 80% loss than iron powder cores, can be used in a 8KHz frequency; saturation magnetic induction 1.05T; permeability 26~125; magnetostrictive coefficient close to 0, no noise when working at a different frequency than MPP has a high DC bias; with the best price-performance ratio. Mainly used in AC inductor, inductance, line filters, power factor correction circuit. Sometimes instead of air-gap ferrite transformer cores.

2. soft ferrite (Ferrites)

Soft ferrite is mainly components of ferrimagnetic oxide Fe2O3, produced by powder metallurgy method. Mn-Zn, Cu-Zn, Ni-Zn and other categories, including production of MN-Zn ferrite and the largest amount, MN-Zn ferrite of low resistivity, 1~10 Ohm-metres, generally below 100KHZ the frequency of use. CU-Zn and NI-Zn Ferrites resistivity 102~104 ohm-metres, at 100kHz~10 MHz radio frequency loss, antenna coils, radio frequency transformers for use in radio.

Magnetic core shape variety, e, I, u, EC, ETD, square (RM and the EP, and PQ), pot (PC, RS, DS) and circular. Very convenient in application.

Because of soft ferrite does not use scarce materials such as nickel can also be high permeability, powder metallurgy method is suitable for mass production, low cost, and because a sintered material hardness, stress-sensitive, very convenient in application. Stability and permeability changes with frequency characteristics, and 150kHz remains unchanged. With the emergence of soft ferrite magnetic powder core greatly reduces the production of, many of the original use magnetic powder core are replaced by soft ferrite.

Minimum. Saturation magnetic flux density value in the 1.4T about permeability ranges from 22~100; Change of initial permeability MI with frequency stability; direct current superimposed performance; but in high frequency loss is high.

(2). the Permalloy dust core

Permalloy dust core primary Molybdenum Permalloy powder core (MPP) and high flux cores (High Flux).

MPP is composed of 81%Ni, 2%Mo, and Fe powder composition. Main features are: saturation magnetic flux density value in the 7500Gs about permeability range, from 14~550; In powder magnetic core with a minimum of loss very good temperature stability, widely used in space equipment, outdoor equipment; magnetostrictive coefficient close to 0, no noise when working at a different frequency. Mainly used in high quality factor Q 300KHz filter, resonance, inductive load coil circuit, on the high temperature stability of LC circuit, inductance and power factor compensation circuit, often used in AC circuits, core prices are the most expensive.

High flux cored HF is by 50%Ni, 50? powder composition. Main features are: saturation magnetic flux density value in the 15000Gs about permeability ranges from 14~160; In the powder cores have high magnetic induction, high DC bias; core volume is small. Mainly used in line filters, AC inductor, the output inductors, power factor correction circuits, commonly used in DC circuits, high DC bias voltage, DC and AC used on much lower. Price is lower than the MPP.

Ferrite manufacturers at home and abroad a lot, only United States Magnetics company production of MN-Zn ferrite as an example of its application. Is divided into three basic categories of materials: basic material for telecommunications, broadband, and EMI, power-type material.

Telecommunications with ferrite permeability from 750~2300, with low dissipation factor, high quality factor Q, stable magnetic conductivity with temperature/time relationship, is the permeability of the slow decline in their work, about every ten years the dropped 3%~4%. Widely used in high Q filters, tunable filters, impedance matching transformer, proximity sensor, load coils.

Broadband ferrite which is often that of high permeability ferrite and magnetic permeability respectively 5000, 10000 and 15000. Its characteristics as having a low loss factor, high permeability, high impedance and frequency characteristics. Widely used in common-mode filter, saturable inductor, current transformers, ground fault protection, insulation transformers, signal and pulse transformers, broadband on the transformer and the EMI.

Power ferrite with high saturation magnetic induction, 4000~5000 Gs. With low loss and low loss/temperature/frequency relationship. In other words, increases with frequency, loss increase little changes with the temperature, loss is small. Widely used in power chokes, parallel filter, switch power supply transformer, inductor, power factor correction circuit.