Development of a soft magnetic material
Application of soft magnetic materials in the industry started in the late nineteenth Century. With the development of power industry and telecommunications technology, started to use low carbon steel manufacturing motor and magnetic head with a soft magnetic alloy, in addition to amorphous soft magnetic alloy tradition, and the rise of another kind of material – amorphous soft magnetic alloy.
Two commonly used types of soft magnetic core
Iron, cobalt, nickel and three kinds of ferromagnetic elements constitute the basic elements of magnetic material.
According to (the main composition, magnetic characteristics, structure characteristics of morphological classification) products:
(1) powder core classes: magnetic core, including: iron core, iron powder core, silicon and high magnetic flux powder core (High Flux), Po Mo alloy powder core (MPP), ferrite core
(2) tape wound core: silicon steel sheet, Po Mo alloy, amorphous and nanocrystalline alloy
Characteristics and application of three common soft magnetic core
(a) powder core class
1 magnetic powder core
Magnetic powder core is made of a soft magnetic materials, magnetic powder and mixed and pressed into the insulating medium. Because of ferromagnetic particles is very small (high frequency use ranged from 0.5 to 5 microns), is also non-magnetic electrically insulating film material is separated, therefore, a hand can be isolated from the eddy current, the material is suitable for the high frequency; on the other hand, because the gap effect between particles, resulting in materials with low permeability rate and constant magnetic properties; and because of small particle size, skin phenomenon does not occur basically, permeability variation with frequency is stable. Mainly used for high-frequency inductor. Magnetic core magnetic properties depend on the powder material permeability, particle size and shape, the filling coefficient, dielectric content, molding pressure and heat treatment process.
Magnetic core used the iron core, Po Mo alloy powder core and sendust core three.
Calculation formula of effective permeability “mu; e core and inductance for: e = DL/4N2S x 10
Of which: D is the core of average diameter (CM), L is the inductance (enjoy), N for the winding turns, S as the core of effective cross-sectional area (cm2).
(1) iron core
Common iron core is composed of carbonyl iron powder and resin carbonyl iron powder. In the powder core in the lowest price. The saturation magnetization value of around 1.4T; permeability range from 22 ～ 100 “mu; I; initial permeability changes with frequency stability; superimposed DC current performance is good; but the high frequency loss and high
(2). Po Mo alloy powder core
Po Mo alloy powder core are mo permalloy powder core (MPP) and high magnetic flux powder core (High Flux).
MPP is composed of 81%Ni, 2%Mo and Fe powder. The main features are: the saturation magnetization value of around 7500Gs; permeability range, from 14 to 550; has the lowest loss in the powder core; temperature stability is excellent, widely used for space equipment, outdoor equipment; magnetostrictive coefficient is close to zero, work in different frequency without noise. Mainly used in 300kHz below the high quality factor Q circuit, LC circuit, commonly used in high requirements for temperature stability of the output inductor, power factor compensation circuit, commonly used in AC circuits, the most expensive powder core.
High flux powder core HF is composed of 50%Ni, 50%Fe powder. The main features are: the saturation magnetization value of around 15000Gs; permeability ranging from 14 to 160; with the magnetic induction intensity was highest in the powder core, DC bias the highest volume of the magnetic core is small. Mainly used in line filter, inductor, inductance of AC output, power factor correction circuit, commonly used in DC circuit, high DC bias voltage, DC high and low alternating with much. Price of less than MPP.
(3) sendust core (Kool M Cores)
Sendust core is composed of 9%Al, 5%Si, 85%Fe powder. The main is to replace the iron core, loss is 80% lower than the iron core, can use at frequencies above 8kHz; saturation magnetic induction of about 1.05T; permeability from 26 to 125; the magnetostrictive coefficient is close to 0, work in different frequency without noise; higher DC bias power than MPP with performance; the best ratio of price. Mainly used in AC inductance, output inductor, line filters, power factor correction circuit. Sometimes instead of air gap is ferrite as the core of transformer.
2 soft magnetic ferrite (Ferrites)
Soft magnetic ferrite is ferrimagnetic oxides with Fe2O3 as the main components, production by powder metallurgy method. There are Mn-Zn, Cu-Zn, Ni-Zn and so on, in which Mn-Zn ferrite yield and the maximum amount, the antenna coil, radio frequency transformer of Mn-Zn ferrite. Core shape variety, E, I, U, EC, ETD, square (RM, EP, PQ), cylindrical (PC, RS, DS) and circle. It is convenient in application. Because of soft magnetic ferrite without the use of nickel and other scarce material can also get high permeability, powder metallurgy method and suitable for mass production, so the cost is low, but also because it is sintered material hardness, is not sensitive to stress, it is convenient in application. And permeability with stable frequency characteristics, remained unchanged in the following 150kHz. With the soft magnetic ferrite, magnetic core production greatly reduced, many of the original use of magnetic powder core place is replaced by soft magnetic ferrite.
Many domestic and foreign ferrite manufacturers, Mn-Zn ferrite is produced only in the United States MagnetICs company as an example to introduce the application status. Divided into three kinds of basic materials: basic material for telecommunications, broadband and EMI material, power type material.
Telecommunication permeability ferrite from 750 to 2300, with the relationship between permeability and low dissipation factor, high quality factor Q, stable temperature / time, is at work in a permeability decreased most slowly, about every 10 years decreased by 3% ~ 4%. Widely used in high Q filter, tunable filter, the load coil, impedance matching transformer, inductance proximity switch power supply, power factor correction circuit.
(two) tape wound core
1 The silicon steel sheet core
Silicon steel sheet is a kind of alloy, the addition of a small amount of silicon in iron (generally below 4.5%) iron silicon alloy called the formation of silicon steel. The core is saturated magnetic induction strength the highest value is 20000Gs; because they have better and magnetoelectric properties, easy mass production, low price, small influence mechanical advantage, in power relay, optional iron or low silicon steel sheet; for large motor, can choose high silicon hot-rolled silicon steel sheet, single orientation or cold rolled non-oriented silicon steel sheet; often used for transformer single oriented cold-rolled silicon steel sheet. Used in power frequency, commonly used strip thickness of 0.2~0.35 mm; in the use of 400Hz, often choose the thickness of 0.1 mm is appropriate. The thinner the thickness, the higher the price.
2 Po Mo alloy
Po Mo alloy usually iron nickel alloy, nickel content in the range of 30~90%. Soft magnetic alloys are widely used. By proper technology, can effectively control the magnetic properties, such as more than 105 of the initial permeability, more than 106 of the maximum permeability, low to 2 “permil; OE coercivity, close to 1 or close to 0 of the rectangular coefficient, good plasticity with face-centered cubic crystal structure of Po Mo alloy with, can be processed into 1 “mu; m slim belt and various forms of. The commonly used alloy are 1J50