First, the magnetic properties of soft magnetic materials commonly used parameters
Saturation magnetic induction Bs: its size depends on the material composition, its physical state corresponding to the magnetization vector inside the material lined up.
Residual magnetic flux density Br: is the characteristic hysteresis loop parameters, H back to 0 when the B value.
Squareness ratio: Br / Bs
Coercivity Hc: is the degree of difficulty that the amount of magnetic material, depending on the material composition and defects (impurities, stress, etc.).
Permeability m: is any point hysteresis loop corresponding to the ratio of B and H, the work is closely related with the device.
Initial permeability mi, maximum permeability mm, differential permeability md, amplitude permeability ma, effective permeability me, the pulse permeability mp.
Curie temperature Tc: the magnetization of ferromagnetic materials decreases with increasing temperature, reaches a certain temperature, the spontaneous magnetization disappears into the paramagnetic Curie temperature of the critical temperature. It determines the upper limit of the magnetic device working temperature.
Hysteresis loss Ph approach is to reduce the coercivity Hc; reduce eddy current loss Pe is thinning of the thickness t and the magnetic materials increase the resistivity ρ. In free still air core loss and core temperature relationship:
Total power dissipation (mW) / surface area (cm2)
3 soft magnetic materials and magnetic parameters of the conversion of the electrical parameters
In the design of soft magnetic devices, the first to identify the device according to the requirements of the circuit the voltage - current characteristics. Voltage - current characteristics of the device with the geometry and the magnetic core is closely related. Designers must be familiar with the material magnetization process and magnetic properties of materials to take hold with the device electrical parameters of conversion relationship. Soft device design usually consists of three steps: the correct selection of magnetic materials; reasonably determine the geometry and size of the core; based on magnetic parameters required to simulate the working status of the corresponding core electrical parameters.
Second, the development of soft magnetic materials and types of
1 the development of soft magnetic materials
Soft magnetic materials in industrial applications began in the late 19th century. With the power of workers and the rise of telecommunications technology, the use of low carbon steel motor starting and transformer, the phone lines in the core of the inductor coil used in small iron, iron oxide, fine wire and so on. To the early 20th century, developed a low-carbon instead of silicon to improve the efficiency of the transformer, reducing wear and tear. Until now, silicon steel sheet used in the power industry continued to hold the first soft magnetic materials. To 20 years, the rise of radio technology, and promote the development of high permeability material, there permalloy and permalloy powder cores. From the 1940s to the 1960s, is the period of rapid development of science and technology, radar, television broadcasting, integrated circuits, inventions, etc., on the soft magnetic materials have higher demands, producing a soft magnetic alloy ribbons and soft ferrite materials . In the 1970s, as telecommunications, automatic control, computer and other industries, developed the head with a soft magnetic alloy, in addition to conventional crystalline soft magnetic alloy, the rise of the the other materials - amorphous soft magnetic alloy .
2 common types of soft magnetic core
Iron, cobalt, nickel, three kinds of magnetic elements constitute the basic set of magnetic element.
By (the main component, magnetic characteristics, structural characteristics) morphological classification of products:
(1) powder core categories: magnetic core, including: iron core, iron powder core Si-Al, high-flux cored (HighFlux), permalloy powder core (MPP), ferrite cores
(2) tape wound core: silicon steel, permalloy, amorphous and nanocrystalline alloys
Three common characteristics and application of soft magnetic core
(A) powder core class
1 magnetic core
Magnetic core is a ferromagnetic powder and mixed dielectric pressed a soft magnetic material. As a small ferromagnetic particles (high-frequency use of 0.5 to 5 microns), and is non-magnetic material separated by electrical insulating film, so one can be isolated vortex, materials suitable for high frequency; the other hand, due to particle the gap between the effects resulting material has a low and constant magnetic permeability characteristics; and because the small particle size, the skin is basically the phenomenon does not occur, permeability variation with frequency also more stable. Mainly used for high frequency inductors. The magnetic properties of magnetic cores depends on the permeability of powder materials, powder size and shape, and their fill factor, dielectric content, molding pressure and heat treatment process, etc.
Commonly used iron core magnetic core has, permalloy powder core and silica-alumina powder iron core three.
Core effective permeability μe and the inductance is calculated as: μe = DL/4N2S × 109
Where: D is the core average diameter (cm), L is inductance (shared), N for the winding turns, S is the effective core cross-sectional area (cm2).
(1) iron core
Commonly used iron core is made from carbon-based carbon-based iron powder and iron powder resin composition. The lowest price in the powder core. Saturation magnetic flux density value of about 1.4T; permeability ranges from 22 to 100; initial permeability μi variation with frequency stability; DC current overlay performance; but the loss of high frequency high.
Iron core initial permeability vs frequency
(2). Permalloy powder core
Permalloy powder cores are mainly molybdenum permalloy powder core (MPP) and high flux cored (HighFlux).
MPP is 81% Ni, 2% Mo and Fe powder form. Main features are: saturation magnetic flux density values ​​around the 7500Gs; permeability range from 14 to 550; in the powder has the lowest core loss; excellent temperature stability, widely used in space equipment, outdoor equipment, etc.; magnetic caused by expansion coefficient close to zero, at different frequencies when no noise generated. Mainly used in the following 300kHz high quality factor Q of the filter, inductive load coil, the resonant circuit, in the high temperature stability requirements on the common LC circuit, the output inductor, power factor compensation circuit, commonly used in AC circuits, cored the most expensive.
High Flux cored HF by 50% Ni, 50% Fe powder form. Main features are: saturation magnetic flux density values ​​around the 15000Gs; permeability ranging from 14 to 160; in the powder core has the highest magnetic flux density, the maximum capacity of the DC bias; core line filters are mainly used in small, AC inductor, the output inductor, power factor correction circuit, commonly used in the DC circuit, high DC bias voltage, high DC and low AC on with much more. Price lower than the MPP.
(3) Si-Al powder iron core (KoolMmCores)
Kool cored by a 9% Al, 5% Si, 85% Fe powder form. Mainly alternative iron core, the core loss of 80% lower than the iron can be used at frequencies above 8kHz; saturation magnetic induction at about 1.05T; permeability from 26 to 125; magnetostriction coefficient close to 0, at different frequencies produce no noise when working; than MPP (molybdenum permalloy powder core) have a higher capacity of the DC bias; has the best cost performance. Mainly used in AC inductor, the output inductor, line filter, power factor correction circuit. Sometimes substitute for the air gap ferrite core transformer used.
2 Ferrite (Ferrites)
Ferrite is ferrimagnetic Fe2O3 oxide-based ingredients, produced by powder metallurgy. A Mn-Zn, Cu-Zn, Ni-Zn and other types, including Mn-Zn ferrite of the largest production and consumption, Mn-Zn ferrite of the low resistivity of 1 ~ 10 ohm - meters, usually in the 100kHZ use the following frequencies. Cu-Zn, Ni-Zn ferrite resistivity of 102 ~ 104 ohm - meters, 100kHz ~ 10 MHz radio frequency band loss is small, the use of the radio with the antenna coil, radio frequency transformers. Wide variety of core shapes, there are E, I, U, EC, ETD, square (RM, EP, PQ), pot (PC, RS, DS), and round and so on. The application is very convenient. As the ferrite and nickel do not use scarce materials can also be high permeability, powder metallurgy method is suitable for mass production and, therefore, low cost, and because the sintered material hardness, the stress is not sensitive to the application is very convenient. And permeability changes with the frequency characteristics of stability, the following remained unchanged at 150kHz. With the emergence of soft magnetic ferrite, magnetic cores greatly reduced the production of many parts of the original use of magnetic cores are replaced by ferrite.
Many domestic and foreign manufacturers of ferrite, in the U.S. only Magnetics produced Mn-Zn ferrite as an example of their application status. Divided into three basic materials: Telecom with basic materials, broadband and EMI materials, power-type material.
Telecom ferrite permeability from 750 to 2300, with low loss factor, high quality factor Q, stable magnetic permeability with temperature / time relationship, is at work in the permeability of a decline in the slowest, about every 10 years, a decline of 3% to 4%. Widely used in high-Q filters, tunable filters, load coils, impedance matching transformers, proximity sensor. Broadband ferrite is often said that the high permeability ferrite, magnetic permeability, respectively 5000,10000,15000. Its characteristics as a low loss factor, high permeability, high impedance / frequency characteristics. Widely used in common mode filter, inductor saturation, current transformer, leakage protection, insulation transformer, signal and pulse transformers, transformer and EMI on the broadband multi-purpose. Power ferrite with high saturation magnetic flux density for 4000 ~ 5000Gs. Low loss / frequency relationship and low loss / temperature relationship. In other words, with the frequency increases, the loss is not increased; with increases in temperature, loss of little change. Widely used in power choke, parallel filters, switching power transformer, switching power supply inductance, power factor correction circuit.
(B) around the core with
1 silicon steel core
Silicon steel is an alloy, the pure iron in a small amount of silicon (typically 4.5% or less) to form silicon-iron alloy called silicon steel. Type of core has the highest saturation magnetic flux density is 20000Gs; because they have good magnetic properties, and easy mass production, cheap, mechanical stress effects, etc, in the power electronics industry to get a very wide range of applications, such as power transformers, distribution transformers, current transformers and other core. Soft magnetic materials is the largest production and use of materials. Power transformer is the largest amount of magnetic material. Especially in the low-frequency, high power under the most applicable. Commonly used cold rolled silicon steel sheet DG3, cold-rolled non-oriented electrical steel DW, cold-rolled oriented silicon steel strip DQ, applicable to all types of electronic systems, home appliances in the middle and low-power low-frequency transformers and chokes, reactors , the inductor core, good toughness of these alloys can be punching, cutting and other processing, there are laminated iron core and winding type. However, a sharp increase in losses at high frequencies, the frequency of use is generally not more than 400Hz. From the application point of view, the choice of silicon to consider two factors: magnetic and costs. For small motors, reactors and relays, optional low-iron or silicon; for large motors, optional high-silicon hot-rolled silicon steel, single-orientation or non-oriented silicon steel sheet cold rolling; often used in a single orientation of cold-rolled transformer silicon steel. In the frequency of use, common strip thickness of 0.2 to 0.35 mm; at 400Hz when used often choose 0.1 mm thickness is appropriate. Thickness of the thinner the higher the price.
2 permalloy
Permalloy often refers to the iron-nickel alloy, nickel content of 30 to 90% range. Is a very wide range of soft magnetic alloys. Through appropriate technology, can effectively control the magnetic properties, such as over 105 of the initial permeability, more than 106 of the maximum permeability, low to 2 ‰ Oersted coercivity, close to 1 or rectangular coefficient close to 0 with face-centered cubic crystal structure of the permalloy has good plasticity, can be processed into thin 1μm band and a variety of use patterns. Commonly used alloy 1J50, 1J79, 1J85 and so on. 1J50 saturation magnetic flux density slightly lower than silicon, but the permeability several times higher than silicon, iron loss silicon steel lower than 2 to 3 times. Made of a high frequency (400 ~ 8000Hz) of the transformer no-load current, suitable for making the following small high frequency transformer 100W. 1J79 has a good overall performance for high-frequency low-voltage transformer, leakage protection switch core, common mode inductor current transformer core and the core. 1J85 of the initial permeability up to hundreds of thousands more, suitable for weak low-frequency or high frequency signal input and output transformers, common mode inductance and high-precision current transformers.
3 amorphous and nanocrystalline soft magnetic alloys (AmorphousandNanocrystallinealloys)
Silicon steel and permalloy soft magnetic materials are crystalline materials, atoms arranged in three-dimensional space in the rules, the formation of periodic lattice structure, the existence of grains, grain boundaries, dislocations, interstitial atoms, such as magnetic anisotropy defects, unfavorable to the soft magnetic properties. From the magnetic physics, the irregular arrangement of atoms, there is cyclical and the amorphous grain boundary structure to obtain excellent soft magnetic properties is very good. Amorphous metals and alloys in the 1970s came a new type of material areas. It's completely different from the traditional preparation techniques methods, instead of using a cooling rate of about one million degrees per second, super-quench solidification technology, thin strip from liquid steel to the finished product once formed, than cold-rolled metal strip manufacturing process to reduce the a number of intermediate processes, this new process is known as a traditional metallurgical technology revolution. As the ultra-rapid cooling solidification, alloy solidification ordered crystalline atomic time to get long-range solid-state alloy is disordered structure, there is no crystalline alloy grain, grain boundary exists, called the amorphous alloy, known as metallurgical materials learn a revolution. This amorphous alloy has 8ttt8 unique properties, such as the excellent magnetic properties, corrosion resistance, wear resistance, high strength, hardness and toughness, high resistivity and electromechanical coupling properties. Because of its excellent performance, simple process, from the 1980s to become domestic and foreign materials science research and development focus. Currently the United States, Japan, Germany has a perfect production scale, and a large number of amorphous silicon alloy products and gradually replace the permalloy and ferrite flooded the market.
Since the 1970s China began research and development of amorphous alloys to work through the "Plan", "75", "85" period of major scientific and technological project completion, a total of 134 achievements in scientific research, the National Invention Award 2, by 16 patents, has nearly a hundred varieties of alloys. Iron and Steel Research Institute, now has four amorphous alloy strips production line, an amorphous alloy core production line components. Production of iron-based stereotypes, iron-nickel based, cobalt-based and nanocrystalline strip and the core for power inverters, switching power supply, power transformer, leakage protection, inductor core components, the annual production value of nearly 2000 million. "95" is the establishment of iron-based amorphous ton production line, enter the international advanced level.
At present, the amorphous soft magnetic alloy to achieve the best individual performance levels are:
Initial permeability mo = 14 × 104
Co-based amorphous maximum permeability mm = 220 × 104
Co-based amorphous coercivity Hc = 0.001Oe
Co-based amorphous squareness ratio Br / Bs = 0.995
Co-based amorphous saturation magnetization 4πMs = 18300Gs
Fe-based amorphous resistivity ρ = 270MΩ/cm
Commonly used types of amorphous alloys are: iron, iron-nickel base, cobalt-based amorphous alloys and iron-based nanocrystalline alloys. And performance characteristics of their national brands in Table and shown, for ease of comparison, also lists crystalline silicon alloy, permalloy 1J79 and the corresponding performance of the ferrite. These types of materials have different characteristics, to be applied in different ways.
Grades of basic components and features:
1K101Fe-Si-B system soft magnet alloy melt-spinning
1K102Fe-Si-B-C system quickly quenched soft magnetic alloy
1K103Fe-Si-B-Ni system the soft magnetic alloy melt-spinning
1K104Fe-Si-B-NiMo system quickly quenched soft magnetic alloy
1K105Fe-Si-B-Cr (and other elements) is a soft magnetic alloy melt-spun
1K106 high-frequency low-loss system Fe-Si-B soft magnetic alloy melt-spinning
1K107 high-frequency low-loss Fe-Nb-Cu-Si-B system magnet-based nanocrystalline soft-spun alloys
1K201 high pulse permeability soft magnetic cobalt-based alloy melt-spun
1K202 high remanence than the soft magnetic cobalt-based alloy melt-spun
1K203 sense of low-loss high-melt-spun soft magnetic cobalt-based alloy
1K204 high-frequency low-loss soft magnetic cobalt-based alloy melt-spun
1K205 high initial permeability soft magnetic cobalt-based alloy melt-spun
1K206 quenched high permeability soft magnetic cobalt-based alloy
1K501Fe-Ni-P-B series of soft magnetic nickel-based melt-spun alloys
1K502Fe-Ni-V-Si-B melt-spinning series of soft nickel-based alloy magnets
400Hz: Amorphous silicon steel core core
Power (W) 4545
Core loss (W) 2.41.3
Excitation power (VA) 6.11.3
Total weight (g) 295276
(1) Fe-based amorphous alloys (Fe-basedamorphousalloys)
Fe-based amorphous alloy is 80% Fe and 20% Si, B class metal elements of the composition, it has a high saturation magnetic induction (1.54T), iron-based amorphous alloy compared with the loss of silicon steel magnetic permeability, excitation current and iron loss and other characteristics are superior to silicon, in particular, low iron loss (oriented silicon steel sheet of 1/3-1/5), instead of silicon to do distribution transformers can be 60-70% energy saving. Fe-based amorphous alloy strip thickness of 0.03mm or so, is widely used in distribution transformers, high-power switching power supply, pulse transformers, magnetic amplifiers, intermediate frequency transformer and inverter core, suitable for use at frequencies below 10kHz
(2) iron-nickel base, cobalt-based amorphous alloys (Fe-Nibased-amorphousalloy)
Fe-Ni-based amorphous alloy is 40% Ni, 40% Fe and 20% of the class composition of metallic elements, it has a moderate saturation magnetic flux density [0.8T], a high initial permeability and high maximum permeability rate and high mechanical strength and excellent toughness. In the medium and low frequencies with low iron loss. Heat treatment in air oxidation does not occur, the magnetic field obtained after annealing a good rectangular loop. 30-50% cheaper prices than 1J79. Fe-Ni-based amorphous alloys in the range of applications and the corresponding Ni permalloy, but the iron loss and high mechanical strength than the crystalline alloy is superior; instead of 1J79, widely used in GFCI, precision current transformer core, the magnetic shielding. Fe-Ni-based amorphous alloys is the development of the first, is currently the largest application of amorphous alloys in the amorphous variety, annual output of nearly 200 tons. Air heat treatment does not occur in nickel-iron-based amorphous alloys (1K503) the State patents and U.S. patents.
(4) Fe-based nanocrystalline alloy (Nanocrystallinealloy)
Fe-based nanocrystalline iron-based alloy by adding a small amount of Nb, Cu, Si, B elements posed by the rapid solidification process of alloy formation of an amorphous material of this amorphous material after heat treatment availability of 10-20nm diameter crystallites, dispersed in the amorphous matrix, known as microcrystalline, nanocrystalline materials or nano-crystalline materials. Nano-crystalline composite material with excellent magnetic properties: high saturation magnetic induction (1.2T), high initial permeability (8 × 104), low Hc (0.32A / M), high magnetic induction under low-loss high-frequency ( P0.5T/20kHz = 30W/kg), resistivity 80μΩ/cm, than permalloy (50-60μΩ/cm) high, the vertical or horizontal magnetic field, obtained high Br (0.9) or low Br values ​​( 1000Gs). Is currently on the market overall performance of the best materials; applicable frequency range: 50Hz-100kHz, the best frequency range: 20kHz-50kHz. Widely used in high-power switching power supply, power inverter, magnetic amplifiers, high frequency transformers, high frequency converters, high-frequency choke core, iron core current transformer, leakage protection switch, common mode inductor core.
(C) the common characteristics of relatively soft core
1 powder cores, ferrite is characterized by comparison:
MPP core: use ampere turns <200,50 Hz ~ 1kHz, μe: 125 ~ 500; 1 ~ 10kHz; μe: 125 ~ 200;> 100kHz: μe: 10 ~ 125
HF core: Use the ampere turns <500, can be used in a larger power supply, in the larger magnetic field can not easily be saturated, can guarantee the minimum inductance DC drift, μe: 20 ~ 125
Iron core: Use the ampere turns> 800, in high magnetic fields are not under the saturated inductance value can guarantee the best DC superimposed stability. In less than 200kHz frequency stability; but high-frequency loss, for the following uses 10kHz.
FeSiAlF core: instead of using the iron core, the use of frequencies greater than 8kHz. DC bias capability ranging between MPP and HF.
Ferrite: low saturation flux density (5000Gs), DC bias with the least capacity
3 silicon steel, permalloy, amorphous alloy is characterized by comparison:
Silicon and FeSiAl material has a high saturation magnetic induction values ​​of Bs, but its low effective permeability values, especially in the high frequency range;
Permalloy has a high initial permeability, low coercivity and losses, magnetic stability, but Bs is not high enough frequency greater than 20kHz, the loss and the effective permeability is not satisfactory, expensive, complex processing and heat treatment .
Co-based amorphous alloy with high permeability, low Hc, in a wide frequency range with low loss, near-zero saturation magnetostriction coefficient, the stress is not sensitive, but the Bs value is low, expensive;
Fe-based amorphous alloy with high Bs value, the price is not high, but low effective permeability values.
Nanocrystalline alloys permeability, Hc values ​​close to the high crystalline permalloy and cobalt-based amorphous, and the saturation magnetic induction Bs and nickel permalloy equivalent heat treatment process is simple, is an ideal low-cost high-performance soft magnetic materials; Although Bs nanocrystalline alloys is lower than the Fe-based amorphous and silicon steel, but under high magnetic induction in the high-frequency loss is far less than they, and have better corrosion resistance and magnetic stability. Nanocrystalline alloys and ferrite compared to less than 50kHz, in a more low-loss high on the basis of the work 2 to 3 times the magnetic induction, a small core size can be more than doubled.