"1. Magnetic core material
Basic concepts
UI value
The initial permeability of the magnetic core indicates the capacity of the material to accommodate and conduct magnetic lines of force（ ui=B/H）
Al value: inductance coefficient. Table the ability of core finished products to help the coil generate inductance. Its value is equal to the value of single turn inductance, and the unit is NH / N2.
Hysteresis loop: 1: B － h curves
BMS: saturated magnetic beam density, which indicates the physical quantity that the magnetic beam density tends to be saturated during the magnetization of the material. The unit of magnetic induction is Tesla = 104 Gauss.
When we slowly apply a current to the magnetic core material, the magnetic flux density (magnetic induction intensity) will also increase. When the current is added to a certain degree, we will find that the magnetic flux density will increase very slowly and approach a progressive line. When it approaches this progressive line, the magnetic flux density at this time is called the saturated magnetic flux density (BMS)
BMS high: it indicates that the same magnetic flux requires small cross-sectional area and small volume of magnetic components.
BRMS: residual magnetic beam density, also known as residual magnetic beam density, indicates that after the magnetization process of the material, the external magnetic field disappears, while a small amount of magnetic lines of force still exist inside the material.
HMS: the minimum external magnetic field strength that can make the material reach the magnetic saturation state, unit: A / M = 104 / 2 π Auster.
HC: coercivity, also known as retention force, is the residual magnetic field intensity caused by the residual magnetic beam density when the external magnetic field disappears after the magnetization process. Because the direction of the residual magnetic field is consistent with the magnetization direction, a reverse external magnetic field must be applied to reduce the residual magnetic beam density to zero.
From the hysteresis loop, we can see that large remanence indicates high UI value of magnetic core. The more inclined the hysteresis loop, the greater the HMS, and the greater the current resistance of the magnetic core. The greater the coercivity, the greater the power loss of the magnetic core.
Iron core:
Iron powder core is a popular term for the magnetic core material Fe3O4. The main component is iron oxide, the price is relatively low, and the saturated magnetic induction intensity is about 1.4T: the permeability range is from 22-100, the initial permeability UI value has good stability with frequency, good DC current superposition performance, but high consumption at high frequency.
The material can be identified from the coating color, for example: 26 materials: yellow body / white bottom, 52 materials: green body / blue bottom. This kind of material is cheap. If the sensitivity is not very high, this material is the first choice. The required materials can be selected according to the sensitivity and IDC requirements. 8 materials have the best current resistance, 26 materials are the worst, and 18 materials are between the two, but the al value of 8 materials is very low. Iron powder core materials are generally used as inductors with small inductance and high current resistance.
This kind of material is most commonly used in toroid core and generally has good current resistance characteristics. Its surface impedance is between Mn Zn system and Ni Zn system and has certain conductivity. Therefore, the surface of core body is provided with insulating coating layer. The 26.18.52 material in toroid core is mainly composed of iron powder. These materials are not only used to make ring normal inductors, but also commonly used to make ring transformers.
Such materials are easily magnetized by external magnetic field. After being magnetized, the L value of finished products will increase by 3 ~ 5%, and the initial value can be restored after standing for 3-5 days.
There are also 8 materials in toroid core. SF53 material, with super current resistance, is commonly used to make low inductance components with current resistance of more than 10A（ Mainboard (common)
The representation method of iron powder core material is generally: T ××-××， The first two or three digits represent the outer diameter of the magnetic ring. Calculation method: outer diameter= ××* 0.01 inch= ××* 0.01 * 25.4 mm; The next two (or one) digits or letters represent the material.
For example, t106-26 represents a magnetic ring with an outer diameter of 1.06 inches (1.06 * 25.4 = 26.9 mm) and a material code of 26.
Iron powder core materials generally use different coating colors to distinguish different materials. The international unified coating standards are as follows:
2 material: red body, transparent (ferrite natural color) bottom
----This material has low permeability (10) and can reduce the AC flux density during operation more than other materials without void loss.
8 material: yellow body, red bottom, initial permeability (35),
---In the case of high bias current, this material has low core loss and good linearity. It is a good high-frequency material and the most expensive material.
18 material: light green body, red bottom, initial permeability (55),
---Like 8 materials, this material has low core loss, high permeability and low cost, and has good DC saturation characteristics
26 material: yellow body, white bottom, initial permeability (75),
---The most popular material is a cost-effective general-purpose material, which is suitable for a wide range of applications such as power conversion and line over filtering.
52 material: light green body, blue bottom, initial permeability (75),
---The magnetic core loss of this material is relatively low at high frequency, and the permeability is the same as that of - 26 material. It is widely used in new high frequency anti current devices.
28 material: gray body, green bottom
---It has good linearity, low cost and relatively low permeability, and is widely used in large-size high-power UPS anti current devices.
40 material: green body, yellow bottom, initial permeability (60),
---The cheapest material, whose characteristics are quite similar to those of 26 materials, is widely used in larger sizes
33 material: it is a material that can replace 8 materials but is not expensive. It is suitable for the case where the core loss is not important at high frequency. It has good linearity at high bias current.
53 material: whole body black (some also represent whole body lake water green); P3 material: sky blue
Material characteristics of iron powder core:
1. High saturation induction strength, can work with high current.
2. Stable performance, effective permeability and excellent frequency characteristics.
3. With high temperature characteristics, it is suitable for the temperature range of - 65 ℃ - + 125 ℃.
4. The circular structure has extremely low electromagnetic radiation, saves shielding materials and reduces the requirements for shielding work. 5. Iron powder core has excellent noise suppression and absorption capacity, and its performance is better than metal lamination and ferrite.
Mn Zn: (70% Fe2O3, 17% MnO, 13% ZnO)
The material has strong conductivity and generally needs to be coated for insulation. The coating layer is generally green. The material is usually selected according to the characteristic requirements. For large inductance, Mn Zn material is usually selected. Mn Zn material is easy to magnetic saturation, that is, idc1 is very small. Find out the corresponding inductance coefficient (al value) through the manufacturer's product catalog, and then use the formula L = al. N ² Calculate the required number of turns. The characteristics of Mn Zn material are unstable. Generally, the sensing range should be 30% or more! This material is obviously affected by external temperature and pressure, so we usually set the sensitivity to xxuh min when making this kind of sample. If the customer has requirements for the sensitivity range, we must use self-drying glue (1005a / 1005b) to fix the base or partition. Remember not to bake!
This kind of material is most commonly used in high inductance ring inductors. It is also widely used in filters composed of EI, EE and UU cores. High frequency transformer, etc; Dr core is occasionally useful.
Mn Zn series materials have high UI value and are suitable for low turn high inductance (current resistance difference of ring inductance). Its UI value is usually expressed by RXX, for example, r2.5k indicates that the UI value is 2500.
In addition, r5k, r7k, r8k, r10k, r12k, r15k, etc. are commonly used.
Even if the materials with the same UI value have different specifications and sizes, the reflected al value is also different, and the al value is directly proportional to its effective cross-sectional area.
Mn Zn material generally has a very small surface impedance, which is almost equivalent to a good conductor of electricity. Therefore, this kind of material must have a good insulating layer to isolate the coil body, otherwise it is very easy to produce high-voltage breakdown between primary coils. The properties of Mn Zn materials, especially the high UI materials, are affected by temperature. The influence of stress is extremely significant, and there is no fixed law to follow. After baking at 100 ℃ ~ 130 ℃, its L value generally increases by 10 ~ 15%.
Mn Zn ferrite material series is a kind of high frequency and low power consumption material, which is characterized by low power consumption under the condition of high frequency and high magnetic flux density. This material is mainly used with the transformer magnetic core of switching power supply, main transformer power supply, main transformer and TV, calculator, display and CRT tube.
Ni Zn ferrite
This kind of material is most widely used in choke inductive coils. Its main component is iron oxide, plus a small amount of trace elements such as zinc oxide, nickel oxide, copper oxide and cobalt oxide. It has stable characteristics and small variability. Each third-party manufacturer has become skilled in manufacturing technology and low price. It is the preferred magnetic core of ordinary choke coil. Due to the different trace elements, this kind of materials show different characteristics.
Ni Zn magnetic ring is usually not painted, and impedance measurement, i.e. Z value, is required. Sometimes a sense of quantity is required. There are not many Ni Zn magnetic rings used in our factory. Generally, it is RH, r6h, rid and other beam types, and the main supplier is Youci. Toroid products sometimes use Ni Zn materials. Generally, it is painted in green, which is the same as the color of Mn-Zn material. Pay attention to distinguish.
Ni Zn material has high surface impedance and is an electrical insulator used for EMI anti-magnetic interference (low impedance at low frequency and high impedance at high frequency)
Ni Zn materials generally have low saturated magnetic beam density (BS) and high coercivity (HC), can not withstand high current and large hysteresis loss, and have high surface impedance.
Korean CSC metal magnetic particle ring:
MPP class
MPP cores iron nickel molybdenum metal magnetic powder core
MPP is composed of 81% Ni, 2% Mo and Fe powder. The main features are: the saturation magnetic induction intensity is about 7500gs; The permeability ranges from 14 to 550; It has the lowest loss in the powder core; Excellent temperature stability, widely used in space equipment, outdoor equipment, etc; The magnetostrictive coefficient is close to zero, and there is no noise when working at different frequencies. It is mainly used in high-quality factor Q filter below 300kHz, induction load coil, resonant circuit, LC circuit with high requirements for temperature stability, output inductance, power factor compensation circuit, etc. it is commonly used in AC circuit, and the price of powder core is the most expensive.
This kind of material is generally expressed as: cmxxx XXX this material idc1 is very good. It is often used as an inductance requiring high current resistance. It is expensive and usually has a very low inductance coefficient. The appearance of the material is different from that of other materials. Generally, there are printing on the coating layer. The first three digits represent the outer diameter of the core, and the last three digits represent the UI value of the core.
UI value range: 26, 60, 75, 90125147160
Mainly used in: high Q filter, load coil, resonant circuit, RF interference filter, transformer, choke, differential mode inductance filter, DC bias output filter.
Sendust iron silicon aluminum magnetic particle core
Fe Si Al powder core is composed of 9% Al, 5% Si and 85% Fe powder. It mainly replaces the iron powder core, and the loss is 80% lower than that of the iron powder core, which can be used at frequencies above 8kHz; The saturation magnetic induction is about 1.05t; The permeability ranges from 26 to 125; The magnetostrictive coefficient is close to 0, and there is no noise when working at different frequencies; Higher DC bias capability than MPP; It has the best performance price ratio. It is mainly used in AC inductance, output inductance, line filter, power factor correction circuit, etc. Sometimes it is also used as transformer core instead of air gap ferrite.
The appearance representation of this kind of annular magnetic ring is basically the same as that of MPP material, except that it is painted in black, and the beginning of the printing is: csxxx XXX, the main component of which is iron silicon aluminum,
UI value range: 26, 60, 75, 90125
Application: power inductor in switching regulator or switching power supply, flyback transformer, pulse transformer, on-line noise filter, choke, dimming lamp phase control circuit, speed regulating motor control equipment.
High flux nickel iron magnetic particle core
It is composed of 50% Ni and 50% Fe powder. The main features are: the saturation magnetic induction intensity is about 15000gs; The permeability ranges from 14 to 160; In the powder core, it has the highest saturation magnetic induction intensity and the highest DC bias capacity; The magnetic core is small. It is mainly used in line filter, AC inductance, output inductance, power factor correction circuit, etc. it is commonly used in DC circuit. It is widely used in high DC bias voltage, high DC current and low AC current. The price is lower than MPP.
Chxxx begins with the letter XXX. It is mainly used in: line noise filter, switch adjustment inductance, pulse transformer and flyback transformer.
UI value range: 26, 60, 75, 90125
Summary: characteristics of the above three magnetic particle cores:
(1) It has high saturation flux density, so it can not be easily saturated in a large magnetization field.
(2) It has high effective permeability.
(3) Good magnetic stability.
Mn-Zn
Inductor design considerations
The frequency characteristics of inductors are mainly affected by three factors
A. The influence of core material loss is the most important, which leads to the negative slope of Q value from the maximum value.
B. Dielectric loss is also an influencing factor, especially in high frequency band.
C. The third factor is the self resonance effect of distributed capacitance and inductance.
The self resonant frequency has a negative impact on the performance of the inductor. The self resonant frequency is determined by the distributed capacitance and self inductance, and the distributed capacitance is determined by the winding method. Minimizing distributed capacitance is a very important consideration in winding design. For the winding of ring magnetic particle core, its effective capacitance is connected in parallel with the inductance. This distributed capacitance is the sum of the capacitances between wires, between layers, and between the winding itself and the magnetic particle core.
Good winding design technology is to minimize the voltage between turns and try to reduce the distributed capacitance. For example, dividing the winding into several groups or using winding row can effectively reduce the electric capacity. In the winding and internal sectional connection technology, it should be avoided to make the input end close to the output end as much as possible, because the two parts have the maximum potential energy between coils, and therefore the maximum effective capacitance is distributed. At the same time, the humidity index and the insulation constant of potting and packaging materials will also increase the distributed capacitance.
For precision wound magnetic core, high time stability and good temperature repeatability are required. Therefore, the winding stress must be released during its temperature cycle. In the magnetic powder core, the coil must be done as much as possible from room temperature to 125 degree temperature cycle. This temperature cycle is not only for releasing stress, but also for removing humidity. After finishing the temperature cycle, the inductor must be finally adjusted.
After winding, the magnetic core must
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