Why is the core saturated? Will air be saturated as a core medium?

Generally, the permeability of the iron core is very high, while the permeability of the air is about 1. Therefore, the power inductors usually used are iron core inductors, while the inductance of air core inductors is very small, the current used is very small, and there is no saturation in the specific use process.

The following is the derivation of the formula between magnetic field strength b, inductance value, current, and permeability

The magnetic induction intensity b is the number of magnetic field lines perpendicular to the unit area; Magnetic flux is the product of the magnetic induction intensity b and the area, that is, =bs, b= s, and the flux is the total magnetic flux of the link of the conductive coil or current loop, that is, =n =li, =li n, substituting b = s = li n s, n turns, the area of s is unchanged, and b is also unchanged after magnetic saturation, if the current increases again, l will decrease, knowing that there is no inductance, it is equivalent to a wire, that is, it loses its inductance. Or, the permeability U=B H, B=Li N S, H=Nik(n turns, i current, k coefficient), then U=Li N S Nik, L=Un 2sk, the number of turns n does not change, the area S does not change, the coefficient K does not change, and the permeability u will be smaller with the increase of current, when saturation the permeability u tends to 1, and then increases, the permeability u tends to be close to 0, from the formula, the inductance is proportional to the permeability, that is, the current has been increasing, the inductance value is also close to 0, there is no inductance value, and the inductance is lost.

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Magnetic saturation phenomenon:

From the microscopic level, the reason why ferromagnetic materials can be magnetic is because they have countless magnetic domains inside, and the magnetic domains are the overall magnetic moments composed of atomic arrays in a small space region inside the ferromagnetic materials, and the magnetic moments composed of the atomic array in each space region represent a magnetic domain, but the direction of the magnetic moment between these magnetic domains is not unified, so when there is no external magnetic field, the magnetic domains in different directions cancel each other, and the ferromagnetic materials are not magnetic from a macroscopic point of view. When an external magnetic field is applied, the direction of the countless magnetic domains in the material becomes uniform due to the influence of the external magnetic field, and the magnetism is macroscopically displayed. The stronger the external magnetic field, the more magnetic domains inside the material are unified in the direction, and the stronger the magnetization of the material at this time, and the stronger the external magnetism on the macroscopic scale.

However, this is not endless, when the external magnetic field strength increases to a certain value, the magnetization of the material will no longer increase, because the internal wandering magnetic domain has basically been unified direction, at this time, the material is said to have reached the saturation magnetization, and its external macroscopic magnetism is saturated, and you will not enhance the magnetism of the material if you increase the external magnetic field. On the contrary, when saturation is not reached, it is unsaturated.

Introduction to Magnetic Saturation:

Magnetic saturation is a physical property of a ferromagnetic material. When the strength of the external magnetic field slowly increases, the magnetic flux density (which you can understand as magnetism) inside the ferromagnetic material also slowly increases. When the magnetic field strength reaches a certain level and is strengthened, the magnetic flux density of ferromagnetic materials increases more and more slowly.

At this point, we can understand this phenomenon as magnetic saturation.

The phenomenon of magnetic saturation is a physical property of magnetic materials, which refers to the fact that due to the limitation of the physical structure of the magnetic permeable material, the magnetic flux through the brigade cannot be increased indefinitely, so as to maintain a certain state.

Magnetic saturation is a physical property of a magnetic material, and after magnetic saturation is generated, it is harmful in some occasions but sometimes beneficial in some occasions. For example, the magnetic saturation regulator uses the magnetic saturation characteristics of the core to achieve the purpose of stabilizing the voltage. If the added voltage of the power transformer greatly exceeds the rated voltage, the current will increase dramatically, and the transformer will soon heat up and burn out.

Suppose there is an electromagnet, when a unit current is passed, the magnetic field induction intensity is 1, when the current increases to 2, the magnetic induction intensity will increase to, when the current is 5, the magnetic induction intensity is 7, but when the current reaches 6, the magnetic induction intensity is still 7, if the current is further increased, the magnetic induction intensity is 7 and no longer increases, then it is said that the electromagnet produces magnetic saturation.

Inductors with magnetic cores have the problem of magnetic saturation, and adding ferrite or other magnetic permeable materials to the core of the inductor can take advantage of its high permeability to increase the inductance, reduce the number of turns, reduce the volume and improve the efficiency. However, due to the limitation of the physical structure of the permeable material, the passing magnetic flux cannot be increased indefinitely. The magnetic flux through a certain volume of permeable material will not increase until a certain amount, no matter how much current or turns you increase, you will reach magnetic saturation.

Especially in circuits with DC current, if the DC current has saturated the core, the AC component of the current will no longer be able to cause the flux to return to the pre-town. The inductor loses its purpose.

1) Core saturation:

u=b/h ；u is a quantity related to the core material; h is a quantity related to current and n;

a .When we talk about "saturation", we are talking about "saturation" because a fixed material has a maximum b or that b will no longer change with h when it reaches a certain value; In other words, within a certain range, b changes according to the relationship between or close to the above formula; When the current is too large, b will no longer change or grow slowly; Let's say the core is saturated; The word saturation is derived from the argument b, which is undoubtedly true;

b.If people had thought about this question from the perspective of U, it would have been fine; We can say that u, or more accurately, delta u, tends to zero, which also seems to be okay; If this is the case, maybe we call the core "zero", if it is inherited like this at that time, it is also right, hehe; So I think I'm right about hugging the main speaker!!

c.However, if we speak from B, we can directly say that B is saturated when it reaches a certain value, but from U, we can say U

Tends to 0 when it is saturated, but what conditions when that? It seems that everything that exists is reasonable, and it is better to define the problem from B, right?

2) Experimental performance:

a. l=u*s/l*n；The inductance is a quantity of the core material that is wound U, which is related to the volume and the number of turns to be wound.

As you can understand, if you tend to 0, the inductance will of course also tend to 0 or, more precisely, significantly decrease;

b.In our switching power supply, the switch tube and the magnetic element are generally connected in series, usually:

i=v l*t Once l is significantly smaller, i is significantly higher, the current suddenly becomes larger, and the life of the switch tube is not guaranteed, hehe.

c.The summary is: the core is saturated, the inductance suddenly decreases, the current rises sharply, the switch tube is not guaranteed, and the connected device is overcurrent, which is very dangerous.

When the excitation current of the motor increases, the magnetic induction intensity of the motor core no longer increases significantly, and when the applied voltage is higher than the rated voltage of the motor, the motor will be magnetically saturated.

The magnetic induction intensity b is the number of magnetic field lines perpendicular to the unit area; Magnetic flux is the product of the magnetic induction intensity b and the area, that is, =bs, b= s, and the flux is the total magnetic flux of the link of the conductive coil or current loop, that is, =n =li, =li n, substituting b = s = li n s, n turns, the area of s is unchanged, and b is also unchanged after magnetic saturation, if the current increases again, l will decrease, knowing that there is no inductance, it is equivalent to a wire, that is, it loses its inductance. Or, the permeability U=B H, B=Li N S, H=Nik(n turns, i current, k coefficient), then U=Li N S Nik, L=Un 2sk, the number of turns n does not change, the area S does not change, the coefficient K does not change, and the permeability u will be smaller with the increase of current, when saturation the permeability u tends to 1, and then increases, the permeability u tends to be close to 0, from the formula, the inductance is proportional to the permeability, that is, the current has been increasing, the inductance value is also close to 0, there is no inductance value, and the inductance is lost.

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