Definition of magnetic concept
Magnetic concept
Permanent magnet material: After being magnetized by an external magnetic field, the magnetism of the permanent magnet material does not disappear, providing a stable magnetic field to the external space. There are four commonly used measurement indicators for neodymium iron boron permanent magnets:
Residual magnetism (Br): Unit: Tesla (T) and Gaussian (Gs) 1Gs=0.0001T
When a magnet is magnetized by an external magnetic field in a closed circuit environment until it reaches technical saturation and then the external magnetic field is removed, the magnetic induction intensity exhibited by the magnet is called remanence. It represents the maximum magnetic flux value that a magnet can provide. From the demagnetization curve, it can be seen that it corresponds to the situation when the air gap is zero, so the magnetic induction intensity of the magnet in the actual magnetic circuit is smaller than that of residual magnetism. Neodymium iron boron is the highest Br practical permanent magnet material discovered today.
Magnetically induced coercivity (Hcb): units are amperes per meter (A/m) and Oster (Oe) or 1 Oe ≈ 79.6A/m
The value of the reverse magnetic field strength required to reduce the magnetic induction intensity to zero when a magnet is magnetized in reverse after technical saturation is called magnetic induction coercivity (Hcb). But at this time, the magnetization of the magnet is not zero, but the added reverse magnetic field and the magnetization of the magnet counteract each other. At this point, if the external magnetic field is removed, the magnet still has a certain amount of magnetic properties. The coercivity of neodymium iron boron is generally above 11000Oe.
Intrinsic coercivity (Hcj): units are amperes per meter (A/m) and Oster (Oe) 1 Oe ≈ 79.6A/m
The reverse magnetic field strength required to reduce the magnetization of the magnet to zero is called intrinsic coercivity. Intrinsic coercivity is a physical quantity that measures the ability of a magnet to resist demagnetization. If the applied magnetic field is equal to the intrinsic coercivity of the magnet, its magnetism will be basically eliminated. The Hcj of neodymium iron boron will decrease with the increase of temperature, so when working in high-temperature environments, a high Hcj grade should be chosen.
Magnetic energy product (BH): Unit: J/m3 or GOe 1 MGOe ≈ 7 96k J/m3
The product of B and H at any point on the demagnetization curve is called the magnetic energy product, while B × The maximum value of H is called the maximum magnetic energy product (BH) max. The magnetic energy product is one of the important parameters for the energy stored in a constant magnet, and the larger the (BH) max, the greater the magnetic energy contained in the magnet. When designing the magnetic circuit, the working point of the magnet should be located as close as possible to B and H corresponding to the maximum magnetic energy product.
Isotropic magnet: A magnet with the same magnetic properties in any direction.
Anisotropic magnets: The magnetic properties may vary in different directions; And there is a direction in which the magnet with the highest magnetic properties is oriented. Sintered neodymium iron boron permanent magnets are anisotropic magnets.
Orientation direction: The direction in which an anisotropic magnet can achieve the best magnetic performance is called the orientation direction of the magnet. Also known as the "orientation axis" or "easily magnetized axis".
Magnetic field intensity: Refers to the size of a magnetic field in a certain location in space, expressed in H, and its unit is amperes per meter (A/m).
Magnetization: refers to the sum of magnetic moment vectors per unit volume inside the material, expressed in M, in amperes per meter (A/m).
Magnetic induction intensity: The definition of magnetic induction intensity B is: B= μ 0 (H+M), where H and M are magnetization and magnetic field strength respectively, and μ 0 is the vacuum permeability. Magnetic induction intensity, also known as magnetic flux density, is the magnetic flux per unit area. The unit is Tesla (T).  
Magnetic flux: The total magnetic induction intensity within a given area. When the magnetic induction intensity B is uniformly distributed on the surface A of the magnet, the magnetic flux Φ The general formula for is Φ = B × A。 The SI unit of magnetic flux is Maxwell.
Relative permeability: The ratio of medium permeability to vacuum permeability, i.e μ r =  μ/μ o。 In the CGS system of units, μ o=1。 In addition, the relative permeability of air is often taken as 1 in practical use, and the relative permeability of copper, aluminum, and stainless steel materials is also approximately 1.
Magnetic conductivity: magnetic flux Φ The ratio to the magnetic electromotive force F is similar to the conductivity in a circuit. It is a physical quantity that reflects the magnetic conductivity of a material.
Permeability coefficient Pc: also known as demagnetization coefficient. On the demagnetization curve, the ratio of magnetic induction intensity Bd to magnetic field intensity Hd, i.e. Pc=Bd/Hd, can be used to estimate the magnetic flux value under various conditions. For isolated magnets, Pc is only related to the size of the magnet, and the intersection of the demagnetization curve and Pc line is the working point of the magnet. The larger Pc, the higher the working point of the magnet, and the less likely it is to be demagnetized. In general, the larger the orientation length of an isolated magnet, the greater the Pc. Therefore, Pc is an important physical quantity in the design of permanent magnet magnetic circuits.
  
Definition of commonly used units in magnetism
Conversion of common units of magnetic quantities:
Magnetic quantity name
SI Symbols and Units
CGS Symbols and Units
Unit conversion
Magnetic flux
Φ
Weber (Wb)
Φ
Maxwell (Mx)
1Mx=10-8 Wb
Magnetic induction intensity
B
Tesla (T)
B
Gaussian (Gs)
1Gs=10-4 T
magnetic field intensity
H
Amperes per meter (A/m)
H
Oe
1Oe=103/4p A/m
Magnetization
M
Amperes per meter (A/m)
M
Gaussian (Gs)
1Gs=103 A/m
Magnetic polarization intensity
J
Tesla (T)
4pM
Gaussian (Gs)
1Gs=10-4 T
Magnetic energy product
BH
J/m3
BH
GOe
1MGOe=102/4p kJ/m3
Vacuum permeability
4p•10-7H/m
－
one
－
 
How many ways can magnetic materials be magnetized?
Generally speaking, there are three ways to magnetize magnetic materials:
Unsaturated magnetization, saturated magnetization, supersaturated magnetization. The use of which method of magnetization machine is mainly determined by the requirements of the product. Generally, saturation magnetization is commonly used in engineering.
1. Unsaturated magnetization:
When magnetizing, the energy cannot reach more than 95% of the saturation magnetization. This magnetization is reversible, meaning that the residual magnetism of the magnet will gradually decrease with time and changes in the external magnetic field. This magnetization method is only used in special working situations and is rarely used.
2. Saturated magnetization:
It refers to the energy required for magnetization to reach the turning point of the magnetization characteristics of a magnetic material. It is generally 1.5 times the intrinsic coercivity (or remanence) of the magnetic material (critical pulling force) -2 times, and is generally 2 times the stable value. This method can saturate the magnet and magnetize it without demagnetization under normal circumstances.
3. Supersaturated magnetization
It refers to the energy required for magnetization energy to exceed the turning point of magnetic material magnetization characteristics, which is generally three times the intrinsic coercivity of magnetic materials. Due to the characteristics of magnetic materials, the surface magnetic field of a magnet only changes slightly with the increase of external magnetization energy after reaching saturation. So in environments with high magnetic energy requirements, this method is adopted.
 
Gauss meter is an important magnetic testing instrument
Gauss meters are important magnetic testing instruments, so wherever there is magnetism, Gauss meters will be used
1. Magnetic induction intensity is a physical quantity used to describe the properties of a magnetic field, represented by B. The direction of B at a certain point in the magnetic field is the direction of the magnetic field at that point, and the magnitude of B represents the strength of the magnetic field at that point.
2. Magnetic lines of force, magnetic flux, and continuity theorem of magnetic flux
We use magnetic field lines to vividly depict the magnetic field. The magnetic field lines of various magnetic fields generated by current are shown in Figure 1. The magnetic field lines are closed lines without heads or tails that surround the current. The direction of the current and the direction of the magnetic field line return conform to the right-hand rule.
3. By using Ampere's loop law, we can conveniently calculate the magnetic field generated by a current with a certain spatial symmetry. For example, calculating the magnetic field strength at point P inside a uniformly wound circular solenoid. Take a concentric circle with a radius of r passing through point P as the closed integral curve.
4. Electromagnetic induction law
The law of electromagnetic induction explains the relationship between induced electromotive force and changes in magnetic flux. The law states that regardless of any reason, the magnetic flux passing through a certain circuit Φ When a change occurs, the induced electromotive force generated in the circuit is:
e=-d Φ/ dt(12)
If the circuit is composed of N turns of coils, then when the magnetic flux changes, each turn will generate an induced electromotive force, and the total induced electromotive force is equal to the sum of the induced electromotive forces of each turn. When the magnetic flux passing through each turn is the same, there are:
e=N × d Φ/ dt(13)
The law of electromagnetic induction is one of the most widely applied laws in magnetic measurement.
When the magnetic flux in equation (13) undergoes periodic changes in a sinusoidal pattern, the relationship between the effective value of the induced electromotive force and the maximum value of the magnetic flux can be derived as follows:
U=4.44 × f × N ×Φ m(14)
We stipulate that the tangential direction of any point on the magnetic field line is the direction of the magnetic field (i.e. B) at that point, and the number of magnetic field lines per unit area perpendicular to the B vector is equal to the magnitude of the B vector at that point. That is to say, in places with strong magnetic fields, the magnetic field lines are denser, while in places with weak magnetic fields, the magnetic field lines are sparser.
The total number of magnetic field lines passing through a certain surface is called the magnetic flux passing through that surface Φ express. Take the area element on the surface, whose normal direction is equal to the direction of B at that point θ The magnetic flux of the element passing through this area is:
d φ= B × cos θ× ds(2)
So the total magnetic flux of S through the surface is
φ=∮ B × cos θ× ds(3)
When B is uniform and S is planar and perpendicular to B, the magnetic flux passing through the S plane is:
φ= B × S(4)
The law of electromagnetic induction is shown above, and we know that this is a relationship commonly used in magnetic measurements.
Explanation of magnetic related terms - magnetization
Magnetization: The process of increasing the magnetism of a magnetic substance without or with weak magnetism. In Japanese, it is called "magnetization", while in English it is called "magnetization".
Demagnetization: also known as demagnetization or demagnetization, the process of weakening or removing the magnetism of a magnetized substance, and sometimes used to explain the phenomenon of magnetic material disappearing. In Japanese, it means "demagnetize" and in English, it means "demagnetize".
Demagnetization: The process of reducing the magnetism of a magnetic substance, or the phenomenon of reducing the magnetism of a magnetic substance.
Magnetizing machine: also known as magnetization power supply, magnetization machine, etc., is an energy storage and control device used for magnetization.
Demagnetization machine: also known as demagnetization machine, demagnetization power supply, or demagnetization power supply, is an energy storage and control device during demagnetization.
Magnetizing coil: A coil used for magnetization, usually wound with copper material conductors, is a component that converts electrical energy into magnetic energy during magnetization.
Magnetic head: generally refers to a magnetizing component with an iron core or magnetic choke, also known as a magnetizing coil or magnetic choke, which is currently not uniformly named in China.
Pulse magnetic field: A pulse type magnetic field generated when a pulse current flows through a magnetizing coil, usually used to magnetize or demagnetize magnetic materials.
What is a magnetizer?
Magnetizing machine, also known as magnetizing machine, magnetizing machine, magnetizing machine. Its function is to magnetize the magnet. Magnets are newly produced and do not possess magnetism. They must be magnetized by a magnetizer before being magnetized.
A magnetizer is a fast saturation magnetizing device designed for filling magnetic fields with various strong magnetic materials, giving them the basic characteristic of never demagnetizing. The magnetizer can quickly saturate the magnetizing equipment and is dedicated to magnetizing various magnetic materials. Magnetizing machine is a device used to achieve product magnetization. Its types include capacitive pulse magnetization machines, non energy storage pulse magnetization machines, and constant current magnetization machines.
The working principle of the magnetization machine (magnetization power supply):
Firstly, the capacitor is charged with DC high-voltage voltage (i.e. energy storage), and then discharged through a coil (magnetizing fixture) with very low resistance. The peak value of discharge pulse current is very high, reaching tens of thousands of amperes. This current pulse generates a strong magnetic field in the magnetizing fixture, which can permanently magnetize the magnetic material placed in the magnetizing fixture. The peak pulse current during the operation of the magnetized electromechanical container is extremely high, and the magnetizing frequency is also relatively high, which requires high performance of the capacitor to withstand the impact current.