Permalloy magnetic core processing

1. Principle of power acquisition by collection unit The fault indicator acquisition unit uses the electromagnetic induction principle of "moving electricity generates magnetism, and moving magnet generates electricity" to generate electricity on the secondary coil through the electromagnetic coupling of the permalloy core. Voltage and current realize the transmission of electric power and achieve the purpose of drawing electricity from the conductor. As shown in the figure, when a primary current flows through the primary winding N1, an alternating magnetic flux Φ1 is generated in the core magnet. This alternating magnetic flux Φ1 passes through the core magnetic circuit and generates an induced voltage value U on the secondary winding. Compared with other electromagnetic mutual inductance transformations, the primary winding here is a cable or wire, and the number of turns is 1 turn. When the alternating magnetic flux Φ1 forms a closed loop in the magnetic core, it will be hindered by magnetic resistance Φr, magnetic space radiation (magnetic leakage ΦL), etc. Part of the magnetic flux will be lost, and only this part of the magnetic flux that passes through the secondary winding Φ2 can effectively transfer electric energy to the secondary side, that is, Φ1=ΦL+Φr+Φ2. It can be seen that under the same working conditions, the smaller the reluctance Φr and magnetic leakage ΦL, the greater the power output by the secondary side will be. Since the permalloy magnetic core acquisition unit needs to meet the requirements of live installation and disassembly, the magnetic core needs to adopt the cutting and snapping mode, that is, the magnetic core needs to be cut into two halves during production and then closed to form a ring magnetic circuit during installation. When the magnetic circuit is closed, an air gap will be generated due to the cutting gap. Compared with the original annular core, its magnetic resistance Φr and magnetic leakage ΦL are greatly increased. Under the same working conditions, the better the cutting process, the smaller the air gap, and the smaller the magnetic resistance. The smaller the resistance Φr and magnetic leakage ΦL will be, the greater the secondary side output power will be. In order to reduce the magnetic circuit loss and increase the secondary side output power level under the same wire current, it is necessary to use magnetic core materials with high magnetic permeability and high saturation magnetic flux density Bs value, making the selection of magnetic core materials tend to be high-end. . After our many experiments, the materials that meet the power extraction requirements of the fault indicator collection unit are: permalloy 1J85, iron-based nanocrystal 1K107.   Physical Properties/Magnetic Properties of Magnetic Materials: 2. The relationship between magnetic flux and power/correlation calculation between theoretical formulas: (1)Φ1=B*Ae (2)B=μ*H (3)μ=AL*Le/0.4*π* N²*Ae(N²=1) (4) H=0.40π*N*I/Le in: μ: magnetic permeability B: Magnetic flux density Ae: core cross-sectional area H: magnetic field strength AL: inductance coefficient Le: equivalent magnetic circuit length It can be seen that at the same primary side current, the higher the magnetic permeability μ, the shorter the equivalent magnetic path length Le of the magnetic core, the larger the core cross-sectional area Ae, and the larger the primary side magnetic flux Φ1.   In order to minimize the losses of Φr and ΦL after the magnetic flux on the primary side is transferred to the secondary side, it is necessary to reduce the reluctance loss and magnetic leakage loss, that is, to increase the magnetic permeability, optimize the effective magnetic path length of the magnetic core, and adopt excellent technology to ensure The cut surfaces of the core fit snugly. In our actual processing practice, the magnetic permeability of 1K107 iron-based nanocrystalline magnetic core after cutting can reach more than 15,000, and the magnetic permeability of 1J85 permalloy magnetic core after cutting can reach more than 12,000. What is the magnetic permeability of permalloy core after cutting? To be broken down in the next episode.   3. Analysis of the reasons for burnt power coil Since the power coil works under power frequency conditions, if the magnetic core is properly designed, the iron loss caused by the eddy current in the magnetic core will not be too large, so the permalloy magnetic core will not burn out. The situation is mainly caused by improper design of the secondary winding. When the operating current on the primary side of the fault indicator rises, the output current on the secondary side will also rise accordingly, that is, I1:I2 =N1:N2 is satisfied. Therefore, it is necessary to consider the winding copper wire according to the possible continuous maximum current on the primary side conductor. The wire diameter and current density on the winding should not be too large, otherwise high heat will be generated on the winding, causing the coil to burn out.   4. Example application 1J85 (0.2mm permalloy) and 1K107 (0.025mm iron-based nanocrystal) are both ultra-high permeability soft magnetic materials. Under power frequency conditions, the eddy current loss is almost negligible. In the current fault indicator acquisition unit In power applications, its excellent magnetic properties are unmatched by other permalloy core magnetic materials. The price of magnetic cores between 1J85 and 1K107 is about 2:1. In large-volume applications, 1K107 has outstanding magnetic performance advantages and price advantages.