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From the wire with large current, a small current can be induced in a certain proportion for measurement, and it can also provide power for relay protection and automatic devices.   Example: For example, there is a very thick cable with a very large current. If you want to measure its current, you need to disconnect the cable and connect the ammeter in series in this circuit. Because it is very thick and the current is very large, a large ammeter is needed. But in fact, there is no such large ammeter, because the specifications of the current meter are all below 5A. What should I do? At this time, you need to use a current transformer.   First select a suitable current transformer, and then pass the cable through the current transformer. At this time, the current transformer will induce current from the cable, and the magnitude of the induced current is just reduced by a certain multiple. Send the induced current to the instrument for measurement, and then multiply the measured result by a certain multiple to get the real result.   For example, now you need to measure the current magnitude of a cable. First, pass a cable through a 500/5 current transformer (500/5 is actually 100 times), then connect the current transformer to the ammeter, and the ammeter measures 4A. From this, we can calculate that the real current of the cable is 4*100=400A.   Wiring diagram: Some friends may say that a clamp meter can also achieve this goal. In fact, there is a current transformer inside the clamp meter, and the principle is similar.   Use: 1) The wiring of the current transformer should comply with the series principle: that is, the primary winding should be connected in series with the circuit to be measured, and the secondary winding should be connected in series with all instrument loads 2) According to the size of the measured current, select the appropriate change, otherwise the error will increase. At the same time, one end of the secondary side must be grounded to prevent the primary side high voltage from entering the secondary low voltage side once the insulation is damaged, causing personal and equipment accidents 3) The secondary side is absolutely not allowed to be open-circuited, because once the circuit is open, the primary side current I1 will all become magnetizing current, causing φm and E2 to increase sharply, causing the core to be over-saturated and magnetized, causing serious heat and even burning the coil; at the same time, after the magnetic circuit is over-saturated and magnetized, the error increases. When the current transformer is working normally, the secondary side is similar to a short circuit. If it is suddenly opened, the excitation electromotive force will suddenly change from a very small value to a very large value, and the magnetic flux in the core will present a severely saturated flat-top wave. Therefore, the secondary winding will induce a very high peak wave when the magnetic field passes through zero, and its value can reach thousands or even tens of thousands of volts, which will endanger the safety of the staff and the insulation performance of the instrument.In addition, the secondary side open circuit makes E2 reach hundreds of volts, which will cause electric shock accidents once touched. Therefore, the secondary side of the current transformer is equipped with a short-circuit switch to prevent the primary side from opening. As shown in Figure 1, K0, during use, once the secondary side is open, the circuit load should be removed immediately, and then the vehicle should be stopped for processing. It can be used again after everything is processed. 4) In order to meet the needs of measuring instruments, relay protection, circuit breaker failure judgment and fault recording devices, current transformers with 2 to 8 secondary windings are installed in the generator, transformer, outgoing line, busbar section circuit breaker, bus tie circuit breaker, bypass circuit breaker and other circuits. For large current grounding systems, it is generally configured in three phases; for small current grounding systems, it is configured in two or three phases according to specific requirements 5) The installation location of the protective current transformer should be set to eliminate the non-protected area of ​​the main protection device as much as possible. For example: if there are two sets of current transformers, and the position allows, they should be installed on both sides of the circuit breaker so that the circuit breaker is within the cross protection range 6) In order to prevent the flashover of the pillar current transformer bushing from causing busbar failure, the current transformer is usually arranged on the outgoing line or transformer side of the circuit breaker 7) In order to reduce the damage caused by internal faults of the generator, the current transformer used for automatic adjustment of the excitation device should be arranged on the outgoing line side of the generator stator winding. In order to facilitate analysis and find internal faults before the generator is connected to the system, the current transformer used for measuring instruments should be installed on the neutral point side of the generator.   Principle: In the power supply and electricity lines, the current and voltage vary greatly from a few amperes to tens of thousands of amperes. In order to facilitate the measurement of secondary instruments, it needs to be converted into a relatively uniform current. In addition, the voltage on the line is relatively high. If it is measured directly, it is very dangerous. The current transformer plays the role of current conversion and electrical isolation. Earlier, most of the display instruments were pointer-type current and voltage meters, so most of the secondary currents of the current transformers were ampere-level (such as 5A, etc.).   The current ratio of the primary winding current I1 to the secondary winding current I2 of the current transformer is called the actual current ratio K. The current ratio of the current transformer when working at the rated working current is called the rated current ratio of the current transformer, expressed as Kn.   Kn=I1n/I2n I. What are the common faults of the current transformer? How to judge and deal with it? What items should be checked during normal inspections. A. Common faults of current transformers are: 1. The secondary side of the current transformer is open 2. The current transformer is overheated during operation 3. Smoke or odor inside the current transformer 4. The screws of the current transformer coil are loose, and there is a short circuit between turns or layers 5. Discharge inside the current transformer, abnormal sound or discharge sparks between the lead and the shell 6. The oil-filled current transformer has serious oil leakage or the oil level is too low   B. Usually, judgment and treatment should be carried out according to the abnormal phenomenon that occurs. For example, use a temperature test wax sheet to check the heating condition, and judge whether it is open circuit according to the sound and meter indication value. Once a fault is found, it should be repaired or replaced immediately. The items of normal patrol inspection generally include:   1. Check for overheating and abnormal odor 2. Regularly check the insulation condition 3. Check whether the three-phase indication value of the ammeter is within the allowable range and whether it is overloaded 4. Whether the porcelain part is clean and complete, whether there is damage and discharge 5. Whether the oil level of the oil-filled current transformer is normal, and whether there is oil leakage 2. Why is the secondary side of the current transformer not allowed to be open circuit? What are the dangers after opening the circuit?   1. Usually, the primary current of the current transformer has nothing to do with the current of the secondary load. When the current transformer is operating normally, since the secondary side impedance is very small (close to the short circuit state), most of the magnetic lines of force generated by the primary current are compensated by the secondary current, the total magnetic flux density is not large, and the secondary side potential is not high. But when the secondary circuit is open, the secondary current is equal to zero, and the primary current completely becomes the excitation current, generating a very high potential in the secondary coil (the peak value can reach several thousand volts or even higher), which may not only damage the secondary insulation, but also threaten personal safety. In addition, excessive increase in the core magnetic flux density may also cause the core to overheat and be damaged.   III. Hazards of long-term overload of current transformer Once the current transformer is overloaded for a long time, the core magnetic flux density will reach saturation, increase the error of the current transformer, and the meter indication will be incorrect, so it is not easy to grasp the actual load or operation. In addition, due to the increase in magnetic flux density, the core and secondary coil will overheat and the insulation will be damaged.   IV. Signs and treatment of the secondary side of the current transformer open circuit: When the secondary side of the current transformer is open, it is often accompanied by the following phenomena:   1. The ammeter and power meter indicate zero, the electric meter does not rotate, and a buzzing sound is emitted. 2. The current transformer itself has a squeaking discharge sound or other abnormal sounds, and the terminal block may be burnt.   When the current transformer is open-circuited, the potential generated is related to the primary current. Therefore, when dealing with the open-circuit fault of the current transformer, it is necessary to reduce the load or make the load zero, and then use insulating tools to handle it. The corresponding protection device should be disabled during the handling.

When we choose an inductor, we need to choose different inductors for different circuit boards. At the same time, we also need to see what the role of the inductor is in the circuit. Only in this way can we pre-select the desired inductor from many inductor types. So what should we pay attention to when using a magnetic ring inductor in the circuit? Today, let's learn about the precautions for selecting a magnetic ring inductor.   We all know the importance of inductor selection to the progress of a plan. If there is a problem with the inductor selection in the plan, it will seriously delay the construction period, waste manpower, funds, etc. and cause significant losses. When selecting a magnetic ring inductor, pay attention to the following points:   1. The inner diameter of the magnetic ring inductor is often larger than its own wire diameter, so as not to cause damage to the circuit board wire.   2. When we choose a magnetic ring inductor, we must also know what its role is in the circuit, that is, what kind of clutter should be resisted in the circuit, whether it is high frequency or low frequency, because this is about the selection of its important component-the magnetic core. There are two main types of magnetic ring inductor cores: manganese core and nickel core. Nickel core anti-interference magnetic ring belongs to high-frequency anti-interference. Its magnetic permeability generally ranges from tens to one thousand. Its magnetic permeability is low, and the loss is very small under high-frequency operation. It can work in high-frequency short waves. Manganese core magnetic ring inductor is opposite to nickel core. The selection of these two magnetic cores must be made by customers according to the actual application of magnetic ring inductor.   3. There is another important factor in the selection of magnetic ring inductor-wire diameter. The size of the wire diameter should be determined according to the actual current of the magnetic ring inductor.   In short, when selecting magnetic ring inductor, if the installation space allows, try to choose a long length, large outer diameter, and inner diameter that fits the connecting wire, so that the anti-interference performance will be stronger.   If the magnetic ring inductor in the circuit is not selected correctly, or it is not installed properly during installation, the magnetic ring inductor will not play the due anti-interference role, resulting in serious consequences of equipment damage. Therefore, the magnetic ring inductor should be used accurately.

The split core current transformer is a sensor instrument that can be used for current measurement and microcomputer protection. Because of the characteristics of the split-type core that can be customized, opened and easy to install, it is widely used in the fields of AC motors, lighting equipment, air compressors, and current monitoring of heating, ventilation and air conditioning devices, power management, building self-control systems, and industrial power grid transformation.   The split core transformer core produced by Hemei Electronics can not only be customized according to customer requirements, but also have a measurement accuracy of up to 0.2S level. In terms of materials, the split-type transformer core uses high-magnetic induction high-quality silicon steel sheets with excellent characteristics such as high magnetic flux density, low iron loss and low magnetostriction; in production and processing, a high-precision slitting machine is used to slit the silicon steel sheets, and then after computer-controlled fully automatic winding and winding forming and high vacuum annealing, it is cut into the size and shape required by the customer by a precision cutting machine, which ensures the accuracy and stability of the core and can be better applied to the field of split-type transformers.   Material: silicon steel, Permalloy   Thickness: 0.23mm, 0.27mm, 0.30mm   Annealing: ultra-high vacuum annealing   Specifications: customized according to customer requirements, ring, rectangle, special shape are all available   Price: Depends on the material and shape   II. Comparison of advantages and disadvantages of open-type current transformer   1. Advantages:   This type of current transformer uses high-quality imported silicon steel sheets with high magnetic permeability as magnetic conductive materials. It has the characteristics of divisible iron core and small magnetic circuit loss. Its semi-circular iron core and secondary winding are vacuum cast in a flame-retardant plastic shell with high-quality epoxy resin, which is moisture-proof, stable in performance, and maintenance-free.   2. Disadvantages:   Since the iron core is separated, the accuracy cannot be too high. Generally, the highest accuracy is 0.5.   During installation, clamp the two semicircular rings on the phase-splitting cable and hold it tightly with a clamp. The three elastic rubber rings press against the cable and integrate it with the cable, which is harmonious and beautiful. It is applicable to 10KV and 35KV cables of 35mm-400mm.   III. Applicable occasions   Applicable occasions: general measurement and protection in power systems with strong mobility or narrow space.

Is the split core transformer good? What are the disadvantages of the split core current transformer?   What is the split core transformer? Is the split core transformer good? The split core current transformer is suitable for indoor devices with a rated voltage of 10kV and below. It is used for circuit control, measurement, line transformation measurement and protection. So what are the disadvantages of the split core current transformer? The link of the induction current in the split core transformer is disconnected, that is, the induction core is not a closed whole, and the magnetic circuit efficiency is reduced at the gap. It is difficult to make a complete fit after the opening, so there will be a certain impact on the induction effect and accuracy.   Is the split core transformer good? The split core current transformer is suitable for indoor devices with a rated voltage of 10kV and below. It is used for circuit control, measurement, line transformation measurement and protection.   Structure introduction of split core current transformer This current transformer adopts a high-strength PVC shell and a fully cast busbar structure. The transformer is directly stuck on the cable. Three elastic rubber rings are against the cable and the cable is integrated. The transformer core is made of high-quality silicon steel sheets, and the secondary wire is evenly wound on the core. The transformer is an split core structure and can be installed without cutting the cable.   Application scope of split core current transformer 1. The altitude of the installation site does not exceed 3000m; 2. Ambient temperature: -25—+40℃; 3. The outer diameter of the primary cable that can be worn: φ8—φ240mm 4. Input: 0~60KA 5. Output: 0~500mA 1A or 5A 5VDC or 4~20MA (customer-defined) There is no pollution, corrosive and explosive media in the atmosphere that seriously affect the insulation performance of the transformer.   What are the disadvantages of split core current transformers 1. The working noise is relatively loud 2. The heat is relatively large 3. The measurement error is relatively large 4. The price is high   The link of the induction current in the split core transformer is disconnected, that is, the induction core is not a closed whole, and the efficiency of the magnetic circuit is reduced at the gap. It is difficult to make it fit perfectly after opening, so it will have a certain impact on the sensing effect and accuracy.

The split core current transformer can convert high voltage into low voltage and large current into small current for measuring or protecting the system. What is its accuracy check like? The following is the editor's summary:   1. Error breakdown The split current transformer test generally uses the comparison of the measured current and the standard current, and the secondary current difference is the error. This inspection method is called the comparison method. The standard product requires two levels higher than the measured product, and the error can be ignored at this time. If the standard product is only one level higher than the measured product, the error of the test result plus the error of the standard product should be considered.   2. Calibration: In addition to the standard product and the calibrator, there should be a current booster that can provide the primary current for the split current transformer, a voltage regulator, and a load that can adjust the current of the current booster.   3. Usually, a calibrator is used to measure the quantity. Since the product calibrator measures the ratio of the current difference between the measured product and the standard product to the secondary current, the requirements for the calibrator are not high. What level of split current transformer can be checked is basically determined by the standard product.   In order to transmit electrical energy, split core current transformers often use AC voltage and high current circuits to deliver electricity to users, and this electricity cannot be directly measured by instruments.

Not necessarily.   The magnetic force F of the magnet is the product of the magnetic field magnetic induction intensity gradient deltaB and the magnetic moment m, F=deltaB*m.   The purpose of adding an iron core to the solenoid coil is to make the magnetic field generated by the solenoid magnetize the magnetic material of the iron core to increase its magnetic moment. The magnetic moment of the helix is ​​m1=NIS, the magnetic moment of the iron core is the volume component of its magnetic field intensity M m2=MV, and the magnetic field intensity M of the magnetic material is the magnetic field intensity H of the solenoid multiplied by the magnetic permeability u of the magnetic material, and the magnetic permeability is the product of the relative magnetic permeability u0 of the vacuum and the relative magnetic permeability ur of the magnetic material (i.e. u=u0*ur).   Finally, F=(m1+m2)*deltaB=(NIS+Mv)*deltaB=(NIS+uo*ur*H*v)*deltaB. The relative magnetic permeability ur of Permalloy is indeed very high. If the current in the solenoid is very small, that is, the magnetic field intensity H generated by the solenoid is very small and has not yet reached the saturation of Permalloy, its suction will indeed increase; but the saturation magnetic induction intensity of Permalloy is low, and the magnetic field generated by the solenoid reaches 7000A/m, which can basically magnetize it to saturation, and its suction will not continue to increase.   Therefore, your answer is not necessarily. When the current of the solenoid is small and has not yet saturated the magnetic core, its suction can be increased; but if the current is large and saturates it, a magnetic material with high saturation magnetic induction intensity and high relative magnetic permeability should be selected.

Classification of magnetic materials   Magnetic materials are divided into two types: soft magnetic materials and hard magnetic materials. Magnetic materials that are easily demagnetized after magnetization are called soft magnetic materials, and their coercive force is very small. Hard magnetic materials (such as magnetic steel and permanent magnetic alloys) are not easy to demagnetize.   Soft ferrite cores are an important category of magnetic materials. They are widely used, such as magnetic rods in radios, magnetic cores in tape recorders and televisions, magnetic rings of deflection coils, magnetic heads of video recorders, and high-frequency transformers in switching power supplies. Soft ferrite cores come in many varieties and shapes, and can be roughly classified as follows:   (1) Classification by shape: mainly threaded cores, ring cores (referred to as magnetic rings), tubular cores, pot cores (i.e. magnetic pots), E-shaped, sun-shaped, U-shaped, T-shaped, I-shaped, and Wang-shaped cores. In addition, there are single-hole, double-hole, and multi-hole cores.   (2) Classification by working frequency: there are low frequency, medium frequency, high frequency and very high frequency cores.   (3) Classification by material: the material grades are as follows: MXO-manganese zinc ferrite; NXO-nickel zinc ferrite; NQ-nickel lead ferrite; NGO-nickel zinc high frequency ferrite; GTO-very high frequency ferrite.

Components related to "magnetism" in circuit boards include Permalloy cores, inductors, transformers, electromagnetic relays, contactors, Hall sensors, etc. This article explains the inspection and maintenance methods of magnetic components in circuit boards.   (1) Inductor Inductor coils are wires wound around an insulating frame, which can be hollow, iron core or magnetic core. In the application of industrial control circuit boards, the most common use is for filtering or energy storage in switching power supplies. Various appearances of inductors. The unit of inductance is Henry, abbreviated as Henry, represented by the letter H. There are also millihenry (mH), microhenry (uH), and nanohenry (nH). The relationship between them is: 1H = 1000mH 1mH = 1000uH 1uH = 1000nH Inductor coils use direct marking method, 22uH, 100 represents 10uH, 4R7 represents 4.7uH, R10 represents 0.1uH, and 22n represents 22nH; some inductors use color ring marking method, and their inductance is the same as the color ring resistor, such as color ring brown, black, brown, and silver represent inductance 100uH ±10% There is a type of inductor used to absorb ultra-high frequency (above 50MHZ) interference, this type of inductor is called magnetic beads. There is another type of commonly used inductor called common mode inductor, also called common mode choke. It is a 4-terminal device led out by two identical windings wound on a ferrite core (Permalloy core). Each set of coils is connected in series in the circuit. If there is a differential mode signal, the magnetic flux generated by the signal through the two coils cancels each other, and the coil has no blocking effect on the differential mode signal. When there is a common mode signal, the magnetic flux generated by the two coils is enhanced, and the coil's blocking effect on the signal is enhanced. This blocking effect is bidirectional, which can not only prevent the front-stage interference signal from entering the rear stage, but also prevent the rear-stage interference signal from entering the front stage. In the maintenance of industrial circuit boards, inductor coils are components that are not easy to damage. Occasionally, they are broken due to corrosion, burned due to excessive current, and short circuits between coil turns. Open circuit damage can be measured with the resistance range of a multimeter. The inductance can be measured with an inductance tester. It is recommended to use a digital bridge to test the inductance. Because most power circuit energy storage inductors operate at higher frequencies, all above 10kHz, the frequency is selected at 10kHz when using a bridge test. In addition to paying attention to the inductance, the test focuses on the D value. The normal D value should be less than 0.1. If the D value is greater than 0.2, it is determined that there is a short circuit between the coil turns.   (2) Transformer The transformer is a device that uses the principle of electromagnetic induction to change the voltage. Common transformers in industrial control circuit boards are power frequency transformers using iron cores and switching transformers using ferrite cores (Permalloy cores). The basic characteristics of an ideal transformer are: the ratio of the input and output AC voltages is the same as the ratio of the number of turns of the input and output coils, so in theory, the AC voltage can be arbitrarily stepped up or down. Transformers with silicon steel sheet cores are generally used in industrial frequency applications of 50~400HZ. The magnetic flux density of the silicon steel sheet core is large. Although there is insulation paint between the stacked silicon steel sheets, there is still eddy current loss in a single silicon steel sheet. This type of core is not suitable for high-frequency applications. The resistivity of ferrite core is much greater than that of metal and alloy magnetic materials, so the eddy current loss is very small. Transformers made of ferrite core are used in relatively high-frequency occasions such as energy storage inductors and switching transformers of switching power supplies. In addition, different new transformer core materials have appeared, such as Permalloy and amorphous nanocrystalline materials, which can take into account both magnetic permeability and eddy current loss. Transformer failure detection method Common transformer damages include coil burnout or internal overheating that burns the coil insulation and causes a short circuit between coil turns. It is easier to judge the coil open circuit by measuring the resistance, while the short circuit between turns is more troublesome to judge because the coil itself has a small resistance and is not easy to distinguish through resistance testing. Generally speaking, transformers with serious internal short circuits between turns generate more heat, which will burn the covering material of the transformer coil and have more or less burnt smell. This situation can be clearly distinguished by observing the appearance of the transformer. Some transformers have internal turn-to-turn short circuits, which are not so obvious from the appearance. Friends who often repair switching power supplies may have such an experience, that is, they have tested and even replaced almost all suspected components of the switching power supply except the transformer, including the Permalloy core, but the power supply has not been repaired yet, and finally they suspect that the switching transformer is damaged. If there is a way to detect transformer damage at the beginning, wouldn’t it be easy? In fact, this is completely possible, and the instrument for detection is still a digital bridge. The method is to put the digital bridge in the 10KHZ test inductance loss D value state, and test it online without removing the transformer. The bridge signal voltage is selected as 0.3V, and the D value of the transformer main winding coil is tested. The normal transformer D value should be <0.1. If the D value is >0.2, the transformer is judged to be damaged. In addition to switching transformers, digital bridges are also applicable to determine whether other types of transformers are damaged, but it should be noted that when selecting the frequency, a frequency close to the actual operating frequency of the transformer should be used.   (3) Electromagnetic relays and contactors Electromagnetic relays and contactors are devices that use the electromagnetic force generated by electromagnetic coils in conjunction with springs and mechanical levers to control the on and off of contacts. Relays usually have a sealed packaging space to minimize the impact of external adverse environments on contacts. Relative to contactors, the contact current they control is smaller; the contact current of contactors is larger. There are also reed relays, whose principles are similar to those of electromagnetic relays, but the contact current is relatively smaller, the contacts are sealed, and are not polluted by dust, moisture and harmful gases, and the response speed and reliability are greatly improved. Common faults of relays and contactors are large contact resistance, burnt contacts, and open circuit when contacts are closed. When testing, the rated voltage can be applied to the coil to detect the conduction and closure of the contacts. Both the coil and the non-powered conditions must be tested. The ohm range of a multimeter can be used to measure the resistance of the contacts when they are on. If there is no abnormality, it is basically close to 0Ω. If it is above 10Ω, it is considered a fault. If the contacts are visible, emergency maintenance can be performed by filing off the ablated and oxidized parts of the contacts to reveal the metallic luster. The relay or contactor can be put back into use. For safety reasons, it is recommended to replace new parts. After the relay coil is energized, the energy is transmitted to the coil and the armature is attracted. After the power is cut off, if no measures are taken, the electromagnetic energy of the coil will inevitably generate a high self-induced electromotive force at both ends of the coil during the transition from power on to power off. There will be a high voltage, which may damage other components. Therefore, a diode should be connected in reverse parallel to the coil to provide a release circuit for the electromagnetic energy of the coil. When testing the quality of the relay online, a reverse coil rated voltage can be applied to the diode end according to the direction of the diode for detection without removing the relay to detect the Permalloy core. In high current occasions such as inverters and servo drives, many current detections require Hall sensors. The working principle of Hall current sensors is based on the Hall effect. A certain current is passed through a conductive sheet in the x direction, and the magnetic field in the z direction passes through the sheet vertically. Then, the electrons in the conductive sheet are acted upon by the Lorentz force in the process of moving toward the negative pole, and gather in the y+ direction, making one end in the y+ direction negatively charged and the other end in the y- direction positively charged. If the voltage VH at both ends is measured, its magnitude is proportional to the current I and the magnetic induction intensity B. If the current I is constant, then the magnitude of VH directly reflects the magnitude of the magnetic induction intensity B, so as long as VH is measured, the magnitude of B can be known. The principle of the Hall current sensor is that the through-core conductor generates a circumferential magnetic field proportional to the current. The magnetic field passes vertically through the Hall sensor in the middle of the iron core. The Hall voltage Vh induced by the sensor is proportional to the measured current of the conductor, so the current of the measured conductor can be measured contactlessly. The actual Hall sensor has three wires, two positive and negative power lines, and one current lead line. A sampling resistor is connected in series between the current lead line M and 0V. The direction and magnitude of the current flowing through the sampling resistor are proportional to the magnitude and direction of the current passing through the sensor wire. Therefore, the magnitude and positive and negative of the voltage at both ends of the sampling Permalloy core resistor reflect the magnitude and direction of the wire current. Detection method of Hall current sensor It is common for the current sensor to be damaged. The most convenient test method is to test the voltage of the output end to 0V after power is turned on. If there is no current in the core wire, the voltage at the sensor signal output end should be 0V. If the measured voltage offset is more than ±1V, it is judged that there is a problem with the Hall current sensor and the Permalloy core. Some Hall sensor Permalloy cores are connected to a single power supply. When there is no current in the corresponding core wire, the signal output voltage is half of the power supply voltage. If a 5V voltage is connected, the output voltage is 2.5V.  

The magnetic core plays an indispensable role in the electronic transformer, and a good magnetic core will affect the effectiveness of the electronic transformer. Traditional magnetic cores are made of ordinary ferrites. However, with the advancement of technology, amorphous magnetic cores have gradually emerged. Compared with traditional magnetic cores, amorphous magnetic cores are favored because of their much higher saturation magnetic density than ordinary ferrite cores, low loss and small size. Amorphous magnetic cores can be divided into strip-type magnetic cores and powder-type magnetic cores according to the shape of the material. Compared with strip-type magnetic cores, powder-type amorphous magnetic cores can achieve more diverse shapes, sizes and even colors, and are more suitable for small and lightweight electronic transformers. In 2019, 70% of transformers will be made of amorphous materials, and the market for powder amorphous magnetic cores is vast.  

Introduction to Permalloy Fe-Ni alloy is the so-called permalloy, which is a very important type of soft magnetic material. It shows high magnetic permeability and low coercive force under weak magnetic field magnetization, and has good cold working properties. By controlling the composition (changing the Ni content, adding one or several alloying elements, such as Mo, Cu, Cr and Ti, etc.) and the process, a variety of permalloys with different characteristics can be obtained. There are many, which can be regarded as the most soft magnetic materials. However, its disadvantage is that it contains more precious metal Ni. Therefore, the cost is relatively high, the production equipment is huge, the process is demanding, and the magnetism is greatly affected by the environment. The Fe-Ni alloy produced in our country has a wide range of specifications and brands, and has been issued by the Ministry of Industry and Information Technology.   Permalloy annealing process precautions Compared with the one-stage annealing (1100℃×3h) in the two-stage continuous annealing (950℃×3h→1100℃×3h), the coercive force is reduced from 217.6 A/m to 8.8A/m, and the coercive force is significantly reduced and saturated. The magnetization intensity increased slightly from 74.22 emu/g to 79.34 emu/g. This shows that the two-stage continuous annealing process is beneficial to removing impurities in the alloy, purifying the alloy, thereby improving the magnetic properties of the alloy.   Permalloy preparation 1. The two-stage continuous annealing process is beneficial to remove impurities in the alloy, purify the alloy, and at the same time improve the magnetic properties of the alloy, that is, the coercive force is reduced and the saturation magnetization is increased. 2. Prolonging the holding time is beneficial to the growth of alloy grains, reducing defects within the crystal, weakening the pinning effect on domain wall movement, and making domain wall movement easier, thus improving magnetic properties. But it’s not that the longer the heat preservation time, the better. Because at high temperatures and long holding times, the reduction and oxidation of hydrogen and impurities in the furnace pollutes the atmosphere in the furnace, and the hydrogen dew point also increases with the increase in temperature, resulting in a decrease in the magnetic properties of the alloy. Therefore, the holding time is extended to 4 hours. On the one hand, it is beneficial to improve production efficiency, and on the other hand, it also obtains better soft magnetic properties. Taking various factors into account, the optimal heat treatment process for IJ79 alloy is determined as follows: raising the temperature to 950°C in the furnace, holding it for 4 hours, then raising the temperature to 1100°C, holding it for 4 hours, and finally cooling the furnace to room temperature. 3. The effect of changes in Ni content in the alloy on its magnetic properties was studied. It was found that if the change in Ni content is too small, the effect on the magnetic properties of the alloy is not significant. Therefore, during the production process, it is only necessary to ensure that the Ni content is within the composition of the standards issued by the Ministry of Metallurgy (YB129-70). 4. Add M to the alloy. The content is beneficial to increase the saturation magnetic induction intensity and reduce the coercive force. Combining various factors, we found ultra-low H. The preferred composition of the alloy is: Ni 78.00wt%, Mo 5.00wt%, Mn 0.90wt% Si 0.40wt%, Fe balance.

1. Advantages of Nanocrystals  Nanocrystalline magnetic rings (ultramicrocrystalline iron cores) also have the advantages of silicon steel, permalloy, and ferrite cores. Right now:  High magnetic induction: saturation state magnetic induction Bs=, which is twice that of permalloy. The transformer core has high power and can exceed 15 kW ~ 20 kW/kg.  High magnetic permeability: The original magnetic permeability μ0 of static data can reach 120,000 to 140,000, which is very similar to that of permalloy. The magnetic permeability of the coil used to output power transformer is more than 10 times that of the ferrite core, which greatly reduces the excitation current output power and improves the efficiency of the transformer.    Low loss: In the frequency range of 20kHz to 50kHz, the ferrite core is 1/2 to 1/5, reducing the transformer core temperature.  High Curie temperature: The Curie temperature of the nanocrystalline magnetic ring (ultra-microcrystalline iron core) reaches 570°C, while the Curie temperature of the ferrite core is only 180°C ~ 200°C.  Because of its advantages, nanocrystalline transformers are used in inverter power supplies, which has a great effect on improving the reliability of switching power supplies:  The loss is small and the temperature of the transformer is low. The long-term practical use of many users has confirmed that the temperature of the nanocrystalline transformer is far lower than the temperature of the IGBT water pipe.  The high magnetic permeability of the transformer core reduces the excitation current output power, reduces copper loss, and improves the efficiency of the transformer. The primary and secondary inductors of the transformer are large, which reduces the impact of current on the IGBT water pipe when the power is turned on and off.  During operation, the magnetic induction is high and the power is high, which can exceed 15Kw/kg. Reduce the volume of the transformer core. Especially for power inverters, the volume reduction increases the space inside the main chassis, which is beneficial to the heat dissipation of the IGBT water pipe.  The load capacity of the transformer is strong, because the magnetic induction during operation is selected to be around 40% of the saturation induction. When the load occurs, it is only due to the increase in magnetic induction that it will become hot, and it will not damage the IGBT due to the saturation of the transformer core. water pipe.  The Curie temperature of the nanocrystalline magnetic ring (ultra-microcrystalline iron core) is high. If the temperature exceeds about 100°C, the ferrite core transformer will no longer be able to work, but the nanocrystalline transformer can work normally.  This advantage of nanocrystals has been understood and adopted by more and more switching power supply manufacturers. A group of manufacturers in China have already adopted nanocrystalline transformer cores and have used them for many years. More and more manufacturers are beginning to use or use it. At present, it has been widely used in inverter welding machines, power systems, electrolytic power supplies for electroplating processes, induction heating equipment, charging power supplies and other industries, and there will be even greater improvements in the next two years.    2. Issues that everyone is concerned about  In the process of using nanocrystalline magnetic rings (ultramicrocrystalline cores) in inverter power supplies, there have been some problems such as noise problems, ductility problems, consistency problems, etc., which have affected the application promotion to a certain extent and caused care. Now these problems have been gradually solved.   (1) Noise problem  Noise is generated for various reasons:  1. Due to the magnetostrictive index of the material itself, the magnetostrictive index of the ferrite core material is relatively large. Although the ferrite core is solid, noise sometimes occurs during use. The composition of nanocrystals is different, and the magnetostrictive index is different. The composition used in the past two years is a general aluminum alloy composition. Therefore, the noise problem in the production of transformers is very obvious, and the application, development and design More and more, different alloy compositions are used for different purposes to meet the magnetic requirements of different components. For example, special components have been developed and designed for power transformers, voltage transformers, common mode inductors, etc. The alloy composition adjusted according to the requirements of the power transformer reduces the magnetostrictive index. It has been confirmed by user applications that the noise problem has been greatly improved.  2. The reason why the transformer core is wound tightly is closely related to the quality of the amorphous strip used. The size error and uneven thickness of the amorphous strip can cause the transformer core to be wound too loosely, which can easily cause noise. . After adjusting the composition, the molten steel has good fluidity, which is beneficial to the forming quality of the amorphous strip. It provides a beneficial guarantee for reducing the noise of the transformer core to a certain extent.  3． The problem at the rectifier circuit level is that the DC component in the power circuit is large, which causes the magnetic induction of the transformer core to increase, causing noise. Our experiments have confirmed that the noise increases as the magnetic induction increases during work. Some manufacturers have adopted DC isolation measures in power circuits and have used nanocrystalline transformer cores without any noise problems for many years.  Through the improvement of left and right, the noise problem has been basically solved.   (2) Ductility problem  The ductility of the nanocrystalline transformer core is mainly reflected in the slag shedding of the transformer core, which is a major problem for users. It is not only a headache for simple installation, but also easily causes short-circuit faults in the power circuit and safety hazards. After many years of practice and research, the ductility problem has been greatly improved through adjustments to ingredients and processing techniques. After the composition is adjusted, the flexibility of the amorphous strip is significantly improved. Thinning of the amorphous ribbon also reduces ductility. In addition, in the process of manufacturing the transformer core, the transformer core is impregnated with non-stress adhesive, which makes the transformer core less fragile and completely eliminates the ductility problem of slagging in the transformer core. At the same time, because the stress-free glue fixes the gaps between the amorphous strips of the transformer core, it is less likely to cause resonance and reduces the generation of noise.    (3) Consistency issues  Consistency is related to the scale of manufacturing operations and the volume of production line equipment. Judging from the quality of amorphous strips, a 500KG production capacity machine is comparable to a 50KG production capacity machine. The same can produce 500KG amorphous strips. Obviously, the former product has better consistency in composition and magnetic energy. The latter one. The conditioning and tempering treatments during processing are the same. Therefore, large-scale manufacturing operations and large production line equipment are beneficial to consistency.  The consistency of nanocrystals in customer applications is manifested in the large discreteness of the saturation state operating voltage and inductor quantity, sometimes more than double the distance. The main reason is that the effect of electromagnetic field quenching and tempering treatment is poor and there is no classification and selection in manufacturing inspection. The subsequent adjustment of the components used in the power transformer not only improves the ductility, but also reduces the residual magnetic intensity of the material, thus increasing the effect of electromagnetic field quenching and tempering and increasing the saturation voltage of the transformer core. , plays an important role in product consistency.    3. Nanocrystalline transformer products  The nanocrystalline transformers used are almost all wound by the equipment manufacturer itself, because each factory has different designs of rectifier circuits, different understanding of nanocrystalline magnetic rings (ultra-microcrystalline iron cores), and different requirements for transformers. The level of mastery of electrical appliance manufacturing and processing technology is different, and the level of produced transformers is also different. Manufacturing high-frequency transformers has become an important step in manufacturing. Therefore, some manufacturers have raised the possibility of systematic production of high-frequency transformers and the requirement for all equipment manufacturers to directly purchase transformers.  Originally, transformers in the frequency range of 20kHz to 50kHz generally used ferrite cores as transformer coils. The most common forms of transformer cores were U-type or EI-type. O-type transformer cores, U-type or EI-type transformer cores were rarely used. There is no structural way to reduce the leakage inductance of the transformer.  Due to the advantages of nanocrystalline magnetic rings (ultra-microcrystalline iron core), it provides ideal materials for the practicality and efficiency of high-frequency transformers. New materials promote the advent of a new construction of high-frequency transformers.  This kind of patented transformer named "Beetle" was later improved by others and called "H" type transformer, which was also patented. These two transformers make full use of nanocrystalline magnetic rings (ultra-microcrystalline). The magnetic characteristics of high magnetic permeability, high magnetic induction intensity, low loss and small magnetic leakage of the toroidal transformer core have broken new ground in the primary and secondary structures of the transformer. The metal protection box of the transformer core is used as the secondary coil of the transformer, which is suitable for large current output. The primary coil is evenly wound around the secondary side, and the leakage inductance is not large. The fixed support point of the transformer is integrated with the bus output, which is beneficial to heat dissipation.    The advantages of this type of transformer are:  1. Large output power: 10 kW～20kW, power can exceed 15 kW～20kW/kg  2. Leakage inductance is small, generally less than 5μH, preferably less than 2μH  3． High efficiency, over 99%  4. Light weight, the net weight of the 15 kW transformer is 3KG, and the volume is 160×150×95 mm  5. The appearance design is beautiful and elegant.    The practical application of nanocrystalline transformers effectively utilizes the characteristics of nanocrystalline soft magnetic materials; it is beneficial to the practicality and standardization of high-voltage power transformers; it is beneficial to the improvement of high efficiency and level of transformers; it is beneficial to inverter welding machines, Electroplating process, electrolysis and other machinery and equipment  Productivity improvements. Currently, there are many manufacturers that can produce this type of transformer.  Nowadays, some entire equipment manufacturing has begun to use "Ω" type transformers to achieve integrated manufacturing. This is a "more, faster, better, and more economical" approach.    4. Conclusion  Due to their excellent characteristics, amorphous and nanocrystalline soft magnetic materials make up for the shortage of silicon steel and ferrite core materials in different applications, bringing various electronic devices to a new level, improving efficiency, Significant environmental protection and energy saving effects have been achieved. New materials show vigorous vitality.  Nowadays, more and more people know about amorphous magnetic cores and nanocrystalline magnetic rings (ultramicrocrystalline iron cores). In addition to transformers, amorphous magnetic cores and nanocrystalline magnetic rings (ultramicrocrystalline iron cores) can As the transformer core material for voltage transformers, series reactors, controllers, filters and other components, its application scope also involves electrical products in people's daily lives, smart meters, DC variable frequency air conditioners, leakage protection circuit breakers, etc. Transformation measurement, power distribution equipment, telemetry sensing technology of power supply system, electric locomotive central air conditioner of railway line system, inverter power supply of electric locomotive, railway signal sensing technology, etc., are also used in aerospace, aviation It has been selected and finalized in various military and national new technology projects such as companies and ships.

With the rapid development of wireless charging, wireless charging is now more and more popular in many industries such as smartphones, smart wearable devices, smart home systems, new energy vehicles, etc., and the sales market worth hundreds of billions of dollars has once again become a trend. However, there are many difficulties in wireless charging, which also cause headaches for those in the industry. The entire industry chain has been developing towards five major aspects: simplicity, fast charging, temperature control, intelligence, and playability.   Recently, mobile phone manufacturers such as Huawei have increased wireless charging power to 15W, which has greatly inspired the entire manufacturing industry. To maintain power wireless charging, wireless charging practitioners currently face many challenges, including: conversion efficiency between electromagnetic induction, increasingly tight magnetic coupling, magnetic interference, thermoelectric effects, position correction, and load adjustment. This will cause several problems such as the charging part of the wireless charging being unable to be pointed, the charging conversion efficiency being high, and the charging time being too long.   As one of the important components of wireless charging technology, Hemei Electronics plays the role of increasing the electromagnetic field and shielding the electromagnetic coil interference in wireless charging equipment. Therefore, wireless charging equipment has a certain influence on the performance and product specifications of permanent magnet materials, Credibility and other requirements are higher.   Although cross-generational products are eye-catching, being unique and fun is not the key to gaining sales. In the end, what customers still care about is their feelings.   Although wireless charging can improve the importance of user experience, it also has the problem of slow charging, so there is an urgent need to relatively increase charging power. However, the traditional ferrite core material has a serious problem of heating during wireless charging, and it can no longer meet the power charging requirements.   In comparison, nanocrystal materials contain various possibilities and have great potential for application in wireless charging in the future. Therefore, in wireless charging applications and RX module design, the advantages of nanocrystalline materials are fully demonstrated.   Nanocrystalline materials have various excellent comprehensive magnetic properties such as high saturation magnetic induction (), magnetic permeability >800, and poor high-frequency loss under high magnetic induction. They are the materials with the best comprehensive performance on the current market. Nowadays, nanocrystals rely on their advantages to excel in the testing of various important parameters of magnetic materials, gradually replacing ferrite cores and becoming the new choice of many wireless charging manufacturers.   According to statistics, the saturation magnetic induction of amorphous Nano-M-Sheet far exceeds that of ferrite cores, and its anti-saturation working ability far exceeds that of ferrite cores. The magnetic induction intensity of the Nano-M-Sheet raw material does not change greatly with temperature, it is not prone to magnetic saturation, and its temperature reliability is better than that of ferrite cores.   Aluminum alloy amorphous strip   In addition, the Nano-M-Sheet material has high saturation magnetic flux and low loss characteristics as well as excellent thermal conductivity. Under the same wireless charging working conditions, the temperature of the Nano-M-Sheet material is higher than that of ferrite. The core temperature is 7~8℃. In contrast, ferrite core materials are easy to reach saturation. When used in wireless charging, as the temperature rises, the magnetic induction decreases, the shielding properties decrease, the vortex increases, and the heating becomes more serious, resulting in polarization. The properties of the Nano-M-Sheet material are very stable below 80°C. As the temperature increases, although the magnetic induction decreases, the change is not significant.   Hemei Electronics is a technology company that integrates design, product development, manufacturing and sales of amorphous and nanocrystalline new soft magnetic materials and electronic devices. Its main business is nanocrystalline strips, ultra-microcrystalline magnetic cores, and permalloy. Magnetic cores, high-power transformer cores, nanocrystalline magnetic ring inductors, electromagnetic ring coils, switching transformers, common mode inductance coils, precision current transformers and other products have the advantages of good stability and high electrical parameters.   At this stage, the industrial production and processing technology of the company's amorphous nanocrystalline amorphous strips includes layer-by-layer processes such as smelting, tape spraying, tape feeding + inspection, and winding. At this stage, the quenching angular velocity exceeds ~30m/second. The thickness of the amorphous ribbon is 18~37um, and the total width of the amorphous ribbon is.   In order to meet new market challenges and comply with the market trend of high efficiency, low loss, and thin specifications, Hemei Electronics' next product development plan for amorphous will be in the promotion of nanocrystalline products, technological improvements, and new products. Development and design are carried out in three aspects.   In terms of research and development of nanocrystalline raw materials, Hc of soft magnetic materials is reduced and Bs is increased to improve alloy composition. For the current 18 μm thin nanocrystalline amorphous strip, we will reduce eddy current loss, increase the frequency bandwidth, and reduce the product thickness to 12~15 μm. By increasing the permeability and improving product consistency, the constant support force quenching target of nanocrystalline amorphous strips is exceeded 12,000~15,000.   According to statistics, when nanocrystalline amorphous ribbons undergo crystallization and constant support force quenching and tempering, magnetic anisotropy will occur, making the long and short directions of the ribbons become hard-to-magnetize axes, thereby controlling the magnetic permeability within a wide range. , producing nanocrystalline soft magnetic materials with different magnetic permeabilities. The characteristic of this low-permeability nanocrystalline soft magnetic material is that it has small eddy current loss and can suppress the decrease in magnetic permeability when higher frequencies coincide with electromagnetic fields. Therefore, it can be used in DC accumulation in high-frequency areas.   In terms of nanocrystalline amorphous strip free online insulation coating technology, amorphous will reduce losses, increase frequency bandwidth, and reduce product thickness to achieve technical improvements. In the future, Amorphous will also develop and design a soft magnetic powder based on cast film technology that can reduce eddy current losses, increase frequency bandwidth, and reduce product thickness to sub-μm level.