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Permalloy metal core: various types of Permalloy materials have their own typical magnetic properties that are superior to silicon steel materials and ferrites, and have higher temperature stability and aging stability.   High initial permeability Permalloy material (IJ79, IJ85, IJ86) cores are often used to make current transformers and small signal transformers; high rectangular Permalloy material (IJ51) cores are often used to make magnetic amplifiers and two-stage pulse transformers; low remanence Permalloy material (IJ67h)   Cores are often used to make small and medium power unipolar pulse transformers   2. Amorphous core:   ⑴ Iron-based amorphous core:   It has the highest saturation magnetic induction intensity (1.451.56T) among almost all amorphous alloy cores, and also has high permeability, low coercivity, low loss, low excitation current and good temperature stability and aging stability.   Mainly used to replace silicon steel sheets, as various forms and different power power distribution transformers, medium frequency transformers, the operating frequency ranges from 50Hz to 10KHz; as the core of high-power switching power supply reactor, the use frequency can reach 50KHz.   ⑵ Iron-nickel based amorphous core:   Medium to low saturation magnetic induction intensity (0.75T), high magnetic permeability, low coercivity, wear resistance and corrosion resistance, good stability. Commonly used to replace Permalloy core as the zero-sequence current transformer core in leakage switch.   ⑶ Cobalt-based amorphous core:   It has the highest magnetic permeability among all amorphous alloy cores, and also has medium to low saturation magnetic induction intensity (0.65T), low coercivity, low loss, excellent wear resistance and corrosion resistance, good temperature stability and aging stability, and impact and vibration resistance. It is mainly used to replace Permalloy core and ferrite core to make high-frequency transformers, filter inductors, magnetic amplifiers, pulse transformers, pulse compressors, etc. in high-end fields (military)   Permalloy is essentially an iron-nickel (FeNi) alloy with very low coercivity, but high saturation magnetic density Bs, magnetic permeability and Curie temperature, close to pure iron. Multi-element Permalloy, the initial relative magnetic permeability can reach 30000~80000, but the resistivity is low, about 10-7Ω-m, it can be processed into extremely thin sheets, so it can be used at working frequencies up to (20~30)kHz. Permalloy thin strips with a thickness of 0.02mm are commonly used in domestic engineering, and there are also 0.005mm thick thin strips, but because the surface of the thin strip must be insulated during the winding process of the magnetic core, its filling factor is greatly reduced, so it is rarely used in engineering. When the application frequency exceeds 30kHz, due to the low resistivity of Permalloy, its loss will increase significantly. High magnetic permeability alloy (Permalloy) High magnetic permeability alloy refers to iron-nickel alloys with high initial and maximum magnetic permeability, and most of the trade names are called "Permalloy".   In addition to high magnetic permeability, Permalloy has relatively low loss, especially good environmental adaptability and stable performance. Although it is expensive, it is still used in power supplies with relatively strict conditions. The main type of Permalloy is iron-nickel alloy, which is composed of nickel (35% to 85%), iron and added molybdenum, copper, tungsten, etc. It was basically finalized in the 1940s and was widely used in the 1970s and 1980s, forming dozens of models, which are generally classified according to the nickel content. Low nickel alloys with a nickel content of 30% to 50% are low nickel alloys, such as China's 1J30, 1J34, 1J50, 1J51, etc. High nickel alloys with a nickel content of 65% to 85% are high nickel alloys, such as China's 1J66, 1J79, 1J80, 1J88, etc. According to the needs of power supplies, various types of Permalloy strips have been developed. There are materials with rectangular, non-rectangular, and linear (constant magnetic conductivity) hysteresis loops. They can be rolled into various specifications with thicknesses from 0.20mm to 0.005mm (5μm). Generally, 0.20mm thick Permalloy is used for 50Hz, and 0.005mm thick Permalloy is used for 500kHz to 1MHz, covering the entire frequency range from industrial frequency to medium frequency to high frequency, and has long broken through the old concept that it can only be used below 20kHz. Like silicon steel and soft ferrites, Permalloy has also been developing rapidly in the past decade. One is to add chromium and other elements to iron-nickel alloys with low nickel content to achieve magnetic conductivity with high nickel content, thereby reducing costs. The reported Ni38Cr8Fe alloy has a magnetic permeability of 100,000 to 300,000 at H=0.4A/m, which is close to the level of high nickel content alloys. What is more outstanding is that in recent years, domestic and foreign companies have successively launched Permalloy products with high initial magnetic permeability of 200,000 to 300,000 and maximum magnetic permeability of 350,000 to 500,000. Another breakthrough is the manufacturing process of Permalloy thin strips, which are rolled into ultra-thin strips with a thickness of 0.01mm to 0.005mm, expanding the frequency application range. When Bm is 0.1T, the loss of 0.126W/g at 500kHz, 0.392W/g at 1MHz, 6.79W/g at 5MHz, and 23.1W/g at 10MHz for 0.005mm thick Ni80Mo5 Permalloy ultra-thin strips. It can be used in power transformers above 1MHz.   Powder cores   1. Magnetic powder cores   Magnetic powder cores are a kind of soft magnetic material made by mixing ferromagnetic powder particles and insulating media. Since the ferromagnetic particles are very small (0.5 to 5 microns for high frequency) and separated by non-magnetic electrical insulating film materials, on the one hand, eddy currents can be isolated and the material is suitable for higher frequencies; on the other hand, due to the gap effect between particles, the material has low magnetic permeability and constant magnetic permeability characteristics; and because the particle size is small, skin phenomenon basically does not occur, and the change of magnetic permeability with frequency is relatively stable. It is mainly used for high-frequency inductance. The magnetic and electrical properties of magnetic powder cores mainly depend on the magnetic permeability of the powder material, the size and shape of the powder, their filling factor, the content of the insulating medium, the molding pressure and the heat treatment process.   Commonly used magnetic powder cores are iron powder cores, Permalloy powder cores and Sendust powder cores.   The calculation formula for the effective magnetic permeability μe and inductance of the magnetic core is: μe = DL/4N2S × 109   Where: D is the average diameter of the magnetic core (cm), L is the inductance (share), N is the number of winding turns, and S is the effective cross-sectional area of ​​the magnetic core (cm2).   (1) Iron powder core   Common iron powder cores are made of carbon-based ferromagnetic powder and resin carbon-based ferromagnetic powder. The price is the lowest among powder cores. The saturation magnetic induction value is about 1.4T; the magnetic permeability ranges from 22 to 100; the initial magnetic permeability μi has good stability with frequency; the DC current superposition performance is good; but the loss is high at high frequency. Changes in the initial magnetic permeability of the iron powder core with the DC magnetic field strength Changes in the initial magnetic permeability of the iron powder core with frequency   (2) Permalloy powder core   Permalloy powder cores mainly include molybdenum permalloy powder cores (MPP) and high flux powder cores (High Flux).   MPP is composed of 81% Ni, 2% Mo and Fe powder. The main features are: saturation magnetic induction value is about 7500Gs; the magnetic permeability range is large, from 14 to 550; it has the lowest loss among powder cores; it has excellent temperature stability and is widely used in space equipment, open-air equipment, etc.; the magnetostriction coefficient is close to zero, and no noise is generated when working at different frequencies. Mainly used in high-quality Q filters below 300kHz, inductive load coils, resonant circuits, LC circuits with high temperature stability requirements, output inductors, power factor compensation circuits, etc., commonly used in AC circuits, and the most expensive among powder cores.   High flux powder core HF is composed of 50% Ni and 50% Fe powder. The main features are: saturation magnetic induction value is around 15000Gs; magnetic permeability ranges from 14 to 160; it has the highest magnetic induction intensity and the highest DC bias capability among powder cores; and the core size is small. Mainly used in line filters, AC inductors, output inductors, power factor correction circuits, etc., commonly used in DC circuits, and is more used in high DC bias, high DC and low AC. The price is lower than MPP.   (3) Kool Mμ Cores   Kool Mμ Cores are composed of 9% Al, 5% Si, and 85% Fe powder. It is mainly used to replace iron powder core, with 80% lower loss than iron powder core, and can be used at frequencies above 8kHz; saturation magnetic induction is about 1.05T; magnetic permeability ranges from 26 to 125; magnetostriction coefficient is close to 0, no noise is generated when working at different frequencies; it has higher DC bias capability than MPP; and has the best performance-price ratio. It is mainly used in AC inductors, output inductors, line filters, power factor correction circuits, etc. Sometimes it is also used as a transformer core instead of air-gap ferrite.   II) Tape-wound core   1. Silicon steel sheet core   Silicon steel sheet is an alloy. The iron-silicon alloy formed by adding a small amount of silicon (generally below 4.5%) to pure iron is called silicon steel. This type of core has the highest saturation magnetic induction value of 20000Gs; because they have good magnetoelectric properties, are easy to mass produce, cheap, and have little mechanical stress, they are widely used in the power electronics industry, such as power transformers, distribution transformers, current transformers and other cores. It is the material with the largest output and usage among soft magnetic materials. It is also the material with the largest usage among magnetic materials for power transformers. It is especially suitable for low frequency and high power. Commonly used are cold-rolled silicon steel sheet DG3, cold-rolled non-oriented electrical steel strip DW, and cold-rolled oriented electrical steel strip DQ, which are suitable for medium and small power low-frequency transformers and chokes, reactors, and inductor cores in various electronic systems and household appliances. This type of alloy has good toughness and can be processed by punching, cutting, etc. The core has stacked and wound types. However, the loss increases sharply at high frequencies, and the general use frequency does not exceed 400Hz. From the application point of view, the selection of silicon steel should consider two factors: magnetism and cost. For small motors, reactors and relays, pure iron or low silicon steel sheets can be selected; for large motors, high silicon hot-rolled silicon steel sheets, single-oriented or non-oriented cold-rolled silicon steel sheets can be selected; single-oriented cold-rolled silicon steel sheets are often used for transformers. When used at power frequency, the thickness of the commonly used strip is 0.2~0.35 mm; when used at 400Hz, 0.1 mm is often selected. The thinner the thickness, the higher the price.   2. Permalloy   Permalloy often refers to an iron-nickel alloy with a nickel content in the range of 30~90%. It is a widely used soft magnetic alloy. Through appropriate processes, magnetic properties can be effectively controlled, such as an initial magnetic permeability of more than 105, a maximum magnetic permeability of more than 106, a coercive force as low as 2‰ Oersted, and a rectangular coefficient close to 1 or close to 0. Permalloy with a face-centered cubic crystal structure has good plasticity and can be processed into 1μm ultra-thin strips and various usage forms. Commonly used alloys include 1J50, 1J79, 1J85, etc. The saturation magnetic induction intensity of 1J50 is slightly lower than that of silicon steel, but the magnetic permeability is dozens of times higher than that of silicon steel, and the iron loss is 2~3 times lower than that of silicon steel. Made into a transformer with a higher frequency (400~8000Hz), the no-load current is small, and it is suitable for making small higher frequency transformers below 100W. 1J79 has good comprehensive performance and is suitable for high-frequency low-voltage transformers, leakage protection switch cores, common-mode inductor cores and current transformer cores. The initial magnetic permeability of 1J85 can reach more than 100,000 105, which is suitable for low-frequency or high-frequency input and output transformers, common-mode inductors and high-precision current transformers for weak signals.   3. Amorphous and Nanocrystalline Soft Magnetic Alloys   Silicon steel and Permalloy soft magnetic materials are both crystalline materials. The atoms are arranged regularly in three-dimensional space to form a periodic lattice structure. There are defects such as grains, grain boundaries, dislocations, interstitial atoms, and magnetocrystalline anisotropy, which are not conducive to soft magnetic properties. From the perspective of magnetic physics, the amorphous structure with irregular atomic arrangement and no periodicity and grain boundaries is very ideal for obtaining excellent soft magnetic properties. Amorphous metals and alloys are a new material field that came out in the 1970s. Its preparation technology is completely different from the traditional method. Instead, it adopts ultra-rapid cooling and solidification technology with a cooling rate of about one million degrees per second. From molten steel to thin strip finished products, it is formed in one step, which reduces many intermediate processes compared to the general cold-rolled metal thin strip manufacturing process. This new process is called a revolution in traditional metallurgical processes. Due to ultra-rapid cooling and solidification, the atoms do not have time to arrange and crystallize in an orderly manner when the alloy solidifies. The solid alloy obtained is a long-range disordered structure without the grains and grain boundaries of crystalline alloys. It is called an amorphous alloy and is called a revolution in metallurgical materials. This amorphous alloy has many unique properties, such as excellent magnetism, corrosion resistance, wear resistance, high strength, hardness and toughness, high resistivity and electromechanical coupling performance. Due to its excellent performance and simple process, it has become the focus of research and development in the material science community at home and abroad since the 1980s. At present, the United States, Japan, and Germany have a complete production scale, and a large number of amorphous alloy products have gradually replaced silicon steel, Permalloy and ferrite to flood the market.

Permalloy and pig iron are both important iron-based materials, but they have significant differences in composition, properties and uses. Here is a detailed comparison of permalloy and pig iron:   Properties of Permalloy Element Main ingredients: Permalloy is mainly composed of about 80% nickel (Ni) and 20% iron (Fe), sometimes also containing a small amount of molybdenum (Mo), chromium (Cr) or other elements to optimize its Magnetic properties.   Magnetic properties High magnetic permeability: Permalloy has extremely high initial magnetic permeability and maximum magnetic permeability, allowing it to achieve high magnetic induction intensity even under low magnetic field intensity.   Low coercivity: Permalloy has a very low coercivity, which means less loss during magnetization and demagnetization, making it suitable for applications that require rapid response to changing magnetic fields.   Low losses: In high-frequency applications, permalloy has low hysteresis losses and eddy current losses, making it excellent in high-frequency electromagnetic equipment.   Magnetic stability: Permalloy can maintain stable magnetic properties over long periods of use.   use Communication equipment: Transformers and filters used for telephone lines and data lines to improve signal transmission quality.   Power electronic equipment: used in high-frequency transformers and inductors to improve the energy efficiency and performance of equipment.   Medical equipment: Used in magnetic shields and inductors in magnetic resonance imaging (MRI) equipment to improve image quality and diagnostic accuracy.   Aerospace and military: used in navigation systems, radar and communication systems to ensure that equipment works efficiently and stably in complex environments.   Characteristics of pig iron Element Main components: Pig iron is mainly composed of iron (Fe) and a higher carbon (C) content, usually between 2.0% and 4.5%. Pig iron also contains impurities such as silicon (Si), manganese (Mn), phosphorus (P) and sulfur (S).   Mechanical properties High hardness and brittleness: Due to the high carbon content, pig iron has high hardness and brittleness, low tensile strength and is easily broken.   Low ductility: Pig iron has little ability to plastically deform and cannot be processed by forging or rolling.   Lower melting point: Pig iron has a lower melting point than pure iron and steel, making it easy to cast into complex-shaped castings.   use Casting parts: Pig iron is widely used to cast various complex-shaped parts, such as pipes, valves, pump casings and machine beds.   Raw material: Pig iron is the raw material for steelmaking and is converted into steel through the steelmaking process.   Wear-resistant parts: Due to its high hardness, pig iron is used in the manufacture of wear-resistant parts such as wear plates and grinder liners.   The main differences between permalloy and pig iron Composition and structure Composition: Permalloy is mainly composed of nickel and iron, while pig iron is mainly composed of iron and carbon and contains other impurities.   Structure: Permalloy is an alloy with high magnetic permeability, while pig iron is an iron-based material with high carbon content.   Magnetic and mechanical properties Magnetic properties: Permalloy has excellent magnetic properties such as high permeability, low coercivity and low losses, making it suitable for high-frequency and high-efficiency magnetic applications. Pig iron has no significant magnetic properties.   Mechanical properties: Permalloy has moderate mechanical properties and is suitable for processing into thin sheets and complex-shaped cores. Pig iron has high hardness and brittleness and is mainly used for casting wear-resistant parts and complex castings.   use Permalloy: widely used in high-frequency transformers, inductors, communication equipment, medical equipment and military fields.   Pig iron: Mainly used for castings, steelmaking raw materials and manufacturing wear-resistant parts.   It can be seen from the above comparison that permalloy and pig iron have significant differences in composition, properties and uses, and each plays an important role in different application fields.

Permalloy is a nickel-iron alloy with high magnetic permeability, which is usually used to make magnetic shielding materials. The magnetic shielding performance of Permalloy is related to its thickness, alloy composition and magnetic field frequency. Generally speaking, increasing the thickness of Permalloy can improve its magnetic shielding effect, but the specific strength of the shielding magnetic field should also consider the following factors:   1. Thickness: The thicker the Permalloy is, the better the shielding effect. The thickness of Permalloy sheets usually used for shielding ranges from 0.1 mm to several millimeters.   2. Magnetic permeability: The higher the magnetic permeability of Permalloy, the better the shielding effect. The magnetic permeability of Permalloy can reach several thousand or even higher.   3. Magnetic field strength: The shielding effect is related to the strength of the external magnetic field. In weak magnetic fields, Permalloy has a better shielding effect, but in strong magnetic fields, its shielding effect may be weakened.   4. Frequency: Permalloy has a good shielding effect on low-frequency magnetic fields (such as DC magnetic fields and power frequency magnetic fields), but a relatively poor shielding effect on high-frequency magnetic fields.   The calculation of the specific shielding magnetic field strength needs to take these factors into consideration, and may require experiments to determine the best shielding effect. If there are specific application scenarios or parameters, more detailed information can be provided to obtain more accurate calculations or suggestions.

In modern power systems, transformers, as a key electrical equipment, play a vital role. Transformers are like the "eyes" of the power world, accurately measuring and transmitting relevant information about electric energy. Transformers are mainly divided into two categories: current transformers and voltage transformers. Current transformers convert large currents into small currents in proportion, allowing measurement and protection equipment to safely and accurately process current signals. It is like a fine "shunt officer", ensuring the accurate acquisition of current information, while ensuring that subsequent equipment is not damaged by excessive current.   Voltage transformers convert high voltages into low voltages, providing suitable voltage signals for measuring instruments and relay protection devices. Like a reliable "voltage reduction messenger", it converts high-voltage and dangerous electric energy into low-voltage signals that can be safely measured and monitored.   The working principle of the transformer is based on electromagnetic induction. Through ingenious winding design and the selection of core materials, accurate conversion of electric energy signals is achieved. In this process, factors such as the magnetic permeability of the core and the turns ratio of the winding have an important impact on the performance of the transformer.   In order to meet the growing demand for high precision and high reliability in power systems, transformer technology is also constantly developing and innovating. New transformer materials and manufacturing processes are constantly emerging, which improves the measurement accuracy and stability of transformers. At the same time, the emergence of digital transformer technology enables transformers to be better integrated with smart grids, achieving more efficient and intelligent power monitoring and control.   In practical applications, the correct selection and installation of transformers are crucial. Different power scenarios require the selection of appropriate transformer models and specifications based on factors such as voltage level, load characteristics, and measurement accuracy requirements. During installation, strict standards and specifications must also be followed to ensure that the transformer can work properly and provide accurate and reliable measurement data.   In short, transformer-related technologies play an indispensable role in the safe and stable operation of power systems. With the continuous advancement of science and technology, it is believed that transformer technology will continue to develop and improve, and contribute greater strength to building a more intelligent, efficient, and reliable power system.

Rogowski coil, also known as Rogwski coil in English, is hollow, that is, it has no solid core. It can be considered as applying the basic Faraday's law of electromagnetic induction to directly generate a voltage signal on the secondary side. The advantage of Rogowski coil relative to ordinary current transformers is that because it has no dead center, there is no dead center saturation phenomenon, and it can directly measure large currents. However, precisely because it has no dead center, the voltage signal induced by the Rogowski coil is very small compared to CT, and it is very easy to be affected by the stray magnetic field of the external environment, so the requirements for the winding process are very high. In addition, the voltage signal induced by the Rogowski coil cannot be used directly as a current signal. It must be differentiated to restore the current signal you want.   Application of Rogowski coil and current transformer: At present, Rogowski coil is only used in places with extremely large currents. Ordinary metering instruments use CT. Current transformer CT (current transformer) uses the principle of transformer. Generally, the large current on the primary side is converted into a small current on the secondary side, and then input to ADC for sampling after I/V conversion. The main differences between Rogowski coil and current transformer 1. Different properties 1. Rogowski coil: It is a toroidal coil evenly wound on non-ferromagnetic materials. 2. Current transformer: It is an instrument that converts a large current on the primary side into a small current on the secondary side for measurement based on the principle of electromagnetic induction. 2. Different structures 1. Rogowski coil: It does not contain ferromagnetic materials, has no hysteresis effect, and has almost zero phase error; there is no magnetic saturation phenomenon, so the measurement range can be from several amperes to hundreds of kiloamperes; the structure is simple, and there is no direct circuit connection with the measured current; the response bandwidth is 0.1Hz-1MHz. 2. Current transformer: The current transformer is composed of a closed solid and winding. Its primary side winding has very few turns and is connected in series in the circuit of the current to be measured.   Design principle of the amplification and integration circuit of the Rogowski coil: The theoretical basis for measuring current with the Rogowski coil is Faraday's law of electromagnetic induction and Ampere's loop law. When the measured current passes through the center of the Rogowski coil along the axis, a corresponding changing magnetic field is generated in the volume surrounded by the toroidal winding.   If you want to accurately restore the measured AC current, you must add an inverting integration circuit. Because the voltage induced by the Rogowski coil is very small, in order to amplify the induced voltage, you must add an amplifier circuit in front of the integrator. Integration is a very important link. The restored signal is very small. For the convenience of measurement, the signal is amplified and then integrated. This can increase the restored signal on the one hand, and on the other hand, the presence of the capacitor can filter out unnecessary interference.

The development of split current transformers has been rapid, and the power industry is particularly important for the development of split current transformers. This is especially true for the accuracy of split current transformers. There are many types of split current transformers that we usually come into contact with. The split current transformers produced by Hemei Electronics include split current transformers, power extraction split current transformers, high-frequency split current transformers, zero-sequence split current transformers, and so on. However, in the power industry, the split current transformers used must be consistent with the use of the power system, and split current transformers with corresponding voltage levels and accuracy must be developed to meet the needs of power system measurement, maintenance and control. Therefore, with the development of science and technology and the application of new materials, the performance of split current transformers is getting better and better, and there are more and more types.   Split current transformers are adapted to the development needs of power construction with a variety of structures such as dry, oil-immersed and gas-insulated. However, with the continuous growth of power transmission capacity, the continuous improvement of grid voltage level and the continuous improvement of maintenance requirements, the general core-type split-type current transformer structure has gradually exposed its weaknesses that are not accustomed to it. Its inherent large size, magnetic saturation, ferromagnetic resonance, small dynamic range and many other shortcomings cannot meet the application requirements of the new generation of power system automation and power digital network, so it is necessary to continuously promote the development of the industry.   Split-type current transformer is an important equipment for power metering, current measurement and microcomputer protection in the power system. Generally, the primary winding of the split-type current transformer is connected in series in the power line during use, and the secondary winding is connected to the measuring instrument, microcomputer protection and automatic control device. Since the traditional split-type current transformer is connected in series in the equipment during the application of the substation, it is directly embedded in different circuits during the initial installation, and the electrical connection of the substation is a hard connection. Therefore, once the split-type current transformer needs to be repaired or replaced, it is necessary to dismantle it from the connection point, which is very inconvenient to maintain. However, the open-type split-type current transformer can be installed and disassembled under power, which is simple to install and maintain. Therefore, the open-type split-type current transformer will be a development direction of current measurement technology.

Application characteristics of split core current transformer:   Split current transformer is an important equipment for electric energy metering, current measurement and microcomputer protection in power system. Generally, the primary winding of split current transformer is connected in series in the power line during use, and the secondary winding is connected with measuring instrument, microcomputer protection and automatic control device. Since the traditional split current transformer is connected in series in the equipment in the application of substation, it is directly embedded in different circuits during initial installation, and the electrical connection of substation is hard connection, so once the split current transformer needs to be repaired and replaced, it needs to be disassembled from the connection point, which is very inconvenient to maintain. However, the open split current transformer can be installed and disassembled with power on, which is simple to install and maintain. Therefore, the open split current transformer will be a development direction of current measurement technology. Due to the special structure of the open split current transformer, it needs to be distinguished from the traditional electromagnetic split current transformer in terms of main materials, process, structure, etc. during design.   This series of split-type current transformers are designed for electrical installations that do not require disassembly or disconnection of existing main busbars or cables. The split core design does not require disconnection of the busbar, making it easy to open and close, easy to install, and beautiful in appearance.   1. Function: General measurement and protection in power systems with strong mobility or cramped space or uninterrupted power systems.   2. Application: Power instruments, electronic multi-function energy meters and field calibrators, instrument measurement and protection.   Electrical characteristics of split-type current transformers   1. Maximum voltage of the equipment: 720V   2. Power frequency withstand voltage: 4000V50Hz/1 min (1mA)   3. Primary rated current range: 0-6000A   4. Secondary rated current range: 1A/5A/mA   5. Frequency: 50/60Hz

Precautions for using split core current transformers   1. In order to prevent the secondary winding from causing high voltage to enter the low voltage side, damage the instrument, and cause harm to people, a protective grounding point should be set. 2. Generally speaking, the connection of split-type current transformers is connected according to the polarity reduction, so the polarity connection must be correct. Once the connection is wrong, it will lead to inaccurate measurement or even short circuit. 3. For split core current transformers that use electric energy measurement, if the secondary circuit is used, then there is no need for automatic devices. The insulation of split-type current transformers is very thick, some insulation wraps are loose, there are wrinkles between the insulation layers, and the vacuum treatment is poor, the impregnation is incomplete, and the air-containing cavity is formed, which is easy to cause partial discharge defects. Among them, split core current transformers have a wide range of applications and can be divided into the following three categories 1. Iron core coil type low-power split-type current transformer. It is a development of the traditional split-type current transformer. The split current transformer is designed according to the high impedance resistor. Under very high primary current, the fullness characteristics are improved, the measurement range is expanded, and the power consumption is reduced. The split current transformer can measure the overcurrent and full offset short-circuit current up to the short-circuit current with high accuracy without fullness. The measurement and maintenance can share a core coil type low-power split current transformer, and its output is a voltage signal. 2. Optical current transformer refers to the use of optical equipment as the measured current sensor. The optical equipment is composed of optical glass, all-optical fiber, etc. 3. Hollow coil split current transformer. It can also be called Rogowski coil current transformer. Hollow coils are often made of enameled wires evenly wound on a ring frame. The frame is made of non-ferromagnetic materials such as plastics and ceramics. Its relative magnetic permeability is the same as the relative magnetic permeability of air. This is a significant feature of hollow coils that is different from current transformers with iron cores.

common faults of split core current transformers:   1. Overheating.   Overheating, smoking, and glue flow in split type current transformers may be caused by poor contact of the primary wiring, severe oxidation of the secondary wiring board surface, short circuit between turns in the split-type current transformer, or insulation breakdown of the primary and secondary sides.   2. The secondary side of the split-type current transformer is open. At this time, the ammeter suddenly has no indication, the sound of the split-type current transformer increases significantly, and ozone can be smelled and slight discharge sounds can be heard near the open circuit.   The damage of the secondary side open circuit is:   a. The split-type current transformer generates a very high voltage, which poses a threat to the safety of equipment and operating personnel.   b. The core loss of the split core current transformer increases, and severe heating may burn the equipment.   c. The core is magnetically saturated, which increases the error of the split-type current transformer.   3. There is a discharge sound or discharge phenomenon inside the split-type current transformer.   If there is a discharge phenomenon on the surface of the split-type current transformer, it may be that the surface of the transformer is too dirty, causing the insulation to decrease. The internal discharge sound is the internal insulation of the current transformer decreasing, causing the primary winding to discharge the secondary winding and the iron core.   4. The internal sound of the split-type current transformer is abnormal.   The reasons are: the fastening screws of the split-type current transformer are loose, the iron core is loose, the vibration of the silicon steel sheet increases, and an abnormal sound that does not change with the primary load is issued; some iron cores have a certain buzzing sound when there is no load or no load due to poor assembly process of silicon steel sheets; when the secondary side is open, due to magnetic saturation and non-sinusoidal magnetic flux, the silicon steel sheet vibrates and the vibration is uneven, emitting a large noise; the split-type current transformer is severely overloaded, which increases the vibration sound of the iron core.   5. The oil-filled split-type current transformer is seriously leaking oil.   If any of the above phenomena are found during the operation of the split-type current transformer, the load should be removed and the power should be cut off immediately.

The split-type current transformer uses a high-strength PVC shell and a fully cast busbar structure. The transformer is directly clamped on the cable, and three elastic rubber rings are pressed against the cable and integrated with the cable. The transformer core is made of high-quality silicon steel sheets, and the secondary wire is evenly wound on the core. The transformer is a split-type structure and can be installed without cutting the cable.   Functional features of split-type current transformer:   Primary current 100A~4000A, secondary current 5A or 1A, complete specifications, accuracy levels 1.0, 0.5   Suitable for fast loading and unloading without disconnection and removal, used for power collection and monitoring   The iron core used has undergone high vacuum heat treatment, with excellent performance and stable accuracy   The shell is made of high impact resistant ethylene PC material, with good safety performance and beautiful appearance   Easy to install, can be fixed by bending piece and pressing plate   Performance meets GB1208-2006 "Current Transformer" technical standard   Safety requirements of split-type current transformer:   Split-type current transformer is more of a later modification project, or a handheld measuring rod, so it involves the interactive operation between personnel and transformer, which puts forward the safety use requirements of split-type transformer. The national standard GB20840 of transformer has not yet defined split-type transformer. So there is no safety requirement. Therefore, we refer more to "GB4793.2 Safety requirements for electrical equipment for measurement, control and testing Part 2: Special requirements for hand-held and hand-operated current transformers for electrical measurement and testing", and the current version number of this standard is 2008. There are 3 categories in total. When using them, you must understand the characteristics of the three types of current transformers, otherwise accidents are likely to occur.

Measurement method   1. The primary wire should be placed in the center of the sensor inner hole, and should not be placed off-center as much as possible;   2. The primary wire should be placed as completely as possible in the sensor inner hole, without leaving any gaps;   3. The current to be measured should be close to the standard rated value IPN of the sensor, and should not differ too much. If conditions are limited, there is only one sensor with a very high rated value, and the current value to be measured is much lower than the rated value. In order to improve the measurement accuracy, the primary wire can be wound a few more times to make it close to the rated value. For example, when a sensor with a rated value of 100A is used to measure a current of 10A, in order to improve the accuracy, the primary wire can be wound around the center of the sensor inner hole ten times (generally, NP=1; one turn in the inner hole, NP=2; ...; nine turns, NP=10, then NP×10A=100A is equal to the rated value of the sensor, thereby improving the accuracy); [2]   4. When the current value to be measured is IPN/10, it can still have a high accuracy at 25℃.   Product Features Whether the Hall sensor is an open-loop or closed-loop principle, the basic performance is not much different. The basic advantages are: fast response time, low temperature drift, high accuracy, small size, wide bandwidth, strong anti-interference ability, and strong overload capacity.   Hemei's main products include common mode inductors, electromagnetic shielding shells, power carrier signal coupling transformers, permalloy cores, silicon steel cores, switch mode power supplies, split core current transformers and other products.     The power supply CT device is the latest product developed by our company, which can be used for 100V-220kv AC transmission lines and can be used as a continuous and stable power supply device. Hemei also provides customers with personalized services such as OEM, ODM and OPM. We welcome sample orders to test and check the quality.

For split core current transformers installed in outdoor overhead lines or cable trenches, the cut surface of the transformer is exposed to the air and will be exposed to rain or soaked in water in the cable trench, which will cause rust and affect product performance. Water accumulation in the secondary terminal will also cause short circuit, so measures need to be taken to prevent rain or water accumulation. There are currently two solutions that can be used, which are briefly introduced as follows:   The first solution is to bury the secondary wire directly into the resin casting body (the wire uses a three-proof silicone wire) to prevent short circuits in the secondary terminal, and add a waterproof silicone ring to the cut surface for sealing and waterproofing. This solution has good protection for the secondary end and the cut surface, and can be widely used in all rain and water immersion occasions. In addition, because the base cannot be fixed in the cable trench, the base installation method is not used. The inner hole with a rubber plug is fixed on the cable. This installation method is used.   The second solution is the "open current transformer + silicone rubber sleeve" solution, which is also used by customers for installation on low-voltage outdoor lines. However, this method can only prevent light rain and cannot prevent immersion in water, so it cannot be used for installation in places where water may accumulate, such as cable trenches. This solution is limited by the specifications of the silicone rubber sleeve, and the inner diameter of the transformer can only be 50mm.   1. Principle of zero-sequence current transformer   In a three-phase four-wire system, the vector sum of the three-phase current is equal to zero, that is, Ia+Ib+Ic=0. If a current transformer is connected to the three-phase four-wire, the induced current is zero. When an electric shock or leakage fault occurs, there is leakage current flowing through the circuit. At this time, the vector sum of the three-phase current passing through the current transformer is not equal to zero, and its vector sum is: Ia+Ib+Ic=I (leakage current). In this way, there is an induced voltage in the secondary coil of the transformer, and this voltage is applied to the electronic amplifier circuit of the detection part. The transformer connected to the protection is called a zero-sequence current transformer. The vector sum of the three-phase current is not equal to zero, and the current generated is the zero-sequence current.   2. Application of zero-sequence current transformer   The zero-sequence current transformer is a single-turn through-type current transformer, but its primary winding is the three-phase conductor of the protected system (the three-phase conductor passes through the transformer ring core together), and the secondary winding reflects the zero-sequence current of the primary system. Zero-sequence current transformers are generally used in conjunction with small current grounding line selection devices, microcomputer detuning devices, etc. When zero-sequence grounding current is generated in the power system, it is used in conjunction with relay protection devices or signals to activate the device components to achieve protection or monitoring.   In the 10kV power supply and distribution system, zero-sequence current transformers are generally divided into high-voltage zero-sequence and low-voltage zero-sequence:   1. High-voltage zero-sequence   When a ground fault occurs on the lower side of the 10kV circuit breaker, the zero-sequence CT can detect the grounding current and trip the circuit breaker. However, when the circuit breaker is equipped with comprehensive protection (the internal software has the function of calculating zero-sequence current), the zero-sequence current can be calculated from the current of the three-phase current transformer, causing the circuit breaker to trip.   2. Transformer low-voltage zero sequence   Install at a position where all N-line currents at the neutral point of the transformer can be detected. If the three-phase load of the three-phase transformer is balanced, the total current passing through the neutral point should be 0. When an asymmetric load occurs during operation, current will pass through the neutral point, which generally does not cause damage to the equipment, but in extreme cases or when the deviation is large, voltage drift will occur, that is, the voltage is unstable and even burns out the electrical equipment or the transformer itself. Therefore, the equipment can be effectively protected by monitoring the neutral point current.   3. Selection of zero-sequence current transformer   1. Installation method   From the aspects of maintenance and installation, try to use an open-and-close zero-sequence current transformer.   2. Product structure   Select according to the actual use. Generally, most of them use cable type, and busbar type is used in very few occasions, such as zero-sequence protection of generator outlet.   3. Selection of zero-sequence current transformer ratio   For 10kV system, high-voltage zero-sequence can be selected according to the calculated protection setting. For example, when the protection setting is 80A, the protection action can be selected as 100/1 or 100/5.   Generally, transformers with a capacity of more than 500kVA are equipped with transformer low-voltage zero-sequence. The calculated current is obtained according to the installed capacity of a single transformer/0.4/1.732.   4. Selection of the inner diameter of the zero-sequence current transformer   When selecting the inner diameter of the zero-sequence current transformer, the inner diameter of the transformer is required to be 20-30mm larger than the outer diameter of the cable to facilitate installation and maintenance.