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1) The wiring of the current transformer should comply with the series connection principle: that is, the primary winding should be connected in series with the measured circuit, 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 high voltage of the primary side from entering the low voltage side of the secondary side once the insulation is damaged, causing personal and equipment accidents   3) The secondary side is not allowed to be open. Once the circuit is open, the primary side current I1 will all become magnetizing current, causing a sudden increase in φm and E2, causing the core to be over-saturated and magnetized, causing severe heat and even burning the coil; at the same time, the magnetic circuit is over-saturated and magnetized, which increases the error. 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, endangering the safety of the staff and the insulation performance of the instrument. In addition, the primary side open circuit makes the secondary side voltage reach several hundred 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. During use, once the secondary side opens, the circuit load should be removed immediately, and then the vehicle should be stopped for processing. It can be used again after everything is handled.   4) In order to meet the needs of measuring instruments, relay protection, circuit breaker failure judgment and fault filtering devices, current transformers with 2 to 8 secondary windings are installed in the generator, transformer, outgoing line, busbar section circuit breaker, busbar 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 location 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 detect 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.

The protective current transformer is generally used for the relay protection circuit of multiple busbars. It is developed for the protection system to detect short-circuit faults. It has different accuracy levels and accuracy limit coefficients, can be expanded to different perforation sizes, and is widely used in low-voltage distribution protection systems. It can also be used to collect low-voltage overload and short-circuit signals and is used in conjunction with protection relays.   Product advantages   Novel structure, beautiful appearance, easy installation, small size, light weight, high accuracy and large capacity.   Structural features   The shell is made of flame-retardant, temperature-resistant 140°C imported polycarbonate injection molding, the core is made of oriented cold-rolled silicon steel strip, and the secondary wire is made of high-strength electromagnetic enameled wire.   The working principle of the current transformer is shown in Figure 1. The primary winding of the current transformer is connected in series in the measured line. I1 is the line current, that is, the primary current of the current transformer, N1 is the primary number of turns of the current transformer, I2 is the secondary current of the current transformer (usually 5A, 1A), N2 is the secondary number of turns of the current transformer, and Z2e is the impedance of the secondary circuit equipment and connecting wires. When the primary current flows in from the P1 terminal of the current transformer and out from the P2 terminal, when the secondary Z2e is connected, the current I2 flows from S1 through the secondary winding of the current transformer, through Z2e to S2, forming a closed loop due to the principle of electromagnetic induction. It can be obtained that the current is I1×N1=I2×N2 in an ideal state, so I1/I2=N2/N1=K, where K is the transformation ratio of the current transformer.

Precision current transformers are used in many fields. Here are some of the main application areas:   Research units: In the field of scientific research, precision current transformers are widely used in various research projects, such as power engineering, physical research, automation, etc.   Laboratory: In various laboratories, such as power laboratories, electromagnetic laboratories, etc., precision current measurement and control are required, and precision current transformers have become essential equipment.   Manufacturing plants: In manufacturing plants, especially in the production of power equipment and electronic products, it is necessary to accurately control the current to ensure the quality and stability of the product. Precision current transformers play an important role in this process.   Current value transfer: In the power transmission and distribution system, the current needs to be accurately measured and controlled to achieve efficient transmission and distribution of power. Precision current transformers play a key role in this process.   Standard transformers: Precision current transformers are also used as standard transformers to calibrate other current measurement devices to ensure their accuracy.   As mentioned above, the application areas of precision current transformers are not limited to these. It is also widely used in many other power systems and equipment.  

Current transformers based on Permalloy cores have the advantages of high sensitivity and low hysteresis losses, making them ideal for use in wide-range applications. There are several key aspects to consider when implementing a wide-range current transformer:   1. Core material selection   The high permeability and low losses of Permalloy cores make them very sensitive when measuring smaller currents. However, for large current measurements, it is also necessary to ensure that the core is not saturated, so the appropriate core size and shape need to be selected.   2. Core size and shape   Selecting the appropriate core size and shape ensures that current can be effectively measured over the entire range. Larger cores can handle larger currents, but core saturation should be avoided.   3. Multi-level transformer design   To achieve a wide range, a multi-level transformer can be designed, that is, multiple windings are integrated in one transformer, each for a different current range. The different current ranges can be accommodated by electronic switching or paralleling multiple windings.   4. Compensation circuit   The use of compensation circuits can improve the linearity and accuracy of the transformer over a wide range. For example, operational amplifiers can be used for signal conditioning to reduce nonlinear errors.   5. Digital signal processing   Combined with digital signal processing technology, the measurement accuracy and dynamic range of the transformer can be further improved by filtering, amplifying and correcting the measurement signal.   6. Calibration and testing   Regularly calibrate the transformer to ensure its accuracy and stability over the entire range. Use standard calibration equipment and methods to verify and adjust the performance of the transformer.   Implementation example   The following are the design steps for a wide-range current transformer based on a Permalloy core:   1. Select the core: Select a Permalloy core with high magnetic permeability and suitable for wide-range applications. For example, use a C-type or toroidal core with a suitable cross-sectional area and length.   2. Design the primary and secondary windings: Design the primary and secondary windings according to the expected current range. Ensure that the secondary winding can effectively sense the flux changes of the primary winding.   3. Multi-level winding design: Integrate multiple secondary windings in the transformer, each corresponding to a different current range. Use an electronic switch or multiplexer to select the appropriate winding.   4. Signal conditioning circuit: Design a signal conditioning circuit, use operational amplifiers and filters to process the sensing signal, and improve the linearity and signal-to-noise ratio of the signal.   5. Digital processing module: Combined with a microcontroller or digital signal processor, the conditioned signal is sampled, processed and corrected. Automatic range switching and digital output can be achieved.   6. Calibration and testing: Use a standard current source to calibrate the transformer to ensure its accuracy throughout the range. Verify the effectiveness of the design through experimental tests, and adjust and optimize it according to the test results.   Through the above steps, a wide-range current transformer based on Permalloy core can be designed and implemented, which is suitable for various current measurement applications with high precision and wide dynamic range.

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.

Have you ever wondered how modern electronic devices get energy from weak electrical signals? The answer is often related to an inconspicuous but crucial component - the power extraction coil. How does this small coil play a key role in the vast network of science and technology? What impact does it have on our lives? Today, we will explore in detail the principles, applications and importance of power extraction coils in modern technology.   1. Basic principles of power extraction coils   1.1 What is a power extraction coil?   It is a device that uses the principle of electromagnetic induction to obtain electrical energy. It is usually composed of a coil wound with one or more wires. When the external magnetic field changes, an electromotive force is induced in the coil to generate current. This process is called electromagnetic induction and is a direct application of Faraday's law of electromagnetic induction.   1.2 Working principle   The working principle is based on Faraday's law of electromagnetic induction, which states that changes in magnetic flux passing through a coil will generate an electromotive force (i.e. voltage) in a conductor. Specifically, when the strength or direction of a magnetic field changes, the electrons in the coil are moved by force, forming a current.   This phenomenon is widely used in modern electrical equipment. For example, in wireless charging devices, the transmitter generates an alternating magnetic field through a coil, and the power extraction coil at the receiving end senses the change in this magnetic field, thereby generating current to charge the device.   2. Historical development of power extraction coils   2.1 Early development   The history of power extraction coils can be traced back to the 19th century. At that time, Michael Faraday and Joseph Henry discovered the phenomenon of electromagnetic induction. Faraday verified through experiments that changes in magnetic flux can generate current in a closed circuit, which laid the foundation for the design and application of modern power extraction coils.   2.2 Technological progress   With the development of electromagnetic theory, the design and manufacturing technology of power extraction coils are also constantly improving. In the early 20th century, power extraction coils began to be widely used in motors and generators for energy conversion and transmission. With the advancement of materials science and manufacturing processes, the efficiency and stability of power extraction coils have been significantly improved.   In modern times, power extraction coils are not only used in traditional power equipment, but also widely used in radio technology, sensors, medical equipment and other fields, becoming an indispensable part of modern science and technology.   3. Diversified Applications   3.1 Wireless Charging   Wireless charging is one of the most common applications of power extraction coils. Through the principle of electromagnetic induction, the power extration coil can transfer the power from the transmitter to the receiver, thereby charging various devices. This technology is widely used in devices such as smartphones, electric toothbrushes, and wireless headphones, greatly improving the convenience of use.   3.2 RFID Technology   Radio Frequency Identification (RFID) technology is also one of the important applications of power extraction coils. In the RFID system, the reader communicates with the tag through an electromagnetic field. The power extration coil in the tag generates current after inducing the electromagnetic field, and then starts the circuit in the tag for data exchange. This technology is widely used in logistics management, identity recognition, asset tracking and other fields.   3.3 Medical Equipment   In medical equipment, power extraction coils also play an important role. For example, in implantable medical devices (such as pacemakers), power extraction coils can obtain energy from the outside wirelessly, thereby extending the service life of the device and reducing the surgical risks of patients.   3.4 Sensor Technology   power extraction coils are also widely used in various sensors. By sensing changes in the external magnetic field, the power extration coil can be used to detect and measure a variety of physical quantities, such as current, voltage, speed, position, etc. These sensors are widely used in industrial automation, vehicle monitoring, environmental monitoring and other fields, greatly improving the intelligence and automation level of the system.   IV. Advantages and Disadvantages   4.1 Advantages   Power extraction coils have many significant advantages. First, they can achieve contactless energy transmission, greatly improving the convenience and safety of the equipment. Second, the design and manufacture of power extraction coils are relatively simple, low cost, and easy to mass produce and apply. In addition, the power extration coil has high efficiency and reliability and can work stably in various harsh environments.   4.2 Disadvantages   However, the power extration coil also faces some challenges. First, the electromagnetic induction efficiency is subject to the design and material selection of the coil, and how to further improve the efficiency is an important topic. Second, the power extration coil may be subject to electromagnetic interference in the application, affecting its normal operation. Finally, with the rapid development of wireless charging and sensor technology, how to meet the growing performance requirements is also an urgent problem to be solved.

Permalloy has a certain application in audio transformers due to its high magnetic permeability and low coercivity. The impact of using Permalloy as the core material of the transformer on the sound quality is mainly reflected in the following aspects:   Low hysteresis loss: The low coercivity of Permalloy means that its hysteresis loss is very low. This can reduce the distortion of the audio signal during transmission, thereby improving the clarity and fidelity of the sound quality.   High magnetic permeability: High magnetic permeability allows the transformer to operate at a lower magnetic field strength, which helps to reduce core loss and transformer self-noise, thereby improving the sound quality. Wide frequency response: Due to the characteristics of Permalloy, the transformer can work effectively over a wide frequency range. This is especially important for audio applications because it is better able to transmit high-frequency and low-frequency signals, providing a smoother and more accurate audio response.   Low distortion: Permalloy transformers are generally able to maintain low harmonic distortion when transmitting audio signals, which has a positive impact on the overall sound quality of audio equipment. However, Permalloy transformers also have some limitations:   Cost: Permalloy is relatively expensive, which makes transformers using this material more expensive.   Saturation flux density: Permalloy has a lower saturation flux density, which means that in high-power applications, the transformer may enter saturation earlier, affecting the sound quality. In general, Permalloy transformers have significant advantages in sound quality, especially in high-fidelity audio equipment. However, its cost and limitations in high-power applications need to be considered in the design.

1. The Nature of Current Transformers   Current transformers are basic devices in power systems that excel at converting high currents into corresponding lower currents. They are essential in both measurement and protection applications in power systems. Their key role is energy conversion, converting high input currents into manageable low output currents that are proportional to the original current.   2. Working Principle of Current Transformers   The working principle of current transformers depends on Faraday's law of electromagnetic induction. The high current flowing through the primary coil of the transformer generates a magnetic field, which in turn induces a current in the transformer core. This induced current is then converted into the secondary coil current.   3. Identifying Errors in Current Transformers   1. Ratio Error   A common error in current transformers is ratio error. This occurs when the transformer cannot accurately convert current according to a predefined ratio. Typically, nonlinear characteristics of the magnetic core and changes in coil impedance cause this error.   2. Phase Error   Phase error is another type of error defined by the phase angle difference between the transformer output and input currents. This difference can seriously affect the operation and protection mechanisms of the power system.   4. Interpretation of factors affecting current transformer errors   1. Coil impedance   Coil impedance has an important impact on current transformer accuracy. Increased impedance leads to a decrease in output current, which causes ratio errors.   2. Core saturation   Core saturation significantly affects transformer performance. Once the core reaches saturation, the performance of the transformer drops sharply, resulting in potential ratio and phase errors.   3. Frequency   The frequency of the input current affects the performance of the current transformer. Any fluctuation in frequency causes changes in impedance, which changes the accuracy of the transformer.   4. Temperature   Temperature changes affect the performance of the current transformer. As the temperature increases, the resistance of the coil increases, resulting in ratio and phase errors.   5. Loading   Changes in load can have a negative impact on transformer performance. An increase in load may increase the error range of the transformer.   6. Insulation   Insulation performance is critical to the accuracy of the current transformer. Damage to insulation may introduce errors within the current transformer.   7. Manufacturing process   The manufacturing process of the current transformer also determines its performance. Advances and improvements in these processes can significantly reduce the error of current transformers.   V. Reduce current transformer errors   1. Choose the right current transformer   The first step to reduce transformer errors is to choose the right current transformer. It should have excellent performance and sufficient capacity to meet the needs of the power system.   2. Follow the installation and use guidelines   When installing and using current transformers, ensure that the integrity of the insulation is maintained, avoid high temperatures, and regularly inspect and maintain them to maintain their performance and accuracy.   3. In summary   Understanding the various factors that affect current transformer errors is essential to properly utilize current transformers and improve the efficiency and safety of power systems. By understanding these factors, we can effectively reduce or avoid current transformer errors.   FAQ   What does the ratio error of a current transformer mean?   Ratio error occurs when a current transformer fails to accurately convert current according to a predetermined ratio.   What are the key factors that affect current transformer errors?   The main factors include coil impedance, core saturation, frequency, temperature, load, insulation, and manufacturing process.   How can we minimize the error of current transformer?   Reducing the error can be achieved mainly by selecting the right transformer, installing and using it correctly, and maintaining it regularly.   How does the error of current transformer affect the power system?   The error of current transformer mainly affects the measurement and protection mechanism of the power system. Both ratio and phase errors can lead to unstable operation of the power system, which may cause accidents.   What is the working principle of current transformer?   The current transformer works according to Faraday's law of electromagnetic induction. When a large current flows through the primary coil, a magnetic field is generated, which induces a current in the core of the transformer. This induced current is then converted into auxiliary coil current.

Permalloy and silicon steel sheet are two different materials with some differences in properties and uses.   1. Permalloy: Permalloy is an alloy material with high strength, high corrosion resistance and high temperature stability.   It is mainly composed of nickel, chromium, phosphorus, boron and other elements, and is widely used in aerospace, chemical industry and manufacturing industries.   Permalloy has excellent mechanical properties and corrosion resistance, and can work stably for a long time in high temperature and corrosive environment.   2. Silicon steel sheet: Silicon steel sheet is a widely used electrical cold-rolled steel, which is characterized by a high silicon content.   Silicon steel sheet is mainly used to make core components of electrical equipment such as motors and transformers, with low magnetic permeability, low magnetic loss and high magnetic saturation induction intensity.   By adding an appropriate amount of silicon, the eddy current loss in the magnetic field can be effectively reduced and the conversion efficiency of the transformer can be improved.   When considering the magnetic conductivity, Permalloy (usually refers to nickel-iron soft magnetic alloy containing molybdenum, such as Permalloy) and silicon steel sheets each have their own characteristics and application fields:   The magnetic permeability of this material is very high, which can reach hundreds of thousands, so it is very suitable for applications that require extremely high magnetic permeability and low hysteresis loss, such as transformers, shielding materials, read-write heads, etc.   Silicon steel sheet:   Silicon steel sheet is a kind of steel containing a certain proportion of silicon, which is usually used in electrical applications, such as core materials for motors, generators and transformers.   The magnetic permeability of silicon steel sheet is low, usually between thousands and tens of thousands, but its advantages are low cost and good mechanical strength and heat resistance.   Silicon steel is mainly used to manufacture the core of high-power equipment, and its silicon content can effectively reduce the eddy current loss and hysteresis loss of the core.   Therefore, Permalloy and silicon steel sheet are two different materials with different application fields and performance characteristics.

I would like to ask about Permalloy:   1. Can Permalloy be used as the core of a 30kHZ transformer?   2. Can Permalloy be milled? I hope you can help answer this question! Permalloy is a metal alloy material with very low resistivity and drastically increased high-frequency loss. It can generally only be used in the low-frequency range.   At the frequency of 30khz, it is recommended to use manganese-zinc ferrite material, which is still cheap.   Permalloy is generally a strip material, most of which are wound or laminated, and generally do not require milling.   Permalloy of conventional thickness cannot meet the working requirements at a frequency of 30kHz. Ultra-thin strips with a thickness of less than 0.05 are required to have a chance.   Permalloy can be made into strips and rods. Rod materials can be milled, but because Permalloy is soft, it has high requirements for milling tools.

Permalloy cores are designed for use in a variety of power applications, and one of the key performance characteristics is its high temperature stability. This means that it is able to maintain good magnetic properties, including high permeability and low energy loss, at higher temperatures. This high temperature resistance makes Permalloy cores ideal for use in power equipment that needs to withstand high temperature environments for a long time, such as certain types of transformers, motors, and power electronic equipment.   Permalloy's high temperature resistance is due to its special alloy composition and microstructure, which are carefully selected and optimized during the design and production of the alloy. The specific ratios of elements such as iron, silicon, aluminum, and nickel, as well as the microstructure obtained through a precise heat treatment process, work together to improve its performance stability at high temperatures.   Although Permalloy cores do have good high temperature resistance characteristics, their performance is still affected to some extent at extreme temperatures. Increased temperature causes the material's magnetic permeability to decrease and energy loss to increase, although this effect is much smaller in Permalloy than in other materials. Therefore, when designing and using power equipment containing Permalloy cores, it is very important to consider its operating temperature range and stability.

For the split current transformer installed in outdoor overhead lines or cable trenches, the cut surface of the transformer will be exposed to the air and will be exposed to rain or soaked in water in the cable trench, which will cause rust and affect the product performance. Water accumulation in the secondary terminal will also cause short circuit, so measures need to be taken to prevent rain or water immersion. Based on our many years of practical experience in manufacturing split current transformers, 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 shown in the figure below. The second solution is the "open type 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. The actual product is shown in the following photos: