Strong magnetic field generator

Abstract

A strong magnetic field generator is provided with a strong magnetic coil driven by a high-voltage pulse power supply, the strong magnetic coil is formed by coiling a tubular copper wire, the periphery of the copper wire is filled and fixed by epoxy resin, the diameter of the tubular copper wire is 4mm, the wall thickness of the tubular copper wire is 1mm, the tubular copper wire is coiled into a cylinder with six turns in each layer and 20 layers in total, gaps are arranged between turns and layers, the central aperture of the cylinder is 42mm, and the height of the cylinder is 140mm. According to the utility model, computer analogue simulation and physical sample field test are carried out, so that a strong magnet of which the electromagnetic field intensity exceeds 6T, the inner diameter is greater than 20mm and the outer diameter is controlled within 200mm can be met. The amplitude of the strong magnetic pulse of the actually measured sample is 7T, the pulse width is 6ms, and the amplitude of the output current of the power supply reaches 6480A.

Description

Technical Field

[0001] This utility model relates to an electromagnetic device, specifically a strong magnetic field generator. Background Technology

[0002] Electromagnetic protection for ammunition is a crucial aspect of ammunition support. With the rapid development of electronic science and technology, the number of civilian and military electromagnetic radiation devices has increased significantly, generating increasingly powerful electromagnetic fields that can interfere with or even damage ammunition and its pyrotechnic components. To eliminate the influence of the electromagnetic environment and improve the safety and reliability of ammunition's electro-pyrotechnic components, electromagnetic protection is typically achieved using single-layer shielding or magnetic coatings, enabling the storage and normal use of ammunition even in weak magnetic environments.

[0003] While simple protective measures can shield against weak electromagnetic environments, strong pulsed magnetic fields pose a significant challenge. Due to their greater penetration and faster changes—typically reaching strengths of several Tesla or even tens of Tesla within milliseconds—conventional shielding materials can easily become magnetically saturated or experience excessive eddy currents, leading to weakened or failed protection. Furthermore, strong pulsed magnetic fields are far more dangerous than weak magnetic environments. The instantaneous nature of these changes can induce currents in the electro-pneumatic devices (EPDs) of munitions, potentially igniting them and causing an explosion. The powerful electromagnetic pulses generated by electromagnetic pulse bombs or nuclear explosions can create strong pulsed magnetic fields over a wide area, severely threatening the safety of munitions and electronic products.

[0004] To ensure the safety of electro-explosive devices in strong pulsed magnetic field environments, further research on electromagnetic shielding and protection is necessary. Since there is currently no high magnetic field generator that meets the requirements, it is necessary to develop a high magnetic field generator that is easy to use, stable in performance, and meets the required specifications. Utility Model Content

[0005] The technical problem to be solved by this utility model is to provide a strong magnetic field generator that can meet the following requirements: the peak magnetic field value is not less than 6T, the pulse duration is not less than 3ms, the average attenuation rate of the magnetic induction intensity of the magnetic field generated on the center line of the magnet in the axial direction is not greater than 0.5% / mm, the accumulated temperature of the strong magnetic field generator of a single pulse discharge is as low as possible, the time interval of continuous pulse excitation is not greater than 3 minutes, and the structure still has high stability after continuous pulse excitation.

[0006] The strong magnetic field generator is characterized by having a strong magnetic coil driven by a high-voltage pulse power supply. The strong magnetic coil is composed of a tubular copper wire coiled together, with epoxy resin filling and fixing the copper wire around it. The tubular copper wire has a diameter of 4mm and a wall thickness of 1mm, and is coiled into a cylindrical shape with m turns per layer and n layers in total. There are gaps between the turns and between the layers. The central hole of the cylindrical shape has a diameter of 42mm and a height of 140mm. The above dimensions can be adjusted within a range of ±45%, where 4<m≤8 and 18<n≤24.

[0007] In an embodiment where the equipment requires cooling during operation, the two ends of the copper wire of the strong magnetic coil are connected to the liquid cooling input and output terminals of the refrigeration equipment through circulating cooling pipes.

[0008] As one embodiment of the high-voltage pulse power supply, the high-voltage pulse power supply includes a signal generator U, a pulse transformer T, and a bootstrap circuit J. The output terminal of the signal generator U is connected to the input terminal of the pulse transformer T through a series resistor and an electronic switch. The output terminal of the pulse transformer T is connected to the input terminal of the bootstrap circuit J, and the output terminal of the bootstrap circuit J is the output terminal of the high-voltage pulse power supply.

[0009] The discharge of the strong magnetic coil is achieved by using an electronic switch that can withstand high voltage and high current. The output terminal of the high voltage pulse power supply is connected to the strong magnetic coil through a trigger vacuum switch.

[0010] As an example, m=6 and n=20 are selected. That is, the copper wire is wound into a cylindrical shape with 6 turns per layer, for a total of 20 layers.

[0011] This invention has undergone computer simulation and on-site testing of physical samples, demonstrating its ability to withstand strong magnets with electromagnetic field strength exceeding 6T, inner diameter greater than 20mm, and outer diameter controlled within 200mm. The measured sample exhibited a strong magnetic pulse amplitude of 7T, a pulse width of 6ms, and a power supply output current amplitude of 6480A. The material selection and parameter combination of this invention have been validated through actual testing, achieving optimal material utilization and best results. Using water cooling and operating at room temperature, the product exhibits stable structure and performance, making it suitable for further applications. This invention provides reliable theoretical and practical examples for the protection of pyrotechnics and electronic products, offering a theoretical and practical foundation for further in-depth electromagnetic field protection analysis. Attached Figure Description

[0012] Figure 1 This is a block diagram of the overall system structure of this utility model.

[0013] Figure 2 This is a schematic diagram of the three-dimensional structure of a strong magnetic coil.

[0014] Figure 3 This is a schematic diagram of the end face structure of a strong magnetic coil.

[0015] Figure 4 This is a schematic diagram of a capacitor charging implementation example.

[0016] Figure 5 This is the controllable charging function curve of this utility model.

[0017] Figure 6 This is a charging time-voltage curve for a capacitor charging embodiment.

[0018] Figure 7 This is the schematic diagram of the equivalent circuit for capacitor discharge.

[0019] Figure 8 This is a waveform diagram of the output current of a high-voltage power supply.

[0020] Figure 9 This is a waveform diagram of the excitation of a strong magnetic coil.

[0021] Figure 10 This is a waveform diagram of the magnetic induction intensity at the center of a strong magnetic coil.

[0022] In the diagram: 1-High voltage pulse power supply, 2-Trigger vacuum switch, 3-Strong magnetic coil, 4-Temperature sensor, 5-Circulating cooling pipe, 6-Refrigeration equipment. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0024] A strong magnetic field generator suitable for laboratory use is required to generate a magnetic field with a peak intensity of at least 6T at the center; the inner diameter of the strong magnetic field generator should be ≥20mm; when the magnetic field intensity generated at the center is 5T±1T, the duration of the magnetic field should be ≥3ms; the average attenuation rate of the magnetic field intensity generated on the center line in the axial direction should be <0.5% / mm; the time interval between continuous magnetic field generation by the magnetic field generator should be <3 minutes; it should comply with national electromagnetic compatibility standards; the cost should be within a reasonable range; and it should be easy to manufacture.

[0025] The core components of the strong magnetic field generator are the high-voltage pulse power supply 1 and the strong magnetic coil 3. Under normal power supply, the strong magnetic coil 3 can generate a strong magnetic field by being driven by the high-voltage pulse power supply 1.

[0026] To achieve the above objectives, the strong magnetic coil 3 needs to withstand a sufficiently high current intensity. Considering cooling factors, it is constructed by winding tubular copper wire. The tubular copper wire has a diameter of 4mm and a wall thickness of 1mm, and is wound into a coaxial solenoid with m turns per layer and n layers in total. The structure is as follows: Figure 2 As shown. Considering heat dissipation and vibration damping, as a preferred embodiment, m=6 and n=20.

[0027] Electromagnetic field simulations of magnets reveal that high current flow leads to significant resistance losses and heat generation. Furthermore, high conductor temperatures alter the conductivity of the copper wire. During continuous pulse excitation, the accumulated heat in the coil causes thermal radiation to the pyrotechnic device placed at its center, potentially igniting it. The effects of external strong magnetic field variations and thermal radiation on the pyrotechnic device are difficult to separate. Therefore, ensuring the stability and continuity of the strong magnetic signal generator while simultaneously addressing heat transfer and electromagnetic field issues becomes crucial. Active cooling is needed to combat the Joule heating caused by the high current in the magnet coil. Common engineering methods for coil cooling include water cooling, air cooling, and oil cooling. Considering the miniaturization, ease of operation, and long-term stability of the strong magnetic signal generator, a hollow conductor with purified water flowing through its center is chosen for active cooling. Even at low flow rates, the cooling water can still generate highly developed turbulence due to the magnetic field, facilitating efficient heat transfer between the conductor and the fluid. In embodiments where cooling is required during equipment operation, the two ends of the copper wire of the strong magnetic coil 3 are connected to the water-cooling input and output terminals of the refrigeration equipment 6 through the circulating cooling pipe 5.

[0028] The temperature rise of the conductor during a single discharge was calculated, with the room temperature set at 20℃, the fluid being liquid water at an inlet temperature of 10℃, a flow rate of 1 kg / min, a conductor diameter of 4 mm, and a wall thickness of 1 mm. Simulation results show that when the maximum amplitude of the magnetic field pulse is 6.8 T, the temperature rise after a single pulse discharge is 41.1℃, the cooling water temperature is 16.8℃, and the pulse discharge interval is 1 min, indicating no thermal stability issues.

[0029] Magnets experience enormous stress under strong magnetic field conditions. At a magnetic field strength of 6.8T, the maximum stress is 12.9MPa. When a pulsed magnetic field is in operation, it will generate vibrations. Supporting materials need to be filled between different conductor layers to overcome stress expansion. The tensile strength limit of the material cannot exceed this value, otherwise structural damage will occur.

[0030] In this invention, the copper conductor is fixed by being filled with epoxy resin, and gaps are provided between turns and between layers. When the preset gap is 2mm, for example... Figure 2 , 3 It has a cylindrical central hole diameter of 42mm and a height of 140mm.

[0031] Regarding the magnetic field, actual measurements show that the magnet can generate a strong magnetic field with a peak value of 6.8T and a duration of 3.4ms. Within a 112mm range along the central axis of the magnet, the magnetic field fluctuation is less than 0.9T. Finally, simulation results show that the temperature rise after a single pulse operation of the strong magnetic coil is only 41.4℃, the maximum stress is 12.9MPa, and the deformation is very small. Therefore, it has structural and temperature stability and can achieve a continuous pulse interval of 1min, fully meeting the requirement of continuous generation of a strong magnetic field with an interval of no more than 3min, thus satisfying the performance requirements.

[0032] High-voltage power supply systems are required to charge to a set voltage value within a specified time, and the charging current must not exceed the overcurrent protection value during charging. Currently, the commonly used charging methods are constant current charging and constant voltage charging. This project designs a new controllable function charging control method. To achieve charging to the set voltage within a set time, a charging function is introduced, and the corresponding charging curve is shown below. Figure 5 It can be seen that dividing the set charging time into two segments, within the time period 0 to aT, the voltage can be charged to 0.9 times the set charging voltage value U. Within the time period aT to T, the voltage is fully charged to U. The charging control quantity will gradually increase according to the rate given by the charging function; here, the value of 'a' needs to be determined. Due to feedback control, the charging process is not a smooth diagonal line, but rather an approximate step-like ascent. The width of each "step" also needs to be determined to find the maximum charging current throughout the entire charging process, thereby determining the capacity of the step-up transformer.

[0033] like Figure 4 As shown, based on the above idea, as an embodiment of a high-voltage pulse power supply, the high-voltage pulse power supply 1 includes a signal generator U, a pulse transformer T, and a bootstrap circuit J for charging a capacitor. The capacitor, through a pulse-controlled electronic switch, serves as a power source for discharging a strong magnetic coil. Figure 4 The output of signal generator U is connected in series with an electronic switch and a resistor, and then connected to the input of pulse transformer T. The output of pulse transformer T is connected to the input of bootstrap circuit J, with the output of bootstrap circuit J serving as the output of the high-voltage pulse power supply 1. Signal generator U generates pulse waveforms, and the conduction time of the electronic switch is 10 to 100 pulse signal cycles. Pulse transformer T boosts the input signal, and then the capacitor is charged through the diode of bootstrap circuit J. Figure 6 This is the measured charging curve of the capacitor by the circuit. In this embodiment, the capacitor value is 3000 microfarads. It can be seen that this charging method differs from both constant voltage charging and constant current charging, but it controls the charging voltage and current. The charging voltage gradually increases, and the charging current is limited to prevent it from becoming excessive. Therefore, it causes less stress on the capacitor, has a wider tolerance range, and the circuit is simple, reliable, and lower in cost.

[0034] The discharge process involves high voltage and high current, requiring high-voltage switch components to withstand a rated voltage of 40.5kV and a rated current of 40kA. A high-voltage, high-current-resistant electronic switch is needed to discharge the strong magnetic coil. This invention employs a trigger vacuum switch (TVS) with a field-induced breakdown structure, i.e., [missing information - likely a specific type of switch]. Figure 7 TVS (Transmission Vacuum Switch). A TVS, also known as a triggered vacuum gap, is a circuit closing device based on vacuum gap and spark gap technology. It features a compact structure, fast dielectric recovery, noiseless operation, high reliability, and strong environmental adaptability. Currently, TVS has a maximum operating voltage >40kV, a maximum operating current >200kA, a vacuum gap typically 1–20mm, and a vacuum pressure ≤10. -4 Pa.

[0035] like Figure 7 The output terminal of the high-voltage pulse power supply 1 is connected to the strong magnetic coil 3 via a trigger vacuum switch 2. In this embodiment, the strong magnetic coil 3 is equivalent to a 10 microhenry inductor and a 0.052 ohm resistor connected in series. The strong magnetic coil 3 in the figure includes a switch M. The design voltage is 3.5 kV and the current is 9.6 kA.

[0036] Figure 8 This is the discharge current curve of a high-voltage power supply using the above parameters. From this, the excitation waveform of the strong magnetic coil and the magnetic field waveform at its center point can also be obtained. For example... Figure 9 , 10 As shown, the highest amplitude of the magnetic field waveform at the center of the strong magnetic coil is 6.5T, and the pulse duration is not less than 3ms, which meets the design requirements.

[0037] The strong magnetic generator of this utility model was tested and verified.

[0038] 1. Preparation before testing: First, conduct a pre-inspection of all components to ensure they are free of defects; perform preliminary debugging of the entire system to ensure that each part is working properly.

[0039] 2. Environmental setup: The experiment was conducted in an environment with a constant temperature of 20℃ and a relative humidity of 50%.

[0040] 3. Instruments and Equipment: Tektronix TDS1012C-SC Oscilloscope

[0041] FE-103 Pulse Gaussmeter

[0042] FE-102 Gaussmeter

[0043] FE-2100PEM Pulse Field Permanent Magnet Measuring Instrument

[0044] The equipment under test is a self-developed pulse magnetic field generator and an HS1850-HAS1-003A water-cooling device.

[0045] A strong magnetic coil and a high-voltage pulse power supply were directly connected. The outlet of the refrigeration equipment was connected to the inlet of the strong magnetic coil, and the outlet of the strong magnetic coil was connected to the inlet of the refrigeration equipment. The outlet temperature of the refrigeration equipment was set to 5℃, and the temperature hysteresis was set to 0.1℃. A temperature sensor was placed at the outlet of the strong magnetic coil to monitor the temperature change of the return water in real time. The pulse gaussmeter probe was placed at the center of the strong magnetic coil to collect real-time magnetic field data. The output of the pulse gaussmeter was connected to the input of an oscilloscope to plot the magnetic field waveform in real time. The experimental results showed that the amplitude of the strong magnetic pulse was 7T, the pulse width was 6ms, and the output current amplitude of the power supply reached 6480A. At this time, the pulse power supply voltage was set to 1500V, and the capacitor value was selected as 10000uF. When the pulse gaussmeter was connected to the oscilloscope, the gaussmeter range of 2V corresponded to a magnetic field of 20T.

[0046] in conclusion,

[0047] (1) The inner diameter of the strong magnetic field generator is 40mm ≥ 20mm, which meets the requirements;

[0048] (2) The peak magnetic field strength at the center is 7T ≥ 6T, which meets the requirements;

[0049] (3) When the magnetic field intensity at the center is 7T, the magnetic field can last for 6ms ≥ 3ms, which meets the requirements.

[0050] (4) The magnetic induction intensity of the magnetic field along the center line of the strong magnetic field generator is 5.9T at a distance of 112mm in the axial direction, and the average decay rate satisfies the following condition: 0.23% / mm <

[0051] 0.5% / mm, which meets the requirements;

[0052] (5) The time interval between continuous magnetic field generation by the magnetic field generator is 1 minute < 3 minutes, which meets the requirements.

[0053] The above results show that the measured central magnetic field amplitude is 7T, the pulse width is 6ms, the power supply output current amplitude reaches 6480A, the continuous pulse discharge interval is 1min, and the outlet temperature is 31℃ after a single pulse discharge. Inspection revealed no deformation or damage inside the strong magnet. This indicates that the strong magnetic generator meets the conditions for generating strong magnetic fields while overcoming the adverse effects of electromagnetic expansion force and temperature rise. It ensures the structural stability, insulation performance, and long-term continuous magnetic field generation requirements of the strong magnetic field generator. It can generate a stable high-intensity magnetic field under specified conditions, achieving the expected design goals and meeting the performance requirements.

[0054] The various embodiments of this utility model can be used interchangeably or simultaneously as needed. Any numerical changes and circuit improvements made under the guidance of this utility model are still within the protection scope of this utility model.

Claims

1. A strong magnetic field generator, characterized in that: A strong magnetic coil (3) driven by a high-voltage pulse power supply (1) is provided. The strong magnetic coil (3) is composed of a tubular copper wire coiled around the copper wire. The copper wire is filled and fixed with epoxy resin. The diameter of the tubular copper wire is 4 mm and the wall thickness is 1 mm. It is coiled into a cylindrical shape with m turns per layer and n layers in total. There are gaps between the turns and between the layers. The central hole of the cylindrical shape is 42 mm in diameter and 140 mm in height. The above dimensions can be adjusted within a range of ±45%, 4 < m ≤ 8, 18 < n ≤ 24.

2. The strong magnetic field generator according to claim 1, characterized in that: The two ends of the copper wire of the strong magnetic coil (3) are connected to the liquid cooling input and output ends of the refrigeration equipment (6) through the circulating cooling pipe (5).

3. The strong magnetic field generator according to claim 1, characterized in that: The high-voltage pulse power supply (1) is equipped with a signal generator U, a pulse transformer T and a bootstrap circuit J. The output terminal of the signal generator U is connected to the input terminal of the pulse transformer T through a series resistor and an electronic switch. The output terminal of the pulse transformer T is connected to the input terminal of the bootstrap circuit J, and the output terminal of the bootstrap circuit J is the output terminal of the high-voltage pulse power supply (1).

4. The strong magnetic field generator according to claim 1, characterized in that: The output terminal of the high-voltage pulse power supply (1) is connected to the strong magnetic coil (3) via a trigger vacuum switch (2).

5. The strong magnetic field generator according to claim 1, characterized in that: Choose m=6 and n=20.

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