A device and method for generating a repetitive pulsed strong magnetic field

Abstract

The present invention provides a device and method for generating a repetitive pulsed strong magnetic field, belonging to the field of strong magnetic fields. The device includes a magnetic coil and a plurality of independent power supply units, wherein the plurality of independent power supply units are connected in parallel to both ends of the magnetic coil; wherein each power supply unit includes an energy supply element, a freewheeling circuit and an electrical switch, wherein the freewheeling circuit is connected in parallel with the energy supply element and then in series with the electrical switch; the freewheeling circuit includes a freewheeling resistor and a unidirectional conducting element connected in series with each other. The present invention adopts a scheme of discharging a single magnet with multiple sets of power supplies, and can generate a repetitive pulsed strong magnetic field by controlling the connection mode of the plurality of power supply units with the magnetic coil and the discharge sequence of the electrical switch, and has the advantages of simple circuit topology and control system, diversified magnetic field waveform, and arbitrary controllable magnetic field polarity, magnetic field strength and repetition frequency.

Description

Technical Field

[0001] The present invention belongs to the technical field of strong magnetic fields, and more specifically, relates to a device and method for generating a repeated pulse strong magnetic field. Background Art

[0002] Strong magnetic fields are used to provide extremely important extreme experimental conditions in modern scientific research. Permanent magnets or superconducting magnet systems are generally used internationally to provide such strong magnetic fields. However, permanent magnet systems must use mechanical motion to achieve magnetic field alternation of magnetic cooling materials, and superconducting magnet systems have problems such as low temperature operating conditions, quench limits, and high cost.

[0003] Pulsed magnetic field refers to the magnetic field generated in space by pulsed current passing through a magnet coil. The direction of the current flowing through the coil determines the polarity of the magnetic field waveform. Intermittently and repeatedly passing pulsed current through the magnet coil will generate a repetitive pulsed magnetic field. Compared with permanent magnets or superconducting magnets, repetitive pulsed magnetic field systems can control the presence or absence of magnetic fields by energizing them. They have the advantages of avoiding the mechanical reciprocating motion of permanent magnets, being cheaper than superconducting magnet systems, and being able to achieve high field strengths, and have been widely studied. Among them, magnetic field intensity, magnetic field stability, and magnetic field waveform repetition frequency are key experimental parameters.

[0004] The current repetitive pulse electromagnetic system generally controls the large current waveform under high voltage by designing the power supply topology to generate a repetitive pulse magnetic field waveform. For example, the Wuhan National Pulse Laboratory uses an AC capacitor as a power source and controls the bidirectional anti-parallel thyristor to achieve a repetitive pulse strong magnetic field with a single discharge of positive and negative polarity and a magnetic field strength of 3T. The system theoretically achieves the maximum energy utilization rate, but due to the power limit of the charger, the field strength that can be achieved is not high. The repetition frequency of the magnetic field waveform is limited by the charging time of the power supply, and its polarity can only be generated alternately positive and negative. For example, for the repetitive pulse strong magnetic field waveform required in scientific experiments such as neutron diffraction and magnetization, the US National Laboratory uses a pulse generator as a power source, provides two current inputs, and uses a bidirectional anti-parallel thyristor as a control switch to cooperate with the power input to achieve a 2Hz bipolar repetitive pulse strong magnetic field. However, the system equipment control is complex, the system components are numerous, and due to the presence of the energy feeding inductor in the circuit, it is not suitable for large inductance magnets.

[0005] In general, the repetitive pulsed high magnetic field devices in the world currently have the following disadvantages: (1) The power supply topology or control system is complex and the construction cost is high; (2) The application range of the magnetic inductance in the electromagnetic device is limited by the energy feeding inductance, and the generated magnetic field strength is relatively low; (3) Using a set of power supplies, the magnetic field strength is limited by the power of the charger, and the repetition frequency is limited by the charging time of the power supply; (4) The repetitive pulsed magnetic field waveform is single. Summary of the invention

[0006] In view of the defects of the existing solutions, the present invention provides a device and method for generating a repetitive pulsed strong magnetic field, which adopts a solution of discharging multiple sets of power supplies to a single magnet to achieve a repetitive pulsed magnetic field. Its purpose is to solve the technical problems of the existing system topology and control system being complex, the application range of the magnetic inductance in the electromagnetic device being limited by the energy feeding inductance, the magnetic field strength being limited by the power supply power, the repetition frequency being limited by the power supply charging time, and the single repetitive magnetic field waveform.

[0007] The present invention provides a repetitive pulsed strong magnetic field generating device, which comprises a magnetic coil and a plurality of independent power supply units, wherein the plurality of independent power supply units are connected in parallel to both ends of the magnetic coil;

[0008] Each power supply unit includes an energy supply element, a freewheeling circuit and an electrical switch. The freewheeling circuit is connected in parallel with the energy supply element and then in series with the electrical switch. The freewheeling circuit includes a freewheeling resistor and a unidirectional conducting element connected in series.

[0009] Furthermore, the energy supply element is a capacitor, the unidirectional conducting element is a diode, and the electrical switch is a controlled thyristor.

[0010] The present invention also provides a method for generating a strong magnetic field based on the above-mentioned repeated pulse strong magnetic field generating device, comprising the following steps:

[0011] (1) Immerse the magnet coil in liquid nitrogen for cooling, and monitor the cooling process of the magnet by measuring the change in the magnet resistance value;

[0012] (2) connecting the positive and negative poles of the plurality of power supply units to the connection terminals of the magnetic coil according to the polarity of the preset magnetic field waveform, and charging the energy supply element in each power supply unit to a preset voltage;

[0013] (3) Multiple power supply units discharge the magnetic coils in sequence according to a preset discharge sequence.

[0014] Furthermore, after each discharge, the resistance change of the magnetic coil caused by heating is monitored, and the preset voltage of each power supply unit is adjusted accordingly.

[0015] Furthermore, in step (2), the preset voltage is determined according to the magnetic field strength required by the waveform.

[0016] Furthermore, in the step (3), the discharge timing is set according to the magnetic field frequency required by the waveform.

[0017] Compared with the prior art, the present invention has many beneficial effects:

[0018] (1) The present invention provides a plurality of independent power supply units, which can avoid the process of replenishing power supply energy during the discharge process, so that the frequency of the magnetic field waveform is not limited by the charging time, and the magnetic field strength is not limited by the power of the charger; on the other hand, the polarity, magnetic field strength and repetition frequency of the magnetic field waveform can be arbitrarily controlled, and the magnetic field waveform is diversified;

[0019] (2) Each power supply unit has the same composition, simple and reliable structure, and no complex control system is required;

[0020] (3) There is no need to use a power feeding inductor in the power supply unit, so the application range of the magnetic inductor is not limited by the power feeding inductor and a higher magnetic field strength can be generated. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a circuit structure diagram of a device for generating a repetitive pulsed strong magnetic field.

[0022] Figure 2 It is a unipolar repetitive pulse strong magnetic field simulation waveform.

[0023] Figure 3 (a) and (b) are the simulated waveforms of unipolar step-type repetitive pulsed strong magnetic field.

[0024] Figure 4 It is a bipolar repetitive pulse strong magnetic field simulation waveform.

[0025] Figure 5 (a) and (b) are the bipolar step-type repetitive pulse strong magnetic field simulation waveforms.

[0026] Figure 6 (a) and (b) are the simulated waveforms of multi-style repetitive pulsed strong magnetic field. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0028] Figure 1 A repetitive pulsed strong magnetic field generating device provided by an embodiment of the present invention is shown. For ease of description, only the parts related to the embodiment of the present invention are shown.

[0029] A repetitive pulse strong magnetic field generating device comprises a magnetic coil and a plurality of independent power supply units CM1, CM2, CM3, CM4, CM5, CM6, CM7, CM8, CM9, CM10, CM11, CM12, CM13, CM14, CM15, CM16, CM17, CM18, CM19, CM20, CM21, CM22, CM23 N , L and R are the inductance and internal resistance of the magnetic coil respectively, and the multiple independent power supply units are connected in parallel to both ends of the magnetic coil;

[0030] The basic composition of each power supply unit is the same. Taking the first power supply unit CM1 as an example, it includes an energy supply element C1, a freewheeling circuit and an electrical switch S1. The freewheeling circuit is connected in parallel with the energy supply element C1 and then in series with the electrical switch S1. The freewheeling circuit includes a freewheeling resistor R connected in series with each other. d1 and a unidirectional conducting element D1.

[0031] Preferably, the energy supply element C1 is a capacitor, the unidirectional conducting element D1 is a diode, and the electrical switch S1 is a controllable thyristor.

[0032] In the prior art, since the power supply part of the repetitive pulse electromagnetic system only includes a single energy supply element, for example, only one capacitor is set, after the capacitor is discharged, it needs to be recharged immediately before the next discharge. The present invention sets a plurality of independent power supply units to fully charge all capacitors before discharge. On the one hand, it can avoid the process of replenishing the power supply energy during the discharge process, so that the frequency of the magnetic field waveform is not limited by the charging time, and the magnetic field strength is not limited by the power of the charger; on the other hand, the polarity, magnetic field strength and repetition frequency of the magnetic field waveform can be arbitrarily controlled, and the magnetic field waveform is diversified. Moreover, each power supply unit has the same composition and is composed of conventional pulse power supplies. It does not require a specially designed power supply system, and the structure is simple and reliable, and does not require a complex control system; further, the power supply unit does not use a feeding inductor, so the scope of application of the magnetic inductor is not limited by the feeding inductor.

[0033] In an embodiment of the present invention, a magnetic field generating method based on the above-mentioned repeated pulsed strong magnetic field generating device comprises the following steps:

[0034] (1) The magnet coil is immersed in liquid nitrogen and cooled to 77K. The cooling process of the magnet is monitored by measuring the change in the magnet resistance value.

[0035] (2) Connecting the positive and negative poles of multiple power supply units to the connection terminals of the magnetic coil according to the polarity of the preset magnetic field waveform, and charging the capacitor in each power supply unit to a set voltage.

[0036] The polarity of the magnetic field waveform depends on the power supply direction of the energy supply element. When the positive and negative poles of the capacitor module are swapped or the terminals of the power supply and the magnetic coil are swapped, the polarity of the waveform will change accordingly. In addition, the magnetic field strength depends on the size of the set voltage, and the magnetic field frequency is controlled by the discharge timing.

[0037] In an embodiment of the present invention, according to the frequency of repetitive pulses, magnetic field strength and magnetic field waveform polarity, combined with the configuration of the existing capacitor module and the magnet coil parameters, the charging voltage and trigger time of the capacitor in each power supply unit are determined by simulation using the Simulink module of Matlab.

[0038] (3) Controlling the electrical switch to discharge the magnetic coil in sequence according to a preset discharge sequence.

[0039] If multiple power supply units are connected to the magnet coil terminals in the same direction, the following will occur: Figure 2 The unipolar repetitive pulse strong magnetic field waveform shown in FIG. 1 is shown in FIG. 1 ; on this basis, adjusting the preset voltage of each power module will produce the following Figure 3 The unipolar step-type pulsed strong magnetic field waveform shown.

[0040] If multiple power supply units are connected to the magnetic coil terminals in alternating directions (i.e., positive connection-reverse connection-positive connection-reverse connection-...), the following will occur: Figure 4 The bipolar high-frequency repetitive pulse strong magnetic field waveform shown in the figure is adjusted on this basis to adjust the preset voltage of each power module, which will produce the following Figure 5 The bipolar step-type pulsed strong magnetic field waveform shown.

[0041] If multiple power supply units are connected to the magnetic coil terminals in any direction and the discharge time is controlled as needed, a variety of repetitive pulse strong magnetic field waveforms with arbitrary polarity and frequency can be generated. Figure 6 An example of the waveform of a repetitive pulsed strong magnetic field is shown.

[0042] Adjustment phase: After each discharge, the resistance change of the magnetic coil caused by heating is monitored, and the set voltage of each power supply is adjusted accordingly.

[0043] Taking into account that the resistance of the magnet coil will change due to the heating of the magnet, in order to avoid the influence of resistance change on the pulse current and magnetic field strength, the resistance change caused by heating of the magnet coil at the end of each discharge is monitored, and then the set voltage of each power supply is adjusted, so that the preset repetitive pulse strong magnetic field waveform can be achieved more accurately.

[0044] In an embodiment of the present invention, a plurality of power supply units connected in parallel at both ends of the magnetic coil are connected to the connection terminals of the magnetic coil according to a preset magnetic field waveform polarity, and then the electrical switch is controlled to discharge according to the discharge timing, so that a repetitive pulsed strong magnetic field with arbitrary waveform intensity, polarity, and frequency can be generated. The repetitive pulsed strong magnetic field generating device proposed by the present invention has the characteristics of simple and reliable power supply topology, simple electromagnetic system control, arbitrary controllable magnetic field waveform intensity, polarity and frequency, magnetic field frequency not limited by power supply charging time, and magnetic field intensity not limited by charging power.

[0045] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A repetitive pulsed strong magnetic field generating device, characterized in that: The device comprises a magnetic coil and a plurality of independent power supply units, wherein the plurality of independent power supply units are connected in parallel to both ends of the magnetic coil; Each power supply unit includes an energy supply element, a freewheeling circuit and an electrical switch. The freewheeling circuit is connected in parallel with the energy supply element and then in series with the electrical switch. The freewheeling circuit includes a freewheeling resistor and a unidirectional conducting element connected in series.

2. The repetitive pulsed strong magnetic field generating device according to claim 1, characterized in that: The energy supply element is a capacitor.

3. The repetitive pulsed strong magnetic field generating device according to claim 1, characterized in that: The unidirectional conducting element is a diode.

4. The repetitive pulsed strong magnetic field generating device according to claim 1, characterized in that: The electrical switch is a controllable thyristor.

5. A method for generating a strong magnetic field based on the repetitive pulsed strong magnetic field generating device according to any one of claims 1 to 4, characterized in that: The steps include: (1) Immerse the magnet coil in liquid nitrogen for cooling, and monitor the cooling process of the magnet by measuring the change in the magnet resistance value; (2) connecting the positive and negative poles of the plurality of power supply units to the connection terminals of the magnetic coil according to the polarity of the preset magnetic field waveform, and charging the energy supply element in each power supply unit to a preset voltage; (3) Controlling the electrical switch to discharge the magnetic coil in sequence according to a preset discharge sequence.

6. The method for generating a strong magnetic field according to claim 5, characterized in that: After each discharge, the resistance change of the magnetic coil caused by heating is monitored, and the preset voltage of each power supply unit is adjusted accordingly.

7. The method for generating a strong magnetic field according to claim 5, characterized in that: In the step (2), the preset voltage is determined according to the magnetic field strength required by the waveform.

8. The method for generating a strong magnetic field according to claim 5, characterized in that: In the step (3), the discharge timing is set according to the magnetic field frequency required by the waveform.

Images