CN112185647B - Device and method for generating periodic background magnetic field - Google Patents
Device and method for generating periodic background magnetic field Download PDFInfo
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- CN112185647B CN112185647B CN201910596627.0A CN201910596627A CN112185647B CN 112185647 B CN112185647 B CN 112185647B CN 201910596627 A CN201910596627 A CN 201910596627A CN 112185647 B CN112185647 B CN 112185647B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F7/00—Magnets
- H01F7/02—Permanent magnets [PM]
- H01F7/0273—Magnetic circuits with PM for magnetic field generation
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F13/00—Apparatus or processes for magnetising or demagnetising
- H01F13/003—Methods and devices for magnetising permanent magnets
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F13/00—Apparatus or processes for magnetising or demagnetising
- H01F13/006—Methods and devices for demagnetising of magnetic bodies, e.g. workpieces, sheet material
Abstract
The invention discloses a device and a method for generating a periodic background magnetic field, which comprises two lead units, two permanent magnet units, a framework unit and a pulse power supply unit, wherein the permanent magnet units are respectively clung to the inner wall of the framework unit, a hollow area is formed in the middle of the permanent magnet units, and the positive electrode and the negative electrode of the pulse power supply unit are respectively connected with the two lead units; based on the characteristic that the permanent magnet can stably maintain magnetism for a long time under the condition of remanence without extra energy consumption, the permanent magnet unit can be magnetized and demagnetized by inputting pulse current, the magnetizing and demagnetizing process is periodically repeated, so that the permanent magnet is continuously magnetized and demagnetized, the control on the background magnetic field switch is realized, the periodic stable background magnetic field can be generated in the background magnetic field area, the problem that the traditional electromagnet needs to continuously input current to generate high electric loss and temperature rise can be solved, and the permanent magnet control system is suitable for different scenes.
Description
Technical Field
The invention belongs to the technical field of background magnetic field generation, and particularly relates to a device and a method for generating a periodic background magnetic field.
Background
The periodic background magnetic field is widely applied to magnetic screeners, magnetic stirrers and magnetic refrigerators as an adjustable magnetic field, the source of the background magnetic field can be divided into a natural magnetic field and an artificial magnetic field, wherein the natural magnetic field comprises a natural magnet, a biological magnetic field, a geomagnetic field and a space magnetic field, the artificial magnetic field comprises an artificial magnet and an electromagnetic field, and the conventional background magnetic field is generated based on the artificial magnetic field due to the uncontrollable nature of the natural magnetic field.
The artificial magnets are mainly classified into alloy permanent magnets and ferrite permanent magnets, among which rare earth alloy permanent magnets have been rapidly developed in the last two decades, and rare earth alloy permanent magnets are compounds composed of different rare earth elements and transition metals (Fe, Co, Ni, Sm, etc.). The permanent magnet has high permanent magnetic performance, high Curie temperature and good temperature stability, and is widely applied to various civil and military fields, such as permanent magnet motors, mobile electronic equipment and the like. The ferrite permanent magnet has low relative stored magnetic energy in unit volume and low saturation magnetic induction intensity, so that the application of the ferrite permanent magnet in the field requiring high magnetic energy density is limited. Because the permanent magnet keeps magnetism all the time, corresponding adjustment can not be carried out under the condition that a magnetic field needs to be temporarily eliminated, for example, a permanent magnet drum magnetic separator screens grains, flour and the like by attracting metal impurities (iron wire block scraps, iron ore and the like) through the permanent magnet, after the permanent magnet drum magnetic separator runs for a certain time, the metal impurities need to be manually removed from the permanent magnet, the whole process is complex, the labor cost is increased, and the controllability is poor.
The electromagnetic field is mainly divided into a superconducting magnet and an electromagnetic coil, wherein the resistance of the superconducting magnet made of superconducting materials is close to 0 in a superconducting state, and the superconducting magnet can be kept in a power-on state basically without loss after current is introduced, so that electric energy does not need to be added in principle, the electric energy consumption is reduced, but the superconducting magnet needs to work at the temperature of liquid helium, and the cost is high in practical industrial and scientific research application. The electromagnetic coil controls the magnetic field by using the current, so that the electromagnetic coil has the magnetic field when being electrified, and the magnetic field disappears after the power is off, and the electromagnetic coil is controllable compared with a permanent magnet. However, if the magnetic field needs to be kept constant for a long time, current needs to be always introduced, and because the coil material has certain resistance, the generated electric loss and temperature rise are high under long-time work, so that the application field of the background magnetic field is limited.
Therefore, it is an urgent need to solve the problem of providing a method for generating a periodic background magnetic field with adjustable control, simple device, and low electrical loss and temperature rise.
Disclosure of Invention
The invention aims to provide a device and a method for generating a periodic background magnetic field, aiming at solving the problems of high electric loss and temperature rise caused by continuous input of current when a controllable stable magnetic field is generated in the prior art.
In order to achieve the above object, the present invention provides a periodic background magnetic field generating device, including a wire unit, a permanent magnet unit, a frame unit, and a pulse power supply unit;
the pulse power supply comprises a framework unit, a pulse power supply unit, a lead unit, a permanent magnet unit, a pulse power supply unit and a power supply unit, wherein the lead unit and the permanent magnet unit are respectively two, the permanent magnet unit is respectively clung to the inner wall of the framework unit, a hollow area is formed in the middle of the permanent magnet unit, and the positive electrode and the negative electrode of the pulse power supply unit are respectively connected with the two lead units;
the lead unit is used for charging and demagnetizing the permanent magnet unit based on the pulse current.
The permanent magnet unit is used as a magnetic field source of the background magnetic field;
the framework unit is used for fixing the position of the permanent magnet unit and improving the intensity of the background magnetic field;
the pulse power supply unit is used for outputting current to generate a pulse current signal to provide the magnetizing and demagnetizing energy of the permanent magnet unit.
Preferably, the wire units are formed by wires, and the number and distribution of the wires in each wire unit can be adjusted according to the actual required direction of the background magnetic field according to the right-hand rule.
Preferably, the wire constituting the wire unit is a long wire or a wire coil.
Preferably, when the wires forming the wire unit are long wires, the wire unit is respectively clung to the outer wall of the framework unit, and the permanent magnet unit is perpendicular to the perpendicular bisector of the cross section of the wire unit.
Preferably, when the wires constituting the wire unit are wire coils, the wire units are respectively wound around the outside of the permanent magnet units.
Preferably, the permanent magnet unit is composed of a permanent magnet, and the shape structure of the permanent magnet can be adjusted according to the actually required magnetic field gradient distribution of the background magnetic field.
Preferably, the permanent magnet unit can generate background magnetic fields with different sizes and distributions by adopting a ferrite permanent magnet with smaller remanence, a rare earth permanent magnet with higher remanence or a structure formed by mixing and assembling a plurality of permanent magnets based on the actually required magnetic field size.
Preferably, the portion of the skeleton unit contacting the wire unit is made of an insulating material, the rest portion of the skeleton unit may be made of a magnetic conductive material, an insulating material or a combination of the magnetic conductive material and the insulating material, and the skeleton unit may be made of different materials according to requirements. When the framework unit adopts a magnetic conductive material, a magnetic circuit can be closed, and a background magnetic field is improved; when the framework unit is made of insulating materials, the magnet is protected, and the breakdown of the lead unit in the discharging process under the high-voltage condition is avoided.
Preferably, the pulse current output by the pulse power supply unit is pulse non-oscillation current or pulse alternating current damped oscillation current; preferably, it may be a square wave current, a triangular wave current, or the like.
In order to achieve the above object, another aspect of the present invention provides a method for generating a periodic background magnetic field, comprising the steps of:
s1, pulse non-oscillating currents with the same magnitude are respectively input into the two lead units, an external non-oscillating magnetic field is generated according to an electromagnetic generating principle, and the permanent magnet units in a non-magnetic state are saturated and magnetized;
s2, the permanent magnet units keep remanence after the discharge, and a continuous background magnetic field is generated in the background magnetic field area;
s3, pulse alternating current damped oscillation currents with the same size are respectively input into the two lead units to generate an external damped oscillation magnetic field, and the remanence of the permanent magnet is reduced along with the reduction of the peak value of the damped oscillation magnetic field, so that the permanent magnet unit is demagnetized;
s4, repeating the steps S1-S3 at intervals to obtain a background magnetic field which changes periodically.
Preferably, the direction of the externally applied magnetic field generated on the permanent magnet unit by the two lead units is the same.
Preferably, the first peak of the pulsed ac damped oscillatory current signal in step S3 is the same size and opposite direction as the peak of the pulsed non-oscillatory current signal magnetized in step S1, and the oscillation period is at least three periods.
Through the technical scheme, compared with the prior art, the invention can obtain the following beneficial effects:
1. the invention provides a method for generating a periodic background magnetic field, which is based on the characteristic that a permanent magnet can stably maintain magnetism for a long time under the condition of remanence without extra energy consumption, a permanent magnet unit can be magnetized only by inputting pulse non-oscillating current, a stable background magnetic field is generated, the permanent magnet unit can be demagnetized by inputting alternating-current damped oscillating current so as to realize the control of a background magnetic field switch, the magnetizing and demagnetizing process is continuously repeated, the permanent magnet is continuously magnetized and demagnetized, and the periodic magnetic field can be generated in the background magnetic field area.
2. The method for generating the periodic background magnetic field provided by the invention can realize the on and off of the background magnetic field under the condition of low energy consumption by controlling the input of the pulse current, can realize the generation of the low-loss stable background magnetic field, and is suitable for different scenes.
3. The invention provides a periodic background magnetic field generating device, which adopts a permanent magnet unit as a background magnetic field, can stably maintain magnetism for a long time, does not need extra energy consumption and has lower energy consumption. The magnetization in different directions can be realized on the permanent magnet unit by changing the position distribution of the wires in the wire unit, so that the direction of the magnetic field in the background magnetic field can be adjusted as required; in addition, by changing the shape structure of the permanent magnet, the magnetic field gradient distribution of the background magnetic field can be adjusted as required, and the whole device has the advantages of simple structure, convenient control, high economy and low maintenance cost.
Drawings
Fig. 1 is a three-dimensional structural diagram of a background magnetic field generating device according to embodiment 1 of the present invention.
FIG. 2 is a cross-sectional view of a periodic magnetic field generating apparatus provided in embodiment 1 of the present invention;
fig. 3 is a distribution of magnetic field lines at one time when the wire unit is energized with current according to an embodiment of the present invention;
FIG. 4 is a magnetic field line distribution of permanent magnets of a tile-shaped structure and a square-shaped structure in a background magnetic field region under the same remanence; the graph (a) is the distribution situation of magnetic field lines generated by the permanent magnet with the tile-shaped structure in the background magnetic field area under the remanence, and the graph (b) is the distribution situation of magnetic field lines generated by the permanent magnet with the square structure in the background magnetic field area under the remanence;
FIG. 5 is a commonly used pulsed non-oscillating current signal waveform;
fig. 6 is a magnetic field line distribution generated by the permanent magnet unit after the magnetization is completed according to the embodiment of the present invention;
FIG. 7 is a schematic diagram of the principle of demagnetization of a permanent magnet unit;
FIG. 8 is a graph of the relationship between the magnetization of a permanent magnet unit with remanence and the change of the intensity of an external magnetic field during demagnetization;
fig. 9 is a three-dimensional structural view of a background magnetic field generating apparatus provided in embodiment 2 of the present invention;
fig. 10 is a cross-sectional structural view of a periodic magnetic field generation device provided in embodiment 2 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In order to achieve the above object, an aspect of the present invention provides a device for generating a periodic magnetic field, including a wire unit, a permanent magnet unit, a frame unit, and a pulse power supply unit.
The pulse power supply comprises a framework unit, a pulse power supply unit, a lead unit, a permanent magnet unit, a pulse power supply unit and a power supply unit, wherein the lead unit and the permanent magnet unit are respectively two, the permanent magnet unit is respectively clung to the inner wall of the framework unit, a hollow area is formed in the middle, and the positive electrode and the negative electrode of the pulse power supply unit are respectively connected with the two lead units;
the lead unit is used for charging and demagnetizing the permanent magnet unit based on the pulse current.
The permanent magnet unit is used as a magnetic field source of the background magnetic field;
the framework unit is used for fixing the position of the permanent magnet unit and improving the intensity of the background magnetic field;
the pulse power supply unit is used for outputting current to generate a pulse current signal to provide the magnetizing and demagnetizing energy of the permanent magnet unit.
Specifically, the wire units are formed by wires, and the number and distribution of the wires in each wire unit can be adjusted according to the actual required direction of the background magnetic field according to the right-hand rule.
Specifically, the wire constituting the wire unit is a long wire or a wire coil.
Specifically, when the lead wires forming the lead wire units are long lead wires, the lead wire units are respectively clung to the outer wall of the framework unit, and the permanent magnet units are perpendicular to the perpendicular bisector of the cross sections of the lead wire units. Specifically, the wires in each wire unit can be uniformly or non-uniformly arranged, and the number of the wires can be different.
Specifically, when the wires constituting the wire unit are wire coils, the wire unit is respectively wound around the outer sides of the permanent magnet units.
Specifically, the permanent magnet unit is composed of a permanent magnet, and the shape and structure of the permanent magnet can be adjusted according to the magnetic field gradient distribution of the background magnetic field required in practice. Specifically, various special-shaped structures can be adopted, and the shape structure of the permanent magnet and the size and shape of the space of the background magnetic field region determine the magnetic field gradient distribution of the background magnetic field; specifically, the shape and structure of the permanent magnet can be a tile shape, a pole shoe shape, a truncated cone shape, and the like. Specifically, the design may be performed according to a simulation software having a magnetic field function module such as comsol.
Specifically, the permanent magnet unit can generate background magnetic fields with different sizes and distributions by adopting a ferrite permanent magnet with smaller remanence, a rare earth permanent magnet with higher remanence or a structure formed by mixing and assembling a plurality of permanent magnets based on the actually required magnetic field size.
Specifically, the portion of the framework unit, which is in contact with the lead unit, is made of an insulating material, the rest portion of the framework unit can be made of a magnetic conductive material, an insulating material or a combination of the magnetic conductive material and the insulating material, and the framework unit can be made of different materials according to requirements. When the framework unit adopts a magnetic conductive material, a magnetic circuit can be closed, and a background magnetic field is improved; when the framework unit is made of insulating materials, the magnet is protected, and the breakdown of the lead unit in the discharging process under the high-voltage condition is avoided.
Specifically, the pulse current output by the pulse power supply unit is pulse non-oscillation current or pulse alternating current damped oscillation current; specifically, a square wave current, a triangular wave current, or the like may be used.
In another aspect, the present invention provides a method for generating a periodic magnetic field, including the steps of:
s1, pulse non-oscillating currents with the same magnitude are respectively input into the two lead units, an external non-oscillating magnetic field is generated according to an electromagnetic generating principle, and the permanent magnet units in a non-magnetic state are saturated and magnetized;
s2, the permanent magnet units keep remanence after the discharge, and a continuous background magnetic field is generated in the background magnetic field area;
s3, pulse alternating current damped oscillation currents with the same size are respectively input into the two lead units to generate an external damped oscillation magnetic field, and the remanence of the permanent magnet is reduced along with the reduction of the peak value of the damped oscillation magnetic field, so that the permanent magnet unit is demagnetized;
s4, repeating the steps S1-S3 at intervals to obtain a background magnetic field which changes periodically.
Specifically, the directions of the external magnetic fields generated on the permanent magnet units by the two lead units are the same.
Specifically, the first peak of the pulsed ac damped oscillatory current signal in step S3 is the same as the peak of the pulsed non-oscillatory current signal magnetized in step S1, and has a direction opposite to the direction of the peak, and the oscillation period is at least three periods.
To further illustrate the device and method for generating a periodic magnetic field according to the embodiments of the present invention, detailed descriptions are provided with reference to the accompanying drawings and specific examples:
examples 1,
Fig. 1 is a three-dimensional structural diagram of a background magnetic field generating device according to an embodiment of the present invention, and a cross-sectional structural diagram of the background magnetic field generating device is shown in fig. 2, the background magnetic field generating device according to the embodiment of the present invention includes two wire units 1a and 1b, two permanent magnet units 2a and 2b, a skeleton unit 3, a background magnetic field area 4, and a pulse power supply unit 5;
the lead wires forming the lead wire units 1a and 1b are long lead wires, the cross section of the framework unit 3 is in a ring shape, an xy coordinate system is established by taking the circle center of the ring as an origin, the lead wire units 1a and 1b are symmetrical about a y axis and cling to the outer wall of the framework unit 3, the permanent magnet units 2a and 2b are symmetrical about an x axis and cling to the inner wall of the framework unit 3, a hollow area, namely a background magnetic field area 4, is formed in the middle, the permanent magnet units are perpendicular to the perpendicular bisector of the cross section of the lead wire units, the positive pole of the pulse power supply unit 5 is connected with the lead wire unit 1a, and the negative pole of the pulse power supply unit 5 is connected with the lead wire unit 1 b; the wire units 1a and 1b are used to control the magnetism of the permanent magnet unit based on the magnitude and direction of the control current. The permanent magnet units 2a and 2b are used as magnetic field sources of the background magnetic field; the framework unit 3 is used for fixing the position of the permanent magnet unit and improving the intensity of the background magnetic field; the pulse power supply unit 5 is used for generating a pulse current signal by controlling the output current to provide the magnetizing and demagnetizing energy of the permanent magnet unit;
specifically, the pulse power supply unit 5 generates and outputs a pulse current signal, and the lead units 1a and 1b generate magnetic fields in the permanent magnet units 2a and 2b according to an electromagnetic principle after receiving the pulse current signal; the pulse current signal generated by the pulse power supply unit 5 is a pulse non-oscillation current signal or an alternating current damped oscillation current signal, and is respectively used for generating a pulse non-oscillation magnetic field and an alternating current damped oscillation magnetic field in the permanent magnet units 2a and 2b, so that the permanent magnet units 2a and 2b are respectively magnetized and demagnetized, and the control of the magnetic field in the background magnetic field area 4 is realized.
Specifically, according to the biot-savart law, the size of a magnetic field generated by current at a certain lead position is inversely proportional to the square of the distance between the current lead and the magnetic field, the leads in the lead units 1a and 1b are uniformly distributed, the number of the leads in each lead unit is the same and is symmetrical about an x axis, and when each permanent magnet unit is symmetrical about a y axis, the energy required by the permanent magnet units 2a and 2b during magnetizing saturation is the lowest. According to the ampere-right-hand rule, when the wire units 1a and 1b are respectively fed with currents which are the same in size, perpendicular to the cross section direction and opposite in direction, the permanent magnet units 2a and 2b can be magnetized uniformly along the y axis under the action of a magnetic field, the directions of external magnetic fields generated on the permanent magnet units by the two wire units are the same, and the generated magnetic fields are as shown in fig. 3.
Specifically, the permanent magnet unit is composed of permanent magnets, various special-shaped structures can be adopted, and the shape structure of the permanent magnets and the size and shape of the space of the background magnetic field region determine the magnetic field gradient distribution of the background magnetic field; specifically, the shape and structure of the permanent magnet can be a tile shape, a pole shoe shape, a truncated cone shape, and the like. Specifically, the design may be performed according to a simulation software having a magnetic field function module such as comsol. As shown in fig. 4, the magnetic field lines of the permanent magnets of the tile-shaped structure and the square structure are distributed in the background magnetic field region under the same remanence, wherein, the graph (a) is the magnetic field line distribution of the permanent magnet of the tile-shaped structure in the background magnetic field region under the remanence, and the graph (b) is the magnetic field line distribution of the permanent magnet of the square structure in the background magnetic field region under the remanence. The distribution of magnetic field generated after the permanent magnets with different shapes are magnetized is different, and the distribution of magnetic field in the background magnetic field area can be changed by changing the shape of the permanent magnets.
The shape of the permanent magnet and the number and position distribution of the wires are determined according to the strength, direction, area and distribution of the required background magnetic field, and after the required background magnetic field generating device is built, the method flow of the periodic background magnetic field generation is mainly carried out according to the following sequence: pulse non-oscillating current is introduced into the wire unit, the permanent magnet obtains the maximum magnetism under the action of peak current, the time required by the residual magnetism of the permanent magnet to generate a stable magnetic field in a background area is completed, alternating current decaying oscillating current is introduced into the wire unit, the magnetism of the permanent magnet is lost after alternating current demagnetization, the magnetic field in the background area disappears, and the steps are repeated at intervals to obtain a periodic background magnetic field.
Specifically, the method for generating the periodic magnetic field comprises the following steps:
s1, pulse non-oscillating currents which are equal in size, perpendicular to the cross section direction and opposite in direction are respectively input into the two lead units, an external non-oscillating magnetic field is generated according to an electromagnetic generating principle, and the permanent magnet units in a non-magnetic state are subjected to saturation magnetization;
specifically, the permanent magnet units 2a and 2b may be N50M ndfeb permanent magnets in a non-magnetic state, and in an initial state, the pulse power supply unit 5 generates a current to generate a pulse non-oscillating current signalThe signals are input into the wire units 1a and 1b, and pulse non-oscillating magnetic fields are generated in the permanent magnet units 2a and 2b to charge the permanent magnet units 2a and 2b until the permanent magnet units are saturated. As shown in fig. 5, the waveforms of the commonly used pulse non-oscillating current signals are respectively a sharp pulse wave, a matrix wave and a triangular wave; the neodymium iron boron part reaches 3 Tesla (magnetic induction intensity unit) under the magnetic field generated at the current peak moment of the wire, the specific size is shown in figure 3, the wire units 1a and 1b are arranged as shown in the figure, and the current density of the cross section of the wire units reaches 4.5 multiplied by 10 at the current peak moment8A/m2The energy of which is supplied by a pulsed power supply unit 5.
S2, the permanent magnet units keep remanence after the discharge, and a continuous background magnetic field is generated in the background magnetic field area;
specifically, after saturation magnetization is completed, the power switch of the pulse power supply unit 5 is turned off, after discharging is completed, the remanence of the N50M ndfeb permanent magnet is about 1.4 tesla, the permanent magnet independently generates a magnetic field in the background magnetic field region 4, the magnetic field lines are distributed as shown in fig. 6, and the average magnetic induction intensity of the background magnetic field region 4 is 0.4 tesla.
S3, pulse alternating current damped oscillation currents which are equal in size, perpendicular to the cross section direction and opposite in direction are respectively input into the two lead units to generate an external damped oscillation magnetic field, and the remanence of the permanent magnet is reduced along with the reduction of the peak value of the damped oscillation magnetic field, so that the permanent magnet units are demagnetized;
alternating current damped oscillation current signals which are same in size, perpendicular to the cross section direction and opposite in direction are respectively input into the wire units 1a and 1b, the damped oscillation current signals are generated by the pulse power supply unit, the first peak value of the damped oscillation current signals is same in size and opposite in direction to the peak value of a pulse non-oscillation current signal generated by the pulse power supply during magnetizing, and the oscillation period is at least three periods, so that the neodymium iron boron permanent magnet can be demagnetized by more than 90%. Specifically, when the peak value of the applied oscillating magnetic field is decreased, the hysteresis loop of the remanence of the permanent magnet is gradually reduced, and when the peak value is attenuated to be close to 0, the hysteresis loop is a closed curve close to the origin (0,0), and the remanence of the permanent magnet is close to 0. FIG. 7 is a schematic diagram of the principle of demagnetization of a permanent magnet unitThe orientation of the molecular circulation changes along with the direction of the alternating oscillating current, and the consistency of the orientation of the molecular circulation is continuously weakened due to the continuous attenuation of the current peak value, and finally, the molecular circulation returns to the disordered arrangement again, so that the magnetism of the permanent magnet disappears. As shown in fig. 8, a relationship curve of the magnetization intensity of the permanent magnet unit with remanence in the demagnetization process and the change of the external magnetic field intensity is recorded as a hysteresis loop, and an xy coordinate system is established with (0,0) as the origin of coordinates, wherein the abscissa is the external magnetic field intensity H, the ordinate is the magnetization intensity M, the hysteresis loop is used for reflecting the relationship between the magnetization intensity M of the magnetic substance and the external magnetic field H, and the remanence B ═ μ can be derived0(H + M) in which the magnetic permeability μ in vacuum0＝4π×10-7H/m. The maximum value of the absolute values of the magnetization intensity of the first quadrant and the third quadrant of the permanent magnet hysteresis loop is in direct proportion to the absolute value of the external magnetic field, when the absolute value of the peak value of the external magnetic field is continuously reduced, the remanence of the permanent magnet hysteresis loop can change along the continuously reduced hysteresis loop and is finally reduced to a closed curve close to the origin, and the remanence of the permanent magnet is close to 0. After the ringing current signal has ended, the permanent magnet units 2a and 2b have at this point lost essentially completely magnetism. The magnetic field is no longer present in the background magnetic field region 4.
S4, repeating the steps S1-S3 at intervals to obtain a background magnetic field which changes periodically.
Examples 2,
Embodiment 2 is the same as the device in embodiment 1 in composition and method for generating periodic background magnetic field, except that the lead wire constituting the lead wire unit is a lead wire coil, as shown in fig. 9, it is a three-dimensional structure diagram of a background magnetic field generating device provided in the embodiment of the present invention, and as shown in fig. 10, its cross-sectional structure diagram is provided, the background magnetic field generating device provided in the embodiment of the present invention includes two lead wire units 1a and 1b, two permanent magnet units 2a and 2b, a skeleton unit 3, a background magnetic field area 4, and a pulse power supply unit 5; the lead wires forming the lead wire units 1a and 1b are lead wire coils, the cross section of the framework unit 3 is rectangular, an xy coordinate system is established by taking the center of the cross section of the framework unit 3 as an original point, the lead wire units 1a and 1b are symmetrical about an x axis and respectively surround the outer sides of the permanent magnet units 2a and 2b, the two lead wire units are in series connection, an insulating layer is arranged between the lead wire units and the permanent magnet units, the permanent magnet units 2a and 2b are symmetrical about the x axis and cling to the inner wall of the framework unit 3, and a hollow area, namely a background magnetic field area 4, is formed in the middle. The positive pole of the pulse power supply unit 5 is connected with the lead unit 1a, and the negative pole of the pulse power supply unit 5 is connected with the lead unit 1 b; the lead units 1a and 1b are used for controlling the magnetism of the permanent magnet units based on the magnitude and direction of control current, pulse currents with the same magnitude and clockwise or anticlockwise directions are respectively introduced into the two lead units in the processes of charging and demagnetizing, and the directions of external magnetic fields generated by the two lead units on the permanent magnet units are the same. The permanent magnet units 2a and 2b are used as magnetic field sources of the background magnetic field; the framework unit 3 fixes the position of the permanent magnet unit, and the background magnetic field intensity is improved; the pulse power supply unit 5 is used for generating a pulse current signal by controlling the output current to provide the magnetizing and demagnetizing energy of the permanent magnet unit.
The invention combines the characteristic that the permanent magnet can stably maintain magnetism for a long time under the condition of residual magnetism without extra energy consumption, inputs pulse non-oscillation and alternating current damped oscillation current signals through the lead to carry out magnetization and demagnetization on the permanent magnet, further realizes the control on the background magnetic field switch, continuously repeats the magnetization and demagnetization process, and can generate a periodic magnetic field in the background magnetic field area by continuously magnetizing and demagnetizing the permanent magnet. Compared with the traditional electromagnet and superconducting magnet technology, the whole device has the advantages of simple structure, convenience in control, high economy and low maintenance cost, and can realize the generation of a low-loss stable background magnetic field. The lead unit is connected with a pulse current signal, the power-on time is in millisecond order, and the energy consumption of the whole device is extremely low.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (5)
1. A periodic background magnetic field generating device is characterized by comprising a lead unit, a permanent magnet unit, a framework unit and a pulse power supply unit;
the pulse power supply comprises a framework unit, two lead units and two permanent magnet units, wherein the two lead units and the two permanent magnet units are respectively attached to the inner wall of the framework unit, a hollow area is formed in the middle of the framework unit, and the positive electrode and the negative electrode of the pulse power supply unit are respectively connected with the two lead units;
the lead unit is used for charging and demagnetizing the permanent magnet unit based on pulse current;
the permanent magnet unit is used as a magnetic field source of a background magnetic field;
the framework unit is used for fixing the position of the permanent magnet unit and improving the intensity of the background magnetic field;
the pulse power supply unit is used for outputting current to generate a pulse current signal to provide the magnetizing and demagnetizing energy of the permanent magnet unit;
the wire units are composed of wires, and the number and distribution of the wires in each wire unit are adjusted according to the direction of the background magnetic field required actually; the lead wires forming the lead wire unit are long lead wires; the lead units are respectively clung to the outer walls of the framework units; the permanent magnet unit is perpendicular to the perpendicular bisector of the section of the lead unit;
the permanent magnet unit is composed of a permanent magnet, and the shape structure of the permanent magnet can be adjusted according to the magnetic field gradient distribution of the background magnetic field required in practice.
2. The apparatus for generating periodic background magnetic field according to claim 1, wherein the permanent magnet unit is capable of generating background magnetic fields with different sizes and distributions based on the actual required background magnetic field, and can be implemented by ferrite permanent magnets with smaller remanence, rare earth permanent magnets with higher remanence or a structure of a mixture of a plurality of permanent magnets.
3. The periodic background magnetic field generation device of claim 1, wherein the portion of the skeleton unit contacting the wire unit is made of an insulating material, and the rest of the skeleton unit is made of a magnetic conductive material, an insulating material or a combination thereof.
4. The periodic background magnetic field generation device according to claim 1, wherein the pulsed current output by the pulsed power supply unit is a pulsed non-oscillating current or a pulsed ac damped oscillating current.
5. A method for generating a periodic background magnetic field based on the generating device of any one of claims 1 to 4, comprising the steps of:
s1, pulse non-oscillating currents with the same magnitude are respectively input into the two lead units, an external non-oscillating magnetic field is generated according to an electromagnetic generating principle, and the permanent magnet units in a non-magnetic state are saturated and magnetized;
s2, the permanent magnet units keep remanence after the discharge, and a continuous background magnetic field is generated in the background magnetic field area;
s3, pulse alternating current damped oscillation currents with the same size are respectively input into the two lead units to generate an external damped oscillation magnetic field, and the remanence of the permanent magnet is reduced along with the reduction of the peak value of the damped oscillation magnetic field, so that the permanent magnet unit is demagnetized;
s4, repeating the steps S1-S3 at intervals to obtain a background magnetic field which changes periodically.
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