Magnetic device, preparation method thereof and power conversion device

Abstract

The invention relates to the technical field of energy, in particular to a magnetic device, a preparation method thereof and a power conversion device. The magnetic core comprises a middle column, and the middle column is used for winding a winding. The middle column comprises a central magnetic core and an outer magnetic core, the outer magnetic core wraps the peripheral face of the central magnetic core, and the magnetic conductivity of the outer magnetic core is smaller than that of the central magnetic core. In the magnetic core, the magnetic core material with high magnetic conductivity can provide the initial sensing value meeting the requirement, and the magnetic core material with low magnetic conductivity can meet the requirement of the anti-saturation characteristic. According to the magnetic core, through combination of different magnetic core materials, the anti-saturation characteristic of a magnetic device can be improved while the initial induction value is guaranteed, and the bias induction value in a large-current and large-power scene is improved.

Description

Technical Field

[0001] The present application relates to the field of energy technology, and in particular to a magnetic device and a preparation method thereof, and a power conversion device. Background Art

[0002] Magnetic devices are important components in power devices such as photovoltaic inverters and energy storage converters. Their structural reliability directly affects the normal operation of power devices.

[0003] As product power increases, the current in magnetic devices also increases, placing higher requirements on the saturation characteristics of magnetic devices. Summary of the invention

[0004] The present application provides a magnetic device and a preparation method thereof, and a power conversion device. The magnetic device can take into account both higher initial inductance and higher anti-saturation performance, and can be suitable for power conversion scenarios with high current and high power.

[0005] In a first aspect, the present application provides a magnetic device, which includes a winding and a magnetic core, wherein the magnetic core includes a middle column for winding the winding; the middle column includes a central magnetic core and an outer magnetic core, wherein the outer magnetic core is wrapped around the outer circumference of the central magnetic core, and the magnetic permeability of the outer magnetic core is less than that of the central magnetic core.

[0006] For the above-mentioned magnetic devices, the core material with high magnetic permeability can provide the required initial inductance, and the core material with low magnetic permeability can meet the requirements of anti-saturation characteristics. By combining different core materials, the core can improve the anti-saturation characteristics of the magnetic device while ensuring the initial inductance, and improve the bias inductance in high current and high power scenarios.

[0007] In one embodiment, the outer magnetic core includes at least two magnetic core layers, and the at least two magnetic core layers are stacked in sequence along the radial direction of the center column; between any two adjacent magnetic core layers, the magnetic permeability of a magnetic core layer away from the center magnetic core is less than the magnetic permeability of a magnetic core layer close to the center magnetic core. The distribution of at least two magnetic core layers can further homogenize the magnetic permeability distribution state of the magnetic core.

[0008] In one embodiment, the difference in magnetic permeability between any two adjacent magnetic core layers is 5-100. Further, the difference in magnetic permeability between any two adjacent magnetic core layers is 10-70. The magnetic permeability of the magnetic core is regularly distributed along the radial direction, which can effectively even out the magnetic flux density of the magnetic device in the application and improve the performance of the magnetic device.

[0009] In one embodiment, the middle column includes at least two sub-columns, and the at least two sub-columns are arranged adjacent to each other in sequence along the axial direction of the middle column; each sub-column is used to wind a winding coil, and the magnetic flux generated by the winding coils wound by any two adjacent sub-columns when energized is different, and the magnetic permeability of the sub-column with a large magnetic flux is smaller than the magnetic permeability of the sub-column with a small magnetic flux. The at least two sub-columns can adapt to the state of uneven magnetic field density distribution that may be generated by different winding coils, further improving the performance of the magnetic device.

[0010] In one embodiment, the difference in magnetic permeability between any two adjacent sub-columns is 5-100. Further, the difference in magnetic permeability between any two adjacent magnetic core layers is 10-70. The magnetic permeability of the magnetic core is regularly distributed along the axial direction, which can effectively even out the magnetic flux density of the magnetic device in the application and improve the performance of the magnetic device.

[0011] In one embodiment, the magnetic core includes two cover plates, which are respectively fixed at both ends of the middle column along the length direction; each cover plate includes a central connecting portion, a first surrounding portion and a second surrounding portion, the first surrounding portion surrounds the outer peripheral surface of the central connecting portion along the circumference of the middle column, the second surrounding portion surrounds the outer peripheral surface of the first surrounding portion along the circumference of the middle column, the central connecting portion is used to connect the end of the middle column, and the first surrounding portion is used to be opposite to the winding along the axial direction of the middle column; the first surrounding portion is closest to the winding, and the magnetic permeability of the first surrounding portion is less than the magnetic permeability of the central connecting portion and the magnetic permeability of the second surrounding portion. The cover plate is formed by a combination of structures with different magnetic permeabilities, which can further improve the performance of the magnetic device.

[0012] In one embodiment, the second surrounding portion includes at least two surrounding layers, and the at least two surrounding layers are sequentially stacked along the radial direction of the central column; between any two adjacent surrounding layers, the magnetic permeability of a surrounding layer away from the central connection portion is greater than the magnetic permeability of a surrounding layer close to the central connection portion. The magnetic permeability of the second surrounding portion decreases stepwise from the inside to the outside along the radial direction of the central column, which can further even out the magnetic flux density of the magnetic device in the application and improve the performance of the magnetic device.

[0013] In one embodiment, the material of the magnetic core is alloy powder composite soft magnetism, so that the magnetic core has a higher saturation magnetic induction intensity and good frequency characteristics, which can optimize the performance of the magnetic device.

[0014] In one embodiment, the magnetic permeability of the magnetic core is less than or equal to 150, which can meet the high anti-saturation characteristic requirements of the magnetic device in high-power and high-current scenarios.

[0015] In one embodiment, the winding surrounds the outer circumference of the middle column along the circumference of the middle column, and the outer circumference of the middle column does not contact the winding. There is a gap between the outer circumference of the middle column and the winding, which can further improve the anti-saturation characteristics of the magnetic device. Under the same anti-saturation characteristics, the magnetic device with a gap can reduce the number of turns of the winding, thereby reducing the production cost.

[0016] In one embodiment, along the radial direction of the center column, the gap between the outer circumference of the center column and the winding is in the range of 2-10 mm. A reasonable gap range can optimize the spatial distribution between the center column and the winding, and improve the anti-saturation characteristics of the magnetic device without increasing the volume of the magnetic device.

[0017] In one embodiment, the middle column includes a plurality of sub-columns connected in sequence along the axial direction of the middle column, the winding includes a plurality of winding coils, and a winding coil is wound around the outer circumference of each sub-column. The magnetic permeability of the appropriate sub-column can be selected according to the characteristic parameters of different winding coils and the power supply conditions to improve the anti-saturation characteristics of the magnetic device.

[0018] In a second aspect, an embodiment of the present application provides a power conversion device, which includes an inductor, a power device, and a capacitor, wherein the capacitor and the power device are connected to form a power conversion circuit, and the inductor is connected in series to the circuit. The inductor is any magnetic device provided in the second aspect above, and the magnetic device can carry a higher overload and meet the overload inductance requirement after the power is increased.

[0019] In a third aspect, an embodiment of the present application provides a method for preparing a magnetic device, which can be used to prepare the magnetic device provided in the first aspect. The method for preparing the magnetic device comprises:

[0020] preparing a central magnetic core;

[0021] An outer magnetic core wrapped around the outer peripheral surface of the central magnetic core is prepared, wherein the magnetic permeability of the outer magnetic core is less than the magnetic permeability of the central magnetic core;

[0022] A winding coil is wound around the outer periphery of the outer magnetic core.

[0023] In one embodiment, the preparation of the central magnetic core comprises:

[0024] The central magnetic core is formed by preparing soft magnetic alloy powder through a powder forming process. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of the structure of a photovoltaic system provided in an embodiment of the present application;

[0026] Figure 2 A schematic diagram of a circuit structure of a power conversion device provided in an embodiment of the present application;

[0027] Figure 3 A schematic diagram of the structure of a magnetic device provided in an embodiment of the present application;

[0028] Figure 4a A schematic structural diagram of a magnetic core of a magnetic device provided in an embodiment of the present application;

[0029] Figure 4b A schematic diagram of a cross section of a magnetic core of a magnetic device provided in an embodiment of the present application;

[0030] Figure 5a A schematic diagram of a cross section of a magnetic core of a magnetic device provided in an embodiment of the present application;

[0031] Figure 5b A schematic diagram of a cross section of a magnetic core of a magnetic device provided in an embodiment of the present application;

[0032] Figure 5c A schematic diagram of a cross section of a magnetic core of a magnetic device provided in an embodiment of the present application;

[0033] Figure 6a A schematic structural diagram of a magnetic core of a magnetic device provided in an embodiment of the present application;

[0034] Figure 6b A schematic diagram of a cross section of a magnetic core of a magnetic device provided in an embodiment of the present application;

[0035] Figure 7a A schematic diagram of the structure of a magnetic device provided in an embodiment of the present application;

[0036] Figure 7b A schematic diagram of a cross section of a magnetic device provided in an embodiment of the present application;

[0037] Figure 8a A schematic diagram of the structure of a magnetic device provided in an embodiment of the present application;

[0038] Figure 8b A schematic structural diagram of a magnetic core of a magnetic device provided in an embodiment of the present application;

[0039] Fig. 9 A schematic diagram of the structure of a magnetic device provided in an embodiment of the present application;

[0040] Fig.10 A schematic diagram of the structure of a magnetic device provided in an embodiment of the present application;

[0041] Fig.11 A schematic diagram of the structure of a magnetic device provided in an embodiment of the present application;

[0042] Fig.12 A partial structural schematic diagram of a magnetic device provided in an embodiment of the present application;

[0043] Fig.13 A schematic diagram of a cross section of a cover plate of a magnetic device provided in an embodiment of the present application;

[0044] Fig.14 A schematic diagram of the structure of a magnetic device provided in an embodiment of the present application;

[0045] Fig.15 A flow chart of a method for preparing a magnetic device provided in an embodiment of the present application;

[0046] Fig.16a A flow chart of a method for preparing a magnetic device provided in an embodiment of the present application;

[0047] Fig.16b A flow chart of a method for preparing a magnetic device provided in an embodiment of the present application;

[0048] Fig.17a A flow chart of a method for preparing a magnetic device provided in an embodiment of the present application;

[0049] Fig.17b A flow chart of a method for preparing a magnetic device provided in an embodiment of the present application.

[0050] Reference numerals:

[0051] 100-PV inverter station; 200-PV panels; 300-grid; 400-energy storage equipment;

[0052] 101- inductor device; 102- power device; 103- capacitor device;

[0053] 10-magnetic device; 1-magnetic core; 11-middle column; 111-center magnetic core; 112-outer magnetic core; 1121, 1121a, 1121b-magnetic core layer; 1101, 1101a, 1101b, 1101c-sub-columns; 12-cover plate; 121-center connecting part; 122-first surrounding part; 123-second surrounding part; 1231, 1231a, 1231b-surrounding layer; 2-winding; 21, 21a, 21b, 21c-winding coil. DETAILED DESCRIPTION

[0054] In the photovoltaic and energy storage industries, magnetic devices play an important role in power conversion. With the development of science and technology, the power of power modules integrated with magnetic devices is getting higher and higher, and the current carried by magnetic devices during operation is also getting larger and larger. In this context, the problem of instantaneous overcurrent in power modules has become increasingly prominent, and higher requirements have been placed on the anti-saturation characteristics of magnetic devices. Among them, the anti-saturation characteristics of magnetic devices are also called bias characteristics, which means that after the magnetic field strength increases to a certain level, the magnetic flux density of the core material no longer increases with the increase of the external magnetic field strength. When the core material reaches the magnetic saturation state, the magnetic permeability of the core material decreases with the increase of the external current, which will cause the inductance of the magnetic device to drop sharply.

[0055] In traditional technology, the following solutions can be selected to improve the anti-saturation characteristics of magnetic devices, so that the power module can maintain sufficient inductance bias when the power module is transiently overcurrent. First, select a high-bias characteristic material with low magnetic permeability to make the magnetic core of the magnetic device. The reduction in magnetic permeability allows the material to withstand a larger saturation current, but it also means that part of the initial magnetic permeability will be sacrificed, resulting in a reduction in the initial inductance of the magnetic device. Second, the magnetic device form in the photovoltaic inverter and the power station's energy storage converter (powerconversion system, PCS) is an assembly solution of a cover plate plus a center column. While ensuring the initial inductance and bias inductance, a high magnetic permeability cover plate can be selected with a low magnetic permeability center column to meet the inductance requirements under rated conditions; this magnetic core structure can increase the volume of the magnetic core and increase the cross-sectional area of ​​the magnetic core participating in magnetization, as well as increase the number of winding turns to increase the initial inductance and bias inductance of the magnetic device to cope with double or even triple overload conditions, resulting in an increase in the size of the power module, and also accompanied by an increase in cost.

[0056] Based on this, the embodiments of the present application provide a magnetic device and a preparation method thereof, and a power conversion device. The magnetic device has high anti-saturation characteristics and initial inductance, which is conducive to meeting the inductance bias requirements of the module's instantaneous overcurrent.

[0057] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings.

[0058] The terms used in the following embodiments are only for the purpose of describing specific embodiments and are not intended to be limiting of the present application. As used in the specification and appended claims of the present application, the singular expressions "a", "an", "said", "above", "the" and "this" are intended to also include expressions such as "one or more", unless there is a clear contrary indication in the context.

[0059] References to "one embodiment" or "some embodiments" etc. described in this specification mean that a particular feature, structure or characteristic described in conjunction with the embodiment is included in one or more embodiments of the present application. Thus, the phrases "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear at different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0060] The power conversion device including the magnetic device provided in the embodiment of the present application can be applied to a photovoltaic system or an energy storage system for AC / DC conversion of electric energy. Figure 1 That is, a schematic diagram of the structure of a photovoltaic system is illustrated, and the photovoltaic system includes a photovoltaic inverter 100, one end of the photovoltaic inverter 100 is used to connect to the photovoltaic module 200, and the other end is used to connect to the power grid 300. The photovoltaic inverter 100 is used to convert the direct current from the photovoltaic module 200 into alternating current, and transmit the alternating current to the power grid 300. A photovoltaic optimizer can also be installed in the photovoltaic system 100, and the photovoltaic optimizer can be used to improve the power generation efficiency of the photovoltaic module 200. In a specific example, the photovoltaic system 100 can also include an energy storage device 400. The alternating current converted by the photovoltaic inverter 100 can also be transmitted to the energy storage device 400 for energy storage.

[0061] The photovoltaic inverter 100 is a power conversion device, wherein the power conversion may include DC to DC, DC to AC, AC to DC, etc. Figure 2 The circuit topology of an AC-to-DC power conversion device provided in an embodiment of the present application is illustrated. Figure 2 As shown, the power conversion device includes an inductor 101, a power device 102 and a capacitor 103. The capacitor 103 is connected to the power device 102 to form an AC-to-DC power conversion circuit, and the inductor 101 is connected in series to the circuit. The capacitor 103 is connected in parallel to the output end of the power conversion circuit for connecting the bus, and the capacitor 103 is generally also referred to as the bus capacitor. The power device 102 can realize the switching function in the circuit. Specifically in the structure of the power conversion device, the inductor 101, the capacitor 103 and the power device 102 can be assembled into a power module in the form of a package.

[0062] Taking the photovoltaic inverter 100 as an example, the inductor 101 therein can generally bear an overload of 1.5 times. However, as the power increases, some overload requirements for the inductor 101 are increased to 3 times or even higher, which also means that the current flowing through the inductor 101 is twice the original overload condition. In order to keep the inductance of the inductor 101 from decreasing, the embodiment of the present application improves the structure of the inductor 101 so that it has better anti-saturation characteristics without increasing the original volume and cost of the inductor 101, so as to meet the overload inductance requirements after the power is increased.

[0063] Figure 3 A magnetic device 10 used in a power conversion device provided in an embodiment of the present application can be used as Figure 2 In some other scenarios, the magnetic device 10 can also be applied as a transformer, a mutual inductor, etc.

[0064] like Figure 3As shown, the magnetic device 10 includes a magnetic core 1 and a winding 2. As a specific example, the magnetic core 1 of the magnetic conductive material of the magnetic device 10 includes a middle column 11, and the middle column 11 is used to wind the winding 2. Figure 3 The magnetic core 1 in the magnetic device 10 shown only includes a center column 11. The center column 11 is a column with a certain length, and its length direction is larger than the dimensions in other directions. The length direction of the center column 11 is defined as the axial direction of the center column 11. The shape of the cross section of the center column 11 perpendicular to the axial direction can be circular, elliptical, square, rectangular, polygonal or other shapes. Along the axial direction of the center column 11, the shape of the cross section of the center column 11 can remain consistent or vary. The winding 2 is spirally wound on the outer circumference of the center column 11. It can be understood that the winding 2 can specifically be a multi-strand wire, an excitation wire, a circuit board winding, etc.

[0065] When the winding 2 is energized, the current passes through the winding 2, and a magnetic field is generated around the winding 2. The magnetic flux lines of the magnetic field pass through the middle column 11, and the magnetic flux distribution at different positions of the middle column 11 is not completely uniform. The closer the middle column 11 is to the winding 2, the greater the magnetic flux density.

[0066] Taking the radial direction of the center column 11 as a reference, the outer circumference of the center column 11 is closest to the winding 2, and the center of the center column 11 is farthest from the winding 2. Through simulation calculation, along the radial direction of the center column 11 from the center of the center column 11 to the outer circumference of the center column 11, the magnetic flux density of the center column 11 has an increasing trend. Of course, the increase in magnetic flux density from the center to the outer circumference of the center column 11 is not necessarily uniform.

[0067] Based on the above-mentioned distribution law of magnetic flux density, the middle column 11 provided in the embodiment of the present application is made of two or more magnetic core materials with different magnetic permeabilities, and the part of the middle column 11 with a large magnetic flux density is made of a magnetic core material with a low magnetic permeability, and the part of the middle column 11 with a small magnetic flux density is made of a magnetic core material with a high magnetic permeability. The saturation magnetic induction intensity of each magnetic core material is determined. When a magnetic core material has a higher initial magnetic permeability, the magnetic core material changes quickly under large current conditions, and the magnetic flux will reach saturation more easily, that is, the anti-saturation characteristic is relatively weak; correspondingly, when a magnetic core material has a lower initial magnetic permeability, the magnetic core material changes slowly under large current conditions, and the magnetic flux will be more difficult to reach saturation, that is, the anti-saturation characteristic is relatively strong.

[0068] Among them, the magnetic core material with low magnetic permeability has a higher bias characteristic, which can ensure that the magnetic device 10 can still retain the required magnetic permeability and inductance under high current or overload conditions. The magnetic core material with high magnetic permeability can provide the required initial inductance, and the magnetic core material with low magnetic permeability can meet the requirements of anti-saturation characteristics. The magnetic core 1 can improve the anti-saturation characteristics of the magnetic device 10 and the bias inductance under high current while ensuring the initial inductance through the combination of different magnetic core materials. It can be considered that the volume size of the magnetic device 10 does not increase, and within the limited effective cutoff area, the magnetic core 1 has a higher anti-saturation characteristic. Alternatively, under the same anti-saturation characteristics, the effective cutoff area of ​​the magnetic core 1 can be reduced, thereby reducing the radial size of the magnetic device 10.

[0069] Figure 4a The structure of the middle column 11 of a magnetic core 1 provided in an embodiment of the present application. Figure 4a As shown, the center column 11 includes a central magnetic core 111 and an outer magnetic core 112. The central magnetic core 111 is columnar, and the outer magnetic core 112 is wrapped around the outer peripheral surface of the central magnetic core 111. The magnetic permeability of the outer magnetic core 112 is less than that of the central magnetic core 111.

[0070] Figure 4b for Figure 4a FIG. 1 is a schematic cross-sectional view of the center column 11, wherein the cross-section cuts through the center column 11 in a direction perpendicular to the axial direction. Figure 4b As shown, along the radial direction of the middle column 11 , the outer magnetic core 112 surrounds the outer circumference of the central magnetic core 111 .

[0071] When the winding 2 is wound around the center column 11 along the circumference of the center column 11, the central magnetic core 111 is far away from the winding 2 relative to the outer magnetic core 112. The central magnetic core 111 is equivalent to the radial center position of the center column 11. The central magnetic core 111 corresponds to the area with low magnetic flux density. The central magnetic core 111 with high magnetic permeability can meet the requirements of initial inductance. The outer magnetic core 112 is closer to the winding 2. The outer magnetic core 112 corresponds to the area with high magnetic flux density. The outer magnetic core 112 with low magnetic permeability can meet the anti-saturation characteristics of the magnetic core 1.

[0072] In a specific embodiment, the central magnetic core 111 is made of a magnetic core material with a magnetic permeability of 26, and the outer magnetic core 112 is made of a magnetic core material with a magnetic permeability of 14. The central magnetic core 111 and the outer magnetic core 112 are both made of alloy powder composite soft magnetic, and the magnetic permeability range is less than or equal to 150, which can meet the high anti-saturation characteristic requirements of the magnetic device 10 in high-power and high-current scenarios.

[0073] The alloy powder composite soft magnetic is prepared by soft magnetic alloy powder, adhesive, insulating agent, lubricant and the like. The soft magnetic alloy powder includes at least one or more of the following: sendustine powder, ferrosilicon powder, iron-nickel powder, amorphous nanocrystalline powder, and carbonyl iron powder. The binder includes at least one or more of epoxy resin, silicone resin, and phenolic resin, the insulating agent includes at least one or more of aluminum oxide, mica powder, silicon dioxide, and glass powder, and the lubricant includes at least one or more of zinc stearate, magnesium stearate, and wax powder. The alloy powder composite soft magnetic makes the magnetic core 1 have a higher saturation magnetic induction intensity and good frequency characteristics, and can optimize the performance of the magnetic device 10.

[0074] Among them, the shape of the cross section of the middle column 11 may be Figure 4b The circle shown in the figure, the corresponding shape of the outer magnetic core 112 can be a circular ring. Along the radial direction of the middle column 11, the thickness of the outer magnetic core 112 can also be kept consistent along the circumference of the middle column 11. That is to say, along the radial direction of the middle column 11, the thickness between the outer wall and the inner wall of any part of the outer magnetic core 112 is the same, so that the outer magnetic core 112 can be evenly distributed around the central magnetic core 111 in the circumferential direction, so that the structure of the magnetic core 1 along the circumferential direction is evenly distributed, which helps to improve the performance of the magnetic device 10.

[0075] As some structural deformations, Figure 5a In the cross-sectional view of a middle column 11 shown, the central magnetic core 111 is elliptical, and the corresponding outer magnetic core 112 is elliptical ring-shaped.

[0076] As some structural deformations, Figure 5b In the cross-sectional view of a middle column 11 shown, the central magnetic core 111 is a rounded rectangle, and the corresponding outer magnetic core 112 is a rectangular ring.

[0077] As some structural deformations, Figure 5c In the cross-sectional view of a middle column 11 shown, the central magnetic core 111 is in the shape of a runway, and the corresponding outer magnetic core 112 is in the shape of a runway ring. The runway shape refers to a shape formed by connecting two parallel straight lines and two semicircles with openings facing each other, with the two ends of one semicircle connected to one end of the same side of the two straight lines, and the two ends of the other semicircle connected to the other end of the same side of the two straight lines. Its shape is similar to a runway in a sports field, so it is called a runway shape.

[0078] exist Figure 5a to Figure 5b In the cross section of the middle column 11 shown in the example, the cross section of the middle column 11 is symmetrically distributed about the center. The regular structure of the middle column 11 can facilitate the winding layout of the winding 2 and is also beneficial to the structural layout of the magnetic device 10 .

[0079] Figure 6a Another structure of the center column 11 is illustrated. Figure 6bAs shown, the middle column 11 includes a central magnetic core 111 and an outer magnetic core 112. The central magnetic core 111 is columnar, and the outer magnetic core 112 is wrapped around the outer peripheral surface of the central magnetic core 111. The outer magnetic core 112 includes at least two magnetic core layers 1121, and the at least two magnetic core layers 1121 are stacked in sequence along the radial direction of the middle column 11. Between any two adjacent magnetic core layers 1121, the magnetic permeability of a magnetic core layer 1121 away from the central magnetic core 111 is less than the magnetic permeability of a magnetic core layer 1121 close to the central magnetic core 111.

[0080] Figure 6b for Figure 6b The cross-sectional view of the center column 11 shown in FIG. 1 is a schematic view of the cross-section of the center column 11, which cuts through the center column 11 along a direction perpendicular to the axial direction. Figure 6b As shown, along the radial direction of the middle column 11, the outer magnetic core 112 surrounds the outer periphery of the central magnetic core 111. Specifically, the outer magnetic core 112 exemplarily includes two magnetic core layers 1121, the first magnetic core layer 1121a close to the central magnetic core 111, and the second magnetic core layer 1121b away from the central magnetic core 111. Along the radial direction of the middle column 11, the first magnetic core layer 1121a surrounds the outer periphery of the central magnetic core 111, and the second magnetic core layer 1121b surrounds the outer periphery of the first magnetic core layer 1121a. The magnetic permeability of the second magnetic core layer 1121b and the magnetic permeability of the first magnetic core layer 1121a are both smaller than the magnetic permeability of the central magnetic core 111, and the magnetic permeability of the second magnetic core layer 1121b is smaller than the magnetic permeability of the first magnetic core layer 1121a. It can be considered that along the radial direction of the middle column 11 from the inside to the outside, the magnetic permeability of the middle column 11 shows a step-by-step downward trend.

[0081] As a specific embodiment, in a specific embodiment, the central magnetic core 111 selects a magnetic core material with a magnetic permeability of 60, the first magnetic core layer 1121a selects a magnetic core material with a magnetic permeability of 26, and the second magnetic core layer 1121b selects a magnetic core material with a magnetic permeability of 14. Taking the overall structure of the middle column 11 as a reference, the magnetic permeability of the middle column 11 decreases from the inside to the outside along the radial direction of the middle column 11 in a step-like manner.

[0082] It should be understood that the outer magnetic core 112 may further include more magnetic core layers 1121 as required, so that the magnetic permeability of the multiple magnetic core layers 1121 decreases from the inside to the outside along the radial direction of the center column 11, and the magnetic permeability of each magnetic core layer 1121 is less than the magnetic permeability of the central magnetic core 111. The difference in magnetic permeability between any two adjacent magnetic core layers is 5-100. The difference in magnetic permeability between the central magnetic core 111 and the adjacent magnetic core layers 1121 is 5-100.

[0083] In a specific embodiment, the difference in magnetic permeability between any two adjacent magnetic core layers is 10-70. The difference in magnetic permeability between the central magnetic core 111 and the adjacent magnetic core layer 1121 is 10-70.

[0084] by Figure 6a and Figure 6b The structure of the center column 11 shown is used as a reference. Figure 7a An example includes Figure 6a and Figure 6b The magnetic device 10 of the center column 11 shown, Figure 7b FIG. 1 is a schematic diagram of the cross-sectional structure of the magnetic device 10 .

[0085] like Figure 7a As shown, along the circumferential direction of the center column 11 of the magnetic core 1, the winding 2 is wound around the outer circumference of the center column 11. Along the radial direction of the center column 11, the winding 2 does not contact the outer circumferential surface of the center column 11. Exemplarily, there is a gap Q between the outer circumferential surface of the center column 11 and the winding 2.

[0086] Combination Figure 7b As shown, the gap Q surrounds the outer circumference of the center column 11, and the gap Q is filled with air, and the magnetic permeability of the air is lower than that of the center column 11. It can be considered that a circle of air as a medium surrounding the circumference of the center column 11 has a lower magnetic permeability than the magnetic permeability of the center column 11, and an air layer structure with a magnetic permeability lower than that of the magnetic core 1 is added. Taking the overall structure of the magnetic device 10 as a reference, the magnetic permeability gradually decreases along the radial direction of the center column 11 from the center of the center column 11 to the winding 2. The existence of the air-filled gap Q can further enhance the anti-saturation characteristics of the magnetic device 10. Under the same anti-saturation characteristics, the magnetic device 10 with the gap Q can reduce the number of turns of the winding 2, thereby reducing the production cost.

[0087] In some scenarios, the air gap Q between the winding 2 and the center column 11 can also improve the voltage resistance characteristics between the winding 2 and the center column 11, prevent the magnetic device 10 from breaking down in high voltage scenarios, and improve the safety and reliability of the power conversion device 100 using the magnetic device 10.

[0088] In a specific embodiment, along the radial direction of the center column 11, the distance between any point of the winding 2 and the outer circumference of the center column 11 is the same, which can ensure that the gap Q is evenly distributed on the periphery of the center column 11, so that the magnetic permeability distribution of the overall structure of the magnetic device 10 is more uniform.

[0089] In a specific embodiment, along the radial direction of the center column 11, the gap Q between the outer peripheral surface of the center column 11 and the winding 2 is in the range of 2-10 mm. A reasonable gap Q range can optimize the spatial distribution between the center column 11 and the winding 2, and improve the anti-saturation characteristics of the magnetic device 10 as much as possible without increasing the volume of the magnetic device 10.

[0090] like Figure 8aAs shown, an embodiment of the present application provides a magnetic device 10, wherein the winding 2 of the magnetic device 10 includes two or more winding coils 21. The two or more winding coils 21 are collectively referred to as a plurality of winding segments 21, and the plurality of winding coils 21 are sequentially wound around the outer periphery of the middle column 11 along the axial direction of the middle column 11. The materials, dimensions, number of turns, and winding density of different winding coils 21 may be different, and these parameters may affect the density distribution of the magnetic field generated after the different winding coils 21 are energized. During the operation of the magnetic device 10, the currents passed through different winding coils 21 may also be different, which may also affect the density distribution of the magnetic field generated after the different winding coils 21 are energized. The plurality of winding coils 21 are wound around the outer periphery of the middle column 11 along the axial direction of the middle column 11, and the density distribution of the magnetic field generated by the plurality of winding coils 21 will show differences along the axial direction of the middle column 11. If the magnetic field densities generated by different winding coils 21 are different, the density of the generated magnetic field will show an uneven distribution along the axial direction of the middle column 11.

[0091] In order to match the uneven distribution of magnetic field density that may be generated by different winding coils 21, the embodiment of the present application provides a center column 11 with a variable axial magnetic permeability. Figure 8b As shown, the middle column 11 includes two or more sub-columns 1101, and the two or more sub-columns 1101 are arranged in sequence along the axial direction of the middle column 11. Different sub-columns 1101 can be selected from magnetic core materials with different magnetic permeabilities.

[0092] Corresponds to Figure 8a The three winding coils 21 of the example, Figure 8b The illustrated middle column 11 includes three sub-columns 1101, and the three sub-columns 1101 are arranged adjacent to each other in the axial direction of the middle column 11. Any two adjacent middle columns 11 can be connected together by bonding, pressing, etc. A winding coil 21 can be wound around the periphery of each sub-column 1101. When different magnetic fluxes are generated by energizing different winding coils 21, sub-columns 1101 with different magnetic permeabilities can be selected accordingly.

[0093] Exemplarily, the magnetic flux generated by the winding coils 21 wound around any two adjacent sub-columns 1101 is different when energized, and the magnetic permeability of the sub-column 1101 corresponding to the winding coil 21 with a larger magnetic flux generated by the magnetic field is smaller than the magnetic permeability of the sub-column 1101 corresponding to the winding coil 21 with a smaller magnetic flux generated by the magnetic field. Fig. 9 Taking the magnetic device 10 shown as an example, along the axial direction of the middle column 11, the three sub-columns 1101 are respectively the first sub-column 1101a, the second sub-column 1101b and the third sub-column 1101c, and the three winding coils 21 are respectively the first winding coil 21a, the second winding coil 21b and the third winding coil 21c.

[0094] In one embodiment, the magnetic flux generated by the first winding coil 21a is greater than the magnetic flux generated by the second winding coil 21b, and the magnetic flux generated by the second winding coil 21b is greater than the magnetic flux generated by the first winding coil 21c. Correspondingly, the magnetic permeability of the first sub-column 1101a is less than the magnetic permeability of the second sub-column 1101b, and the magnetic permeability of the second sub-column 1101b is less than the magnetic permeability of the third sub-column 1101c. Exemplarily, the magnetic permeability of the first sub-column 1101a is 14, the magnetic permeability of the second sub-column 1101b is 26, and the magnetic permeability of the third sub-column 1101c is 60.

[0095] In one embodiment, the magnetic flux generated by the second winding coil 21b is greater than the magnetic flux generated by the first coil 21a, and the magnetic flux generated by the first winding coil 21a is greater than the magnetic flux generated by the third winding coil 21c. Correspondingly, the magnetic permeability of the second sub-column 1101b is less than the magnetic permeability of the first sub-column 1101a, and the magnetic permeability of the first sub-column 1101a is less than the magnetic permeability of the third sub-column 1101c. Exemplarily, the magnetic permeability of the first sub-column 1101a is 26, the magnetic permeability of the second sub-column 1101b is 14, and the magnetic permeability of the third sub-column 1101c is 60.

[0096] In one embodiment, the magnetic flux generated by the third winding coil 21c is greater than the magnetic flux generated by the first coil 21a, and the magnetic flux generated by the first winding coil 21a is greater than the magnetic flux generated by the second winding coil 21b. Correspondingly, the magnetic permeability of the third sub-column 1101c is less than the magnetic permeability of the first sub-column 1101a, and the magnetic permeability of the first sub-column 1101a is less than the magnetic permeability of the second sub-column 1101b. Exemplarily, the magnetic permeability of the first sub-column 1101a is 26, the magnetic permeability of the second sub-column 1101b is 60, and the magnetic permeability of the third sub-column 1101c is 14.

[0097] It should be understood that the magnetic device 10 can also include more winding coils 21 as needed, and the corresponding middle column 11 includes multiple sub-columns 1101, and a winding coil 21 is wound around the outer periphery of each sub-column 1101. According to the size of the magnetic flux generated by each winding coil 21, the corresponding magnetic permeabilities of different sub-columns 1101 are different, and finally the magnetic permeability of the middle column 11 is distributed differently along the axial direction of the middle column 11. Among them, the difference in magnetic permeability between any two adjacent sub-columns 1101 is 5-100, and further, the difference in magnetic permeability between any two adjacent sub-columns 1101 is 10-70. The regular distribution of the magnetic permeability of the middle column 11 can effectively even out the magnetic flux density of the magnetic device 10 in the application and improve the performance of the magnetic device 10.

[0098] In some embodiments, the middle column 11 of the magnetic core 1 includes a plurality of sub-columns 1101 arranged in sequence along the axial direction. For each sub-column 1101, the magnetic flux generated by the winding coil 21 wound around the sub-column 1101 will be strengthened from inside to outside along the radial direction of the middle column 11. Based on this, Fig.10 As shown, at least one of the sub-columns 1101 may include a central magnetic core 111 and an outer magnetic core 112. The outer magnetic core 112 is wrapped around the central magnetic core 111 along the circumference of the central column 11. The magnetic permeability of the central magnetic core 111 is greater than the magnetic permeability of the outer magnetic core 112. The magnetic permeability of the sub-column 1101 decreases from the inside to the outside in a stepped manner along the radial direction of the central column 11. The outer magnetic core 112 may also include a plurality of magnetic core layers 1121 stacked in sequence along the radial direction of the central column 11. Between any two adjacent magnetic core layers 1121, the magnetic permeability of the magnetic core layer 1121 close to the central magnetic core 111 is greater than the magnetic permeability of the magnetic core layer 1121 away from the central magnetic core 111. It can be considered that Fig.10 The structure of the magnetic core 1 in the magnetic device 10 is as follows: Figure 4a and Figure 8b The combination of the structural forms of the magnetic core 1 shown.

[0099] like Fig.11 A magnetic device 10 is shown, the magnetic device 10 comprises a magnetic core 1 and a winding 2, wherein the magnetic core 1 comprises a middle column 11 and two cover plates 12, and the winding 2 is wound around the outer circumference of the middle column 11. The two cover plates 12 of the magnetic core 1 are respectively fixed at both ends of the length direction of the middle column 11, the magnetic core 1 is in an "I" shape or an "I" shape, and the length direction of the middle column 11 is also the axial direction of the middle column 11. As a part of the magnetic core 1, the magnetic flux lines of the magnetic field generated by the winding 2 when it is energized will also pass through the cover plates 12.

[0100] Fig.12 The example shows a partial structure of a magnetic device 10, including a portion of a center column 11, a portion of a winding 2 and a cover plate 12. Fig.12As shown, along the radial direction of the middle column 11 from inside to outside, each cover plate 12 includes a central connecting portion 121, a first surrounding portion 122 and a second surrounding portion 123. In order to conveniently illustrate the different structures of the magnetic device 10, the structures of each part are distinguished and illustrated by dotted lines and shadows. Among them, the central connecting portion 121 is used to connect the end of the middle column 11, the first surrounding portion 122 surrounds the outer periphery of the central connecting portion 121 along the circumference of the middle column 11, and the second surrounding portion 123 surrounds the outside of the first surrounding portion 122 along the circumference of the middle column 11. Along the axial direction of the middle column 11, the orthographic projection of the winding 2 on the cover plate 12 falls within the range of the first surrounding portion 122 and has no overlap with the second surrounding portion 123. Among them, the first surrounding portion 122 is closest to the winding 2, the magnetic flux corresponding to the first surrounding portion 122 is the largest, and the first surrounding portion 122 uses a magnetic core material with a relatively low magnetic permeability. The central connecting portion 121 and the second surrounding portion 123 are made of a magnetic core material having a magnetic permeability greater than that of the first surrounding portion 122 .

[0101] In some embodiments, along the radial direction of the center column 11 from inside to outside, the magnetic flux corresponding to the second surrounding portion 123 has a decreasing trend. Fig.13 As shown, the second surrounding portion 123 includes two or more surrounding layers 1231 distributed along the radial direction of the center column 11. Between any two adjacent surrounding layers 1231, the magnetic permeability of the surrounding layer 1231 close to the first surrounding portion 122 is smaller than the surrounding layer 1231b far away from the first surrounding portion 122, so that the magnetic permeability of the second surrounding portion 123 decreases from the inside to the outside in a step-like distribution along the radial direction of the center column 11, which can further make the magnetic flux density of the magnetic device 10 in the application uniform and improve the performance of the magnetic device 10.

[0102] Fig.13 Two surrounding layers 1231 are shown, namely, the surrounding layer 1231a and the surrounding layer 1231b. Along the circumference of the center column 11, the surrounding layer 1231a surrounds the outer periphery of the first surrounding portion 122, and the surrounding layer 1231b surrounds the outer periphery of the surrounding layer 1231a. The magnetic permeability of the surrounding layer 1231b is greater than the magnetic permeability of the surrounding layer 1231a.

[0103] In some embodiments, Fig.14 A magnetic device 10 is shown, and the magnetic device 10 includes a magnetic core 1 and a winding 2. The magnetic core 1 includes a plurality of middle columns 11 and two cover plates 12. Exemplarily, the magnetic core 1 includes three middle columns 11, and the two ends of each middle column 11 are respectively fixed to the two cover plates 12. The three middle columns 11 are arranged between the two cover plates 12 along the radial direction of the middle column 11, and the three middle columns 11 share the two cover plates 12. A group of windings 2 is wound around the outer circumference of each middle column 11. Along the arrangement direction of the three middle columns 11, each middle column 11 and a portion of the corresponding two cover plates 12 can be regarded as a Fig.11For the convenience of illustration, the two adjacent middle columns 11 are separated by a dotted line. The structure of each middle column 11 and a portion of the corresponding two cover plates 12 can be referred to in Fig.11 The magnetic device 10 shown in the figure, wherein each cover plate 12 and a portion of the structure corresponding to the middle column 11 are Fig.12 or Fig.13 The structural distribution is shown.

[0104] In summary, in a magnetic device 10 provided in an embodiment of the present application, at least one of the middle column 11 and the cover plate 12 of the magnetic core 1 can be prepared by selecting a combination of materials with different magnetic permeabilities, so that the magnetic core 1 can meet the anti-saturation characteristics of the magnetic device 10 while maintaining a high initial inductance, thereby improving the bias inductance of the magnetic device 10 under large current, and optimizing the performance of the magnetic device 10 in high current and high power scenarios.

[0105] Based on the structure of the magnetic core 1, the embodiment of the present application also provides a preparation direction of a magnetic device, and the preparation method can be used to prepare the magnetic device 10. Specifically, the magnetic device 10 includes the magnetic core 1 and the winding 2, and the magnetic core 1 includes a middle column 11 for winding the winding 2. In one embodiment, the middle column 11 includes a central magnetic core 111 and an outer magnetic core 112, and the outer magnetic core 112 is wrapped around the outer peripheral surface of the central magnetic core 111, and the magnetic permeability of the outer magnetic core 112 is less than the magnetic permeability of the central magnetic core 111.

[0106] like Fig.15 As shown, the preparation direction of the magnetic device includes the following steps:

[0107] S1: prepare the central magnetic core;

[0108] According to different core materials, suitable preparation process is selected to prepare Figure 4a The central magnetic core 111 is shown.

[0109] S2: preparing an outer magnetic core wrapped around the outer peripheral surface of the central magnetic core, wherein the magnetic permeability of the outer magnetic core is less than the magnetic permeability of the central magnetic core;

[0110] S3: A winding coil is wound around the outer periphery of the outer magnetic core.

[0111] According to different magnetic core materials, a suitable preparation process is selected to prepare the outer peripheral surface of the central magnetic core 111. Figure 4a The outer magnetic core 112 shown is wrapped around the outer circumference of the central magnetic core 111 to form the middle column 11 of the magnetic core 1 .

[0112] After the above steps S1 and S2, the Figure 4aThe magnetic core 1 shown in the figure comprises a middle column 11. Along the radial direction of the middle column 11, the magnetic permeability of the outer magnetic core 112 is less than the magnetic permeability of the central magnetic core 111. After the above step S3, the winding coil 21 is wound around the outer periphery of the middle column 11 to form a winding 2, and the winding 2 is obtained. Figure 7a The structure shown. The winding coil 21 is a conductor, and the number of the winding coil 21 is one or more, and one or more winding coils 21 constitute the winding 2. When the winding 2 is energized, a magnetic field is generated, and the magnetic flux at the position of the outer magnetic core 112 is greater than the magnetic flux of the central magnetic core 111. The central magnetic core 111 with a higher magnetic permeability ensures the initial inductance requirement of the magnetic device 10, and the outer magnetic core 112 with a lower magnetic permeability can improve the anti-saturation characteristics of the magnetic device 10, thereby improving the bias characteristics of the magnetic device 10 under high current and high power.

[0113] In one embodiment, alloy powder composite soft magnetic material is used to prepare the central magnetic core 111, and there are multiple specific preparation processes.

[0114] In a specific embodiment, Fig.16a As shown, the above step S1 of preparing the central magnetic core includes the following steps:

[0115] S111: preparing a central magnetic core from soft magnetic alloy powder using a powder forming process.

[0116] In this step, the soft magnetic alloy powder is specifically alloy powder composite soft magnetic, and the powder molding process includes but is not limited to one or more processes of powder pressing molding, powder extrusion molding, and slurry casting molding.

[0117] In a specific embodiment, Fig.16b As shown, the above step S1 of preparing the central magnetic core includes the following steps:

[0118] S121: preparing a magnetic blank from soft magnetic alloy powder by a powder forming process;

[0119] In this step, the soft magnetic alloy powder is specifically alloy powder composite soft magnetic, and the powder molding process includes but is not limited to one or more processes of powder pressing molding, powder extrusion molding, and slurry casting molding.

[0120] S122: Carving the magnetic blank to form a central magnetic core.

[0121] In this step, the engraving method includes but is not limited to one or more processes such as cutting, chipping, and grinding.

[0122] In one embodiment, alloy powder composite soft magnetic material is used to prepare the outer magnetic core 112, and there are multiple specific preparation processes.

[0123] In a specific embodiment, Fig.17aAs shown, the above step S2 of preparing the outer magnetic core wrapped around the outer peripheral surface of the central magnetic core includes:

[0124] S211: Using a powder molding process, the soft magnetic alloy powder is molded on the periphery of the central magnetic core to form an outer magnetic core.

[0125] In this step, the soft magnetic alloy powder is specifically alloy powder composite soft magnetic, and the powder molding process includes but is not limited to one or more processes of powder pressing molding, powder extrusion molding, and slurry casting molding. The soft magnetic alloy powder is molded on the periphery of the central magnetic core 111 to obtain an outer magnetic core 112 that circumferentially wraps the central magnetic core 111.

[0126] In a specific embodiment, Fig.17b As shown, the above step S2 of preparing the outer magnetic core wrapped around the outer peripheral surface of the central magnetic core includes:

[0127] S221: preparing a magnetic blank from soft magnetic alloy powder by a powder forming process;

[0128] In this step, the soft magnetic alloy powder is specifically alloy powder composite soft magnetic, and the powder molding process includes but is not limited to one or more processes of powder pressing molding, powder extrusion molding, and slurry casting molding.

[0129] S222: Carving the magnetic blank to form an outer magnetic core;

[0130] In this step, the engraving method includes but is not limited to one or more processes such as cutting, chipping, and grinding.

[0131] S223: Put the outer magnetic core onto the outer circumference of the central magnetic core.

[0132] In this step, the outer magnetic core 112 is mounted on the outer periphery of the central magnetic core 111 along the axial direction of the center column 11 .

[0133] It should be understood that in the structure where the outer core 112 includes multiple core layers 1121, each core layer 1121 can be stacked in sequence outside the central core 111 using a process similar to step S211 to finally form the outer core 112. Alternatively, each core layer 1121 can be prepared using a process similar to step S221 and step S222, and then the multiple core layers 1121 are sequentially mounted to obtain the outer core 112, and finally the outer core 112 is mounted on the outer peripheral surface of the central core 111.

[0134] In some embodiments, the middle column 11 includes a plurality of sub-columns 1101 arranged in sequence along the axial direction. Each sub-column 1101 can be prepared and formed by a method similar to step S111, and then the plurality of sub-columns 1101 are combined together by pressing or the like to obtain the middle column 11. Alternatively, each sub-column 1101 can be prepared and formed by a method similar to step S121 and step S122, and then the plurality of sub-columns 1101 are combined together by pressing or the like to obtain the middle column 11. Alternatively, a sub-column 1101 is prepared and formed by a method similar to step S111, and then another sub-column 1101 is prepared on one side of the sub-column 1101 by a powder molding process, and other sub-columns 1101 are prepared in this manner to finally obtain the middle column 11.

[0135] In some embodiments, the magnetic core 1 includes a center column 11 and two cover plates 12 connected to both ends of the center column 11. The structure of each cover plate 12 is Fig.12 As shown in the distribution form, the cover plate 12 includes a central connecting portion 121 , a first surrounding portion 122 and a second surrounding portion 123 .

[0136] In one embodiment, the central connecting portion 121 may be prepared by a process similar to step S111 , or may be prepared by a process similar to steps S111 and S112 .

[0137] In one embodiment, the first surrounding portion 122 may be formed on the periphery of the central connecting portion 121 by a process similar to step S211 , or may be formed on the periphery of the central connecting portion 121 by a process similar to step S221 , step S22 , and step S223 .

[0138] In this embodiment, the second surrounding portion 123 can be formed on the periphery of the first surrounding portion 122 by a process similar to step S211, or by a process similar to step S221, step S22, and step S223.

[0139] The method for preparing a magnetic device provided in the embodiment of the present application can prepare a magnetic core 1 with different magnetic permeability parts, and the magnetic core 1 is obtained by assembling a combination of different magnetic permeabilities, and there is a magnetic permeability step difference between the parts with different magnetic permeabilities. Among them, the part of the magnetic core 1 with high magnetic permeability can ensure that the magnetic device 10 has a higher initial inductance, and the part with low magnetic permeability can ensure that the magnetic device 10 has a higher anti-saturation characteristic, so that the magnetic device 10 has a higher bias inductance under high current and high power.

[0140] It should be understood that the magnetic device 10 provided in the embodiment of the present application can be used in a device with a power conversion function, and such a device can be widely used in scenes such as photovoltaic systems, charging networks, energy storage systems, or powertrain systems of new energy vehicles. Specifically, the device with a power conversion function may include energy storage converters, transformers, photovoltaic inverters, motor controllers, uninterruptible power supplies (UPS) or power supplies, etc., which are used to achieve power conversion. In such equipment, the magnetic device 10 can carry a higher overload, meet the overload sensitivity requirements after the power is increased, and ensure the normal operation of the equipment.

[0141] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A magnetic device, characterized in that: The magnetic device comprises a winding and a magnetic core, wherein the magnetic core comprises a center column for winding the winding; The center column includes a central magnetic core and an outer magnetic core. The outer magnetic core is wrapped around the outer peripheral surface of the central magnetic core. The magnetic permeability of the outer magnetic core is smaller than that of the central magnetic core.

2. The magnetic device according to claim 1, characterized in that The outer magnetic core comprises at least two magnetic core layers, and the at least two magnetic core layers are stacked in sequence along the radial direction of the middle column; Between any two adjacent magnetic core layers, the magnetic permeability of a magnetic core layer far away from the central magnetic core is smaller than the magnetic permeability of a magnetic core layer close to the central magnetic core.

3. The magnetic device according to claim 2, characterized in that: The difference in magnetic permeability between any two adjacent magnetic core layers is 5-100.

4. The magnetic device according to any one of claims 1 to 3, characterized in that: The central column comprises at least two sub-columns, and the at least two sub-columns are arranged adjacent to each other in sequence along the axial direction of the central column; Each of the sub-columns is used to wind a winding coil, and the magnetic fluxes generated by the winding coils wound by any two adjacent sub-columns when energized are different, and the magnetic permeability of the sub-column with a larger magnetic flux is smaller than the magnetic permeability of the sub-column with a smaller magnetic flux.

5. The magnetic device according to claim 4, characterized in that: The difference in magnetic permeability between any two adjacent sub-columns is 5-100.

6. The magnetic device according to any one of claims 1 to 5, characterized in that: The magnetic core includes two cover plates, and the two cover plates are respectively fixed to two ends of the middle column along the length direction; Each of the cover plates comprises a central connecting portion, a first surrounding portion and a second surrounding portion, wherein the first surrounding portion surrounds the outer circumference of the central connecting portion along the circumference of the central column, and the second surrounding portion surrounds the outer circumference of the first surrounding portion along the circumference of the central column, wherein the central connecting portion is used to connect the end of the central column, and the first surrounding portion is used to be opposite to the winding along the axial direction of the central column; The magnetic permeability of the first surrounding portion is smaller than the magnetic permeability of the central connecting portion and the magnetic permeability of the second surrounding portion.

7. The magnetic device according to claim 6, characterized in that: The second surrounding portion includes at least two surrounding layers, and the at least two surrounding layers are stacked in sequence along the radial direction of the center column; Between any two adjacent surrounding layers, the magnetic permeability of a surrounding layer far away from the central connecting portion is greater than the magnetic permeability of a surrounding layer close to the central connecting portion.

8. The magnetic device according to any one of claims 1 to 7, characterized in that: The material of the magnetic core is alloy powder composite soft magnetic.

9. The magnetic device according to any one of claims 1 to 8, characterized in that: The magnetic permeability of the magnetic core is less than or equal to 150.

10. The magnetic device according to any one of claims 1 to 9, characterized in that: The winding surrounds the outer circumference of the center column along the circumferential direction of the center column, and the outer circumferential surface of the center column is not in contact with the winding.

11. The magnetic device according to claim 10, characterized in that: Along the radial direction of the center column, the gap between the outer circumferential surface of the center column and the winding ranges from 2 to 10 mm.

12. The magnetic device according to claim 10 or 11, characterized in that: The center column comprises a plurality of sub-columns connected in sequence along the axial direction of the center column, the winding comprises a plurality of winding coils, and one of the winding coils is wound around the outer circumference of each of the sub-columns.

13. A power conversion device, characterized in that: The power conversion device comprises an inductor, a power device and a capacitor, the capacitor and the power device are connected to form a power conversion circuit, and the inductor is connected in series to the circuit; The inductive device is a magnetic device according to any one of claims 1 to 12.

14. A method for preparing a magnetic device, characterized in that: The preparation method comprises: preparing a central magnetic core; Preparing an outer magnetic core wrapped around the outer circumference of the central magnetic core to form a middle column of the magnetic core, wherein the magnetic permeability of the outer magnetic core is less than the magnetic permeability of the central magnetic core; A coil is wound around the outer periphery of the center column to form a winding.

15. The preparation method according to claim 14, characterized in that: The preparation of the central magnetic core comprises: The central magnetic core is formed by preparing soft magnetic alloy powder using a powder molding process.

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