Electromagnetic induction device

Abstract

The present invention relates to an electromagnetic induction device having a variable air gap equipped with a heat sink. Specifically, the device according to the present invention comprises a core in which the variable air gap is housed. The air gap further comprises a first ferromagnetic plate, intended to guide magnetic flux, which may originate from the core and may collectively have a saturation magnetic field that is less than the saturation magnetic field of the core. The variable air gap according to the present invention further comprises lateral protrusions extending from lateral surfaces of the first plate, forming the heat sink.

Description

Technical Field

[0001] The present invention relates to the electronic and electrical fields. In particular, the present invention relates to a magnetic inductor having variable induction and reduced magnetic and thermal losses compared to devices known in the prior art.

[0002] Advantageously, the magnetic inductor according to the present invention is implemented in an AC / DC or DC / DC power converter, in particular in a Dual Active Bridge ("DAB") converter. Background Art

[0003] Magnetic sensors are devices well known to those skilled in the art and are implemented in many applications.

[0004] Typically, a magnetic inductor consists of a core made of ferromagnetic material and a winding formed around a section of the core. The core may also include an air gap. This device is characterized by a characteristic quantity called the magnetizing induction, L, which depends on the ferromagnetic material, the geometry of the core (and its air gap), and the winding, in particular the number of turns forming this winding.

[0005] Some applications, in particular electronic converters, may require high values ​​of magnetizing induction L for nominal operation, while lower magnetizing induction may be required for some operating points.

[0006] This is particularly the case with the so-called LLC resonant converter topology.

[0007] In fact, the magnetizing induction of the transformer of the LLC converter should be high at the nominal operating voltage in order to limit the switching losses and ensure good efficiency, but should be able to be significantly reduced in order to ensure the continuity of the power delivered to the load when the input voltage drops (see the case of server power supply systems that must ensure data backup in the event of a power outage as described in document [1] cited at the end of the description).

[0008] This problem can lead to sizing converters of this type to have low inductance values ​​to ensure standby functionality, thus compromising efficiency.

[0009] For DAB converter topologies, the value of the so-called "series" inductance in series with the magnetizing inductance of the transformer determines the operating range of the converter.

[0010] The power transferred is inversely proportional to the value of the series inductance, L, and the phase shift between the input and output voltages set by the driver.

[0011] In some cases, the series sensing function may be implemented by a component other than the transformer. However, in other cases, the series sensing function is ensured by the leakage inductance of the same transformer.

[0012] In both cases, the single series inductance value limits the operating range and proves to be less flexible for driving a DAB converter, as described in document [2] cited at the end of the description. In order to overcome these problems, it is possible to consider implementing a magnetic inductor with a variable magnetizing inductance L or series inductance depending on the magnetic flux (and therefore on the current I flowing in the winding). More specifically, it may be necessary to have a magnetic inductor that has a high magnetizing inductance L or series inductance at low currents I and a lower magnetizing inductance L or series inductance at high currents I.

[0013] However, the size of the magnetic inductor is usually designed to operate below the saturation current I sat The winding operates within the range of the current I flowing in it, therefore, the ferromagnetic core is not saturated.

[0014] In this area, as long as the current I is lower than the saturation current I sat , the magnetizing induction L remains independent of the current I. However, once the current I exceeds the saturation current I sat When the value of , the core becomes magnetically saturated, causing its magnetic permeability to decrease rapidly, and thus the magnetizing induction L to decrease rapidly.

[0015] Therefore, whenever variability of the magnetizing induction L is required during magnetic induction operation, different solutions can be considered. Generally, these solutions suggest extending the operating range of the magnetic inductor into a nonlinear mode, before the ferromagnetic material is completely saturated. To this end, lower permeability and / or adjustment of the air gap size can be considered.

[0016] As long as either of these two solutions is implemented, the value of the current I is higher than the saturation current I sat In this case, the entire core will be saturated evenly.

[0017] However, these solutions are not satisfactory.

[0018] In fact, when the inductor is subjected to high-frequency currents I (typically above 10 kHz), saturation of the entire core can be a source of significant volumetric magnetic losses in the inductor and in the entire component in which it is integrated.

[0019] Furthermore, these losses can cause the core to heat up.

[0020] Furthermore, in saturation mode, the magnetic flux lines, which are no longer confined in the core, can interfere with components arranged close to the magnetic inductor. In particular, these interferences can be a source of electromagnetic incompatibility and / or eddy current losses.

[0021] Thus, in the documents [3] to [7] cited at the end of the description, methods for determining the core dimensions and, in particular, the air gap dimensions, can already be suggested, allowing the saturation of the core to be located in said air gap.

[0022] Nevertheless, the proposed sizing method is not satisfactory.

[0023] In fact, even if the saturation of the core remains localized near the air gap, the air gap is still a site of magnetic losses and overheating, which may disturb the operation of the entire component.

[0024] Furthermore, these magnetic and thermal losses limit the realization of such magnetic inductors to currents I having high frequencies, in particular currents I having high frequencies which can reach 500 kHz.

[0025] It is therefore an object of the present invention to provide an electromagnetic induction device having a variable magnetization induction L and having reduced magnetic losses and heating compared to devices known in the prior art.

[0026] Another object of the present invention is to provide an electromagnetic induction device that can operate at higher frequencies than devices known in the prior art. Summary of the Invention

[0027] The object of the present invention is achieved at least in part by an electromagnetic induction device, the electromagnetic induction device comprising:

[0028] - ferromagnetic core;

[0029] - at least one air gap, called the variable air gap, which defines a volume V in the core, in which ferromagnetic main plates are arranged substantially parallel and along a direction parallel to the field lines that can flow in the core, the main plates having a cross-section configured so that all said plates have a saturation magnetic field lower than the saturation magnetic field of the ferromagnetic core, the main plates also being provided with lateral protrusions for diffusing heat that may be generated in the main plates when they are traversed by a magnetic field higher than their saturation magnetic field, said lateral protrusions extending from the lateral surfaces of said plates in a direction substantially orthogonal to said lateral surfaces.

[0030] According to one embodiment, the lateral projections connect the main plates in pairs, forming secondary plates perpendicular to said main plates.

[0031] According to one embodiment, the ferromagnetic core, the main plate and the lateral protrusions are made of the same ferromagnetic material.

[0032] According to one embodiment, all motherboards are identical.

[0033] According to one embodiment, the empty volume Vv of said volume V left empty by the main plate and the lateral projections is at least partially filled with a heat absorbing material having a thermal conductivity higher than 10 W / m / K, preferably comprising aluminum oxide.

[0034] According to one embodiment, the ferromagnetic core includes a ferromagnetic material selected from the following: FeX type metal alloy, where X includes one of the elements selected from Si, Al, Co, Ni, a ferrite oxide having an A(Fe, B)2O4 type spinel structure, where A=(Mn, Ni)B=(Co, Cu, Al, ..).

[0035] According to one embodiment, the ferromagnetic core comprises two planar ends, the two ends being substantially parallel to each other, facing each other and having a surface area S, the two ends defining a variable air gap, the main plate being arranged perpendicular to the ends, advantageously, the ferromagnetic core comprises a frame having a polygonal shape, even more advantageously a frame having a rectangular shape.

[0036] According to one embodiment, the main board has a cross-sectional surface area S t The sum of the cross-sectional surface areas of all main boards is less than the surface area S.

[0037] According to one embodiment, the ferromagnetic core comprises two pedestals, each of the pedestals being provided with two substantially parallel main surfaces, respectively referred to as an inner surface and an outer surface, the pedestals being respectively facing each other according to their inner surfaces, a variable air gap being formed in one of the pedestals, the core further comprising a plurality of legs, the plurality of legs being substantially parallel to each other and extending between the two inner surfaces, the plurality of legs comprising at least one main leg, at least one lateral leg and at least two leakage legs;

[0038] The device further comprises at least one primary winding and at least one secondary winding, each winding comprising a main section wound around a main leg, and leakage sections respectively referred to as a primary leakage section and a secondary leakage section, each leakage section being wound around a different leakage leg.

[0039] According to one embodiment, the variable air gap is provided between the two leakage legs, and the main plate is in the form of fins.

[0040] According to one embodiment, the fin is oriented according to a direction defined by an axis joining two leakage legs, an air gap being provided between the two leakage legs.

[0041] According to one embodiment, the recess opens onto the inner surface of the base in question.

[0042] According to one embodiment, the recess opens onto the outer surface of the base in question.

[0043] According to one embodiment, at least one main leg comprises a single main leg, at least two leakage legs comprise four leakage legs, wherein the main leakage section comprises two main leakage sections, so that the primary winding comprises, in sequence, a main leakage section, a main section, and one of the further main leakage sections, each of the main leakage sections being wound around a different leakage leg, and wherein the secondary leakage section comprises two secondary leakage sections, so that the secondary winding comprises, in sequence, a secondary leakage section, a main section, and one of the further secondary leakage sections, each of the secondary leakage sections being wound around a different leakage leg.

[0044] According to one embodiment, the at least one lateral leg comprises four lateral legs, the four lateral legs and the four leakage legs describing a circle centered on the main leg, and wherein the lateral legs and the leakage legs alternate in a regular manner, each segment being arranged radially opposite a second leakage segment relative to the main leg.

[0045] According to one embodiment, the at least one lateral leg comprises two lateral legs, the at least two leakage legs comprise four leakage legs, forming two groups of two leakage legs, the two groups being referred to as the first group and the second group, the four leakage legs and the two lateral legs describing a circle centered on the main leg, and wherein the lateral legs and the groups alternate in a regular manner.

[0046] According to one embodiment, the at least one air gap comprises a first air gap and a second air gap disposed midway between the first and second groups of leakage legs, respectively.

[0047] According to one embodiment, each of the primary leakage sections is formed around any one of the leakage legs of the first group, respectively, and each of the secondary leakage sections is formed around any one of the leakage legs of the second group, respectively.

[0048] According to one embodiment, a groove is formed on either of the inner surfaces, spaced apart from and surrounding each leakage leg, with the groove being interposed between the leakage leg and the main leg. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Other characteristics and advantages will become apparent from the following description of an electromagnetic induction device according to the invention, given as a non-limiting example, with reference to the accompanying drawings, in which:

[0050] Figure 1 is a schematic perspective view of a variable air gap according to the present invention;

[0051] Figure 2 is a schematic perspective view of another configuration of a variable air gap according to the present invention;

[0052] Figure 3 is a diagrammatic representation of a ferromagnetic core that may be implemented in the context of the present invention;

[0053] Figure 4 This is a graph showing the induction L (vertical axis, unit "H") of an electromagnetic induction device as a function of the current I (horizontal axis, unit "A") flowing through the coil;

[0054] Figure 5 is a schematic diagram of an electromagnetic induction device according to a first embodiment of the present invention;

[0055] Figure 6a 、 Figure 6b is possible in the context of the present invention according to the side view ( Figure 6a ) and top view ( Figure 6b ) is a schematic diagram of a half core;

[0056] Figure 7 is a schematic diagram of an electromagnetic induction device according to a first embodiment of the present invention, and realizes Figure 6a and Figure 6b The two core halves shown;

[0057] Figure 8 is a schematic diagram of an electromagnetic induction device according to a first variation of the second embodiment of the present invention;

[0058] Figure 9 is a schematic cross-sectional view of a half core according to a second variation of the second embodiment of the present invention, according to an inner surface;

[0059] Figure 10 is a schematic perspective view of a half core according to a second variation of the second embodiment of the present invention;

[0060] Figure 11 is a schematic cross-sectional view of a core half provided with a winding according to a second variant of a second embodiment of the invention, according to an inner surface;

[0061] Figure 12 is a schematic diagram of an open air gap at the outer surface of the base in contact with a heat sink. DETAILED DESCRIPTION

[0062] The invention relates to an electromagnetic induction device provided with a variable air gap, wherein the variable air gap is provided with a heat dissipation device.

[0063] In particular, the device according to the invention comprises a core housing a variable air gap. Furthermore, the air gap comprises a first ferromagnetic plate for guiding the magnetic flux that may originate from the core and for operating in a saturation mode with a magnetic flux value lower than that required for saturation of the core, the magnetic flux being conserved throughout the magnetic circuit.

[0064] The variable air gap according to the invention further comprises lateral protrusions forming heat sinks and extending from the lateral surfaces of the first plate.

[0065] More particularly, the present invention relates to an electromagnetic induction device 100 ( Figures 1 to 3 ).

[0066] The electromagnetic induction device 100 may be a magnetic inductor with an inductance L integrated into an AC / DC or DC / DC power transformer, in particular a DAB converter.

[0067] The electromagnetic induction device 100 includes a ferromagnetic core 200 (e.g. Figure 1 、 Figure 2 and Figure 3 ).

[0068] The ferromagnetic core 200 may include at least one ferromagnetic material selected from the following: FeX type metal alloy, wherein X includes one element selected from Si, Al, Co, Ni, ferrite oxide having an A(Fe, B)2O4 type spinel structure, wherein A=(Mn, Ni)B=(Co, Cu, Al, ..).

[0069] The ferromagnetic core 200 can be crossed by field lines induced by a current I flowing in at least one conductive coil 300 (or winding) formed around a section of the ferromagnetic core 200 and extending according to a main axis XX′.

[0070] "Main axis" should be understood as the axis of symmetry of the conductive coil.

[0071] In particular, the conductive coil 300 is made of a winding of conductive wire (eg, copper wire) around a section of the ferromagnetic core 200 .

[0072] The ferromagnetic core 200 also includes an air gap, more specifically a variable air gap 400 ( Figure 1 and Figure 2 ).

[0073] In particular, the air gap 400 is formed by a recess or absence of material in the ferromagnetic core 400 .

[0074] The recess or absence of material results in a break in the continuity of the ferromagnetic material forming the ferromagnetic core 400 .

[0075] The variable air gap 400 defines a volume V in the ferromagnetic core 200 that corresponds to the volume of material that was removed or is absent.

[0076] The main board 500 made of a ferromagnetic material is disposed in the volume V defined by the variable air gap 400 .

[0077] A "plate" should be understood as an element having a generally planar shape and being thin. In particular, the plate comprises two lateral surfaces 501 which are substantially parallel to each other and connected by a profile.

[0078] Furthermore, the main plates 500 are substantially parallel to each other and are arranged according to a direction parallel to field lines that may flow in the ferromagnetic core 200 .

[0079] According to the invention, the orientation of the plate, in particular the main plate, is defined by the orientation of its lateral surfaces 501. In other words, the field lines are parallel to the direction of the plane formed by the lateral surfaces of the main plate 500.

[0080] The main plate 500 also has a cross section with a surface area St, so that all of the main plate 500 has a first magnetic field B sat1 The saturation magnetic field B sat1 , which is lower than the second magnetic field B sat2 The saturation magnetic field of the ferromagnetic core 200.

[0081] A "cross-sectional surface" is understood to be a cross-sectional surface according to a plane of the cross-sectional surface perpendicular to the field lines passing through the main panel.

[0082] The magnitude of the magnetic field B passing through the ferromagnetic core 200 depends on the current I flowing in the coil 300. In particular, when the current I flowing in the coil 300 is equal to the first saturation current I sat1 and the second saturation current I sat2 When the first magnetic field B is reached sat1 and the second magnetic field B sat2 .

[0083] Therefore, the characteristics of the electromagnetic induction device 100 , and more particularly its magnetizing induction L, will depend on the current I flowing in the coil 300 .

[0084] On this surface, Figure 4 1 is a graph showing different working modes of the electromagnetic induction device 100 having the same mainboard 500 .

[0085] "Identical main boards" should be understood as boards having the same shape, the same dimensions and the same material.

[0086] Such a device 100 has three operating modes or levels "A", "B" and "C" associated with the current I flowing in the coil 300, which are respectively below the first saturation current I sat1 , including the first saturation current I sat1 With the second saturation current I sat2 between, and greater than the second saturation current I sat2 .

[0087] More specifically, mode "A" corresponds to a linear mode in which the ferromagnetic core 200 and the main plate 500 are not saturated. In this mode, the magnetic permeability of the ferromagnetic core 200 and the main plate 500 has little or no dependence on the magnetic field flowing in the core, so that the induction L is also substantially constant and equal to the first induction L1.

[0088] Mode "B" is characterized by a decrease in the induction L to a second induction L2.

[0089] In particular, this decrease is due to the saturation of the main board 500 at a temperature above the first magnetic field B. sat1 Under the action of the magnetic field, the magnetic permeability of the mainboard 500 is significantly reduced, reaching a value close to 1.

[0090] Finally, mode "C" corresponds to the saturation mode of the ferromagnetic core 200 and the main plate 500, which is caused by the current being higher than the second saturation current I sat2 The current flowing in the coil 300 is caused. In this mode, the induction L drops again to the value L3.

[0091] According to the present invention, the main board 500 is further provided with ferromagnetic lateral protrusions 600 .

[0092] "Protrusions" are to be understood as elements that protrude from the surface on which they are provided.

[0093] When the main board 500 is subjected to a magnetic field greater than its saturation magnetic field B sat1 The lateral protrusions 600 are particularly used to diffuse heat that may be generated in the main board 500 when a magnetic field passes through.

[0094] In particular, the lateral protrusion 600 extends from the lateral surface 501 of the main board 500 according to a direction substantially orthogonal to the lateral surface 501 ( Figure 1 and Figure 2 ).

[0095] The lateral protrusion 600 may have a rectangular, circular, square, or triangular cross-section.

[0096] The lateral protrusions 600 may be connected to the main board 500 in pairs, thereby forming a secondary board 700 ( Figure 2 ).

[0097] In a particularly advantageous manner, the secondary plate 700 is dimensioned so that the secondary plate 700 is not affected by the magnetic field flowing in the core when the magnetic field is lower than the second magnetic field B. sat2 Therefore, when the main board 500 is saturated, the secondary board 700 limits the magnetic flux from escaping around the air gap area. In other words, the secondary board 700 ensures the guidance of the magnetic flux in the air gap and in fact limits any lateral radiation of the magnetic field.

[0098] Furthermore, lateral protrusion may be limited to a volume V defined by the variable air gap.

[0099] Advantageously, the ferromagnetic core 200 , the first plate 500 and the lateral protrusions 600 are made of the same ferromagnetic material.

[0100] Still advantageously, the empty volume Vv of the volume V vacated by the first plate 500 and the protrusion 600 can be at least partially filled with the heat dissipation material 601 ( Figure 5 ) is filled, the heat dissipation material has a thermal conductivity higher than 10 W / m / K, and advantageously, the heat dissipation material includes aluminum oxide.

[0101] The presence of the heat dissipating material allows to assist the cooling of the lateral protrusions 600 by dissipating the heat generated in the air gap towards a heat sink.

[0102] According to the first embodiment of the electromagnetic induction device 100 , the ferromagnetic core 200 includes two planar ends 202 a and 202 b having a surface area S, the two planar ends being substantially parallel to and opposite to each other.

[0103] The end portions 200 a and 200 b define a variable air gap 400 , and the main plate 500 is disposed perpendicular to the variable air gap 400 .

[0104] The main board 500 has a cross-section with a cross-sectional surface area St, and the sum of the cross-sectional surface areas of all main boards 500 is less than the surface area S.

[0105] The ferromagnetic core may comprise a frame having a polygonal shape, even more advantageously a frame having a rectangular shape.

[0106] For example, Figure 5 As shown, the magnetic core 200 comprises five parallelepiped segments 201-205 made of ferromagnetic material, which are connected in pairs by their ends to form a rectangular frame. Two segments 204 and 205 form one side of the rectangular frame and are separated by an air gap 400 (spacing g) at their ends 200a and 200b.

[0107] The principle of determining the dimensions of the device according to the invention is based on the following formation of square side frames / and Figure 5 Nevertheless, this dimensioning principle is not limited to this configuration and can be easily adapted to other types of core geometries by a person skilled in the art.

[0108] In this example, the same main plate 500 connects the ends 200a and 200b with a spacing g. The small portion of the end surface area 200a and 200b covered by the cross section of the main plate is denoted as f.

[0109] The magnetic resistance R of the air gap structure of the main board made of ferromagnetic material with a magnetic permeability of s is e It is expressed as follows:

[0110]

[0111] Considering N pThe reluctance of the air gap structure is simply calculated by applying the reluctance network method to each of the components of the structure. The thickness of these plates is denoted as e p , which is smaller than the spacing g (e p <<g).

[0112] In addition, the secondary plate includes a magnetic permeability of μ p of ferromagnetic material and divides the air gap into several secondary air gaps placed in series.

[0113] Therefore, the reluctance R of each secondary air gap is es It is expressed as follows:

[0114]

[0115] The total reluctance of the air gap structure including the primary and secondary plates is N of the separated plates. p The sum of the secondary reluctances:

[0116]

[0117] These expressions can be derived Figure 5 The induction L(μ c , μ s ), which is expressed as follows: in

[0118] This expression for induction is the same as that obtained for a constant air gap, where the gap spacing g is given by F(μ s , f) weighted.

[0119] This term therefore allows adjusting the air gap distance that appears in the induction value without changing the geometry of the magnetic circuit. To do this, it is necessary to generate the permeability μ of the mainboard according to the variation of the applied current s changes.

[0120] According to the law of conservation of magnetic flux, a main plate with a relatively small cross-section compared to the surface area S is penetrated by a higher magnetic induction than the core. This consideration allows a saturation effect to be generated locally, in particular on the main plate 500 .

[0121] Magnetic induction B in the motherboard st Corresponding to the magnetic induction B in the ferromagnetic core c This magnification varies with the fraction of the surface area f and is given by the following relationship:

[0122]

[0123] As the current I flowing in the coil increases, the magnetic induction also increases. However, once the current I flowing in the coil reaches the saturation current I sat , the magnetic induction in the motherboard reaches the saturation value B sat , while the ferromagnetic core remains in linear mode.

[0124] In this regard, the value of the saturation current is given by the following relationship:

[0125]

[0126] For currents above saturation current l sat The current I, the magnetic permeability μ of the motherboard s To determine the magnitude of induction variation that can be achieved with current control, consider the case of low induction (I<<I sat ) under nominal operation (excluding saturation), and then at high induction (I>>I sat ) in which saturation occurs on the motherboard (μ s =1). The induction changes in these two extreme cases are given by the following equations:

[0127]

[0128] Figure 6a 、 Figure 6b and Figure 7 Another configuration of the ferromagnetic core is proposed in connection with the first embodiment of the electromagnetic induction device 100. In this alternative configuration, the ferromagnetic core comprises two core halves 2001 and 2002 of the ETD type (double E-shaped with a cylindrical central leg), which is well known to those skilled in the art.

[0129] Combine Figure 6a and Figure 6b The measurements of the ferromagnetic core halves are given and reported in the following table:

[0130] Measurements Dimensions (mm) A 59.8 B 21.65 D2 44.70 D3 21.65 E 31 F 22.5

[0131] Two identical half cores are mounted opposite each other with an air gap formed at the center post 207 ( Figure 7 ). In this example, the spacing g of the air gap is equal to 5 mm.

[0132] The air gap structure consists of five 0.41 mm thick primary boards (21.65 mm x 5 mm) and two 1 mm thick secondary boards (21.65 mm x 21.65 mm) evenly spaced.

[0133] The magnetic permeability of the ferromagnetic material is 1500 and the saturation induction is 430 mT. The central leg 207 is wound with 5 turns of wire.

[0134] Under these conditions, the saturation current is 6A, for voltages below I sat The induction current of the core is 16mH and drops to 3mH after saturation of the main plate. The heat exchange surface formed by the secondary plate allows improved cooling by natural air convection and limits heating in the structure to 100°C.

[0135] The remaining paragraphs of the description relate to the second embodiment of the electromagnetic induction device 100 .

[0136] In particular, the electromagnetic induction device 100 corresponding to this second embodiment can be implemented as a component of a power converter of the “Dual Active Bridge” (DAB) type and essentially embeds the aforementioned elements.

[0137] in this regard, Figure 8 and Figures 9 to 11 2 are schematic plan views of half cores 2003 and 2004 that can be implemented according to the first and second variations of this second embodiment, respectively.

[0138] According to this second embodiment, the ferromagnetic core 200 comprises an assembly of two half-cores 2003 and 2004 .

[0139] In this respect, the ferromagnetic core 200 comprises two bases 101 , each provided with two substantially parallel main surfaces, respectively referred to as an inner surface 101 a and an outer surface 101 b .

[0140] The pedestals face each other according to their inner surfaces 101 a and a variable air gap 400 is in one of the pedestals, more particularly in the volume thereof.

[0141] The core further comprises a plurality of legs which are substantially parallel to one another and which extend between the two inner surfaces 101 a.

[0142] The plurality of legs include at least one main leg 102 , at least one lateral leg 103 , and at least two leakage legs 104 and 105 .

[0143] The device further comprises at least one primary winding 301 and at least one secondary winding 302 .

[0144] Each of the primary winding 301 and the secondary winding 302 comprises a main section wound around the main leg 102 , and leakage sections referred to as a primary leakage section and a secondary leakage section, respectively, each wound on a different leakage leg 104 and 105 .

[0145] Advantageously, the variable air gap 400 is provided between the two leakage legs, and the main board is in the form of fins.

[0146] More advantageously, the fin is oriented according to a direction defined by an axis joining two leakage legs, the air gap being provided between the two leakage legs.

[0147] Furthermore, the recess may open to any one of the inner and outer surfaces of the base including the air gap.

[0148] in this regard, Figure 12 FIG. 4 is a schematic diagram of an air gap 400 opened at the outer surface 101 b of the base 101 in contact with a heat sink.

[0149] The ferromagnetic core may include a single main leg 102 and four leakage legs 104 and 105 .

[0150] In this respect, the main leakage section comprises two main leakage sections, such that the primary winding 301 comprises in sequence one of a main leakage section 301a, a main section 301b and a further main leakage section 301c, each of the main leakage sections being wound around a different leakage leg.

[0151] In an equivalent manner, the secondary leakage section comprises two secondary leakage sections, so that the secondary winding 302 comprises in sequence one of a secondary leakage section 302a, a main section 302b and a further secondary leakage section 302c, each of the secondary leakage sections being wound around a different leakage leg.

[0152] According to the first variant ( Figure 8 ), the at least one lateral support foot 103 includes four lateral support feet 103.

[0153] More particularly, the four lateral legs 103 and the four leakage legs 104, 105 describe a circle centered on the main leg 102, wherein the lateral legs and leakage legs alternate in a regular manner.Each primary leakage segment is also arranged radially opposite one of the secondary leakage segments relative to the main leg.

[0154] The device thus described comprises both the transformer functionality and the series inductor functionality.

[0155] The transformer function is ensured by the main sections 301 b and 302 b of the primary winding 301 and the secondary winding 302 , respectively, which are wound around the main legs.

[0156] The series induction generated at the primary winding and the secondary winding is ensured by the main leakage sections 301a and 301c and the secondary leakage sections 302a and 302c.

[0157] Thus, the magnetic flux called "transformer flux" generated at the main leg by the passage of current in the primary winding follows a circular path successively through the base, the lateral leg, the further base, and again through the main leg.

[0158] In an equivalent manner, the primary "leakage" flow follows a different profile that connects the two leakage legs of the primary circuit and passes through the thickness of the cylindrical base along a line connecting the bases of the two primary leakage legs. The secondary leakage flow follows a similar profile described by the two secondary leakage legs.

[0159] The implementation of a variable air gap between the two main leakage legs allows for imparting variable leakage sensor properties on the device.

[0160] In an equivalent manner, the implementation of a variable air gap between the two secondary leakage legs allows to impart variable leakage sensor properties on the device.

[0161] According to the second variant ( Figures 9 to 11 ), the ferromagnetic core includes two lateral legs 103 and four leakage legs 104 and 105.

[0162] The two leakage legs 104 and the two leakage legs 105 form two groups of two leakage legs, which are referred to as a first group 106 and a second group 107 , respectively.

[0163] Furthermore, the four leakage legs and the two lateral legs describe a circle centered on the main leg, and wherein the lateral legs and groups alternate in a regular manner.

[0164] Advantageously, the at least one air gap 400 comprises a first air gap 401 and a second air gap 402 disposed midway between the leakage legs of the first and second groups 106 , 107 , respectively.

[0165] In particular, each of the main leakage sections is formed around one leakage leg and the other leakage leg of the first group, respectively.

[0166] In an equivalent manner, each of the secondary leakage sections is formed around one leakage leg and the other leakage leg of the second set 107 , respectively.

[0167] According to this second variant, the proximity between the leakage legs of one and the same set of leakage legs allows for a more precise control of the leakage.

[0168] Magnetic flux barriers 800 may also be formed in the base 101 to limit the magnetic flux between the leakage leg and the lateral leg. In particular, these magnetic flux barriers 800 may include recessed areas between each of the elements of the first group 106 and the second group 107 and the lateral leg.

[0169] In particular, the recessed area may extend from the edge and according to the radius of the considered base.

[0170] Finally, regardless of the variant considered, the groove may be formed on any of the internal surfaces, at a distance from and surrounding each leakage leg, and interposed between the leakage leg and the main leg.

[0171] The process for manufacturing the core according to the invention may involve injection molding technology ("PIM" or "powder injection molding") This technology is particularly suitable for the large-scale production of parts with complex geometries.

[0172] Injection molding first performs the step of forming a raw material.

[0173] In particular, the raw materials include a mixture of organic materials (or polymer binders) and inorganic powders (metal or ceramic) used to form the final part.

[0174] The raw material is injected into an injection molding machine, the technology of which is known to those skilled in the art. The injection molding machine allows the polymer injected together with the powder to melt in the cavity and give the powder the desired shape.

[0175] The raw material formed and melted in this manner is subjected to cooling, whereby it solidifies and is fixed into the shape applied by the injection molding machine.

[0176] The part formed from the raw material is then demolded and debindered to remove the organic material.

[0177] Afterwards, the part can be consolidated by sintering.

[0178] References

[0179] [1] Jeong et al., “Analysis on Half-Bridge LLC Resonant Converter by Using Variable Inductance for High Efficiency and Power Density Server Power Supply,” 2017 IEEE Applied Power Electronics Conference and Exhibition (IEEE APEC), March 26-30, 2017.

[0180] [2] Saeed et al., “Extended Operational Range of Dual-Active-Bridge Converters by using Variable Magnetic Devices,” 2019 IEEE Applied Power Electronics Conference and Exhibition (IEEE APEC), March 17-21, 2019,

[0181] [3]US3603864,

[0182] [4] US5440225,

[0183] [5]US4728918,

[0184] [6] US2015 / 0109086,

[0185] [7]US2010 / 0085138.

Claims

1. An electromagnetic induction device (100), comprising: ferromagnetic core (200); at least one air gap, the air gap being referred to as a variable air gap (400), and defining a volume V in the ferromagnetic core, wherein a ferromagnetic main plate (500) is provided in the volume V, the ferromagnetic main plate (500) being arranged in parallel and along a direction parallel to a field line capable of flowing in the ferromagnetic core, the ferromagnetic main plate (500) having a cross-section configured so that all the ferromagnetic main plates have a saturation magnetic field lower than the saturation magnetic field of the ferromagnetic core (200), the ferromagnetic main plate (500) being further provided with a lateral protrusion (600) for diffusing heat that can be generated in the ferromagnetic main plate (500) when the ferromagnetic main plate (500) is passed through by a magnetic field higher than its saturation magnetic field, the lateral protrusion (600) extending from a lateral surface (501) of the ferromagnetic main plate in a direction orthogonal to the lateral surface (501); The ferromagnetic core (200) comprises two bases (101), each base being provided with two parallel main surfaces, respectively referred to as an inner surface (101a) and an outer surface (101b), the bases (101) facing each other according to their inner surfaces (101a), the variable air gap (400) being formed in one of the bases, the ferromagnetic core (200) further comprising a plurality of legs, the plurality of legs being parallel to each other and extending between the two inner surfaces, the plurality of legs comprising at least one main leg (102), at least one lateral leg (103) and at least two leakage legs (104, 105); The device further comprises at least one primary winding (301) and at least one secondary winding (302), each winding comprising a main section (301b, 302b) wound around the main leg (102), and leakage sections respectively referred to as primary leakage sections (301a, 301c) and secondary leakage sections (302a, 302c), each leakage section being wound around a different leakage leg.

2. The device according to claim 1, wherein the lateral protrusions (600) connect the ferromagnetic main plates (500) in pairs, thereby forming secondary plates (700) perpendicular to the ferromagnetic main plates (500).

3. The device according to claim 1, wherein the ferromagnetic core (200), the ferromagnetic main plate (500) and the lateral protrusions are made of the same ferromagnetic material.

4. The device according to claim 1, wherein all ferromagnetic main plates (500) are identical.

5. The device according to claim 1, wherein the empty volume V having the volume V left by the ferromagnetic main plate (500) and the lateral protrusions is v At least partially filled with a heat absorbing material having a thermal conductivity higher than 10 W / m / K, the heat absorbing material comprising aluminum oxide.

6. The device according to claim 1, wherein the ferromagnetic core (200) comprises a ferromagnetic material selected from the following: a metal alloy of the FeX type, wherein X comprises one of the elements selected from Si, Al, Co, Ni, a ferrite oxide having an A(Fe,B)2O4 type spinel structure, wherein A=(Mn,Ni), B=(Co,Cu,Al).

7. The device according to claim 1, wherein the ferromagnetic core (200) includes two planar ends (200a, 200b), the two planar ends are parallel to each other, face each other and have a surface area S, the two planar ends define the variable air gap (400), the ferromagnetic main plate (500) is arranged perpendicular to the planar ends, and the ferromagnetic core (200) includes a frame having a polygonal shape.

8. The device according to claim 7, wherein the ferromagnetic main plate (500) has a cross-sectional surface area of ​​S t The sum of the cross-sectional surface areas of all ferromagnetic main boards (500) is smaller than the surface area S.

9. The device according to claim 1, wherein the variable air gap (400) is provided between two of the leakage legs, and the ferromagnetic main plate is in the form of a fin.

10. The device of claim 9, wherein the fin is oriented according to a direction defined by an axis joining the two leakage legs, the air gap being provided between the two leakage legs.

11. The device according to claim 1, wherein the recess opens onto the inner surface (101a) of the base under consideration, and wherein the air gap is formed by the recess in the ferromagnetic core.

12. The device according to claim 1, wherein the recess opens onto the outer surface (101b) of the base in question, and wherein an air gap is formed by the recess in the ferromagnetic core.

13. The device according to claim 1, wherein the at least one main leg (102) comprises a single main leg (102), the at least two leakage legs comprise four leakage legs, wherein the main leakage section comprises two main leakage sections, so that the primary winding comprises, in sequence, the main leakage section (301a), the main section (301b) and one of the further main leakage sections (301c), each of the main leakage sections being wound around a different leakage leg, and wherein the secondary leakage section comprises two secondary leakage sections, so that the secondary winding comprises, in sequence, the secondary leakage section (302a), the main section (302b) and one of the further secondary leakage sections (302c), each of the secondary leakage sections being wound around a different leakage leg.

14. A device according to claim 13, wherein the at least one lateral leg comprises four lateral legs, the four lateral legs and the four leakage legs describing a circle centered on the main leg (102), and wherein the lateral legs and the leakage legs alternate in a regular manner, each segment being arranged radially opposite to a second leakage segment relative to the main leg (102).

15. The device according to claim 13, wherein the at least one lateral leg comprises two lateral legs, the at least two leakage legs comprise four leakage legs, forming two groups of two leakage legs, the two groups being respectively referred to as a first group (106) and a second group (107), the four leakage legs and the two lateral legs describing a circle centered on the main leg (102), and wherein the lateral legs and the first and second groups (106, 107) alternate in a regular manner.

16. The apparatus of claim 15, wherein the at least one air gap comprises a first air gap (401) and a second air gap (402) disposed midway between the leakage legs of the first group (106) and the second group (107), respectively.

17. The device according to claim 16, wherein each of the primary leakage sections is formed around any one of the leakage legs (104) of the first group (106), and each of the secondary leakage sections is formed around any one of the leakage legs (105) of the second group (107).

18. The apparatus of claim 7, wherein the ferromagnetic core (200) comprises a frame having a rectangular shape.

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