Electromagnetic induction device

Abstract

The present invention relates to an electromagnetic induction device with a variable air gap provided with heat dissipation means. Specifically, the device according to the present invention includes a core housing the variable air gap. The air gap further includes a first ferromagnetic plate for guiding magnetic flux that may be generated in the core. The magnetic flux may collectively have a saturation magnetic field that is smaller than the saturation magnetic field of the core. The variable air gap according to the present invention further includes lateral protrusions forming the heat dissipation means, the lateral protrusions extending from the side surfaces of the first plate.

Description

[Technical field]

[0001] The present invention relates to the field of electronics and electricity, in particular to a magnetic inductor having a variable inductance with reduced magnetic and thermal losses compared to devices known in the prior art.

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

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

[0004] Generally, a magnetic inductor includes a core made of a ferromagnetic material and a winding formed around a portion of the core. The core may also include an air gap. The device is characterized by a characteristic quantity called the magnetizing inductance L, which depends on the ferromagnetic material, the geometry of the core (and its air gap), and the winding (especially the number of turns forming the winding).

[0005] Some applications, especially electronic converters, may require a high magnetizing inductance value L for nominal operation and a low magnetizing inductance for some operating points.

[0006] This is especially the case for the so-called LLC resonant converter topology.

[0007] In fact, the magnetizing inductance of the transformer of an LLC converter should be high at the nominal operating voltage to limit switching losses and ensure good efficiency, but can be significantly reduced to ensure continuity of power supplied to the load when the input voltage drops (see the case of a server power supply system that must guarantee data backup in the event of a power outage, as described in non-patent document 1 at the end of this specification).

[0008] This issue can lead to sizing this type of converter with a low inductance value to ensure backup functionality, which can result in a loss of efficiency.

[0009] In the case of a DAB converter topology, the so-called "series" inductance value, placed in series with the magnetizing inductance of the transformer, determines the operating range of the converter.

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

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

[0012] In both cases, a single series inductance value proves to limit the operating range and to be less flexible for driving DAB converters. This is described in Non-Patent Document 2 at the end of this specification. To overcome these problems, it may be considered to implement a magnetic inductor with a variable series or magnetizing inductance L depending on the magnetic flux (and therefore depending on the current I flowing in the winding). More specifically, a magnetic inductor with a high magnetizing L or series inductance at low currents I and a low inductance at high currents I would be required.

[0013] However, magnetic inductors generally have a saturation current I, which is the current I that flows through the windings and does not saturate the ferromagnetic core. sat It is sized to operate at a lower range than

[0014] In this region, the current I is equal to the saturation current I sat The magnetizing inductance L remains independent of the current I as long as it is smaller than the saturation current value I satAs soon as this is exceeded, magnetic saturation of the core occurs, which causes the magnetic permeability and, therefore, the magnetizing inductance L to decrease rapidly.

[0015] Therefore, if a variation of the magnetizing inductance L is required during the operation of the magnetic inductor, different solutions can be considered. Generally, these solutions propose to extend the operating range of the magnetic inductor to nonlinear modes prior to full saturation of the ferromagnetic material. For this, a lower magnetic permeability and / or a reduction in the size of the air gap can be considered.

[0016] By implementing either of these two solutions, the saturation current I sat Saturation occurs uniformly throughout the core for values ​​of current I higher than

[0017] However, these solutions are not satisfactory.

[0018] Indeed, the passage of a high frequency current I (typically higher than 10 kHz) through an inductor can saturate the entire core, causing significant volumetric magnetic losses in the inductor and in the entire component in which it is incorporated.

[0019] These losses can also result in heating of the core.

[0020] Furthermore, in saturation mode, the magnetic flux lines that are no longer confined to the core can disturb components located near the magnetic inductor: in particular, these disturbances can cause electromagnetic incompatibility and / or losses due to eddy currents.

[0021] It has therefore been proposed in Patent Documents 1 to 5 listed at the end of the specification that by a method of sizing the core, and in particular the air gap, it is possible to position the saturation of the core within said air gap.

[0022] However, this proposed sizing method is not satisfactory.

[0023] In fact, even if the core saturation remains near the air gap, the air gap can cause magnetic losses and overheating, disrupting the operation of the entire component.

[0024] Furthermore, these magnetic losses and heat generation limit the implementation of such magnetic inductors to high frequency currents I, specifically currents I that can reach 500 kHz. [Prior art documents] [Patent documents]

[0025] [Patent Document 1] U.S. Pat. No. 3,603,864 [Patent Document 2] U.S. Pat. No. 5,440,225 [Patent Document 3] U.S. Pat. No. 4,728,918 [Patent Document 4] US Patent Application Publication No. 2015 / 0109086 [Patent Document 5] US Patent Application Publication No. 2010 / 0085138 [Non-patent literature]

[0026] [Non-Patent Document 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 Exposition, March 26th-30th, 2017 [Non-Patent Document 2] Saeed et al., “Extended Operational Range of Dual-Active-Bridge Converters by using Variable Magnetic Devices”, 2019 IEEE Applied Power Electronics Conference and Exposition, March 17th-21th, 2019 Summary of the Invention [Problem to be solved by the invention]

[0027] It is therefore an object of the present invention to provide an electromagnetic induction device with a variable magnetizing inductance L in which magnetic losses and heating are reduced compared to devices known from the prior art.

[0028] Another object of the invention is to provide an electromagnetic induction device which can operate at higher frequencies than devices known from the prior art. [Means for solving the problem]

[0029] The object of the invention is at least partially achieved by an electromagnetic induction device comprising a ferromagnetic core and at least one air gap, referred to as a variable air gap, defining a volume V in the core, in which ferromagnetic main plates are arranged, the ferromagnetic main plates being arranged substantially parallel to each other and in a direction parallel to the magnetic field lines that may flow in the core. The main plates have a cross section configured such that all of the plates have a saturation field lower than the saturation field of the ferromagnetic core. The main plates are also provided with lateral projections for dissipating heat that may be generated in the main plates when the main plates are traversed by a magnetic field higher than the saturation field of the main plates. The lateral projections extend from the sides of the plates along a direction substantially perpendicular to the sides.

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

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

[0032] According to one embodiment, all the main plates are identical.

[0033] According to one embodiment, the volume V vacated by the main plate and the lateral protrusions is the free volume V v is at least partially filled with a heat sink material having a thermal conductivity greater than 10 W / m / K. Preferably, the heat sink material comprises alumina.

[0034] According to one embodiment, the ferromagnetic core comprises at least one ferromagnetic material selected from among a metal alloy of the FeX type (X comprises one of the elements selected from Si, Al, Co, Ni), a ferrite oxide with spinel structure of the A(Fe,B)2O4 type (A=(Mn,Ni), B=(Co,Cu,Al,...).

[0035] According to one embodiment, the ferromagnetic core comprises two essentially parallel flat ends, facing each other and having a surface area S. The two ends define the variable air gap and the main plate is arranged perpendicular to the ends. The ferromagnetic core has an advantageously polygonal, and more advantageously rectangular, frame.

[0036] According to one embodiment, the main plate has a cross-sectional surface area S t and the sum of the cross-sectional surface areas of all the main plates is less than said surface area S.

[0037] According to one embodiment, the ferromagnetic core includes two bases, each of which is provided with two main surfaces, referred to as an inner surface and an outer surface, respectively. The inner and outer surfaces are substantially parallel, the bases face each other along the inner surface of the bases, and the variable air gap is formed in one of the bases. The core further includes a number of legs essentially parallel to each other and extending between the two inner surfaces, the number of legs including at least one main leg, at least one side leg, and at least two leakage legs. The device further includes at least one primary winding and at least one secondary winding, each of the primary winding and secondary winding including a main section and a leakage section wound around the main leg. The leakage sections are referred to as a primary leakage section and a secondary leakage section, respectively, each wound around a different leakage leg.

[0038] According to one embodiment, the variable air gap is located between the two leakage legs and the primary plate is in the form of a fin.

[0039] According to one embodiment, the fins are oriented along a direction defined by an axis joining two leakage legs between which the air gap is located.

[0040] According to one embodiment, the recess opens onto the inner surface of the considered base.

[0041] According to one embodiment, said recess opens onto an outer face of said considered base.

[0042] According to one embodiment, the at least one main leg includes a single main leg; the at least two leakage legs include four leakage legs, and the primary leakage section includes two primary leakage sections, such that the primary winding includes one of the primary leakage section, the main section, and the other primary leakage section in sequence, each of the primary leakage sections being wound on a different leakage leg; and the secondary leakage section includes two secondary leakage sections, such that the secondary winding includes one of the secondary leakage section, the main section, and the other secondary leakage section in sequence, each of the secondary leakage sections being wound on a different leakage leg.

[0043] According to one embodiment, the at least one side leg includes four side legs, the four side legs and the four leakage legs form a circle around the main leg, the side legs and the leakage legs are regularly alternatingly arranged, and each section is arranged diametrically opposite a secondary leakage section with respect to the main leg.

[0044] According to one embodiment, the at least one side leg includes two side legs and the at least two leakage legs include four leakage legs forming two groups of two leakage legs, which are called a first group and a second group, respectively, and the four leakage legs and the two side legs describe a circle centered on the main leg, and the side legs and the groups are regularly alternated.

[0045] According to one embodiment, the at least one air gap includes a first air gap and a second air gap disposed midway between the leakage legs of the first and second groups, respectively.

[0046] According to one embodiment, each of the primary leakage sections is formed around one of the leakage legs of the first group, and each of the secondary leakage sections is formed around one of the leakage legs of the second group.

[0047] According to one embodiment, a groove may be formed on either one of said inner surfaces around each leakage leg at a predetermined distance from each leakage leg, said groove being interposed between the leakage leg and the main leg.

[0048] Further characteristics and advantages are set out in the following description of an electromagnetic induction device according to the invention, given by way of non-limiting example with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0049] [Figure 1] FIG. 1 is a schematic perspective view of a variable air gap according to the present invention; [Diagram 2] FIG. 2 is a schematic perspective view of another configuration of a variable air gap according to the present invention; [Diagram 3] FIG. 2 illustrates a ferromagnetic core that may be implemented in accordance with the present invention. [Figure 4] 1 is a graph showing the change in inductance 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. [Diagram 5] 1 is a schematic perspective view of an electromagnetic induction device according to a first embodiment of the present invention. [Figure 6a] 1 is a schematic side view of a half core that may be implemented in accordance with the present invention; [Figure 6b] FIG. 2 is a schematic top view of a half core that may be implemented in accordance with the present invention. [Figure 7] FIG. 6B is a schematic diagram of an electromagnetic induction device according to a first embodiment of the present invention, in which two half-cores as shown in FIG. 6a and FIG. 6b are implemented; [Figure 8] 10 is a schematic diagram of an electromagnetic induction device according to a first modification of the second embodiment of the present invention. FIG. [Figure 9] FIG. 11 is a schematic cross-sectional view taken along an inner surface of a half core according to a second modification of the second embodiment of the present invention. [Figure 10] FIG. 11 is a schematic perspective view of a half core according to a second modified example of the second embodiment of the present invention. [Figure 11]FIG. 11 is a diagram showing a cross section along an inner surface of a half core provided with a winding according to a second modified example of the second embodiment of the present invention. [Figure 12] FIG. 1 is a schematic diagram of an air gap opening to an outer surface of a base in contact with a cold source. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] The present invention relates to an electromagnetic induction device with a variable air gap provided with heat dissipation means.

[0051] In particular, the device according to the invention comprises a core in which a variable air gap is housed, said air gap further comprising a first ferromagnetic plate for conducting a magnetic flux that may occur in the core, the first ferromagnetic plate being intended to operate in a saturation mode for magnetic flux values ​​lower than that required for saturation of the core, the magnetic flux being conservative throughout the magnetic circuit.

[0052] The variable air gap according to the provisions of the invention further comprises lateral protrusions forming heat dissipation means, the lateral protrusions extending from the sides of the first plate.

[0053] More specifically, the present invention relates to an electromagnetic induction device 100 (FIGS. 1 to 3).

[0054] The electromagnetic induction device 100 may be a magnetic inductor having an inductance L and is integrated into an AC / DC or DC / DC power transformer, in particular a DAB converter.

[0055] The electromagnetic induction device 100 includes a ferromagnetic core 200 (shown in FIGS. 1, 2 and 3).

[0056] The ferromagnetic core 200 includes at least one ferromagnetic material selected from a metal alloy of the FeX type (X includes one of the elements selected from Si, Al, Co, and Ni), a ferrite oxide of the A(Fe,B)2O4 type with a spinel structure (A=(Mn,Ni), B=(Co,Cu,Al,...).

[0057] The ferromagnetic core 200 can be traversed by magnetic field lines induced by a current I flowing in at least one conductive coil 300 (or winding). The coil 300 is formed around a portion of the ferromagnetic core 200 and extends according to a main axis XX'.

[0058] "Main axis" will be understood to mean the axis of symmetry of the conductive coil.

[0059] Specifically, the conductive coil 300 is made by winding a conductive wire, such as a copper wire, around a portion of the ferromagnetic core 200 .

[0060] The ferromagnetic core 200 also includes an air gap, more specifically a variable air gap 400 (FIGS. 1 and 2).

[0061] Specifically, the air gap 400 is formed by a recess or lack of material in the ferromagnetic core 400 .

[0062] The depressions or missing material disrupt the continuity of the ferromagnetic material that forms the ferromagnetic core 400 .

[0063] The variable air gap 400 defines a volume V within the ferromagnetic core 200 that corresponds to the volume of material that has been removed or is missing.

[0064] A main plate 500 made from a ferromagnetic material is disposed within the volume V defined by the variable air gap 400 .

[0065] By "plate" it is understood that an element is of generally flat and thin shape. In particular, the plate comprises two sides 501 that are essentially parallel to each other and connected by a contour.

[0066] Furthermore, the main plates 500 are essentially parallel to one another and are arranged according to a direction parallel to the magnetic field lines that may enter the ferromagnetic core 200 .

[0067] According to the invention, the orientation of a plate, in particular the main plate, is defined by the orientation of its side surface 501. In other words, the magnetic field lines are parallel to the direction of the plane formed by the sides of the main plate 500.

[0068] The main plate 500 has a surface area S t and has a cross section with a surface area S t The entire main plate 500 is in the saturation magnetic field B sat1 (1st magnetic field B sat1 ) is adapted to have a first magnetic field B sat1 is the saturation magnetic field of the ferromagnetic core 200 (second magnetic field B sat2 This is lower than the 100% saturation temperature (hereinafter referred to as the 100% saturation temperature

[0069] "Cross-section" will be understood to mean a cross-section along a cross-sectional plane perpendicular to the magnetic field lines intersecting the main plate.

[0070] The amplitude of the magnetic field B across the ferromagnetic core 200 depends on the current I flowing through the coil 300. In particular, the first magnetic field B sat1 and second magnetic field B sat2 and the current I flowing through the coil 300 is the first saturation current I sat1 and the second saturation current I sat2 This is reached when it is equal to

[0071] Therefore, the behavior of the electromagnetic induction device 100 , and more specifically, its magnetizing inductance L, depends on the current I flowing through the coil 300 .

[0072] In this regard, FIG. 4 is a graphical representation of different operating modes of electromagnetic induction devices 100, all of which have identical main plates 500.

[0073] "Identical main plates" is understood to mean plates of the same shape, same size and same material.

[0074] Such a device 100 has three operating modes or levels "A", "B" and "C" related to the current I flowing through the coil 300, each of which has a first saturation current I sat1 A level smaller than the first saturation current I sat1 and the second saturation current I sat2 and the second saturation current I sat2 It is a level greater than that.

[0075] 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 permeability of the ferromagnetic core 200 and the main plate 500 is almost independent or independent of the magnetic field flowing in the core, and therefore the induction L is also essentially constant and equal to the first induction L1.

[0076] Mode "B" is characterized by the inductance L decreasing to a second induction L2.

[0077] In particular, this drop is due to the saturation of the main plate 500 and the first magnetic field B sat1 Under the influence of a magnetic field higher than 1000 nm, its permeability decreases significantly, reaching a value close to 1.

[0078] Finally, in mode “C”, the second saturation current I sat2 This corresponds to a saturation mode of the ferromagnetic core 200 and the main plate 500 caused by a current higher than 0.1 V. In this mode the inductance L drops again to a value L3.

[0079] According to the invention, the main plate 500 is also provided with ferromagnetic lateral protrusions 600 .

[0080] A "protrusion" will be understood to mean a member that protrudes from the surface on which it is disposed.

[0081] The lateral protrusions 600 are specifically designed to prevent the main plate 500 from being pulled out of its saturation magnetic field B sat1The purpose of this is to dissipate the heat that tends to be generated within the main plate 500 when it is traversed by a magnetic field larger than

[0082] In particular, a lateral protrusion 600 extends from a side surface 501 of the main plate 500 along a direction essentially perpendicular to said side surface 501 (FIGS. 1 and 2).

[0083] The lateral protrusion 600 may have a rectangular, circular, square or triangular cross-section.

[0084] The lateral projections 600 may connect the main plates 500 in pairs to form secondary plates 700 perpendicular to the main plates 500 (FIG. 2).

[0085] In a particularly advantageous manner, the secondary plate 700 is arranged so that the magnetic field flowing in the core is a second magnetic field B sat2 4. The secondary plate 700 is dimensioned such that it does not saturate when the main plate 500 is saturated below 4. Thus, when the main plate 500 saturates, the secondary plate 700 limits the overflow of the magnetic flux around the air gap area. In other words, the secondary plate 700 ensures the guidance of the magnetic flux in the air gap, in effect limiting the lateral radiation of the magnetic field.

[0086] Furthermore, the lateral protrusion may be restricted to a volume V defined by the variable air gap.

[0087] Advantageously, the ferromagnetic core 200, the first plate 500 and the lateral projection 600 are made from the same ferromagnetic material.

[0088] More advantageously, the volume V vacated by the first plate 500 and the protrusion 600 is the free volume V v may be at least partially filled with a heat interface material 601 (FIG. 5) having a thermal conductivity higher than 10 W / m / K. Advantageously, the heat interface material comprises alumina.

[0089] The presence of heat dissipation material can aid in the cooling provided by lateral protrusions 600 by conducting heat generated in the air gap towards a heat sink.

[0090] According to a first embodiment of the electromagnetic induction device 100, the ferromagnetic core 200 includes two flat ends 200a, 202b having a surface area S, which are essentially parallel to each other and facing each other.

[0091] The ends 200a, 202b define a variable air gap 400, and the main plate 500 is disposed perpendicular to the ends 200a, 202b.

[0092] The main plate 500 has a cross-sectional surface area S t and the sum of the cross-sectional surface areas of all the main plates is less than the surface area S.

[0093] The ferromagnetic core may comprise a polygonal, and more advantageously rectangular, frame.

[0094] 5, the magnetic core 200 includes five parallelepiped sections 201-205 made of ferromagnetic material, joined in pairs at their ends to form a rectangular frame. Two sections 204 and 205 form one side of the rectangular frame and are separated by an air gap 400 (having a distance g) at their ends 200a and 200b.

[0095] The sizing principle of the device according to the invention is presented below based on a core forming a square side frame and shown in Figure 5. However, this sizing principle is not limited to this configuration and can be easily adapted by a person skilled in the art to other types of core geometries.

[0096] In this example, an identical primary plate 500 connects ends 200a and 200b with a gap g between them. The percentage of end surface area 200a and 200b that is covered by a portion of the primary plate is indicated by the symbol f.

[0097] And the magnetic permeability μ s The reluctance R of an air gap structure with only a primary plate made of ferromagnetic material is e is expressed as follows:

number

[0098] N p As long as the secondary plates are taken into account, the reluctance of an air gap structure is easily calculated by applying the reluctance network method to each of the components of the structure. The thickness of these plates is denoted by the symbol e p and is small compared to the interval g (ep< <g)。

[0099] In addition, the secondary plate has a magnetic permeability μ p of ferromagnetic material and divides the air gap into a number of secondary air gaps arranged in series.

[0100] Therefore, the reluctance R of each secondary air gap es is expressed as follows:

number

[0101] The total reluctance of the air gap structure, including the primary and secondary plates, is the N p is the sum of the secondary reluctances, i.e.

number

[0102] From these equations, the inductance L(μ c ,μ s ), which can be expressed as follows:

number

[0103] The formula for this inductance is given by the term F(μ s ,f) is identical to the formula obtained for a constant air gap.

[0104] This term therefore allows the change of the air gap distance appearing in the inductance value without changing the geometry of the magnetic circuit. To do this, the permeability μ s It is necessary to vary the current as a function of the applied current.

[0105] A primary plate having a cross section with a relatively small surface area compared to the surface area S is traversed by a higher magnetic induction than the magnetic induction across the core, according to the law of conservation of magnetic flux. Such considerations can cause saturation effects locally, particularly in the primary plate 500.

[0106] Magnetic induction in the primary plate B st is the magnetic induction B in the ferromagnetic core c This amplification is a function of the surface area fraction f and is given by the following relation:

number

[0107] When the current I flowing through the coil increases, the magnetic induction also increases. However, when the current I flowing through the coil exceeds the saturation current I sat As soon as it reaches the saturation value B sat while the ferromagnetic core remains in the linear mode.

[0108] In this regard, the value of the saturation current is given by the following relationship:

number

[0109] Saturation current I satFor currents higher than s is equal to 1. In order to obtain the amplitude of the inductance fluctuation that can be obtained by current control, a low inductance (I< sat ), followed by high induction (I>>I) where saturation occurs in the primary plate. sat ) operation (μ s = 1) is considered. The variation in inductance between these two extreme cases is given by

number

[0110] Figures 6a, 6b and 7 show another configuration of the ferromagnetic core associated with the first embodiment of the electromagnetic induction device 100. In this alternative configuration, the ferromagnetic core includes two half-cores 2001 and 2002, which are of the ETD type (double E with a cylindrical central leg) cores known to those skilled in the art.

[0111] The measurement results for the ferromagnetic half-cores were obtained with reference to Figures 6a and 6b and are reported in the following table. [Table 1]

[0112] Two identical half-cores are mounted opposite each other with an air gap formed at the central post 207 (Figure 7), in this example the air gap spacing g is equal to 5 mm.

[0113] The air gap structure includes five equally spaced primary plates (21.65 mm x 5 mm) of 0.41 mm thickness and two secondary plates (21.65 mm x 21.65 mm) of 1 mm thickness.

[0114] The ferromagnetic material has a permeability of 1500 and a saturation induction of 430 mT. The central post 207 is wound with five turns of conductive wire.

[0115] ​Under these conditions, the saturation current is 6A. sat For currents below 1000 Hz, the inductance of the core is 16 mH, decreasing to 3 mH after saturation of the primary plate. The heat exchange surface provided by the secondary plate improves the cooling by natural convection, making it possible to limit the heating inside the structure to 100 °C.

[0116] The following description relates to a second embodiment of the electromagnetic induction device 100.

[0117] In particular, the electromagnetic induction device 100 corresponding to this second embodiment can be implemented as a component of a “dual active bridge” (DAB) type power converter, essentially incorporating the elements described above.

[0118] In this regard, FIGS. 8 and 9-11 are schematic plan views of half-cores 2003 and 2004 that may be implemented according to first and second variants, respectively, of this second embodiment.

[0119] According to this second embodiment, the ferromagnetic core 200 comprises an assembly of two half-cores 2003 and 2004 .

[0120] In this regard, the ferromagnetic core 200 includes two bases 101, each of which is provided with two major surfaces, referred to as inner surface 101a and outer surface 101b, respectively, which are essentially parallel.

[0121] The bases face each other along their inner surfaces 101a, and a variable air gap 400 is located in one of the bases, and more particularly within its volume.

[0122] The core further includes a number of legs, which are essentially parallel to one another and extend between the two inner surfaces 101a.

[0123] The multiple legs include at least one main leg 102 , at least one side leg 103 , and at least two leakage legs 104 and 105 .

[0124] The device further includes at least one primary winding 301 and at least one secondary winding 302 .

[0125] Each of the primary winding 301 and the secondary winding 302 includes a main section wound around the main leg 102 and a leakage section, referred to as the primary leakage section and the secondary leakage section, respectively, each wound around a different leakage leg 104 and 105.

[0126] Advantageously, the variable air gap 400 is located between the two leakage legs and the primary plate is in the form of a fin.

[0127] More advantageously, the fins are oriented according to a direction defined by an axis joining the two leakage legs between which an air gap is located.

[0128] Additionally, the recess may connect to either the inner or outer surface of the base that includes the air gap.

[0129] In this regard, FIG. 12 shows a schematic diagram of an air gap 400 opening to the outer surface 101b of the base 101 in contact with a cold source.

[0130] The ferromagnetic core may include one main leg 102 and a total of four leakage legs 104 and 105 .

[0131] In this regard, the primary leakage section includes two primary leakage sections such that the primary winding 301 includes, in order, a primary leakage section 301a, a main section 301b, and one of the other primary leakage sections 301c, each of which is wound around a different leakage leg.

[0132] Similarly, the secondary leakage section includes two secondary leakage sections such that the secondary winding 302 includes, in order, one of the secondary leakage section 302a, the main section 302b, and the other secondary leakage section 302c, each of which is wound around a different leakage leg.

[0133] According to a first variant (FIG. 8), the at least one lateral leg 103 comprises four lateral legs 103 .

[0134] More specifically, the four side legs 103 and the four leakage legs 104, 105 are arranged in a regular alternating pattern in a circle centered on the main leg 102. Each primary leakage section is further arranged diametrically opposite one of the secondary leakage sections with respect to the main leg.

[0135] The device described thus far includes a transformer function and a series inductor function.

[0136] The transformer function is ensured by the main sections 301b, 302b of the primary winding 301 and secondary winding 302 respectively, which surround the main legs.

[0137] The series inductance occurring in the primary and secondary windings is compensated for by the primary leakage sections 301a and 301c and the secondary leakage sections 302a and 302c.

[0138] Thus, the magnetic flux, called "transformer flux", generated in the main leg by passing a current through the primary winding follows a looped path that passes successively through the base, the side leg, the other base, and then back across the main leg.

[0139] Similarly, the primary "leakage" flow follows another contour connecting the two leakage legs of the primary circuit, which crosses the cylindrical base through its thickness along a line connecting the bases of the two primary leakage legs. The secondary leakage flow follows a similar contour described by the two secondary leakage legs.

[0140] By varying the air gap between the two leakage legs, the device is endowed with the properties of a variable leakage inductor.

[0141] Similarly, a variable air gap can be provided between the two secondary leakage legs, giving the device the properties of a variable leakage inductor.

[0142] According to a second variant (FIGS. 9 to 11), the ferromagnetic core comprises two side legs 103 and four leakage legs 104 and 105.

[0143] The two leakage legs 104 and the two leakage legs 105 form two groups of two leakage legs, referred to as a first group 106 and a second group 107, respectively.

[0144] Furthermore, the four leakage legs and two side legs form a circle around the main leg, with the side legs and the groups being regularly alternatingly arranged therein.

[0145] Advantageously, the at least one air gap 400 includes 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.

[0146] In particular, each of the primary leakage sections is formed around one and the other leakage leg of the first group, respectively.

[0147] Similarly, each of the secondary leakage sections is formed around one of the leakage legs and the other of the leakage legs of the second group 107, respectively.

[0148] According to this second variant, the leakage legs of the same group are close to each other, which allows for more precise control of leakage.

[0149] Flux barriers 800 may also be formed in the base 101 to restrict magnetic flux between the leakage leg and the side leg. In particular, these flux barriers 800 may include recessed regions between each of the elements of the first group 106 and each of the elements of the second group 107 and the side leg.

[0150] In particular, the recessed region may extend from the edge along a radius of the considered base.

[0151] Finally, regardless of the variant considered, a groove may be formed on either of the inner surfaces around each leakage leg at a predetermined distance from the leakage leg, the groove being interposed between the leakage leg and the main leg.

[0152] The manufacturing process of the core according to the invention may involve the injection molding technique ("PIM" or "Powder Injection Molding"), which is particularly well suited for the mass production of parts with complex shapes.

[0153] In injection molding, the first step is to mold the raw material.

[0154] In particular, the feedstock comprises a mixture of organic materials (or polymeric binders) and inorganic powders (metal or ceramic) to form the final part.

[0155] The raw materials are injected into an injection molding machine, the technology of which is known to those skilled in the art, which makes it possible to melt the polymer injected together with the powder in a cavity and give said powder the desired shape.

[0156] The thus shaped and molten material is then cooled and solidified, setting into the shape imparted by the injection molding machine.

[0157] Parts formed from the raw materials are then demolded and debound to remove organic matter.

[0158] The part may then be consolidated by sintering. [Explanation of symbols]

[0159] 100: Electromagnetic induction device 102: Main landing gear 103: Side legs 104: Leaky leg 105: Leaky leg 200: Ferromagnetic core 300: Coil 301a: Primary Leakage Section 301b: Main section 301c: Primary Leakage Section 302a: Secondary leakage section 302b: Main section 302c: Secondary leakage section 400: Variable air gap 500: Ferromagnetic main plate 501: Side 600: Lateral protrusion 700: Secondary plate 800: Flux Barrier

Claims

1. A ferromagnetic core (200); At least one air gap, called the variable air gap (400), An electromagnetic induction device (100) comprising: the air gap defines a volume V within the core; A plurality of ferromagnetic main plates (500) are disposed within the volume V; The plurality of ferromagnetic main plates (500) are arranged substantially parallel to each other and parallel to magnetic field lines that may flow within the core; the plurality of ferromagnetic main plates (500) have cross sections configured such that all of the plurality of ferromagnetic main plates (500) have a saturation magnetic field lower than the saturation magnetic field of the ferromagnetic core (200); The plurality of ferromagnetic main plates (500) further comprises a plurality of lateral protrusions (600); the lateral protrusions (600) are configured to dissipate heat that may be generated within the ferromagnetic main plates (500) when the ferromagnetic main plates (500) are traversed by a magnetic field higher than the saturation magnetic field of the ferromagnetic main plates; The plurality of lateral protrusions (600) extend from the side surfaces (501) of the plurality of ferromagnetic main plates (500) along a direction substantially perpendicular to the side surfaces (501). Electromagnetic induction device (100).

2. 2. The apparatus of claim 1, wherein the lateral protrusions (600) connect the ferromagnetic main plates (500) in pairs to form secondary plates (700) perpendicular to the ferromagnetic main plates (500).

3. the ferromagnetic core (200), the plurality of ferromagnetic main plates (500) and the plurality of lateral protrusions are made of the same ferromagnetic material; 3. Apparatus according to claim 1 or 2.

4. All ferromagnetic main plates (500) are identical.

4. Apparatus according to any one of claims 1 to 3.

5. A vacant volume V, which is a volume V vacated by the plurality of ferromagnetic main plates (500) and the plurality of lateral protrusions. ｖ is at least partially filled with a heat sink material having a thermal conductivity greater than 10 W / m / K; The heat sink material preferably comprises alumina.

5. Apparatus according to any one of claims 1 to 4.

6. The ferromagnetic core (200) is made of a metal alloy of the FeX type and A(Fe,B) ２ O ４ The ferromagnetic material is selected from among ferrite oxides of the spinel structure type, Here, X comprises one element selected from Si, Al, Co, and Ni; A=(Mn, Ni), B=(Co, Cu, Al,...), 6. Apparatus according to any one of claims 1 to 5.

7. The ferromagnetic core (200) includes two flat ends (200a, 200b) that are substantially parallel to each other; The ends are opposed to one another and have a surface area S; The two ends define the variable air gap (400); The plurality of ferromagnetic main plates (500) are arranged perpendicular to the end portions, The ferromagnetic core (200) preferably has a polygonal frame, more preferably a rectangular frame.

7. Apparatus according to any one of claims 1 to 6.

8. The plurality of ferromagnetic main plates (500) have a cross-sectional surface area S ｔ and a cross section having a The apparatus of claim 7, wherein the sum of the cross-sectional surface areas of all the ferromagnetic main plates (500) is less than said surface area S.

9. The ferromagnetic core (200) includes two bases (101), Each of said bases comprises two main surfaces, called the inner surface (101a) and the outer surface (101b), The inner surface and the outer surface are substantially parallel to each other, The bases (101) face each other along the inner surface (101a) of the bases; The variable air gap (400) is formed in one of the bases; The core (200) further comprises a plurality of legs that are generally parallel to one another and extend between the two inner surfaces; The plurality of legs includes at least one main leg (102), at least one side 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 of the primary and secondary windings includes a main section (301b, 302b) wound around the main leg (102) and leakage sections referred to as primary leakage sections (301a, 301c) and secondary leakage sections (302a, 302c); Each of the primary leakage section (301a, 301c) and the secondary leakage section (302a, 302c) is wound around a different leakage leg; 7. Apparatus according to any one of claims 1 to 6.

10. The variable air gap (400) is disposed between the two leakage legs; the plurality of ferromagnetic main plates (500) being in the form of fins; 10. The apparatus of claim 9.

11. the fins are oriented along a direction defined by an axis joining two leakage legs between which the air gap is disposed.

11. The apparatus of claim 10.

12. The recess opens onto the inner surface (101a) of the considered base, 12. Apparatus according to any one of claims 9 to 11.

13. the recess is open on the outer surface (101b) of the considered base, 13. Apparatus according to any one of claims 9 to 12.

14. the at least one main landing gear (102) comprises a single main landing gear (102); the at least two leakage legs include four leakage legs; the primary leakage section includes two primary leakage sections, such that the primary winding includes, in order, one of the primary leakage section (301a), the main section (301b), and the other primary leakage section (301c); each of the primary leakage sections is wrapped around a different leakage leg; the secondary leakage section includes two secondary leakage sections, such that the secondary winding includes, in order, one of the secondary leakage section (302a), the main section (302b), and the other secondary leakage section (302c); Each of the secondary leakage sections is wrapped around a different leakage leg.

14. Apparatus according to any one of claims 9 to 13.

15. the at least one side leg includes four side legs; The four side legs and the four leakage legs form a circle centered on the main leg (102), The side legs and the leakage legs are regularly alternately arranged; Each section is disposed diametrically opposite a secondary leakage section with respect to said main leg (102).

15. The apparatus of claim 14.

16. The at least one side leg includes two side legs, the at least two leakage legs include four leakage legs; The four leakage legs are referred to as a first group (106) and a second group (107) and form two groups of two leakage legs, The four leakage legs and the two side legs form a circle centered on the main leg (102), The side legs and the groups (106, 107) are regularly alternated.

15. The apparatus of claim 14.

17. The at least one air gap includes a first air gap (401) and a second air gap (402); the first air gap (401) and the second air gap (402) are disposed midway between the leakage legs of the first group (106) and the second group (107), respectively; 17. The apparatus of claim 16.

18. Each of the primary leakage sections is formed around one of the leakage legs (104) of the first group (106); each of the secondary leakage sections is formed around one of the leakage legs (105) of the second group (107); 20. The apparatus of claim 17.

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