JP2023502403A - Electromagnetic induction device - Google Patents

Abstract

The present invention relates to an electromagnetic induction device with a variable air gap provided with heat dissipation means. In particular, the device according to the invention comprises a core inside which the variable air gap is housed. The air gap further includes a first ferromagnetic plate for guiding magnetic flux that may occur in the core. The magnetic fluxes may collectively have a saturation field that is less than the saturation field of the core. Said variable air gap according to the terms of the invention further comprises a lateral protrusion forming a heat dissipation means, said lateral protrusion extending from said first plate side.

Description

The present invention relates to the fields of electronics and electricity. In particular, the present invention relates to magnetic inductors with variable inductance that have reduced magnetic and thermal losses compared to devices known in the prior art.

Advantageously, the magnetic inductor according to the invention is implemented in an AC/DC or DC/DC power converter, in particular a DAB (“Dual Active Bridge”) converter.

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

Generally, a magnetic inductor includes a core made from ferromagnetic material and windings formed around a portion of the core. The core may also contain air gaps. The device is characterized by a characteristic quantity called the magnetizing inductance L, which is determined by the ferromagnetic material, the geometry of the core (and its air gap) and the windings (particularly the number of turns).

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.

This is particularly the case for so-called LLC resonant converter topologies.

In fact, the magnetizing inductance of the LLC converter's transformer should be high at the nominal operating voltage to limit switching losses and ensure good efficiency, but when the input voltage drops, the load supplied to the load can be greatly reduced to ensure continuity of power supply (must ensure data backup in the event of a power failure, as described in Non-Patent Document 1 listed at the end of this specification). server power supply system that does not

This problem leads to sizing this type of converter with a low inductance value to ensure backup functionality, which can compromise efficiency.

For the 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.

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.

In some cases, it is possible to implement the series inductor function by a component separate from the transformer. However, the series inductance function may also be guaranteed by the leakage inductance of the same transformer.

In either case, a single series inductance value limits the operating range and proves to be less flexible for driving DAB converters. This is described in Non-Patent Document 2 listed at the end of this specification. To overcome these problems, one might consider implementing a magnetic inductor with a magnetizing inductance L or variable series depending on the magnetic flux (and thus on the current I flowing in the winding). More specifically, a magnetic inductor with a high magnetization L or series inductance at low currents I and a low inductance at high currents I would be required.

However, magnetic inductors are generally sized to operate in the range of current I through the windings below the saturation current I _sat at which the ferromagnetic core is not saturated.

In this region the magnetizing inductance L remains independent of said current I as long as the current I is less than the saturation current I _sat . However, magnetic saturation of the core occurs as soon as the current I exceeds the saturation current value I _sat , which causes the permeability and consequently the magnetizing inductance L to decrease sharply.

Therefore, different solutions can be considered if variation of the magnetizing inductance L is required during operation of the magnetizing inductance. In general, these solutions propose extending the operating range of the magnetic inductor to nonlinear modes prior to full saturation of the ferromagnetic material. For this reason, it is possible to consider lowering the magnetic permeability and/or reducing the size of the air gap.

Implementing either of these two solutions will cause saturation to occur uniformly across the core at values of current I higher than the saturation current _Isat .

However, these solutions are not satisfactory.

In fact, when a high frequency current I (generally higher than 10 kHz) flows through the inductor, the entire core will saturate and significant volumetric magnetic losses will occur in the inductor and the components in which it is incorporated. can cause to give

These losses can also cause heating of the core.

Furthermore, in saturation mode, magnetic flux lines no longer confined in the core can disturb components located near the magnetic inductor. Specifically, these disturbances can cause losses due to electromagnetic mismatches and/or eddy currents.

It was therefore proposed in US Pat.

However, this proposed sizing method is unsatisfactory.

In fact, even if core saturation remains near the air gap, the air gap can cause magnetic losses and overheating, interfering with the operation of the entire component.

These magnetic losses and heat generation also limit the implementation of such magnetic inductors to high frequency currents I, in particular currents I reaching 500 kHz.

U.S. Pat. No. 3,603,864 U.S. Pat. No. 5,440,225 U.S. Pat. No. 4,728,918 U.S. Patent Application Publication No. 2015/0109086 U.S. Patent Application Publication No. 2010/0085138

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 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 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.

Yet another object of the invention is to provide an electromagnetic induction device capable of operating at higher frequencies than devices known from the prior art.

The object of the present invention is at least partially achieved by an electromagnetic induction device comprising a ferromagnetic core and at least one air gap, called variable air gap, said air gap defining a volume V within said core. and within said volume V a ferromagnetic main plate is disposed. The ferromagnetic main plates are oriented substantially parallel to each other and parallel to magnetic lines of force that may flow within the core. The main plates have a cross section configured such that all of the plates have a saturation field lower than that of the ferromagnetic core. The main plate is also provided with lateral protrusions to dissipate heat that may be generated within the main plate when the main plate is traversed by a magnetic field higher than its saturation field. belongs to. The lateral protrusion extends from the side surface of the plate along a direction substantially orthogonal to the side surface.

According to one embodiment, said lateral projections connect said main plates in pairs so as to form secondary plates perpendicular to said main plates.

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

According to one embodiment, all main plates are identical.

According to one embodiment, the empty volume V _v , the volume V vacated by said main plate and said lateral projections, is at least partially made of a heat sink material having a thermal conductivity higher than 10 W/m/K. be filled. Preferably, said heat sink material comprises alumina.

According to one embodiment, the ferromagnetic core is a metal alloy of FeX type (where X comprises one of the elements selected from Si, Al, Co, Ni), A ₍ Fe,B) _2O4 type spinel structure ferrite oxide (A=(Mn, Ni), B=(Co, Cu, Al, . . . )).

According to one embodiment, said ferromagnetic core comprises two essentially parallel flat ends, said 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. Said ferromagnetic core preferably has a polygonal, more preferably rectangular frame.

According to one embodiment, said main plate has a cross-section with a cross-sectional surface area St, and the sum of the cross-sectional surface areas of all main plates is smaller than said surface area _S.

According to one embodiment, the ferromagnetic core comprises two bases, each of which is provided with two main surfaces, referred to as the inner surface and the outer surface, respectively. The inner and outer surfaces are generally parallel and the bases face each other along the inner surfaces of the bases and the variable air gap is formed in one of the bases. The core further includes a plurality of legs essentially parallel to each other and extending between the two inner surfaces, the plurality of legs comprising at least one main leg, at least one side leg, and at least 2 leaky legs. The apparatus further comprises at least one primary winding and at least one secondary winding, each of the primary and secondary windings having a main section and a leakage section wound around the main leg. include. The leaky sections are respectively referred to as the primary leaky section and the secondary leaky section, each wrapped around a different leaky leg.

According to one embodiment, said variable air gap is arranged between said two leaky legs and said primary plate is in the form of a fin.

According to one embodiment, said fins are oriented along a direction defined by an axis connecting two leaky legs between which said air gap is arranged.

According to one embodiment, the recess opens into the inner surface of the considered base.

According to one embodiment, said recess opens into the outer surface of said considered base.

According to one embodiment, said at least one main leg comprises a single main leg. The at least two leaky legs include four leaky legs and the primary leaky section includes two primary leaky sections. This is such that the primary winding comprises in sequence one of the primary leakage section, the main section and the other primary leakage section, each of the primary leakage sections winding on a different leakage leg. It is Also, the secondary leakage section includes two secondary leakage sections, wherein the secondary winding comprises one of the secondary leakage section, the main section, and the other secondary leakage section. Contained in turn, each of said secondary leaky sections is wrapped around a different leaky leg.

According to one embodiment, said at least one side leg comprises four side legs, said four side legs and said four leaky legs describe a circle centered on said main leg, said side legs and Regularly alternating with the leaky legs, each section is positioned diametrically opposite a secondary leaky section with respect to the main leg.

According to one embodiment, said at least one side leg comprises two side legs and said at least two leaky legs comprise four leaky legs, forming two groups of two leaky legs, wherein are respectively referred to as the first group and the second group. The four leaky legs and the two side legs describe a circle centered on the main leg, and the side legs and the groups are regularly alternated.

According to one embodiment, said at least one air gap comprises a first air gap and a second air gap positioned intermediate between said leaky legs of said first group and said second group respectively.

According to one embodiment, each of said primary leaky sections is respectively formed around either one of said leaky legs of said first group). Each of the secondary leaky sections is respectively formed around either one of the leaky legs of the second group.

According to one embodiment, in either one of said inner surfaces, a groove may be formed around each leaky leg with a predetermined distance from each leaky leg. This groove is interposed between the leaky leg and the main leg.

Other features and advantages are presented in the following description of the electromagnetic induction device according to the invention. An electromagnetic induction device is given as a non-limiting example with reference to the accompanying drawings.

1 is a schematic perspective view of a variable air gap according to the invention; FIG. Fig. 3 is a schematic perspective view of another construction of variable air gap according to the present invention; Fig. 3 shows a ferromagnetic core that can be implemented with the present invention; 4 is a graph showing changes in inductance L (vertical axis, unit "H") of an electromagnetic induction device as a function of current I (horizontal axis, unit "A") flowing through a coil. 1 is a schematic perspective view of an electromagnetic induction device according to a first embodiment of the present invention; FIG. 1 is a schematic side view of a half-core that can be implemented with the present invention; FIG. 1 is a schematic top view of a half core that can be implemented with the present invention; FIG. Figure 6 is a schematic diagram of an electromagnetic induction device according to a first embodiment of the present invention, implemented with two half-cores as shown in Figures 6a and 6b; FIG. 5 is a schematic diagram of an electromagnetic induction device according to a first modification of the second embodiment of the present invention; FIG. 11 is a schematic cross-sectional view along the inner surface of a half core according to a second modification of the second embodiment of the present invention; 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; FIG. 10 is a view showing a cross section along the inner surface of a half core provided with windings according to a second modification of the second embodiment of the present invention; FIG. 4 is a schematic view of an air gap opening to the outer surface of the base in contact with a cold source;

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 invention comprises a core in which the variable air gap is accommodated. Further, the air gap includes a first ferromagnetic plate for guiding magnetic flux that may occur in the core, the first ferromagnetic plate being in saturation mode for flux values lower than that required for saturation of the core. is intended to work with Magnetic flux is conservative throughout the magnetic circuit.

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

More particularly, the present invention relates to electromagnetic induction device 100 (FIGS. 1-3).

The electromagnetic induction device 100 can be a magnetic inductor with an inductance L and is incorporated in an AC/DC or DC/DC power transformer, especially a DAB converter.

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

The ferromagnetic core 200 is a FeX-type metal alloy (X includes one element selected from Si, Al, Co, and Ni), A(Fe, B) ₂ O ₄ -type spinel structure ferrite oxidation. material (A=(Mn, Ni), B=(Co, Cu, Al, . . . )).

The ferromagnetic core 200 may be traversed by magnetic field lines induced by current I flowing in at least one conductive coil 300 (or winding). Coil 300 is formed around a portion of ferromagnetic core 200 and extends along major axis XX'.

"Main axis" will be understood to mean the axis of symmetry of the electrically conductive coil.

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

Ferromagnetic core 200 also includes an air gap, more particularly variable air gap 400 (FIGS. 1 and 2).

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

A recess or lack of material interrupts the continuity of the ferromagnetic material forming the ferromagnetic core 400 .

The variable air gap 400 defines a volume V within the ferromagnetic core 200 corresponding to the volume of material removed or missing.

A main plate 500 made of ferromagnetic material is positioned within a volume V defined by a variable air gap 400 .

A "plate" will be understood to be an element of generally flat and thin shape. In detail, the plate comprises two sides 501 that are essentially parallel to each other and connected by a contour.

Moreover, the main plates 500 are essentially parallel to each other and are arranged according to directions parallel to the magnetic lines of force that may enter the ferromagnetic core 200 .

According to the invention, the orientation of the plate, in particular the main plate, is defined by the orientation of its side surfaces 501 . In other words, the magnetic lines of force are parallel to the direction of the plane formed by the sides of the main plate 500 .

The main plate 500 also has a cross-section with a surface area S _t , which is adapted such that all of said main plates 500 have a saturation magnetic field B _sat1 (referred to as the first magnetic field B _sat1 ) _. ing. The first magnetic field B _sat1 is lower than the saturation magnetic field of the ferromagnetic core 200 (referred to as the second magnetic field B _sat2 ).

"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.

The amplitude of the magnetic field B across ferromagnetic core 200 depends on the current I flowing through coil 300 . Specifically, the first magnetic field B _sat1 and the second magnetic field B _sat2 are reached when the current I flowing through the coil 300 is equal to the first saturation current I _sat1 and the second saturation current I _sat2 respectively.

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

In this regard, FIG. 4 is a graphical representation of different modes of operation of an electromagnetic induction device 100 in which the main plates 500 are all identical.

"Identical main plate" is understood to mean plates of the same shape, the same dimensions and the same material.

Such a device 100 has three operating modes or levels "A", "B", "C" associated with the current I flowing through the coil 300, each of which is less than the first saturation current I _sat1 a level comprised between the first saturation current I _satl and the second saturation current I _sat2 and a level greater than the second saturation current I _sat2 .

More specifically, mode "A" corresponds to a linear mode in which ferromagnetic core 200 and main plate 500 are not saturated. In this mode, the magnetic permeability of the ferromagnetic core 200 and main plate 500 is largely independent or independent of the magnetic field flowing through the core, so the induction L is also essentially constant and the _first induction L1 be equivalent to.

Mode "B" is characterized by the inductance L falling to a _second induction L2.

In particular, this drop is due to the saturation of the main plate 500, under the influence of a magnetic field higher than the first magnetic field B _sat1 , its permeability drops significantly, reaching a value close to unity.

Finally, mode “C” corresponds to the saturation mode of ferromagnetic core 200 and main plate 500 caused by a current flowing through coil 300 that is higher than the second saturation current _Isat2 . _In this mode the inductance L drops again to the value L3.

According to the invention, the main plate 500 is also provided with ferromagnetic lateral projections 600 .

"Protrusion" will be understood to mean a member that protrudes in the plane in which it is placed.

The lateral protrusions 600 are specifically intended to dissipate the heat that tends to be generated in the main plate 500 when the main plate 500 is traversed by a magnetic field greater than its saturation magnetic field B _sat1 .

Specifically, lateral projections 600 extend from a side surface 501 of the main plate 500 along a direction essentially perpendicular to the side surface 501 (FIGS. 1 and 2).

Lateral protrusion 600 may have a rectangular, circular, square, or triangular cross-section.

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

In a particularly advantageous manner, the secondary plate 700 is dimensioned such that it does not saturate when the magnetic field flowing in the core is lower than the second magnetic field B _sat2 . Thus, when the main plate 500 saturates, the secondary plate 700 limits flux overflow around the air gap region. In other words, the secondary plate 700 ensures guidance of the magnetic flux in the air gap and effectively limits lateral radiation of the magnetic field.

Additionally, the lateral protrusion can be limited to the volume V defined by the variable air gap.

Advantageously, the ferromagnetic core 200, the first plate 500 and the lateral protrusions 600 are made from the same ferromagnetic material.

More advantageously, the void volume Vv, which is the volume _V vacated by the first plate 500 and the protrusion 600, is at least partially filled by a heat dissipating material 601 (FIG. 5) having a thermal conductivity higher than 10 W/m/K. can be effectively filled. Advantageously, the heat dissipating material comprises alumina.

The presence of the heat-dissipating material can aid cooling by the lateral protrusions 600 by directing the heat generated in the air gap toward the heat sink.

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

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

The main plate 500 has a cross-section with a cross-sectional surface area St, and the sum of the cross-sectional surface areas of all main plates is less than the surface area _S.

The ferromagnetic core may comprise a polygonal, more advantageously rectangular frame.

For example, as shown in FIG. 5, the magnetic core 200 includes five parallelepiped sections 201-205 constructed from a ferromagnetic material, which at their ends form a rectangular frame. are joined in pairs. Two sections 204 and 205 form one side of the rectangular frame and are separated by an air gap 400 (with a distance g) at their ends 200a and 200b.

The principle of sizing the device according to the invention is presented below on the basis of a core forming a square side frame and/or shown in FIG. However, this sizing principle is not limited to this configuration only and can be readily adapted to other types of core geometries by those skilled in the art.

In this example, the same primary plate 500 connects ends 200a and 200b with a spacing g. The percentage of end face regions 200a and 200b covered by a portion of the primary plate is indicated by f.

Then, the reluctance R _e of an airgap structure provided with only primary plates made of ferromagnetic material with permeability μ _s is expressed as follows.

As long as the _Np secondary plate is considered, the reluctance of an airgap structure is easily calculated by applying the reluctance network method to each of the structure's components. The thickness of these plates is denoted by the symbol _ep and is small compared to the spacing g (ep<<g).

Further, the secondary plate comprises a ferromagnetic material of permeability μ _p and divides the air gap into a plurality of secondary air gaps arranged in series.

Therefore, the reluctance R _es of each secondary air gap is expressed as follows.

The total reluctance of an airgap structure including primary and secondary plates is the sum of the _Np secondary reluctances separating the plates. i.e.

From these equations we can deduce the inductance L(μ _c , μ _s ) of the device shown in FIG.

This inductance expression is identical to that obtained for a constant airgap whose spacing g is weighted by the term F(μ _s ,f).

Thus, this term allows changing the distance of the air gap appearing in the value of the inductance without changing the geometry of the magnetic circuit. For this, it is necessary to vary the magnetic permeability _μs of the primary plate as a function of the applied current.

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 across the core, according to the law of conservation of magnetic flux. Such considerations allow local saturation effects to occur, particularly at the primary plate 500 .

The magnetic induction _Bst in the primary plate corresponds to the amplification of the magnetic induction _Bc in the ferromagnetic core. This amplification is a function of the surface area fraction f and is given by the relation:

As the current I flowing through the coil increases, so does the magnetic induction. However, as soon as the current I through the coil reaches the saturation current I _sat , the magnetic induction of the primary plate reaches the saturation value B _sat while the ferromagnetic core remains in linear mode.

In this regard, the saturation current value is given by the following relationship.

For currents higher than the saturation current I _sat , the magnetic permeability μ _s of the primary plate is equal to one. To determine the amplitude of the inductance variation that would be obtained by current control, nominal operation at low induction (I<<I _sat ) excluding saturation was followed by high induction (I>>I _sat ) (μ _s =1) is considered. The variation in inductance between these two extreme cases is given by:

6a, 6b and 7 show another configuration of the ferromagnetic core associated with the first embodiment of the electromagnetic induction device 100. FIG. In this alternative configuration, the ferromagnetic core includes two half cores 200 ₁ and 200 ₂ , which are ETD type (double E with cylindrical central leg) cores known to those skilled in the art.

Measurement results for the ferromagnetic half-core were obtained with respect to Figures 6a, 6b and are reported in the table below.

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

The air gap structure consists of 5 primary plates (21.65 mm x 5 mm) with a thickness of 0.41 mm and 2 secondary plates (21.65 mm x 21.65 mm) with a thickness of 1 mm, which are equally spaced. include.

The ferromagnetic material has a magnetic permeability of 1500 and a saturation induction of 430 mT. Five turns of conductive wire are wound around the central post 207 .

Under these conditions the saturation current is 6A. For currents below I _sat the core inductance is 16 mH and decreases to 3 mH after saturation of the primary plate. The heat exchange surfaces developed by the secondary plates improve cooling by natural convection, allowing heating within the structure to be limited to 100°C.

The following description relates to the second embodiment of the electromagnetic induction device 100. FIG.

Specifically, 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, and the above elements are essentially Inclusive.

In this regard, FIGS. 8 and 9-11 are schematic plan views of _{half -} cores 200-3 and 200-4 that may be implemented according to the first and second variations, respectively, of this second embodiment.

According to this second embodiment _, the ferromagnetic core 200 comprises an assembly of _two half-cores 200-3 and 200-4.

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

The bases face each other along their inner surface 101a and a variable air gap 400 lies in one of the bases, more particularly in its volume.

The core further includes a plurality of legs, which are essentially parallel to each other and extend between the two inner surfaces 101a.

The plurality of legs includes at least one main leg 102, at least one side leg 103, and at least two leaky legs 104 and 105.

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

Each of primary winding 301 and secondary winding 302 includes a main section wound around main leg 102 and a leakage section, referred to as the primary and secondary leakage sections, respectively, Each is wrapped around a different leaky leg 104 and 105 .

Advantageously, the variable air gap 400 is arranged between the two leaky legs and the primary plate is in the form of fins.

More advantageously, the fins are oriented according to the direction defined by the axis joining the two leaky legs between which the air gap is arranged.

Additionally, the recess may lead to either the inner or outer surface of the base containing the air gap.

In this regard, FIG. 12 shows a schematic illustration of an air gap 400 opening into the outer surface 101b of the base 101 in contact with the cold source.

The ferromagnetic core may include one main leg 102 and a total of four leaky legs 104 and 105 .

In this regard, the primary leakage section includes two primary leakage sections, which in turn include primary winding 301, primary leakage section 301a, main section 301b, and one of the other primary leakage sections 301c. so that each of the primary leakage sections is wrapped around a different leakage leg.

Similarly, the secondary leakage section includes two secondary leakage sections, which secondary winding 302 is one of secondary leakage section 302a, main section 302b, and other secondary leakage section 302c. , with each of the secondary leaky sections wrapped around a different leaky leg.

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

More specifically, the four side legs 103 and the four leaky legs 104, 105 describe a circle centered on the main leg 102, in which the side legs and leaky legs are regularly alternated. Each primary leaking section is also positioned diametrically opposite one of the secondary leaking sections with respect to the main leg.

The device described so far includes a transformer function and a series inductor function.

The transformer function is ensured by main sections 301b, 302b of the primary winding 301 and secondary winding 302, respectively, surrounding the main landing gear.

The series inductance that occurs in the primary and secondary windings is ensured by primary leakage sections 301a and 301c and secondary leakage sections 302a and 302c.

Thus, the magnetic flux, called "transformer flux", produced in the main leg by passing current through the primary winding, passes continuously through the base, the side leg, the other base, and again in a loop across the main leg. follow the path of

Similarly, the primary "leaky" flow follows another contour connecting the two leaky legs of the primary circuit. This contour traverses the cylindrical base through its thickness along a line joining the bases of the two primary leaky legs. The secondary leakage flow also follows a similar contour described by the two secondary leakage legs.

By varying the air gap between the two leaky legs, the properties of a variable leakage inductor can be imparted to the device.

Similarly, a variable air gap can be provided between the two secondary leaky legs to impart the properties of a variable leakage inductor to the device.

According to a second variant (FIGS. 9-11), the ferromagnetic core includes two lateral legs 103 and four leaky legs 104 and 105. FIG.

The two leaky legs 104 and the two leaky legs 105 form two groups of two leaky legs, referred to as the first group 106 and the second group 107 respectively.

Furthermore, the four leaky legs and the two side legs describe a circle centered on the main leg, in which the side legs and said groups are regularly alternated.

Advantageously, the at least one air gap 400 includes a first air gap 401 and a second air gap 402 positioned intermediate between the leaky legs of the first group 106 and the second group 107, respectively.

Specifically, each of the primary leaky sections is formed around one and the other of the first group of leaky legs, respectively.

Similarly, each of the secondary leaky sections is formed around one of the leaky legs and the other of the leaky legs of the second group 107, respectively.

According to this second modification, since the leaky legs of the same group are close to each other, the leak can be controlled more accurately.

A flux barrier 800 may also be formed in the base 101 to limit magnetic flux between the leakage leg and the side leg. Specifically, 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 legs.

In particular, the recessed area may extend from the edge along the radius of the considered base.

Finally, regardless of the variation considered, on either one of the inner surfaces, a groove may be formed around each leaky leg at a predetermined distance from each leaky leg. This groove is interposed between the leaky leg and the main leg.

The manufacturing process for cores according to the present invention may involve injection molding techniques (“PIM” or “powder injection molding”). This technique is particularly well suited for mass production of parts with complex geometries.

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

Specifically, the raw materials include mixtures of organic materials (or polymeric binders) and inorganic powders (metals or ceramics) to form the final part.

The raw material is injected into an injection molding machine, a technique known to those skilled in the art. The injection molding machine allows the polymer injected with the powder to melt in the cavity and give the powder the desired shape.

The material thus molded and melted is cooled to solidify and set into the shape imparted by the injection molding machine.

Parts formed from raw materials are then demolded and debound to remove organics.

The part can then be consolidated by sintering.

100: Electromagnetic induction device 102: Main leg 103: Side leg 104: Leakage leg 105: Leakage 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 (18)

a ferromagnetic core (200);
at least one air gap referred to as 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) positioned within said volume V;
the plurality of ferromagnetic main plates (500) are oriented substantially parallel to each other and parallel to magnetic lines of force that may flow within the core;
the plurality of main plates (500) having a cross-section configured such that all of the plurality of plates have a saturation magnetic field lower than that of the ferromagnetic core (200);
the plurality of main plates (500) further comprising a plurality of lateral projections (600);
The plurality of lateral protrusions (600) dissipate heat that may be generated within the plurality of main plates (500) when the plurality of main plates (500) are traversed by a magnetic field higher than its saturation magnetic field. configured to dissipate
The plurality of lateral projections (600) extend from side surfaces (501) of the plurality of plates along a direction substantially orthogonal to the side surfaces (501).
An electromagnetic induction device (100). The plurality of lateral protrusions (600) connect the plurality of main plates (500) in pairs to form a plurality of secondary plates (700) perpendicular to the plurality of main plates (500). 2. The apparatus of claim 1, wherein: the ferromagnetic core (200), the plurality of main plates (500) and the plurality of lateral protrusions are made of the same ferromagnetic material;
3. Apparatus according to claim 1 or 2. all main plates (500) are identical,
4. Apparatus according to any one of claims 1-3. A void volume Vv, which is the volume _V vacated by the plurality of main plates (500) and the plurality of lateral projections, is at least partially formed by a heat sink material having a thermal conductivity higher than 10 W/m/K. filled and
the heat sink material preferably comprises alumina,
5. Apparatus according to any one of claims 1-4. the ferromagnetic core (200) comprises a ferromagnetic material selected from FeX-type metal alloys and A(Fe,B) _{2O4 -} type spinel-structured ferrite oxides;
where X contains one of the elements selected from Si, Al, Co, Ni,
A = (Mn, Ni), B = (Co, Cu, Al, ...),
6. Apparatus according to any one of claims 1-5. said ferromagnetic core (200) comprising two flat ends (200a, 200b) substantially parallel to each other;
the ends face each other and have a surface area S;
the two ends define the variable air gap (400);
said main plate (500) is arranged perpendicular to said edge,
said ferromagnetic core (200) advantageously has a polygonal frame, more advantageously a rectangular frame,
7. Apparatus according to any one of claims 1-6. the plurality of main plates (500) having a cross-section with a cross- _sectional surface area St;
8. Apparatus according to claim 7, wherein the sum of the cross-sectional surface areas of all main plates (500) is less than said surface area S. The ferromagnetic core (200) comprises two bases (101),
each of said bases comprises two major surfaces, referred to as inner surface (101a) and outer surface (101b);
The inner surface and the outer surface are substantially parallel,
the bases (101) face each other along an inner surface (101a) of the bases;
said variable air gap (400) is formed in one of said bases,
said core (200) further comprising a plurality of legs substantially parallel to each other and extending between said two inner surfaces;
said plurality of legs comprising at least one main leg (102), at least one side leg (103) and at least two leaky legs (104, 105);
The device further comprises at least one primary winding (301) and at least one secondary winding (302),
Each of said primary and secondary windings comprises a main section (301b, 302b) wound around said main leg (102), a primary leakage section (301a, 301c) and a secondary leakage section (302a, 302b). 302c) and a leak section referred to as
each of the primary leaky section (301a, 301c) and the secondary leaky section (302a, 302c) is wrapped around a different leaky leg;
7. Apparatus according to any one of claims 1-6. said variable air gap (400) is positioned between said two leaky legs;
wherein the primary plate is in the form of fins;
10. Apparatus according to claim 9. said fins are oriented along a direction defined by an axis connecting two leaky legs between which said air gap is disposed;
11. Apparatus according to claim 10. said recess is open to said inner surface (101a) of the considered base,
12. Apparatus according to any one of claims 9-11. said recess is open to said outer surface (101b) of said considered base;
13. Apparatus according to any one of claims 9-12. said at least one main leg (102) comprising a single main leg (102);
said at least two leaky legs comprising four leaky legs;
The primary leakage section includes two primary leakage sections, such that the primary winding is one of the primary leakage section (301a), the main section (301b) and the other primary leakage section (301c). containing in order,
each of the primary leaky sections is wrapped around a different leaky leg;
The secondary leakage section includes two secondary leakage sections such that the secondary winding comprises the secondary leakage section (302a), the main section (302b) and the other secondary leakage section (302c). ) in order, and
each of the secondary leaky sections is wrapped around a different leaky leg;
14. Apparatus according to any one of claims 9-13. said at least one side leg comprises four side legs;
said four side legs and said four leaky legs describe a circle centered on said main leg (102);
the lateral legs and the leaky legs are regularly alternated;
each section is positioned diametrically opposite a secondary leakage section with respect to said main leg (102);
15. Apparatus according to claim 14. said at least one side leg comprises two side legs;
said at least two leaky legs comprising four leaky legs;
said four leaky legs forming two groups of two leaky legs, referred to as a first group (106) and a second group (107);
said four leaky legs and said two side legs describe a circle centered on said main leg (102);
the lateral legs and the groups (106, 107) are regularly alternated;
15. Apparatus according to claim 14. said at least one air gap comprises a first air gap (401) and a second air gap (402);
said first air gap (401) and said second air gap (402) are arranged intermediate between said leaky legs of said first group (106) and said second group (107) respectively;
17. Apparatus according to claim 16. each of the primary leaky sections is formed around either one of the leaky legs (104) of the first group (106);
each of said secondary leaky sections is respectively formed around either one of said leaky legs (105) of said second group (107);
18. Apparatus according to claim 17.

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