WO2024160945A1

WO2024160945A1 - Electromagnetic device with improved refrigeration

Info

Publication number: WO2024160945A1
Application number: PCT/EP2024/052480
Authority: WO
Inventors: Miguel Ángel ARIZA BAQUERO; Raquel RODRÍGUEZ MUNÍN; Pablo RODRÍGUEZ GONZÁLEZ
Original assignee: Premo, Sl
Priority date: 2023-02-03
Filing date: 2024-02-01
Publication date: 2024-08-08

Abstract

An electromagnetic device with improved refrigeration comprising a magnetic core (10), with at least one electroconductive coil (20) wound around the magnetic core (10) surrounding one central axis (X), and at least one cooling structure (30) including a thermal conductive element (31) in close contact with a heat sink (32) constitutive of an enclosure of the electromagnetic device, the thermal conductive element (31) being in close contact with at least one dissipation surface of the magnetic core (10); wherein the thermal conductive element (31) is a flat wall tightly inserted in a slit (11) of the magnetic core (10) which divides the magnetic core in two independent magnetic core portions, the enclosure comprises two halves, each including one heat sink (32), wherein an air gap, or an electrical insulator, interrupts the non-magnetic thermally conductive element (31) preventing electric contact between the two halves of the enclosure.

Description

DESCRIPTION

ELECTROMAGNETIC DEVICE WITH IMPROVED REFRIGERATION

Technical field

The present invention concerns to an electromagnetic device with improved refrigeration.

The electromagnetic device comprises a magnetic core with an electroconductive coil wound therearound. The improved refrigeration is obtained by at least one cooling structure including a thermal conductive element, made of a non-magnetic material, in close contact with a heat sink, the thermal conductive element including a flat wall tightly inserted in a slit of the magnetic core which divides the magnetic core in two independent magnetic core portions.

Background of the Invention

Different approaches have been attempted to try and remove heat (produced by the Foucault currents generated) from the core of magnetic power unit particularly in the case of power transformers. Some of these are the increasing of wire size to reduce resistive losses; immersion of the transformer in circulating coolant oil; air cooling of the transformer windings; increasing the operating frequency of the transformer to reduce windings; and increasing the thermal conductivity of the insulating potting compound around the transformer windings. All of these, however, impact on the mechanical size and weight of the transformer designs limiting the use of these applications. Without proper cooling the efficiency and reliability of these transformers and inductors are considerably reduced.

DE19814896 discloses a power transformer for high current having a closed cylindrical core of soft magnetic high permeability material high saturation induction and low magnetic losses. This is wound with a primary coil and a secondary coil. The core is within a casing that is then filled with a suitable resin. At least one heat pipe (9) for cooling the unit is set in the centre. The heat pipe forms at least one part of the winding of the transformer.

The contact surface between the duct and the magnetic core is reduced, so the circulation of a cooling fluid through the pipe is required to increase the cooling, which complicates and makes the solution more expensive. US6777835B1 discloses an electrical power cooling technique and particularly an apparatus for cooling a high-power electrical transformer and electrical motors by using thermally conductive material interleaved between the turn layers of a high-power transformer and iron core laminates to provide a low resistant thermal path to ambient. The strips direct excess heat from within the interior to protrusions outside of the windings (and core) where forced air or thermally conductive potting compound extracts the heat. This technique provides for a significant reduction of weight and volume along with a substantial increase in the power density while operating at a modest elevated temperature above ambient. In an embodiment a transformer is made of material such as laminated iron, ferrite and other core materials and the transformer is formed of insulated copper windings wrapped around the core. Heat is dissipated through the core to a base plate, while thermally conductive strips are placed in preselected positions between the windings and are preferably of high modulus graphite laminate material, to conduct heat along its fibre orientation, which is unidirectional.

US US2004257187 A1 discloses an electromagnetic device, comprising a first tubular magnetic core section; a second tubular magnetic core section spaced apart from and in substantially parallel alignment with the first tubular magnetic core section and a primary conductive winding, wherein a first portion of the primary conductive winding is disposed within the first tubular magnetic core section and a second portion of the primary conductive winding is disposed within the second tubular magnetic core section. The magnetic device further comprises a heat extraction means with conductive elements, such as cooling fins, in communication with at least a portion of the outer surface of the first tubular magnetic core section and at least a portion of the outer surface of the second tubular magnetic core section.

US2015155088A1 discloses a heat dissipation structure of a transformer for dissipating heat generated from a core of the transformer, comprising a heat dissipating plate that includes a bottom plate mounted to a housing of the transformer, and an extended plate extended upward from the bottom plate. The extended plate includes a center plate and a pair of side plates disposed at opposite sides of the center plate. The pair of side plates are separated from the center plate.

CN113257545A. refers to a high-power, high-efficiency, heat-dissipating high-frequency transformer comprising an aluminum plate radiator that includes a first aluminum plate, a second aluminum plate and a third aluminum plate arranged one after the other. GB2597670A1 relates to thermal management of an electromagnetic device such as a transformer, including a core assembly, windings 204, a primary thermally conductive plate and several secondary thermally conductive plates.

All the above documents include a cooling structure on one side of the electromagnetic device, producing an uneven cooling of the magnetic core.

The present invention solves the above and other problems.

Description of the Invention

The present invention concerns to an electromagnetic device with improved refrigeration, as defined in claim 1.

The proposed electromagnetic device comprises, in a manner already known in the available state of the art: a magnetic core with at least one electroconductive coil wound therearound surrounding one central axis, the magnetic core including at least one slit, parallel to the central axis, dividing the magnetic core in several independent magnetic core portions, and at least one cooling structure each including a heat sink in thermal connection with at least one thermal conductive element, each thermal conductive element including a flat wall, made of a non-magnetic metal, tightly inserted in one of the slits of the magnetic core in thermal connection with the magnetic core portions.

The thermal conductive element is an element made of a non-magnetic material, which does not interfere with the magnetic fields generated in the electromagnetic device during its operation, and with a high thermal conductivity, for example above 120 W/mK, above 160 W/mK, or preferably above 210 W/mK. Typically, the thermal conductive element will be made of a non-magnetic metal such aluminium or an aluminium alloy.

The close contact between the thermal conductive element and the at least one dissipation surface of the magnetic core permits the transference of heat from the magnetic core, where it is generated when the electromagnetic device is in operation, to the thermal conductive element. Also, the close contact between the thermal conductive element and the heat sink permits the transfer of said heat from the thermal conductive element to the heat sink, where the heat is dissipated.

The heat sink will also be made of a material with high thermal conductivity, for example above 120 W/mK, above 160 W/mK, or preferably above 210 W/mK. Typically, the heat sink will be made of a non-magnetic metal such aluminium or an aluminium alloy.

The heat sink will preferably include a dissipation configuration in contact with a cooling fluid, for example the surrounding air but also can be a cooling liquid of a cooling circuit.

The dissipation configuration can include, for example, a surface provided with grooves, ribs, rods, or any other surface broadening configuration intended to increase the exposed surface of the heat sink to the cooling fluid.

Thermal connection shall be understood to be a physical contact between elements allowing heat transfer by conduction between them, or a contact though an interposed heat transfer medium, such a heat-conducting composition, allowing heat transfer by conduction between them through said heat transfer medium.

A thermal connection will exist, for example, between parts of the same single-piece object, between two welded components, or between two overlapped surfaces without a gap between them, or between two overlapped surfaces without a gap between them but including a heat-conducting composition between them to fill any imperfection, increasing the overall thermal conductivity. The heat-conducting composition is preferably a spreadable paste with a relevant thermal conductivity, for example above 5 W/mK, above 10 W/mK, or preferably above 40 W/mK.

According to the present invention, the thermal conductive element includes a flat wall tightly inserted in a slit of the magnetic core, said slit dividing the magnetic core in at least two independent magnetic core portions. Preferably, said slit divides the region of the magnetic core surrounded by the electroconductive coil, so that the at least one thermal conductive element is inserted in said region of the magnetic core surrounded by the electroconductive coil.

According to that, the magnetic core will be divided into at least two independent magnetic core portions facing each other, defining a slit in between, and the thermal conductive element is proposed to include at least one portion shaped as a flat wall tightly inserted in said slit of the magnetic core, between the at least two independent magnetic core portions.

This construction greatly increases contact surfaces between the dissipation magnetic core and the thermal conductive element, increasing the cooling of the electromagnetic device.

Preferably, the magnetic core portions are facing each other through corresponding dissipation surfaces, and the slit will be therefore defined between said dissipation surfaces. The thermal conductive element will include two opposed main surfaces, corresponding to the two opposed main surfaces of the flat wall shape, each in close contact with one of said dissipation surfaces.

The present invention also proposes, in a manner not known, the following: the cooling structure is divided in two halves, overlapped in the central axis direction, each half including one heat sink and a portion of the thermal conductive elements thermally connected to the correspondent head sink; and inductive currents through the cooling structure are prevented though an air gap, or an electrical insulator, located between the portions of the thermal conductive elements surrounded by the coil and/or between portions of the cooling structure surrounding the coil.

According to the above, the cooling structure includes at least two heat sinks, one integrated on each half of the cooling structure, and the at least one thermal conductive element is divided in at least two independent portions, each portion being in thermal connection with one of the heat sinks.

The two halves of the cooling structure are overlapped in the central axis direction, so that the portions of the at least one thermal conductive element of one half is separated from the portions of the other half through a division transversal to the central axis direction.

Preferably the at least one thermal conductive element is inserted in the region of the magnetic core surrounded by the electroconductive coil, and the cooling structure may also surround externally the magnetic device. In this case, undesired inductive currents may be generated through the cooling structure if made of an electrically conductive material such aluminium of aluminium alloy. To prevent such inductive currents, a circular electrical circuit with a region surrounded by the electroconductive coil shall be prevented. To prevent these inductive currents, the electrical connection between the portions of the at least one thermal conductive element shall be interrupted, through an air gap or an electrical insulator, in the region of the magnetic core surrounded by the electroconductive coil.

Additionally or alternatively, the interruption of the circular circuit, preventing the inductive currents, can be achieved by interrupting the electrical connection between the two halves of the cooling structure though the region of the cooling structure not surrounded by the electroconductive coil. In this case, the inductive currents will be prevented even if the portions of the at least one thermal conductive element surrounded by the electroconductive coil are in electrical connection.

According to an embodiment of the invention, the flat wall included in the at least one thermal conductive element are parallel to the central axis around which the at least one electroconductive coil is wound.

The at least one thermal conductive element can include several parallel thermal conductive elements, dividing the magnetic core through at least two parallel slits.

Alternatively, the at least one thermal conductive element can include one or several parallel thermal conductive elements, dividing the magnetic core through at least two parallel slits, and one or several thermal conductive elements perpendicular to the previously mentioned thermal conductive elements, further dividing the magnetic core through at least one additional slit perpendicular to the previously mentioned at least two parallel slits.

Each heat sink can be, for example, an enclosure housing the magnetic core, or a portion of said enclosure. The external walls of the enclosure can, for example, dissipate heat to the surrounding air acting as a heat sink.

The thermal conductive elements may further include external thermal conductive elements, made of a non-magnetic metal and in thermal connection with the heat sink, adjacent to the exterior of the magnetic core, in thermal connection with the magnetic core and/or in thermal connection with the flat wall tightly inserted in one of the slits of the magnetic core. According to this embodiment, the external thermal conductive element will be in thermal connection with the exterior of the magnetic core, directly or through an interposed heat transfer medium, evacuating heat from the exterior of the magnetic core to the heat sink, and/or will be in thermal connection with at least one flat wall tightly inserted in one slit of the magnetic core, helping the flat wall in the evacuation of heat from the inside of the magnetic core to the heat sink.

The thermal conductive element and the heat sink can be parts of a single body element which constitutes the cooling structure. This simplifies the fabrication thereof and improves the heat transference between the thermal conductive element and the heat sink.

Each half of the cooling structure can be made, for example, of a casted non-magnetic metal, of a casted non-magnetic aluminium, or of a casted non-magnetic aluminium alloy. The fabrication of each half of the cooling structure through casting allows for the creation of tailored shapes adapted to increase the heat dissipation and/or to reduce the fabrication cost of the electromagnetic device making easier and simpler its assembly. Preferably, each half of the cooling structure will have a shape producible in a two-part mould.

Alternatively, each half of the cooling structure can be made of an extruded non-magnetic metal, of an extruded non-magnetic aluminium, or of an extruded non-magnetic aluminium alloy extruded in a direction perpendicular to the central axis. In this case, the portions of the thermal conductive element of each half of the cooling structure shall be one flat wall or several flat walls parallel to each other, to allow its fabrication through extrusion, but the portions of the thermal conductive element of the tow halves of the cooling structure can be parallel or perpendicular to each other.

The fabrication of each half of the cooling structure though an extrusion process greatly increases the fabrication speed, reducing its cost, and allows for a high dimensional precision on the obtained pieces. In this case, the cooling structure will have a constant cross section along its entire length, or a constant cross section along its entire length with parts thereof removed by milling.

The aluminium and many aluminium alloys are known for being non-magnetic materials and for having a high thermal conductivity.

According to this invention the heat sink is an enclosure, or a portion of an enclosure, of the electromagnetic device. According to that, the electromagnetic device will be contained in an enclosure, typically a rigid enclosure for protection thereof, and the entire enclosure, or a portion thereof, will constitute the heat sink, the thermal conductive element being in close contact with said enclosure or with part thereof. The walls of the enclosure will dissipate the heat, said walls being therefore part of the cooling structure.

According to an embodiment of the invention, a thermal conductive composition encloses the magnetic core and the at least one coil wound around the magnetic core. The thermal conductive composition will be also in close contact with one side of heat sink, for transferring heat from the thermal conductive composition to the heat sink, preferably leaving an opposed side thereof uncovered for heat dissipation. When the heat sink is an enclosure or a portion of an enclosure of the electromagnetic device, the thermal conductive composition will be contained in said enclosure, preferably poured therein.

Preferably, the thermal conductive composition comprises a mixture of a silicone resin and at least a first filler or of a silicone resin and a first filler including natural mineral filler. Optionally, the thermal conductive composition further comprises a second filler including aluminium hydroxide.

According to an additional embodiment, the magnetic core can further include a magnetic gap, perpendicular to the slit, for enhancing the magnetic behaviour of the magnetic core, said gap completely dividing each of the independent magnetic core portions in two separate sections.

The magnetic core can include, for example, a central region with a prismatic or cylindrical shape elongated in a direction parallel to the central axis, the at least one coil being wound around said central region. Said central region of the magnetic core will be divided by the slit.

Optionally, the magnetic core further includes a frame region surrounding a central opening, the central region of the magnetic core being contained in said central opening, connected to the frame region on both ends and dividing the central opening in two. Said frame region of the magnetic core will be also divided by the slit.

The at least one coil can be wound around a bobbin interposed between the at least one coil and the magnetic core.

It will be understood that references to geometric position, such as parallel, perpendicular, tangent, etc. allow deviations up to ± 5° from the theoretical position defined by this nomenclature.

It will also be understood that any range of values given may not be optimal in extreme values and may require adaptations of the invention to these extreme values are applicable, such adaptations being within reach of a skilled person.

Brief of the

The foregoing and other advantages and features will be more fully understood from the following detailed description of an embodiment with reference to the accompanying drawings, to be taken in an illustrative and non-limitative manner, in which:

Fig. 1 shows a perspective view of the electromagnetic device according to a first embodiment of the present invention, without including the cooling structure;

Fig. 2 shows a perspective exploded view of the electromagnetic device shown in Fig. 1 , further including a cooling structure, formed by a lower portion of an enclosure with a flat wall connected thereto and an upper portion of an enclosure with another flat wall connected thereto, and also including a thermal conductive composition filling said enclosure;

Fig. 3 shows a perspective view of the electromagnetic device according to a second alternative embodiment of the present invention where the magnetic core is divided through one slit, parallel to the central axis, and one gap perpendicular to said central axis, this view not including the cooling structure and the conductive composition;

Fig. 4 shows an assembled view of the electromagnetic device shown in Fig. 3, further including the cooling structure and the conductive composition;

Fig. 5 shows a perspective exploded view of the electromagnetic device shown in Fig. 4, showing the cooling structure divided in two halves, each half including one heat sink thermally connected to a portion of the thermal conductive element tightly inserted in a slit of the magnetic core, where the heat sinks are on opposed sides of the electromagnetic device, and also including a thermal conductive composition contained between said two heat sinks;

Fig. 6 shows a perspective exploded view of the electromagnetic device according to an alternative embodiment similar to the one shown in Fig. 5, on which each half of the cooling structure include one flat wall, being both flat walls perpendicular to each other, the magnetic core including two slits perpendicular to each other;

Fig. 7 shows a perspective exploded view of the electromagnetic device according to an alternative embodiment similar to the one shown in Fig. 5, on which each half of the cooling structure include two flat walls parallel to each other and one flat wall perpendicular to the other flat walls, the magnetic core including two parallel slits and one additional slit perpendicular to the other two parallel slits;

Fig. 8 shows a perspective exploded view of the electromagnetic device according to an alternative embodiment similar to the one shown in Fig. 7, on which each half of the cooling structure include two flat walls perpendicular to each other, the magnetic core including two slits perpendicular to each other, and wherein the lower half of the cooling structure include two thickenings of the thermal conductive element, in the shape of columns parallel to the central axis, attached to the ends of one of the flat walls, and wherein this lower half further includes cooling channels through the heat sink and through said columns, producing an active cooling of the cooling structure;

Figs. 9 and 10 show a vertical cross section of the thermal conductive element shown in Fig. 8 coplanar with the central axis, showing the exploded view in Fig. 9 and the ensembled view in Fig. 10.

Fig. 11 shows a perspective exploded view of the electromagnetic device according to an alternative embodiment similar to the one shown in Fig. 8, on which each half of the cooling structure include one flat wall, and wherein the lower half of the cooling structure includes, on four corner regions surrounding the magnetic core, four thickenings of the thermal conductive element in the shape of columns parallel to the central axis, said columns being thermally connected to the ends of said flat wall through an interposed external thermal conductive element shaped as a flat wall perpendicular to the flat wall inserted in the slit of the magnetic core, and wherein this lower half further includes cooling channels through the heat sink and through said columns, producing an active cooling of the cooling structure.

Detailed Description of the Invention and of particular embodiments

The present invention is directed to an electromagnetic device comprising a magnetic core 10, with an electroconductive coil 20 wound around a central axis X surrounding the magnetic core 10 or part thereof, and a cooling structure 30 in close contact with the magnetic core 10.

The magnetic core 10 is formed by several independent magnetic core portions 10’ facing each other through correspondent dissipation surfaces parallel to the central axis X, defining a slit 11 between them. The magnetic core 10 can also be divided through a gap 12 perpendicular to the central axis, to improve the magnetic behaviour of the device.

For example, in the embodiment shown in Figs. 1 to 5 and 11 the magnetic core includes one slit 11 parallel to the central axis X, and one gap 12 perpendicular to the central axis, dividing the magnetic core 10 in four magnetic core portions 10’.

In the embodiments shown in Figs. 6 and 8 the magnetic core includes two slits 11 perpendicular to each other and both parallel to the central axis X, and one gap 12 perpendicular to the central axis, dividing the magnetic core 10 in eight magnetic core portions 10’.

Finally, in the embodiment shown in Fig. 7, the magnetic core includes two slits 11 parallel to each other and one slit perpendicular to the other slits, all parallel to the central axis X, and one gap 12 perpendicular to the central axis, dividing the magnetic core 10 in twelve magnetic core portions 10’.

In all cases, the cooling structure 30 comprises two halves overlapped in the central axis direction, each half including one heat sink 32 in thermal connection with a portion of the thermal conductive element 31. Preferably, each half of the cooling structure is a single-piece metallic element obtained from a casting or extruding operation or welded together.

The portion of the thermal conductive element 31 tightly inserted in the slit 11 is shaped as a flat wall, which is in close contact with the dissipation surfaces of each independent magnetic core portions 10’, i.e., with each main surface of the flat wall being in close contact with one of the dissipation surfaces.

The non-magnetic thermally conductive element 31 of both halves of the cooling structure is interrupted by an air gap, or by an electrical insulator, preventing electric contact between the two halves of the cooling structure through the portion inserted in the magnetic core 10 and surrounded by the conductive coil 20.

According to the embodiment shown in Fig. 2, each half of the heat sink 32 is shaped as a top-open box, forming a portion of an enclosure for the electromagnetic device, with the flat wall erecting on its center, perpendicularly to the base of said enclosure, said flat wall being constitutive of a portion of the non-magnetic thermally conductive element 31 inserted in the core. In this embodiment, the electromagnetic device comprises two symmetric cooling structures, each defining one half of the enclosure, so that when the electromagnetic device is assembled, an enclosure is formed by the combination of the two head sinks 32, completely enclosing the electromagnetic device.

According to this first embodiment, said enclosure is filled with a thermal conductive composition 40 which surrounds the magnetic core 10 and the coil 20, enhancing the thermal transmission of heat also through said thermal conductive composition 40 from the magnetic core 10 towards the head sink 32.

In the second embodiment, each half of the cooling structure includes a heat sink 32 defining only a base plate or a top plate, which can be a part of an enclosure if additional walls are attached thereto, or can be a mere base plate or top plate to support all the components of the electromagnetic device and to facilitate the anchoring thereof to a support, for example using screws in through holes provided in said base plate and top plate.

Said plate can also include side walls parallels to the thermal conductive element, only on two sides thereof, the side walls providing a more secure enclosure than the simple base plate and being producible through an extrusion process together with the flat wall.

According to the second embodiment, the thermal conductive composition 40 is moulded and hardened between the heat sinks of the cooling structure 30.

Optionally, each half of the cooling structure include at least one flat wall and also two side walls parallel to said at least one flat wall, the flat wall and side walls of one half being perpendicular to the flat wall and side walls of the other half, so that the two side walls of one half and the other two side walls of the other half can completely enclose the device between four side walls and two head sinks, while making each half through extrusion in a cheap and easy manner.

According a preferred embodiment, the magnetic core includes a central region, elongated in the direction of the central axis X, contained within a central opening of a frame region and connected to said frame region by its ends. The electroconductive coil 20 is wound around the central region, for example on a bobbin 50 interposed between the coil 20 and the central region of the magnetic core 10.

The central region can be cylindrical, or a prismatic shape such a cube-like shape. In both embodiments, the slit 11 divides the central region and also the frame region vertically in half, but in the first embodiment the slit 11 divides the frame region transversally into two C shaped portions, and in the second embodiment the slit 11 divides the frame region longitudinally into two thinner frames, each half of the thermal conductive element having an E shape to be inserted not only in the central region of the magnetic core, but also between the thinner frames. In this case, each half of the thermal conductive element 31 will have an upper edge, away from the heat sink 32 connected thereto, with an E-shaped profile defining one central protrusion inserted in the central region of the magnetic core, and two lateral protrusions inserted in the frame region of the magnetic core away from the central region. This embodiment can be seen on Figs. 4 and 5.

In both embodiments the gap 12 divides the central region and the frame region horizontally in half.

The non-magnetic thermally conductive element 31 can include cooling channels connected to a cooling circuit, preferably including a cooling liquid pump.

The cooling channels can be defined in the heat sink and/or in the portion of the at least one thermally conductive element 31 of at least one of the halves of the cooling structure 30. For example, in the embodiments shown in Figs. 8 and 11 only the lower half of the cooling structure includes the cooling circuit, but both halves can include similar or symmetric configurations including cooling channels.

At least some of the cooling channels can be defined in the flat wall inserted in the slit 11 , when sufficiently thick, or can be defined in external thermally conductive elements in thermal connection with the flat wall tightly inserted in the slit 11 .

For example, it is proposed to include cooling channels in thickened portions of the external thermally conductive elements, thicker than the flat wall inserted in the slit 11 of the magnetic core 10.

Said thickened portions, which can be shaped as a column, as shown in embodiments of Figs. 8 and 11 , will be thermally connected to the edges of the flat walls inserted in the slit of the magnetic core 10 directly, as in Fig. 8, or though interposed external thermal conductive element also shaped as flat walls perpendicular to the flat wall inserted in the slit 11 as in Fig. 11. The cooling channels may include several parallel bores 61 and at least one transverse bore 62 intersecting those several parallel bores 61 interconnecting them, as shown in Figs. 9 and 10.

Preferably, at least some of the parallel bores 61 are blind bores, typically parallel to the central axis X, defined in the portion of the at least one thermally conductive element 31 of at least one of the halves of the cooling structure 30. Each blind bore will include an inner wall 63 tightly inserted therein and connected to a cap attached to the open end of each blind bore, for example through a thread, the inner wall 63 longitudinally dividing the blind bore in two channels and defining a connection between those two channels at a bottom of the blind bore, producing a cooling effect along the entire longitude of the blind bore.

Typically, the inner wall 63 is shorter than the blind bore where it is inserted, or has a transverse opening at its distal end, creating said two parallel channels in each blind bore, one connected to one segment of the transverse bore and the other connected to the other segment of the transverse bore, urging the cooling fluid towards the bottom of each blind bore.

According to the embodiment shown in Figs. 9 and 10, the blind bores pass through the heat sink 32, with an open end on one side of the head sink 32 opposed to the side of the head sink connected to the thermal conductive element 31. Those parallel bores 61 are aligned and are intersected, on a region adjacent to the open end thereof, by one transverse bore 62 which, in this embodiment, is coplanar and perpendicular to the parallel bores 61 , said transverse bore completely crossing the head sink 32 attached thereto.

Claims

1 . An electromagnetic device with improved refrigeration comprising: a magnetic core (10) with at least one electroconductive coil (20) wound therearound surrounding one central axis (X), the magnetic core (10) including at least one slit (11 ), parallel to the central axis (X), dividing the magnetic core (10) in several independent magnetic core portions (10’), and at least one cooling structure (30) each including a heat sink (32) in thermal connection with at least one thermal conductive element (31), each thermal conductive element (31) including a flat wall, made of a non-magnetic metal, tightly inserted in one of the slits (11 ) of the magnetic core (10) in thermal connection with the magnetic core portions (10’); characterized in that the cooling structure (30) is divided in two halves, overlapped in the central axis (X) direction, each half including one heat sink (32) and a portion of the thermal conductive elements (31) thermally connected to the correspondent head sink (32), and inductive currents through the cooling structure (30) are prevented though an air gap, or an electrical insulator, located between the portions of the thermal conductive elements (31) surrounded by the coil (20) and/or between portions of the cooling structure (30) surrounding the coil (20).

2. The electromagnetic device according to claim 1 wherein the at least one thermal conductive element (31 ) are several parallel and/or perpendicular thermal conductive elements (31).

3. The electromagnetic device according to claim 1 or 2 wherein each heat sink (32) is an enclosure housing the magnetic core (10), or a portion of said enclosure.

4. The electromagnetic device according to claim 1 , 2 or 3 wherein the thermal conductive elements (31) further include external thermal conductive elements, made of a non-magnetic metal and in thermal connection with the heat sink (32), adjacent to the exterior of the magnetic core (10), in thermal connection with the magnetic core (10) and/or with the flat wall tightly inserted in one of the slits of the magnetic core.

5. The electromagnetic device according to any preceding claim wherein each half of the cooling structure (30) is a single-piece element made of casted metal, casted aluminium or casted aluminium alloy, or a single-piece element made of extruded metal, extruded aluminium, or extruded aluminium alloy extruded in a direction perpendicular to the central axis (X).

6. The electromagnetic device according to any preceding claim 1 to 4 wherein each half of the cooling structure (30) is a single-piece element made of extruded metal, extruded aluminium or extruded aluminium alloy extruded in a direction perpendicular to the central axis (X), the flat wall of one half being perpendicular to the flat wall of the other half.

7. The electromagnetic device according to claim 6 wherein each half of the cooling structure further includes two side walls, parallel to the flat wall, adjacent to an external side of the magnetic core (10).

8. The electromagnetic device according to any preceding claim wherein the magnetic core (10) and the at least one electroconductive coil (20) are embedded in a thermal conductive composition (40), the thermal conductive composition (40) being in thermal contact with each heat sink (32).

9. The electromagnetic device according to claim 8 wherein the thermal conductive composition comprises: a mixture of a silicone resin and at least a first filler or of a silicone resin and a first filler including natural mineral filler; or a mixture of a silicone resin and at least a first filler or of a silicone resin and a first filler including natural mineral filler and a second filler including aluminium hydroxide.

10. The electromagnetic device according to any preceding claim wherein the magnetic core further includes a magnetic gap (12), perpendicular to central axis (X), for enhancing the magnetic behaviour of the magnetic core (10), said gap (12) completely dividing each of the independent magnetic core portions (10’) in two separate sections.

11. The electromagnetic device according to any preceding claim wherein the at least one coil (20) is wound around a bobbin (50) interposed between the at least one coil (20) and the magnetic core (10).

12. The electromagnetic device according to any preceding claim wherein the cooling structure (30) further includes cooling channels connected to a cooling circuit.

13. The electromagnetic device according to claim 12 wherein the cooling channels are defined in the heat sink and/or in the portion of the at least one thermally conductive element (31 ) of at least one of the halves of the cooling structure (30).

14. The electromagnetic device according to claim 12 or 13 wherein the cooling channels includes several parallel bores (61 ) and at least one transverse bore (62) intersecting those several parallel bores (61 ) interconnecting them.

15. The electromagnetic device according to claim 14 wherein at least some of the parallel bores (61) are blind bores defined in the portion of the at least one thermally conductive element (31) of at least one of the halves of the cooling structure (30) and include an inner wall (63) tightly inserted therein, the inner wall (63) longitudinally dividing the blind bore in two channels and defining a connection between those two channels at a bottom of the blind bore.