METHOD FOR PRODUCING AN ELECTRICAL TRANSFORMER BY ADDITIVE MANUFACTURING

Abstract

The invention relates to a method for additive manufacturing of an electrical transformer (20) comprising: (i) - a step of depositing a powder bed comprising at least a first powder made of an electrically conductive material and a second powder made of an electrically insulating material, and (ii) - a step of local melting of the powder bed to obtain a solidified layer of material defining: a portion of a turn (53) of a primary winding (31) and / or a portion of a turn (54) of a secondary winding (32), and a portion of a body (57) of the electrical transformer (20), (iii) - a step of moving the manufacturing plate, - steps (i), (ii) and (iii) being repeated so as to obtain interlaced windings (31, 32) as well as a body (57) made of electrically insulating material making it possible to electrically insulate the turns (53) of the primary winding (31) and the turns (54) of the secondary winding (32). Figure 9

Description

Title of the invention: METHOD FOR PRODUCING AN ELECTRICAL TRANSFORMER BY ADDITIVE MANUFACTURING

[0001] The present invention relates to a method for producing an electrical transformer by additive manufacturing. The invention finds a particularly advantageous, but not exclusive, application with planar transformers used in DC-DC power converters.

[0002] Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies both to new types of aircraft and those currently in circulation, requiring the implementation of technological solutions to make them compliant with current regulations. Civil aviation has been mobilizing for several years now to make a contribution to the fight against climate change.

[0003] Technological research efforts have already made it possible to significantly improve the environmental performance of aircraft. The Applicant takes into consideration the impact factors in all phases of design and development to obtain less energy-intensive, more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental impacts with the aim of improving the energy efficiency of aircraft.

[0004] Consequently, the Applicant is constantly working to reduce its climate impact by using methods and operating virtuous development and manufacturing processes and minimizing greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0005] This sustained research and development work focuses on new generations of aircraft engines, the lightening of aircraft, particularly through the materials used and lighter on-board equipment, as well as the development of the use of electrical technologies to provide propulsion.

[0006] [Fig.l] shows an example of a simplified architecture of a DC voltage distribution network in an aircraft. In order to supply a high-voltage electrical network of the aircraft, a generator 1 is connected to a high-pressure shaft of a turbomachine 2 via an accessory gearbox (not shown) or AGB for "accessory gearbox" in English. This accessory gearbox comprises gener- normally one or more gear trains which are rotated by the high pressure shaft of the turbomachine 1 by means of an angle transmission device on the high pressure shaft.

[0007] The generator 1 is electrically connected to an alternating direct current (AC / DC) converter 3 so as to be able to electrically supply high voltage electrical loads 4 and high voltage actuators 5 of a high voltage electrical network 6. The high voltage electrical network 6 may for example have an operating voltage of the order of 270 Volts.

[0008] A direct-direct converter 7 (or DC-DC converter) makes it possible to establish an interconnection between the high-voltage electrical network 6 and a low-voltage electrical network 8 to which low-voltage electrical loads 9 and low-voltage electrical actuators 10 are connected. The low-voltage electrical network 8 may, for example, have an operating voltage of the order of 28 Volts.

[0009] Furthermore, a battery 11 can also be electrically connected to the low voltage electrical network 8 via a DC-DC converter 12. A fuel cell 13 can be electrically connected to the low voltage electrical network 8 via a DC-DC converter 14.

[0010] As shown in [Fig. 2], the DC-DC converter 7 comprises a high voltage bridge 17 and a low voltage bridge 18 electrically connected to each other via an electrical transformer 20 and a coil 21. Each bridge 17, 18 comprises a plurality of electronic switches 24, such as transistors, in particular of the MOSFET type, associated with a freewheeling diode 25.

[0011] The electrical transformer 20 is constituted by a planar transformer comprising a magnetic core 28 and a winding 29 provided with at least one primary winding 31 and one secondary winding 32, as shown in [Fig. 3]. This winding 29 is conventionally produced in multi-layer printed circuit technology (called "PCB" for "Printed Circuit Board" according to the English terminology). In an embodiment according to which the winding 29 is constituted by a primary winding 31 and a secondary winding 32, a certain number of conductive layers, generally made of copper, is dedicated to the primary winding 31 and the remaining conductive layers are dedicated to the secondary winding 32. Each layer 35 has a thickness of between 17.5 pm and 210 pm corresponding to one turn of the transformer. The insulation between these layers 35 is provided by a pre-impregnated material 36.The thickness of this pre-impregnated material 36 is determined according to the dielectric property sought inside the transformer 20, namely the inter-turn capacitance. Then, all of the conductive layers 35 and pre-impregnated 36 are laminated together in order to create the structure of the transformer 20. Finally, the interconnection between the turns is carried out using vias.

[0012] As illustrated in [Fig.4], the layer transition with through-vias 37 requires some overlap 38 between two consecutive turns, so that several vias 37 can be used for the layer transition 35 and the maximum current per via 37 is not exceeded. Therefore, the effective winding length per layer 35 is reduced, the number of turns per layer 35 always being less than one (incomplete turn).

[0013] Furthermore, the interconnections in the integrated circuit by vias 37 add a routing constraint to form the geometry of the transformer. These vias 37 also generate additional losses to the overall electrical losses in the transformer. It should also be noted that the pre-impregnated epoxy resin material, generally FR4 (for "Flame Retardant 4" according to English terminology), used as the insulating material of the transformer 20, is a very poor thermal conductor, thus limiting integration and the increase in power density.

[0014] The invention aims to effectively remedy the aforementioned drawbacks by proposing a method for the additive manufacturing of an electrical transformer comprising: (i) - a step of depositing, on a manufacturing tray, a powder bed comprising at least a first powder made from an electrically conductive material arranged in a first zone of the manufacturing tray and a second powder made from an electrically insulating material arranged in a second zone of the manufacturing tray, and (ii) - a step of local melting of the powder bed to obtain a solidified layer of material defining: - a portion of a turn of a primary winding and / or a portion of a turn of a secondary winding made of the electrically conductive material, and - a portion of a body of the electrical transformer made of the electrically insulating material, (iii) - a step of moving the manufacturing plate by a distance equivalent to a thickness of the solidified layer of material, steps (i), (ii) and (iii) being repeated so as to obtain an interlaced primary winding and a secondary winding as well as a body made of electrically insulating material making it possible to electrically insulate the turns of the primary winding and the turns of the secondary winding from each other.

[0015] The invention thus makes it possible to produce a transformer without interconnection vias having very good thermal conductivity and capable of supporting high-temperature applications. The invention makes it possible to have more freedom in the geometry of the electrical transformer, which allows the reduction of the overall electrical losses of the transformer. The invention also allows better heat dissipation. heat using an electrically insulating material made of ceramic.

[0016] According to one implementation of the invention, the local melting of the powder bed is carried out by exposing the powder bed to a laser beam.

[0017] According to one implementation of the invention, said method comprises a step of spreading the first powder and the second powder to obtain the powder bed having a predetermined thickness.

[0018] According to one implementation of the invention, said method comprises a step of forming a first connection terminal and a second connection terminal electrically connected to the primary winding.

[0019] According to an implementation of the invention, each turn of the primary winding extending between a first end and a second end, said method comprises a step of interconnection between the turns of the primary winding, so that the first ends of the turns are all electrically connected to the first connection terminal and the second ends of the turns are all electrically connected to the second connection terminal to obtain a primary winding formed of turns electrically connected in parallel with each other.

[0020] According to one implementation of the invention, the first connection terminal and the second connection terminal are flat terminals extending in the same plane.

[0021] According to one implementation of the invention, said method comprises a step of interconnection between the turns of the secondary winding so as to electrically connect in series the turns of said secondary winding.

[0022] According to an implementation of the invention, each turn of the secondary winding extending between a first end and a second end, said method comprises a step of producing a plurality of inclined connection planes each ensuring an electrical connection between a first end of a given turn with a second end of an adjacent turn.

[0023] According to one implementation of the invention, said method comprises a step of forming a first connection terminal and a second connection terminal electrically connected to the secondary winding.

[0024] According to one implementation of the invention, said method comprises: - a step of forming an intermediate connection terminal arranged at one end of a first turn of the secondary winding, - a step of producing at least one pillar extending vertically from said intermediate connection terminal to the first connection terminal of the secondary winding.

[0025] According to one implementation of the invention, the first connection terminal of the secondary winding extends in the same plane as the second connection terminal.

[0026] According to one implementation of the invention, said method comprises a step of coupling the primary winding and the secondary winding with a magnetic core.

[0027] According to one implementation of the invention, the magnetic core is produced independently of the "primary winding-secondary winding-electrical transformer body" assembly.

[0028] According to one implementation of the invention, the magnetic core is produced by additive manufacturing simultaneously with the "primary winding-secondary winding-electrical transformer body" assembly by adding, in the powder bed, a third powder made from a magnetic material.

[0029] According to one implementation of the invention, the electrically conductive material is chosen from copper, a copper-based alloy, aluminum or an aluminum-based alloy.

[0030] According to one implementation of the invention, the electrically insulating material is a ceramic material.

[0031] The invention also relates to an electrical transformer obtained by an additive manufacturing process as previously defined.

[0032] The present invention will be better understood and other characteristics and advantages will become apparent upon reading the detailed description which follows, comprising embodiments given by way of illustration with reference to the appended figures, presented as non-limiting examples, which may serve to complete the understanding of the present invention and the description of its embodiment and, where appropriate, contribute to its definition, in which:

[0033] [Fig-1] [Fig.l], already described, shows a simplified architecture of a network of dis direct voltage contribution in an airplane;

[0034] [Fig.2] [Fig.2], already described, is an electrical diagram of a DC converter- continuous used in the architecture of [Fig.l];

[0035] [Fig.3] [Fig.3], already described, is a schematic representation of a trans electrical trainer used in the DC-DC converter of [Fig.2];

[0036] [Fig.4] [Fig.4], already described, is a perspective view of a mul- winding transformer printed circuit board layer with vias allowing interconnections to be established between the different conductive layers;

[0037] [Fig.5] [Fig.5] is a schematic representation of a manufacturing device additive allowing the production of an electrical transformer according to the present invention;

[0038] [Fig.6] [Fig.6] is a schematic representation illustrating the interlacing of the primary and secondary windings of an electrical transformer according to the present invention;

[0039] [Fig.7a] [Fig.7a] is a perspective view of an electrical transformer according to the present invention;

[0040] [Fig.7b] [Fig.7b] is a sectional view of the electrical transformer of [Fig.7a];

[0041] [Fig.8] [Fig.8] is a perspective view of an electrical transformer according to the present invention without the insulating body;

[0042] [Fig.9] [Fig.9] is a perspective view of the primary windings and interlaced condaries of an electrical transformer according to the present invention;

[0043] [Fig. 10] [Fig. 10] is a perspective view of a primary winding of an electrical transformer according to the present invention;

[0044] [Fig. 11] [Fig. 11] is a perspective view of a secondary winding of an electrical transformer according to the present invention;

[0045] [Fig. 12] [Fig. 12] is a perspective view of an alternative embodiment of an electrical transformer according to the present invention in which the magnetic core is formed by two attached parts;

[0046] [Fig. 13] [Fig. 13] is a perspective view of an alternative embodiment of an electrical transformer according to the present invention comprising spiral-shaped windings;

[0047] [Fig. 14] [Fig. 14] is a perspective view of an alternative positioning of electrical connection terminals of an electrical transformer according to the present invention.

[0048] It should be noted that in the figures the structural and / or functional elements common to the different embodiments have the same references. Thus, unless otherwise stated, such elements have identical structural, dimensional and material properties.

[0049] [Fig. 5] shows a device 40 for additive manufacturing on a powder bed for producing an electrical transformer 20 according to the invention. This device 40 comprises a manufacturing plate 41 movable in vertical translation and arranged above a powder reservoir 42. A system 43 provided with a roller makes it possible to equalize a thickness of a powder bed 44 deposited on the manufacturing plate 4L. The device 40 also comprises means 45 for generating a laser beam 46 coupled to oscillating mirrors 47 controlled by computer to orient and move the laser beam 46 along the 3 dimensions X, Y and Z.

[0050] The various steps of the additive manufacturing process for an electrical transformer 20 are described below. This process comprises a step of depositing, on the manufacturing plate 41, a powder bed 44. The powder bed 44 comprises at least a first powder 50 made from an electrically conductive material arranged in a first zone ZI of the manufacturing plate 41 and a second powder 51 made in an electrically insulating material arranged in a second zone Z2 of the manufacturing plate 41. The first zone Z1 of the manufacturing plate 41 and the second zone Z2 of the manufacturing plate 41 are two zones distinct from each other.

[0051] The electrically conductive material is chosen from copper, a copper-based alloy, aluminum or an aluminum-based alloy. Advantageously, the electrically insulating material is a ceramic material, in particular magnesium oxide.

[0052] The roller system 43 spreads the first powder 50 and the second powder 51 to obtain a powder bed 44 having a predetermined thickness.

[0053] The method also comprises a step of local melting of the powder bed 44 to obtain a solidified layer of material defining: - a portion of a turn 53 of a primary winding 31 and / or a portion of a turn 54 of a secondary winding 32 made from the electrically conductive material, and - a portion of a body 57 of the electrical transformer 20, visible in [Fig.7a], made of the electrically insulating material.

[0054] [Fig.7b] shows the different elements (portions of turns of the primary winding 31, portions of turns 54 of the secondary winding 32 and the portions of the body 57) forming the different layers of solidified materials.

[0055] Advantageously, the local melting of the powder bed 44 is carried out by exposing the powder bed 44 to the laser beam 46 or LBM process for Laser Beam Melting according to the English terminology. Alternatively, the local melting of the powder bed 44 can be carried out by an electron beam or Electron Beam Melting (EBM) according to the English terminology or by binder jetting also called "Binder Jetting" according to the English terminology.

[0056] The manufacturing plate 41 is then moved vertically downwards by a distance equivalent to a thickness of the solidified layer of material, in particular less than 1 mm.

[0057] The steps of depositing a powder bed 44, of locally melting the powder bed 44 and of moving the manufacturing plate 41 are repeated so as to obtain an interlaced primary winding 31 and a secondary winding 32 as well as a body 57 visible in FIGS. 7a and 7b made of electrically insulating material making it possible to electrically insulate the turns 53 of the primary winding 31 and the turns 54 of the secondary winding 32 from each other. By "interlaced" is meant the fact that the two windings 31, 32 with helical turns are screwed into each other, as illustrated in [Fig. 6] and / or that there is an alternation of flat turns between the two windings 31, 32 in the interlaced assembly.

[0058] As illustrated in Figures 9 and 10, the method comprises a step of forming a first connection terminal BT1 and a second connection terminal BT2 electrically connected to the primary winding 31.

[0059] Each turn 53 of the primary winding 31 extending between a first end 53.1 and a second end 53.2, said method comprises a step of interconnection between the turns 53 of the primary winding 31, so that the first ends 53.1 of the turns 53 are all electrically connected to the first connection terminal BT1 and the second ends 53.2 of the turns 53 are all electrically connected to the second connection terminal BT2 to obtain a primary winding 31 formed of (np) turns electrically connected in parallel with each other.

[0060] Advantageously, the first connection terminal BT1 and the second connection terminal BT2 are flat terminals extending in the same plane.

[0061] As illustrated in Figures 9 and 11, the method comprises a step of interconnection between the turns 54 of the secondary winding 32 so as to electrically connect in series the (ns) turns of said secondary winding 32.

[0062] Each turn 54 of the secondary winding 32 extending between a first end 54.1 and a second end 54.2, the method comprises a step of producing a plurality of inclined connection planes 58 each ensuring an electrical connection between a first end 54.1 of a given turn 54 with a second end 54.2 of an adjacent turn 54.

[0063] The method comprises a step of forming a first connection terminal HT1 and a second connection terminal HT2 electrically connected to the secondary winding 32. Advantageously, the first connection terminal HT1 of the secondary winding 32 extends in the same plane as the second connection terminal HT2. The connection terminals HT1 and HT2 are arranged at the level of a last turn of the secondary winding 32.

[0064] Furthermore, an intermediate connection terminal PI is formed in a plane of one end of a first turn 54 of the secondary winding 32. The method comprises a step of producing at least one pillar 60 extending vertically from said intermediate connection terminal PI to the first connection terminal HT1 of the secondary winding 32. The number of pillars 60 depends on the desired rigidity of the mechanical connection between the terminals PI and HT1.

[0065] According to an implementation of the method according to the invention, the primary winding 31 is produced so as to comprise np=10 turns 53 electrically connected in parallel with each other along a height of the primary winding 31 so as to form a single turn in the primary. The connection of the turns 53 in parallel makes it possible to increase the flow of current and to reduce electrical losses, in other words, to increase the efficiency of the electrical transformer 20.

[0066] The secondary winding 32 is made so as to comprise ns=9 turns electrically connected in series with each other. The offset of 1 turn is due to the interlacing between the two windings 31, 32.

[0067] In this example, there is therefore a number of turns np of the primary winding 31 greater than the number of turns ns of the secondary winding 32. Alternatively, the number of turns ns of the secondary winding 32 may be greater than the number of turns np of the primary winding 31.

[0068] The transformation ratio is either l:ns in the case of a voltage-boosting transformer, or ns:l in the case of a voltage-stepping transformer.

[0069] The method advantageously comprises a step of coupling the primary winding 31 and the secondary winding 32 with a magnetic core 61 visible in FIGS. 7, 8 and 12. The magnetic core 61 is for example made of ferrite or another magnetic material suitable for the application, for example based on rare earths.

[0070] The magnetic core 61 can be produced independently of the "primary winding 31-secondary winding 32-body 57 of electrical transformer 20" assembly. The added magnetic core 61 can be produced by an additive manufacturing process similar to that implemented. Alternatively, the magnetic core 61 can be produced by uniaxial compression, sintering or any other technique adapted to the application.

[0071] In the embodiment of [Fig.12], the magnetic core 61 comprises an E-shaped portion 63, the central branch of the E is arranged inside the opening delimited by the primary winding 31 and the secondary winding 32. The magnetic core 61 comprises an I-shaped portion 64 arranged on the E-shaped portion so as to loop the paths of the magnetic flux circulating inside the magnetic core 61.

[0072] Alternatively, the magnetic core 61 can be produced by additive manufacturing simultaneously with the "primary winding 31-secondary winding 32-body 57 of electrical transformer 20" assembly by adding, in the powder bed 44, a third powder made from a magnetic material.

[0073] In the embodiment of Figures 7 to 11, the turns 53, 54 of the primary winding 31 and the secondary winding 32 each extend in a plane and therefore have a flat annular shape. Alternatively, in the embodiment of [Fig. 13], the turns 53, 54 have a helical shape.

[0074] In the embodiment of [Fig. 14], the connection terminals HT1 and HT2 of the secondary winding 32 are each arranged at one end of the secondary winding 32. Thus, a connection terminal HT1 is arranged at the first turn of winding 32 and the HT2 connection terminal is arranged at the last turn of winding 32.

[0075] Of course, the various features, variants and / or embodiments of the present invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive.

[0076] Furthermore, the invention is not limited to the embodiments described above and provided solely by way of example. It encompasses various modifications, alternative forms and other variants that may be envisaged by those skilled in the art within the scope of the present invention and in particular all combinations of the different operating modes described above, which may be taken separately or in association.

Claims

Claims

1. A method of additive manufacturing of an electrical transformer (20), characterized in that said method comprises: (i) - a step of depositing, on a manufacturing plate (41), a powder bed (44) comprising at least a first powder (50) made of an electrically conductive material arranged in a first zone (Z1) of the manufacturing plate (41) and a second powder (51) made of an electrically insulating material arranged in a second zone (Z2) of the manufacturing plate (41), and (ii) - a step of local melting of the powder bed (44) to obtain a solidified layer of material defining: - a portion of a turn (53) of a primary winding (31) and / or a portion of a turn (54) of a secondary winding (32) made of the electrically conductive material, and - a portion of a body (57) of the electrical transformer (20) made of the electrically insulating material,(iii) - a step of moving the manufacturing plate (41) by a distance equivalent to a thickness of the solidified layer of material, - steps (i), (ii) and (iii) being repeated so as to obtain an interlaced primary winding (31) and a secondary winding (32) as well as a body (57) made of electrically insulating material making it possible to electrically insulate the turns (53) of the primary winding (31) and the turns (54) of the secondary winding (32) from each other.,

2. Method according to claim 1, characterized in that it comprises a step of spreading the first powder (50) and the second powder (51) to obtain the powder bed (44) having a predetermined thickness.

3. Method according to claim 1 or 2, characterized in that it comprises a step of forming a first connection terminal (BT1) and a second connection terminal (BT2) electrically connected to the primary winding (31).

4. Method according to claim 3, characterized in that each turn (53) of the primary winding (31) extending between a first end (53.1) and a second end (53.2), said method comprises a step of interconnection between the turns (53) of the primary winding (31), so that the first ends (53.1) of the turns (53) are all electrically connected to the first connection terminal (BT1) and that the second ends (53.2) of the turns (53) are all electrically connected to the second connection terminal (BT2) to obtain a primary winding (31) formed of turns electrically connected in parallel with each other.

5. Method according to claim 3 or 4, characterized in that the first connection terminal (BT1) and the second connection terminal (BT2) are flat terminals extending in the same plane.

6. Method according to any one of claims 1 to 5, characterized in that it comprises a step of interconnection between the turns (54) of the secondary winding (32) so as to electrically connect in series the turns of said secondary winding (32).

7. Method according to claim 6, characterized in that each turn (54) of the secondary winding (32) extending between a first end (54.1) and a second end (54.2), said method comprises a step of producing a plurality of inclined connection planes (58) each ensuring an electrical connection between a first end (54.1) of a given turn (54) with a second end (54.2) of an adjacent turn (54).

8. Method according to any one of claims 1 to 7, characterized in that it comprises a step of forming a first connection terminal (HT1) and a second connection terminal (HT2) electrically connected to the secondary winding (32).

9. Method according to claim 8, characterized in that it comprises: • a step of forming an intermediate connection terminal (PI) arranged at one end of a first turn (54) of the secondary winding (32), • a step of producing at least one pillar (60) extending vertically from said intermediate connection terminal (PI) to the first connection terminal (HT1) of the secondary winding (32).

10. Method according to any one of claims 1 to 9, characterized in that it comprises a step of coupling the primary winding (31) and the secondary winding (32) with a magnetic core (61).

11. Method according to claim 10, characterized in that the magnetic core (61) is produced independently of the "primary winding (31)-secondary winding (32)-body (57)" assembly. electrical transformer (20)".

12. Method according to claim 10, characterized in that the magnetic core (61) is produced by additive manufacturing simultaneously with the "primary winding (31)-secondary winding (32)-body (57) of electrical transformer (20)" assembly by adding, in the powder bed (44), a third powder made from a magnetic material.

13. Method according to any one of claims 1 to 12, characterized in that the electrically conductive material is chosen from copper, a copper-based alloy, aluminum or an aluminum-based alloy.

14. Method according to any one of claims 1 to 13, characterized in that the electrically insulating material is a ceramic material.

15. Electrical transformer (20) obtained by an additive manufacturing process defined according to any one of the preceding claims.

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