METHOD FOR PRODUCING AN ELECTRICAL TRANSFORMER BY ADDITIVE MANUFACTURING

Abstract

The invention relates to an additive manufacturing process for 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 locally melting the powder bed to obtain a layer of solidified 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 build platform, - steps (i), (ii) and (iii) being repeated so as to obtain intertwined windings (31, 32) as well as a body (57) made of an electrically insulating material enabling the turns (53) of the primary winding (31) and the turns (32) to be electrically isolated from each other. (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 manufacturing 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 worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new types of aircraft and those currently in operation, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively working for several years now to contribute to the fight against climate change.

[0003] Technological research efforts have already led to significant improvements in the environmental performance of aircraft. The Applicant takes into account the factors impacting all phases of design and development in order to obtain aeronautical components and products that are less energy-intensive, more environmentally friendly, and 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 that minimize 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 weight reduction 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. 1 shows a simplified example of the architecture of a DC power distribution network in an aircraft. To supply power to the aircraft's high-voltage electrical system, a generator 1 is connected to a high-pressure shaft of a turbomachine 2 via an accessory gearbox (not shown). This accessory gearbox includes generally one or more gear trains which are driven in rotation by the high-pressure shaft of the turbomachine 1 by means of a right-angle gearbox on the high-pressure shaft.

[0007] The generator 1 is electrically connected to an AC / DC converter 3 so as to be able to supply electrically high voltage 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 around 270 Volts.

[0008] A DC-DC converter 7 (or DC-DC converter) allows an interconnection to be established between the high voltage electrical network 6 and a low voltage electrical network 8 on 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 consists of a planar transformer comprising a magnetic core 28 and a winding 29 having at least one primary winding 31 and one secondary winding 32, as shown in [Fig. 3]. This winding 29 is conventionally made using multilayer printed circuit board (PCB) technology. In an embodiment where the winding 29 consists of a primary winding 31 and a secondary winding 32, a certain number of conductive layers, generally made of copper, are dedicated to the primary winding 31 and the remaining conductive layers are dedicated to the secondary winding 32. Each layer 35 has a thickness between 17.5 µm and 210 µm, corresponding to one turn of the transformer. Insulation between these layers 35 is provided by means of a pre-impregnated material 36.The thickness of this pre-impregnated material 36 is determined according to the desired dielectric property inside the transformer 20, namely the inter-turn capacitance. Next, all the conductive layers 35 and pre-impregnated material 36 are laminated together to create the structure of the transformer 20. Finally, the interconnection between the turns is achieved using vias.

[0012] As illustrated in [Fig. 4], the layer transition with through vias 37 requires a certain 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. Consequently, 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 via vias 37 add a routing constraint to form the geometry of the transformer. These vias 37 also generate additional losses beyond the overall electrical losses in the transformer. It should also be noted that the epoxy resin pre-impregnated material, generally FR4 (for "Flame Retardant 4" in Anglo-Saxon terminology), used as the insulating material of the transformer 20, is a very poor thermal conductor, thus limiting integration and increasing power density.

[0014] The invention aims to effectively overcome the aforementioned drawbacks by proposing an additive manufacturing process for an electrical transformer comprising: (i) - a step of depositing, onto a build platform, a powder bed comprising at least a first powder made of an electrically conductive material disposed in a first zone of the build platform and a second powder made of an electrically insulating material disposed in a second zone of the build platform, and (ii) - a local melting step of the powder bed to obtain a solidified material layer defining: - a portion of a turn of a primary winding and / or a portion of a turn of a secondary winding made of electrically conductive material, and - a portion of the body of the electrical transformer made of electrically insulating material, (iii) - a step of moving the manufacturing platform a distance equivalent to the thickness of the solidified material layer, steps (i), (ii) and (iii) being repeated so as to obtain an interlaced primary winding and secondary winding and a body of electrically insulating material enabling the turns of the primary winding and the turns of the secondary winding to be electrically isolated from each other.

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

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

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

[0018] According to one embodiment 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 one embodiment of the invention, each turn of the primary winding extending between a first end and a second end, said method includes an interconnection step between the turns of the primary winding, such 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 embodiment of the invention, the first connection terminal and the second connection terminal are planar terminals extending in the same plane.

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

[0022] According to one embodiment of the invention, each turn of the secondary winding extending between a first end and a second end, said method comprises a step of making a plurality of inclined connecting 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 embodiment 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 embodiment of the invention, said method comprises: - a step of forming an intermediate connection terminal located at one end of a first turn of the secondary winding, - a step of constructing at least one pillar extending vertically from said intermediate connection terminal to the first connection terminal of the secondary winding.

[0025] According to one embodiment 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 embodiment 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 embodiment of the invention, the magnetic core is made independently of the "primary winding-secondary winding-electric transformer body" assembly.

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

[0029] According to one embodiment 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 embodiment 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 features and advantages will become apparent upon reading the following detailed description, which includes embodiments given by way of illustration with reference to the accompanying figures, presented by way of non-limiting examples, which may serve to complete the understanding of the present invention and the explanation of its implementation and, where appropriate, contribute to its definition, on which:

[0033] [Fig-1] Fig. 1, already described, shows a simplified architecture of a network of continuous voltage distribution in an aircraft;

[0034] [Fig.2] Fig.2, already described, is an electrical diagram of a DC- continuous used in the architecture of [Fig.1];

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

[0036] [Fig.4] Fig.4, already described, is a perspective view of a winding multilayer printed circuit transformer equipped with vias allowing interconnections 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] The [Fig.7b] is a cross-sectional view of the electrical transformer of the [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 intertwined secondary windings of an electrical transformer according to the present invention;

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

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

[0045] [Fig. 12] The [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] The [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] The [Fig. 14] is a perspective view of a variant of the 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 reference numerals. Thus, unless otherwise stated, such elements have identical structural, dimensional, and material properties.

[0049] Figure 5 shows a powder bed additive manufacturing device 40 for producing an electrical transformer 20 according to the invention. This device 40 comprises a build platform 41 movable in vertical translation and arranged above a powder reservoir 42. A system 43 equipped with a roller allows for leveling the thickness of a powder bed 44 deposited on the build platform 41. The device 40 also includes means for generating a laser beam 46 coupled to computer-controlled oscillating mirrors 47 to orient and move the laser beam 46 along the three dimensions X, Y, and Z.

[0050] The various stages of the additive manufacturing process for an electrical transformer 20 are described below. This process includes a stage of depositing a powder bed 44 onto the build platform 41. The powder bed 44 comprises at least one first powder 50 made of an electrically conductive material disposed in a first zone ZI of the manufacturing platform 41 and a second powder 51 made of an electrically insulating material disposed in a second zone Z2 of the manufacturing platform 41. The first zone ZI of the manufacturing platform 41 and the second zone Z2 of the manufacturing platform 41 are two distinct zones with respect to each other.

[0051] The electrically conductive material is selected 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 process also includes a step of local melting of the powder bed 44 to obtain a layer of solidified 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, visible on the [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 portions of the body 57) forming the different layers of solidified materials.

[0055] Advantageously, the local melting of the powder bed 44 is achieved by exposing the powder bed 44 to the laser beam 46, or the LBM process (Laser Beam Melting) according to Anglo-Saxon 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 Anglo-Saxon terminology, or by binder jetting, also called "Binder Jetting" according to Anglo-Saxon terminology.

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

[0057] The steps of depositing a powder bed 44, locally melting the powder bed 44, and moving the build platform 41 are repeated so as to obtain an intertwined primary winding 31 and a secondary winding 32, as well as a body 57, visible in Figures 7a and 7b, made of electrically insulating material, allowing the turns 53 of the primary winding 31 and the turns 54 of the secondary winding 32 to be electrically isolated from each other. By "intertwined," it is understood that the two helical windings 31 and 32 are screwed into each other, such that... illustrated on [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 includes a step of forming a first BT1 connection terminal and a second BT2 connection terminal 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 includes an interconnection step between the turns 53 of the primary winding 31, such 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 respect to each other.

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

[0061] As illustrated in Figures 9 and 11, the method includes an interconnection step 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 includes a step of making a plurality of inclined connecting 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 includes 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 last turn of the secondary winding 32.

[0064] In addition, 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 includes a step of making 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 made 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 increases the current flow and reduces electrical losses, in other words, increases the efficiency of the electrical transformer 20.

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

[0067] In this example, we therefore have 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 step-up transformer, or ns:l in the case of a step-down transformer.

[0069] The process advantageously includes a step of coupling the primary winding 31 and the secondary winding 32 with a magnetic core 61 visible in figures 7, 8 and 12. The magnetic core 61 is for example made of ferrite or of 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-electric transformer body 57 20" assembly. The added magnetic core 61 can be produced by an additive manufacturing process similar to that used. Alternatively, the magnetic core 61 can be produced by uniaxial compression, sintering, or any other technique suitable for the application.

[0071] In the embodiment of [Fig.12], the magnetic core 61 has an E-shaped part 63, the central branch of the E being disposed inside the opening delimited by the primary winding 31 and the secondary winding 32. The magnetic core 61 has an I-shaped part 64 disposed on the E-shaped part so as to close 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 assembly "primary winding 31-secondary winding 32-electric transformer body 57 20" by adding, in the powder bed 44, a third powder made of a magnetic material.

[0073] In the embodiment shown in Figures 7 to 11, the turns 53, 54 of the primary winding 31 and the secondary winding 32 each extend in a plane and thus 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 HT1 and HT2 connection terminals of the secondary winding 32 are each arranged at one end of the secondary winding 32. Thus, one HT1 connection terminal is arranged at the first turn of the winding 32 and the HT2 connection terminal is arranged at the last turn of the winding 32.

[0075] Of course, the different features, variants and / or embodiments of the present invention can be combined with each other in various ways insofar as 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 a person skilled in the art may consider within the scope of the present invention, and in particular all combinations of the different modes of operation described above, which may be taken separately or in combination.

Claims

1. Demands Additive manufacturing process for an electrical transformer (20), characterized in that said process comprises: (i) - a step of depositing, on a manufacturing platform (41), a powder bed (44) comprising at least a first powder (50) made of an electrically conductive material disposed in a first zone (Z1) of the manufacturing platform (41) and a second powder (51) made of an electrically insulating material disposed in a second zone (Z2) of the manufacturing platform (41), and (ii) - a step of locally melting the powder bed (44) to obtain a layer of solidified 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 platform (41) a distance equivalent to the thickness of the solidified material layer, - steps (i), (ii) and (iii) being repeated so as to obtain an interlaced primary winding (31) and a secondary winding (32) and a body (57) of electrically insulating material allowing to electrically insulate from each other the turns (53) of the primary winding (31) and the turns (54) of the secondary winding (32), - the turns (53,54) of the primary winding (31) and the secondary winding (32), each extending in a plane, - said method comprising an interconnection step between the turns (54) of the secondary winding (32) so as to electrically connect the turns of said secondary winding (32) in series, - 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 making a plurality of inclined connecting 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).

2. A 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. A 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 an interconnection step between the turns (53) of the primary winding (31), such 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 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 planar terminals extending in the same plane.

6. A method according to any one of claims 1 to 5, 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).

7. A method according to claim 6, characterized in that it comprises: • a step of forming an intermediate connection terminal (PI) disposed at one end of a first turn (54) of the secondary winding (32), • a step of making at least one pillar (60) extending vertically from said intermediate connection terminal (PI) to the first connection terminal (HT1) of the secondary winding (32).

8. A method according to any one of claims 1 to 7, characterized in that it comprises a primary winding coupling step (31) and the secondary winding (32) with a magnetic core (61).

9. Method according to claim 8, characterized in that the magnetic core (61) is made independently of the "primary winding (31)-secondary winding (32)-body (57) of electrical transformer (20)" assembly.

10. Method according to claim 8, 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 of a magnetic material.

11. A method according to any one of claims 1 to 10, characterized in that the electrically conductive material is selected from copper, a copper-based alloy, aluminum, or an aluminum-based alloy.

12. A method according to any one of claims 1 to 11, characterized in that the electrically insulating material is a ceramic material.

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